The pathogenesis of sarcopenia is part of a complex process of age-related changes in musculoskeletal cellular as well as tissue structure and function (Doherty 2003; Lang, et al. 2010). Social and lifestyle behaviours such as physical inactivity, smoking, poor diet, being obese, as well as age-related hormonal, neurological, immunological and metabolic factors are important risk factors (M.S. John Pathy 2006). Genetic susceptibility also plays a role in sarcopenia formation(Muscaritoli, et al. 2010). The putative causes of sarcopenia have been catergorised into "intrinsic" and "extrinsic" factors (M.S. John Pathy 2006; Muscaritoli, et al. 2010). Reductions in anabolic hormones (testosterone, estrogens, growth hormones, insulin like growth factor-1), increases of apoptotic activities in the myofibers, increases of proinflammatory cytokines (e.g. TNF-α, IL-6), oxidative stress due to accumulation of free radicals, changes of the mitochondrial function of muscle cells and a decline in the number of α-motoneurons are some of the intrinsic factors involved (Lang, et al. 2010; Muscaritoli, et al. 2010). Deficient intake of energy and protein, reduced intake of vitamin D, acute and chronic co-morbidities and reduced physical activity are some of the extrinsic conditions leading to sarcopenia (Cruz-Jentoft, et al. 2010b; Muscaritoli, et al. 2010). Figure 2 shows the factors contributing to sarcopenia and its consequences.

What is not known is which factors or pathways are relatively more or less important with regards to the severity and rate of development of sarcopenia components; muscle mass, strength and quality. Each factor potentially contributes differently to the loss of muscle mass, strength and quality and it is likely that there is considerable individual variability in the interactions of these factors (M.S. John Pathy 2006).

grip. Muscle strength alone has been shown to be the most useful indicator of age-related changes in muscle for use in clinical practice (Hairi NN 2010). Grip strength is a good simple measure of muscle strength and correlates with leg strength (Cruz-Jentoft, et al. 2010a). Other measures of muscle strength include knee flexion /extension and peak expiratory flow (PEF) (Cruz-Jentoft, et al. 2010a). With regards to physical performance, a wide range of tests are available including Tinetti Performance Oriented Mobility Test, Gait Speed, Functional Independence Measure and the Timed Get-Up-and-Go (TGUG) test (Guralnik and Luigi 2003). Cut-off points depend upon the measurement technique chosen and on the availability of reference studies. The EWGSOP recommends the use of normative (healthy young adult) rather than other predictive reference populations (Cruz-Jentoft, et al. 2010a). To date, sarcopenia has not been included in common classifications of disease (i.e. International Classification of Diseases), although some recent initiatives are trying to move

The aetiology of sarcopenia is multifactorial (Cruz-Jentoft, et al. 2010b; Lang, et al. 2010; Y Rolland 2008 ). Multiple risk factors contribute to the development and progression of sarcopenia. These risk factors can be grouped into several categories such as constitutional factors, the aging process, certain life habits such as decreased protein intake, disuse or poor physical activity including lack of exercise, the use of tobacco and alcohol intake, changes in living conditions such as prolonged bed rest and immobility and chronic health conditions

The pathogenesis of sarcopenia is part of a complex process of age-related changes in musculoskeletal cellular as well as tissue structure and function (Doherty 2003; Lang, et al. 2010). Social and lifestyle behaviours such as physical inactivity, smoking, poor diet, being obese, as well as age-related hormonal, neurological, immunological and metabolic factors are important risk factors (M.S. John Pathy 2006). Genetic susceptibility also plays a role in sarcopenia formation(Muscaritoli, et al. 2010). The putative causes of sarcopenia have been catergorised into "intrinsic" and "extrinsic" factors (M.S. John Pathy 2006; Muscaritoli, et al. 2010). Reductions in anabolic hormones (testosterone, estrogens, growth hormones, insulin like growth factor-1), increases of apoptotic activities in the myofibers, increases of proinflammatory cytokines (e.g. TNF-α, IL-6), oxidative stress due to accumulation of free radicals, changes of the mitochondrial function of muscle cells and a decline in the number of α-motoneurons are some of the intrinsic factors involved (Lang, et al. 2010; Muscaritoli, et al. 2010). Deficient intake of energy and protein, reduced intake of vitamin D, acute and chronic co-morbidities and reduced physical activity are some of the extrinsic conditions leading to sarcopenia (Cruz-Jentoft, et al. 2010b; Muscaritoli, et al. 2010). Figure 2 shows the

What is not known is which factors or pathways are relatively more or less important with regards to the severity and rate of development of sarcopenia components; muscle mass, strength and quality. Each factor potentially contributes differently to the loss of muscle mass, strength and quality and it is likely that there is considerable individual variability in

in this direction.

**3. Aetiology and pathogenesis of sarcopenia**

factors contributing to sarcopenia and its consequences.

the interactions of these factors (M.S. John Pathy 2006).

(Cruz-Jentoft, et al. 2010b). Table 2 shows the risk factors of sarcopenia.

Source: Cruz-Jentoft AJ, Landi F, Topinkova E *et al*. Understanding sarcopenia as a geriatric syndrome. Current Opinion in Clinical Nutrition and Metabolic Care. 2010; 13: 1-7

Table 2. Risk factors of sarcopenia

#### **4. Functional consequences of sarcopenia**

Age-related loss of muscle mass and strength result in decreased functional limitation and physical disability among older people. Using the Nagi Model of Disablement pathology (e.g. sarcopenia) first leads to impairment such as lower extremity weakness (Steven M Albert and Vicki A Freedman 2010). When this crosses some threshold, functional impairment begins to show (which is measurable via gait speed below age-sex appropriate norm) and this in turn will lead to physical disability, e.g. needing help to cross the street (Steven M Albert and Vicki A Freedman 2010). This is as shown in Figure 3.

Sarcopenia in Older People 35

**Physical disability (ADL)**

Grip strength§ 2.83 (1.91, 4.20) 1.79 (1.17, 2.74) 1.09 (0.72, 1.65) Quadriceps strength§ 4.48 (2.43, 8.27) 3.24 (1.68, 6.23) 2.07 (1.14, 3.78)

aLM/height + 1.89 (1.25, 2.86) 1.29 (0.84, 1.99) 1.41 (0.88, 2.26) aLM/fat mass<sup>≠</sup> 2.99 (2.05, 4.38) 2.79 (1.93, 4.05) 2.08 (1.37, 3.15) residuals 2.95 (2.00, 4.36) 2.18 (1.43, 3.32) 1.75 (1.10, 2.78)

specific force §, ¶ 1.95 (1.26, 3.03) 1.63 (1.07, 2.49) 1.19 (0.77, 1.85)

specific force §, # 3.38 (1.82, 6.30) 2.71 (1.44, 5.08) 2.01 (1.05, 3.83) \*Adjusted for country of birth, age group, education level, PASE score, co-morbidity, stroke, arthritis,

Source: Hairi NN, Cumming R, Naganathan V *et al.* Loss of Muscle Strength, Mass (Sarcopenia), and Quality (Specific Force) and Its Relationship with Functional Limitation and Physical Disability: The Concord Health and Ageing in Men Project. Journal of the American Geriatrics Society. 2010: 58: 2055-2062 Table 3. Prevalence ratios for low muscle strength, muscle mass and muscle quality and

The relationship between age-related muscle changes and poor physical function is complex. Muhlberg and Siber described three possible "vicious loops" that involve feedback from physiological and behavioural systems. The "vicious loops" are the immobilization loop, the nutritional loop and the metabolic loop (M.S. John Pathy 2006). The vicious loop between sarcopenia and immobilization is described as: sarcopenia → neuromuscular impairment → falls and fractures → immobilization → sarcopenia. The second loop is the "nutritional" vicious loop between sarcopenia and malnutrition: sarcopenia → immobilization → decline of nutrition skills (empty refrigerator) → malnutrition impaired protein synthesis → sarcopenia. Finally, the "metabolic" vicious loop between sarcopenia and the decline of protein reserve in the body: sarcopenia → decline of protein reserve of the body → diminished capacity to meet the extra demand of protein synthesis associated

As sarcopenia (loss of muscle strength, muscle mass and quality) was found to be associated with poor physical function, improvements in muscle strength would prevent

Upper extremity

Lower extremity

+Additionally adjusted for obesity. ≠Additionally adjusted for height. § Additionally adjusted for pain.

physical disability, CHAMP Study.

disease and injury → sarcopenia.

**5. Prevention and treatments for sarcopenia**

ǁ Ratio of grip strength (measured in kg of force) to arm lean mass


**3. Breaking the bad news**

Psychologists agree that the approach by a professional such as an Ophthalmologist in breaking the news of imminent visual impairment or eventual blindness is not unlike that for terminal illness or death; hence the phases of adjustment are similar [4]. The seven phases of adjustment to blindness are: (1) trauma (physical or social), (2) shock and denial, (3) mourning and withdrawal, (4) succumbing and depression, (5) reassessment and reaffirmation, (6) coping and mobilization, and (7) self-acceptance and self-esteem [5]. The duration and outcome of the stages are unpredictable. The social and relational factors discussed in the previous section are among others that will influence the sequence.

synchronization promotion, altered levels of melatonin and serotonin, suppressed corticostriatal glutamatergic neurotransmission, immune response boosting, decreased levels of reac-

Coping with Visual Impairment: Helping our Patients Face the Truth

http://dx.doi.org/10.5772/intechopen.78675

89

Invoking healing through prayer has been compared with the placebo effect, influenced by personality, expectancy, optimism, and motivation. Randomized controlled studies, have been inconclusive about the benefits of prayer, though faith has had documented positive impact on outcomes in treatment groups studied. Considerations given to the Hawthorne and Rosenthal effects have been attributed to some of these outcomes [6]. The Hawthorne effect refers to change that occurs as a result of the act of observation or measurement, whereas the Rosenthal effect refers to change resulting from observer or rater expectancy. Study conditions may foster exaggeration of measurement results on the part of the subject, and relaxation of the measurement criteria on the part of the observer respectively. With specific reference to glaucoma, I have found that patients with a positive attitude maintain functional

Andrade and Radhakrishnan [6] examined the correlation of medical and psychosocial benefits to religious affiliations and practices by posing a series of questions (see Appendix 7.1). The results were inconclusive and as such a definite relationship could not be determined. The door to research of this nature remains open, with respect to religious and theological

Optimism in our patients facing blindness has a positive impact on the way they experience environmental stimuli, and how this information is used in coping strategies optimism may contribute to the well-being of persons who have lost their vision both directly and by promoting problem-focused coping and engagement in positive social comparisons [7]. Research has found that non-acceptance of vision loss, using avoidance or ventilation coping, and not facing reality with a positive outlook may lead to negative feelings and low adaptation. Ophthalmologists' attitudes towards the underlying disease, and how they convey hope or despair to patients, can influence psychosocial adaptation in patients. The concept of neuroplasticity and the individualistic nature of healing and repair cannot be minimized. Shifting the focus to realistic goals such as optimal IOP in glaucoma, and discussing breakthroughs in neuro-therapy such as stem cell research will help keep hope alive and foster positive outlook.

Murphy [8] writes of her experience with a poor visual prognosis, where second opinion changed her life in a day, from despair to hope. An ophthalmologist diagnosed her sudden onset of loss of vision as macular hemorrhage of questionable etiology, giving a 2-week period before anticipated total vision loss. Her second opinion from a younger eye surgeon (and has a good prognosis), gave a diagnosis of Central Serous Maculopathy which is self-limiting. Patients are entitled to this review, and doctors should have no insecurities about this, as

tive oxygen species as measured by ultra-weak photon emission and reduced stress.

vision despite advanced disc and Retinal Nerve Fiber Layer (RNFL).

customs and beliefs.

**5. The second opinion**

medical research is very dynamic.

Professionals must stress the positive in all situations, and outline to family members that all aspects of vision must be appreciated and respected. While 20/20 to 20/40 may be the gold standard to function vocationally in everyday life, many will come to appreciate the ability to distinguish light and dark, colors, large gratings and basic physical forms. Conducting acuity tests with the Berkley Rudimentary Vision Charts to establish and define Log Mar vision below the 20/400 line is a good start. At this point, patients with advanced glaucoma, diabetic retinopathy, age related macular degeneration, retinitis pigmentosa, and many others must realize the value of whatever residual vision they have. This will encourage compliance with the control of ocular and systemic diseases leading to blindness.

Patients deal with the sudden traumatic nature of the bad news with denial and disbelief. They view the abyss of isolation and torment socially [5]. Three factors that influence the severity and intensity of shock are: (1) the significance of the loss to the individual, (2) the suddenness or unexpectedness of the event, and (3) the degree of visual loss. Denial often lasts as long as the multiple opinions and therapies continue to change; when the eye care professional admits "we have done all we can do."

Tedrick [4] reports that self-pity is the main characteristic in the mourning and withdrawal phase. In this phase, individuals refrain from activities that they once loved to partake in. Tuttle and Tuttle [5] outlined the "D's" of depression as despair, discouragement, disinterest, distress, despondency and dissentment. The next stage in the adjustment process is reassessment and reaffirmation. In this phase/stage the client self-examines their life and finds meaning (purpose for living).

In the next stage (coping and mobilization), the patient will find information and resource that will support them in the change [4]. This phase has cultural overtones that determine how smoothly, and at what rate it progresses. In Jamaica, the go-to is the Society for the Blind and the philanthropic body that supports rehabilitation is the Lions Clubs spread across the island. As the patient crosses this phase into the final of self-acceptance, he/she gains selfconfidence, and is able to accept the prognosis and move on with life. This may take a long time, and some may never get there.


*<IP_ADDRESS> Characteristic variable Δ (*Δe*)*

The sign of the change rate (secondary difference) of the error change is defined as a characteristic quantity that describes the dynamic process as overshoot or callback. For example, for the curve shown in **Figure 19**, there are two cases:

1.ABC segment: Δ(*Δe*) > 0, it is in the overshoot segment.

2.CDE segment: Δ(*Δe*) < 0, which is in the callback segment.

The essential characteristics of the above-designed characteristic variables are that they are not an absolute quantity, but a symbol variable, or a relative quantity. Symbol variables are used to characterize the direction of the dynamic process change trend, and relative quantities are used to characterize the speed of the dynamic process change. The above-mentioned symbol variables and characteristic variables (relative quantities) that characterize the degree of change in a dynamic process are collectively referred to as qualitative variables.

In order to use computers to realize human-like intelligent control, it is necessary to try to teach human operation experience, qualitative knowledge and intuitive reasoning to the computer, and let it apply this knowledge through flexible and flexible judgment, reasoning and control algorithms to perform human-like intelligent control. The main source of online information obtained by a computer is the input *R* and output *Y* of the system, from which the error *e* and the error change *Δe* can be calculated. Through *e* and *Δe*, the characteristic quantities that characterize the dynamic characteristics of the system can be further obtained. The computer can capture the characteristic information of the dynamic process with the aid of the above-mentioned characteristic quantities, and recognize the dynamic behavior of the system as a basis for control decisions. According to the dynamic characteristics and dynamic behavior of the system, the most effective control form is selected from a variety of control modes to precisely control the controlled object. Computers can use qualitative knowledge and intuitive reasoning in the control process. This is fundamentally different from traditional control theories, and it is precisely this point that embodies human intelligence. This method solves the contradiction of speed, stability and accuracy in the control process very well.

#### *3.2.2 Humanoid intelligent control principle*

The composition of human-like intelligent controller is similar to the basic structure of an expert controller, which consists of the following four parts.

4.Control rule set. The control rule set is actually a rule-based controller. The process of control decision is to implement a mapping from the feature pattern set to the control rule set. In general, the number of feature patterns is greater than or equal to the number of control rules.

The working process of the human-like intelligent controller can be summarized into three steps: First, the system judges the characteristic mode of the dynamic process according to the calculated characteristic variables; second, the inference mechanism searches for a matching control rule according to the characteristic mode class; third, the controller executes the above control rules to control the controlled object [15].

 In addition, in the human-like intelligent control, a combination of variable gain proportional control, proportional differential control, and open-loop and closedloop control is also used.

#### *3.3.1 Human intelligence integration principle*

#### *<IP_ADDRESS> Human-like intelligent integration principle*

The introduction of integral control in the control system is an important way to reduce the steady-state error of the system. **Figure 21(c)** shows the integral process of the integral control action on the error in conventional PID control. This integral effect simulates human memory characteristics to a certain extent. It "remembers" all the information about the existence and changes of errors. The disadvantages of the integral control function based on this integral form are: first, the integral control function is not targeted, and sometimes does not meet the objective needs of the control system; second, because this integral effect is always integrated as long as the error exists, it is easy to cause integral saturation in the application of actual practice, which will reduce the rapidity of the system. Third, the integral parameters of this integral control are not easy to select, and improper selection will cause the system to oscillate.

The reason why the integral control function is not good is that the integral control function does not well reflect the intelligent control decision-making thoughts of experienced operators. In the integral curve interval (a, 6) in **Figure 21(c)**, the integral effect is opposite to the control effect of an experienced operator. At this time, the system has overshoot. The correct control strategy should be to add a negative control value to the constant value to reduce the overshoot and reduce the error as soon as possible. However, the integral control effect in this interval increases a positive control amount. This is because the integral result in the (0, *α*) interval is difficult to be offset and the sign is changed, so the integral control amount remains positive. As a result, the system overshoot cannot be reduced quickly, which prolongs the transition process time of the system.

In the (6, *c*) section of the above integral curve, the system error changes from a maximum value to a decreasing direction, and there is a trend of steady state change. At this time, a certain proportional control effect should be added, but the integral control effect should not be added. Otherwise, it will cause system callback. *Overview of Some Intelligent Control Structures and Dedicated Algorithms DOI: http://dx.doi.org/10.5772/intechopen.91966*

#### **Figure 21.**

*Error and error integration curve. (a) (y (t)) Unit step response curve for second-order system. (b) (e (t)) Unit step response curve for second-order system. (c) In conventional PID control Integral control is the process of integrating errors. (D) Integrate on equal intervals.*

In order to overcome the shortcomings of the integral control function described above, the integral curve shown in **Figure 21(d)** is used, that is, the integration is performed in the intervals (a, b), (c, d), and (e, f). The integral can provide the correct additional control amount for the integral control function in a timely manner, and can effectively suppress the increase of system error; while in the interval (0, a), (b, c), and (d, e), stop integral role to facilitate the system to transition to a steady state by virtue of inertia. At this time, the system is not in a state of out of control, it is also restricted by control functions such as proportion.

This integral function better simulates human memory characteristics and human-like intelligent control strategies. It selectively "remembers" useful information and "forgets" useless information, so it can overcome the shortcomings of general integral control. It has the characteristics of non-linear integration of human-like intelligence, which is called such integration of human-like intelligence.

#### *<IP_ADDRESS> Human-like intelligent integration control algorithm*

In order to introduce the function of intelligent integration into the control algorithm, we must first solve the problem of logical judgment of introducing intelligent integration.

**Figure 22.** *Structure of a humanoid intelligent controller.*

This condition can be determined by comparing the intelligent integration curve in **Figure 21** with **Figure 22** and **Table 2** [16].

When the error *en* and the error change *Δen* at the current sampling time have the same sign, that is, *en•Δen >* 0, the error is integrated; on the contrary, the error *en* and the error change *Δen* have different signs, that is, when *en•Δen* < 0, errors are not integrated. This is the basic condition for introducing intelligent integration. Considering the extreme points of errors and error changes, that is, the boundary conditions, the conditions for introducing intelligent integration and not introducing intelligent integration can be synthesized as follows:

When *e•Δe* > 0 or *Δe* = 0 *and e* 6¼ 0, the error is integrated, that is, intelligent integration; when *e•Δe* < 0 *or e =* 0, the error is not integrated, that is, no integration effect is introduced.

The digital simulation results show that the human-integrated intelligent integral control algorithm significantly improves the steady-state accuracy of the fuzzy control system due to the introduction of intelligent integral control. Compared with ordinary fuzzy controllers, the human-integrated intelligent integral control algorithm has the advantage of high steady-state accuracy. Compared with conventional PID control, this control algorithm has the advantages of fast response speed, small overshoot, or no overshoot. Therefore, this is a control algorithm with simple structure and good control performance for intelligent control.

#### *3.3.2 Multiple modes of human-like intelligent control*

The computer control systems of most production processes are continuous discrete hybrid systems. In such a system, the detection of time-continuous signals and the output of computer-controlled quantities, considering the problem of signal reproduction, require the correct selection of discrete-time sampling periods. In the control process, the main consideration is to help improve the control quality as much as possible.

#### *<IP_ADDRESS> Effect of sampling period on digital control*

The upper limit of the sampling period is selected, but the choice of the lower limit of the sampling period is restricted by many factors. The smaller the sampling

#### *Overview of Some Intelligent Control Structures and Dedicated Algorithms DOI: http://dx.doi.org/10.5772/intechopen.91966*

period is better to reproduce the signal. However, if the sampling period is too small, the signal-to-noise ratio is low, the quantization noise is large, and it is easy to be interfered, which affects the control performance. In process control, the lower limit of the control cycle selection is limited by the control algorithm operation time. Therefore, the sampling period and the control period are not both as small as possible.

As for the analog design method of the digital controller, the smaller the sampling period, the closer the characteristics of the digital controller are to the characteristics of the analog controller. As for the discrete design methods of digital controllers, most are based on the discretized object model. The discretization model of the object depends on the selection of the sampling period, so the sampling period not only affects the distribution of the zero and pole positions of the model, but also affects the accuracy of the model. Too long a sampling period may even lead to the loss of useful high-frequency information, thereby reducing the model order.

#### *<IP_ADDRESS> Human-like intelligent sampling control for lag process*

A large number of controlled processes have varying degrees of time lag, which brings difficulties to the process system. The ratio of the lag time to the capacity lag time constant *T* reflects the difficulty of control. As the *τ/T* value increases, the difficulty of control increases accordingly. When approaching or exceeding *T*, the effect of using ordinary PID control is very poor, and Smith predictive control must be used. However, Smith control requires an accurate controlled process model, and complex controlled processes are often difficult to establish accurate mathematical models. Therefore, many improvements have been made to Smith control, and some control algorithms have emerged to overcome lag. Nevertheless, it should be said that the problem of large lag process control is still a topic of great concern in the control field.

As we all know, for an object with a pure lag time *τ*, its control effect must be reflected in time *τ*. Therefore, control within time is of no value, so the sampling control shown in **Figure 23** is generated. The sampling period *T*s is slightly larger than *τ*, and the control time (on time) *Δt* is about *1*/*10 T*s. This choice will bring two disadvantages: first, the interference and sampling will be seriously out of sync. Because the pure lag time of the controlled process is generally large,*T*s is chosen to be large, and the control time *Δt* is very small. In this way, the system is in an openloop state during the *T*s *Δt* time of each sampling cycle, and some urgent needs cannot be obtained. Useful information such as changes in output y(*t*) caused by fixed-value disturbances or a given input that requires y(*t*) to track as quickly as possible. Second, the feedback information obtained is too small and untargeted, which makes the control in a blind state, resulting in a long transition process.

The disadvantages of the above sampling control are passive waiting and blind control. In short, such control lacks the intelligent sampling characteristics of the lag

**Figure 23.** *Sampling control principle.*

process of manual control. The basic strategy of manual sampling control to overcome large lags can be described as follows:

Wait ! look ! tune ! wait again ! look again ! adjust again ……

According to the above control strategy, the principle of a human-like intelligent sampling control system is shown in **Figure 24**. Among them, INT indicates intelligent device; *F*(*s*) indicates fixed value interference; *Gcj*(*s*) indicates controller; *Y*(*s*) indicates controlled variable; *Gp*ð Þ*s* e�*τs* indicates controlled object; *B* indicates intermediate feedback coefficient; *R*(*s*) indicates interference; *P* takes the constant "1" or "0".

The function of the intelligent device is to control an intelligent sampling switch *K*, which "opens" or "closes" when certain conditions are met, that is shown in Eq. (11),

$$K = \begin{cases} \text{0} \ (\text{Discounted}) & e \cdot \dot{e} < \text{0} \text{ or } |e| < \delta\\ \text{1} \ (\text{Closed}) & e \cdot \dot{e} > \text{0} \text{ or } \dot{e} = \text{0}, |e| \ge \delta \end{cases} \tag{16}$$

In the formula, *e*, *e*\_ are the error and the first derivative of the error; *δ* is the insensitive region.

When the controlled variable deviates from the expected value, the smart device sends a signal that the *K* switch is closed for sampling, and the controller controls in time until the controlled variable has a tendency to return to a balanced position; when the controlled system error value is within the allowable range, switch *K* disconnect, the system is in an open-loop working state. At this time, the energy required to be maintained by the object is supplied by the controller or the stored energy of the object.

In **Figure 24**, *Gcj*(s) represents the *j th* controller *j* ∈ (1,2), which is attractive considering that the given interference and fixed value interference often have different control laws and effects. Its selection is made automatically by the logical relationship of the design like Eq. (9):

$$\mathbf{G}\_{\circ j}(s) = \begin{cases} \mathbf{G}\_{\varepsilon 1}(s), & dc(t)/dt \neq \mathbf{0} \\ \mathbf{G}\_{\varepsilon 2}(s), & dc(t)/dt = \mathbf{0} \end{cases} \tag{17}$$

Among them, *c t*ðÞ¼ *L*�1 1 *Ts*þ1 *R s*ð Þ h i,*T* is determined as needed. In this way, the adaptability and effectiveness of the controller are enhanced, and it is ensured that

**Figure 24.** *Intelligent sampling control schematic diagram.*

*Overview of Some Intelligent Control Structures and Dedicated Algorithms DOI: http://dx.doi.org/10.5772/intechopen.91966*

**Figure 25.** *Human-like intelligent switch control simulation result.*

the corresponding controller is selected with different interference. The introduction of intermediate proportional feedback *B* is mainly for design convenience.

Through further analysis of the above-mentioned intelligent sampling control mechanism, it can be seen that when the switch *K* is closed and the system is in closed-loop control, whether the system is a follow-up system or a fixed value system, e*τs* will appear in the characteristic equation, but by setting appropriately due to the logic judgment function of the smart device, the control parameters of the smart device can be established only in a short period of time, so that the unstable factors are eliminated. When the switch is open and the system is in open loop, e*τs* has no effect on stability. In the above-mentioned intelligent mining control scheme, a smart device is used to determine whether the system is openloop or closed-loop. In the open-loop process, the controller is in the active waiting phase with an observation function. The purpose of this waiting is to prepare for better control. In the closed-loop process, the controller is in the control phase, which is a manifestation of waiting action for strongly targeted. This control method cleverly avoids the adverse effects brought by e*τs* , and successfully solves the stability problem of the system.

Intelligent sampling control is a novel control method with open loop in the closed loop and closed loop in the open loop. Its entire working process is similar to an experienced operator. It can continuously observe and perform real-time correction as required. Therefore, this control has strong robustness and fastness, and can be easily realized by a microcomputer program.

#### *3.3.3 Programming of human-like intelligent control*

Here is a programming example of human-like intelligent switch control simulation, the simulation results are shown in **Figure 25**, write the MATLAB program as follows:

k = 1;% scaling factor K g1 = tf (1, [8 6 1]);% continuous system model G (s) g2 = feedback (k \* g1,1); tt = 1; y = [0 0.0329];% output matrix initialization u = ones (1,100);% input matrix initialization

u (1) = 0; e = [0 0.9671];% deviation matrix initialization for n = 3: 1: 200 e (n) = k \* (u (n-1) -y (n-1)); if (e (n) -e (n-1) <= 0.0001) & (y (n-1) <= 1)% Judge whether the steadystate and boundary conditions are satisfied tt = tt-1; if tt == 0% judging whether it is within a switching action period u = (u (n) + 0.31 \* e (n)) \* ones (1,200);% Switch action content tt = 40;% set smart switch action period end end e (n) = k \* (u (n-1) -y (n-1)); y (n) = 1.489 \* y (n-1) -0.549 \* y (n-2) + 0.0329 \* e (n-1) + 0.0269 \* e (n-2);% difference equation end t = 0: 1: n-1; g3 = step (g2, t); graphical output of plot (t, y, t, g3)% response curve

Here is a programming example of human-like intelligent integral control simulation, the simulation results are shown in **Figure 26**, write the MATLAB program as follows:

y = [0 0.132];% output matrix initialization u = ones (1,1000);% input matrix initialization u (1) = 0; e = [0 0.868];% deviation matrix initialization c = [0 0];% process matrix initialization kp = 0.803;% PID scale factor ki = 0.282;% PID integration coefficient kd = 0.02;% PID differential coefficient esum = e (2); for n = 3: 1: 100% conventional PID control system for reference y (n) = 1.559 \* y (n-1) -0.559 \* y (n-2) + 0.3 \* c (n-1) + 0.1 \* c (n-2); e (n) = u (n) -y (n);

**Figure 26.** *Intelligent sampling control schematic diagram.*

*Overview of Some Intelligent Control Structures and Dedicated Algorithms DOI: http://dx.doi.org/10.5772/intechopen.91966*

esum = esum + e (n);% deviation summation c (n) = kp \* (e (n)) + kd \* (e (n) -e (n-1)) + ki \* esum;% PID link output y (n) = 1.559 \* y (n-1) -0.559 \* y (n-2) + 0.3 \* c (n-1) + 0.1 \* c (n-2);% c (n) signal drives the differential equation end t = 0: 1: n-1; plot (t, y)% response curve output for n = 3: 1: 100% humanoid intelligent integral control y (n) = 1.559 \* y (n-1) -0.559 \* y (n-2) + 0.3 \* c (n-1) + 0.1 \* c (n-2); e (n) = u (n) -y (n); esum = esum + e (n); edrta = e (n) \* (e (n) -e (n-1)); if (edrta> 0) & (e (n) = 0) c (n) = kp \* (e (n)) + kd \* (e (n) -e (n-1)) + ki \* esum;% for integration else c (n) = kp \* e (n) + kd \* (e (n) -e (n-1)); end y (n) = 1.559 \* y (n-1) -0.559 \* y (n-2) + 0.3 \* c (n-1) + 0.1 \* c (n-2); end t = 0: 1: n-1; plot (t, y, 'r')% response curve output


Surgical Interventions in Ocular Diseases

*Hariprasad Vokuda, Srinivasa, Roopashree Rao and Kinjal H. Porwal*

### **Abstract**

THE COLORFUL WORLD WE SEE IS THE RESULT OF THE BEAUTIFUL CREATION OF THE HUMAN BODY – THE HUMAN EYE. Eye surgery has advanced swiftly over the last 25 years. The development of new technology, tools, and techniques has turned corrective eye surgery into a common procedure.

**Keywords:** eye diseases, blindness, eye surgery, vision correction

### **1. Introduction**

There are various eye diseases causing blindness which can be corrected by various types of eye surgeries. This article focuses on procedures which can correct the visual acuity to near normal and treat the eye diseases.

### **1.1 Pediatric age group**

The most common causes of blindness are:

Cataract is one of the common cause of blindness in childhood, which can be treated by surgery. Children with cataract have delayed development and poor quality of life. Nearlly 200,000 or more children are affected by blindness due to untreated cataracts, from cataract surgery complications, or from cataract associated ocular anomalies [1]. Lot more children are affected by the visual difficulties, that increase as the child grows, caused by gradually progressive partial cataracts. Overall risk of cataract during the growing years is as high as 1 per 1000 [2].

### **1.2 In young age**

### *1.2.1 Refractive errors*

Refractive errors happen when the shape of the eye keeps light from focusing correctly on the retina (a light-sensitive layer of tissue at the back of the eye). There are various types of refractive errors and each type of refractive error is significant enough to cause reduced visual acuity.

### *<IP_ADDRESS> Myopia (near-sightedness)*

Myopia or near-sightedness is a condition wherein the patient has difficulty in seeing far objects. It is the condition in which parallel light rays from infinity, as they refract on cornea and lens, converge at a focus in front of the retina [3].

It can be due to increased axial length in an enlarged eyeball (axial myopia), steep cornea with regular curvature (refractional myopia), anteriorly displaced lens, or increased refractive index of aqueous humor or decreased refractive index of vitreous (index myopia) [3].

Myopia usually begins in the age span of 6 to 14 years. High myopia or pathological myopia maybe associated with degenerative changes in retina and choroid which can cause retinal detachment.

### *<IP_ADDRESS> Hyperopia (far-sightedness)*

Hyperopia or far-sightedness is a condition wherein the patient has difficulty in seeing near objects. It is the condition in which parallel light rays from infinity converge on a focus behind the retina after refracting on the cornea and lens [3].

It can be due to decreased axial length of eyeball (axial hyperopia), posteriorly displaced lens, absence of lens or aphakia (leading to high hyperopia), flat cornea with regular curvature (refractional hyperopia), or decreased refractive index of aqueous humor (index hyperopia) [3].

At birth the human eye usually has a hyperopia of +2.25D that increases and peaks at about 8 years [3].

### *<IP_ADDRESS> Astigmatism*

Astigmatism is a condition in which the light rays, after refracting, do not converge to a single point. Due to variations in the curvatures of the cornea or the lens in different axes, instead of focusing the light from a point source to a single point, the image consists of two lines, separated from each other. It is necessary to correct astigmatic refractive errors only when patients experience symptoms such as decreased visual acuity or eye fatigue from constantly adjusting accommodation to optimize the seeing between the two focal lines [3].

### *1.2.2 Surgical management of refractive error*

Surgery has a limited role in correcting refractive error in pediatric patients. Uncorrected high refractive errors have significant negative role on a child's intellectual and social development. When conservative methods like glasses and contact lens fail, surgery has to be considered to prevent amblyopia and blindness in the child. The main indications for surgery in the children are anisometropic amblyopia and bilateral high errors. The goal of pediatric refractive surgery is different from those of adult refractive surgery. Full correction of a refractive error is not critical

### *DOI: http://dx.doi.org/10.5772/intechopen.104590 Surgical Interventions in Ocular Diseases*

here. Allowing for adequate visual development and preventing visual suppression of one or both eyes is the key.

Laser vision procedures for children include PRK(photorefractive keratectomy), LASEK(laser-assisted subepithelial keratectomy) and LASIK(laser in-situ keratomileusis). PRK and LASEK are preferred over LASIK to avoid the risk of flap complications like dislocation and striae, and also because of the difficulty of examining the LASIK flap after the procedure. Performing laser vision procedures in children requires extensive logistical planning. Most laser centres do not have the necessary arrangements to provide anesthesia, to children. In most cases, the laser apparatus has to be taken to a surgical centre where general anesthesia can be performed, which is expensive and involves lot of labour. Main risk after surface ablation is the development of corneal haze and ectasia. Inspite of drawbacks in laser refractive procedures in children, surface ablation is a good option for correcting refractive error in this children.

### *<IP_ADDRESS> Phakic IOL(intraocular lens) implantation*

Iris-fixated and posterior chamber IOL's have been used in correcting refractive error, thereby improving binocular fusion and preventing amblyopia.

They can correct, wider range of refractive error as compared to laser surgery and it can be reversible. But they carry the risks of endothelial cell loss, IOL rotation, pigment dispersion, anterior subcapsular cataract formation and secondary glaucoma.

Pediatric refractive surgery is still a relatively less performed procedure to treat refractive error in children, due to less data on long term outcomes on efficacy and safety.

### **1.3 Pediatric glaucoma**

It is one of the most challenging and sight threatening condition, for an ophthalmologist to treat.

It can be classified into:

Raised intraocular pressure (IOP), increased axial length, corneal odema and haab's striae are the characteristic features of pediatric glaucoma.

Management is by step by step approach, beginning with medications and finally ending up with the surgery.

Angle surgeries are the first choice in case of congenital glaucoma, progressive and refractory glaucoma.

The basic principle of the surgery here is to address the issue of deceased aqueous outflow due to trabecular dysgenesis. Angle surgery includes goniotomy and trabeculotomy. Goniotomy is an ab interno procedure, which tries to open up the blocked trabecular meshwork, while trabeculotomy is an ab externo procedure, where the angle structures are opened up through the Schlemm canal.

If the above procedures are not successful, then trabeculectomy or glaucoma drainage devices (GDD) can be used as a final approach.

Glaucoma surgeries can also lead to complications like, hypotony, choroidal detachment, retinal detachment, endophthalmitis, cataract, tube extrusion, corneal decompensation in cases of GDD.

### **1.4 Middle age and old age**

### *1.4.1 Cataract*

Cataract is clouding of normal clear lens. It is associated with the breakdown of the lens architecture or clumping of the highly concentrated soluble proteins of the lens or both [4, 5]. Cataracts usually progress slowly and are painless, so vision and lifestyle of person can be affected without them realizing it. Cataracts usually cause gradually progressive diminution of vision which usually do not show pinhole improvement. Common symptoms include reduction in visual acuity, glare, colored halos and occasionally monocular diplopia [6].

Worldwide, cataract is the number one cause of preventable blindness. The only definite treatment is cataract surgery, which includes removal of the cataractous lens and implantation of an intraocular lens.

Age related cataract is the most common type of cataract and occurs due to cumulative effect of various environmental factors like UV light, X-irradiation, toxins, metals, corticosteroids, drugs, and diseases including diabetes mellitus. Traumatic cataract may occur following blunt trauma leading to a cataract with characteristic flower shaped pattern, or penetrating trauma (accidental or surgical) leading to complete lens opacification [7]. It can also occur following electric shocks, chemical injuries and irradiation. Systemic disorders like diabetes mellitus, galactosemia, Fabry's disease, Alport's syndrome, myotonic dystrophy can cause metabolic cataracts.

### *<IP_ADDRESS> Management of pediatric cataract*

The management of cataracts in childhood is tedious and often difficult, requiring many visits over many years. Success requires a dedicated team effort that often involves parents, primary care pediatricians, surgeons, anaesthesiologists, technicians, orthoptists, low vision rehabilitation specialities, and community health workers. Pediatric cataract surgery should only be performed by ophthalmic surgeons who perform them on a weekly or biweekly basis so that they can perform them with a high level of competency [8]. Due to this reason, in many places only one surgeon performs these surgeries. Whenever possible, pediatric cataracts should be referred to higher centers where large number of pediatric surgeries are performed and there is availability of multispeciality team. After the postoperative period, these patients can be followed up with the regional doctors and maybe referred to higher center only when necessary. Ophthalmologists interested in performing pediatric cataract surgery should pursue fellowship training at a higher center, to attain specific skills to perform such surgeries. After completing such fellowship, these surgeons should also take instructional courses to learn new techniques as they arise.

### *<IP_ADDRESS> Preoperative measurements*

To get the best possible visual outcomes, determination of power of intraocular lens implant is necessary, which requires several preoperative measurements. A dilated

### *DOI: http://dx.doi.org/10.5772/intechopen.104590 Surgical Interventions in Ocular Diseases*

refraction has to be performed necessarily, especially if planning to operate only on one eye, to avoid anisometropia postoperatively, which can be detrimental to patients later on. Measurements of axial length of the eye, the corneal refractive power and curvature, and the anterior chamber depth are necessary for calculation intraocular lens power. Corneal topography, intraocular pressure measurement and endothelial cell count are certain additional tests which can be done in some special cases.

### *<IP_ADDRESS> Nonsurgical management*

As of now, there is no medical treatment that is effective in treatment or prevention of cataracts. Nutritional, pharmacological, and specific medical interventions like reducing UV-B exposure and smoking maybe helpful in preventing cataract, but the most important risk factor, aging, cannot be modified [7].

### *<IP_ADDRESS> Surgical management*

Cataract surgery is the most common surgery performed on an outpatient basis all around the world [9]. The most common type of cataract surgery performed worldwide is phacoemulsification, wherein the cataractous lens is fragmented into smaller particles using ultrasound energy and aspirated through a handpiece. Another method, not commonly used nowadays, is ECCE (Extracapsular Cataract Extraction) wherein in the lens nucleus is delivered intact through a limbal incision of about 10 mm [10]. Another technique, more commonly used in developing countries, small incision cataract surgery. Three important steps in this technique are a well-constructed scleral tunnel with a larger internal opening than the external scleral incision, a triangular capsulotomy technique, and lens-delivery technique relies on use of fluidics and eye positioning to irrigate the nucleus through our funnel-shaped wound and out of the eye [11].

The goal of the modern cataract surgery includes implantation of intraocular lens in addition to removal of the cataractous lens. The intraocular lens is usually placed inside the capsular bag, which is known as posterior chamber IOL (PCIOL), or in the sulcus as sulcus lens, or in the anterior chamber known as anterior chamber IOL (ACIOL). There are many types of IOLs used in cataract surgery like monofocal, multifocal, trifocal and toric IOLs. The main goal in using such IOLs is vision improvement and reducing spectacles and contact lens dependency.

Recently, a new technique called Femtosecond laser assisted cataract surgery (FLACS) is becoming popular. Here, the laser is used to perform certain steps of cataract surgery like clear corneal incisions, capsulorhexis, lens fragmentation, and if required making corneal arcuate incisions for astigmatism correction [12].

### *<IP_ADDRESS> Single-piece intraocular lenses*

IOLs are composed of two elements: an optic and haptics. The optic is the central area responsible for refraction, and the haptics are the appendages from the center optic that hold it in place [13]. Single-piece IOLs (also referred to as one-piece) are named as such due to both elements being composed of the same material (acrylic, silicone or PMMA) [14].

### *<IP_ADDRESS> Premium IOLs*

They have unique features in terms of material, design and refractive designs, as compared to monofocal IOLs [15]. These premium IOLs can correct presbyopia and

### *Vision Correction and Eye Surgery*

astigmatism, which the regular design IOLs cannot do. Centration is the key, to have accurate visual outcomes in cases of premium IOLs. The center of the undilated pupil is used as the axial center for IOLs [16].

Patients with multifocal IOLs can comfortably see both near and distance objects, as compared to monofocal IOLs which have single point of focus for one distance, as compared to multifocal IOLs, which have multiple focal points of distance and near vision [17]. They work on the principle of neuroadaptation and neural suppression. Multifocal IOLs are classified into Refractive, Diffractive and Hybrid IOLs [15, 18]. Refractive IOLs create multiple focal points with concentric zones of different dioptric power [18]. Diffractive IOLs have multiple diffractive zones on the posterior lens surface. Hybrid IOLs have the features of both refractive and diffractive IOLs. Multifocal IOLs can also be classified as bifocal or trifocal IOLs. Bifocal IOLs have both a near and far focus, while trifocal IOLs have far, intermediate and near focus [15]. Toric IOLs are used in patients with corneal astigmatism to give a sharp and clear vision, post cataract surgery. Calculation of preoperative astigmatism is of utmost importance prior to toric IOL implantation for accurate results [19]. In addition, proper centration and rotational orientation of toric IOL is very much necessary [16].

For people with inherent astigmatism, who want spectacle free option have Toric muiltifocal IOL as an excellent alternative [15]. Along with it, there are two more categories of premium IOLs, namely:Accommodative and extended depth of focus (EDF) IOLs. Accommodative IOLs provide a dynamic refractive power with contraction and relaxation of the ciliary muscles [15]. Accomodative IOLs are not the preferred choice nowadays, eventhough it is FDA approved [20]. EDF IOLs on the other hand, is based on the principle of extended focus, provides a fairly good distance, intermediate and near vision in patients [15].

### *<IP_ADDRESS> Single-piece vs. three-piece IOLs*

Three-piece IOLs are more versatile and they can be placed within the capsule or in the ciliary sulcus in the case of posterior capsule rupture or in case of weak zonules [13]. Single-piece IOLs are not designed to be placed in the ciliary sulcus, as it might lead to various complications like UGH (uveitis, glaucoma, hyphema) syndrome, due to movement of the lens over time [13, 15, 21]. The main advantage of single-piece IOLs is of softer, longer haptics, which unfolds smoothly and in a evenly distributed manner, causing relatively less stress on to the capsule and a more uniform contact holding it in place, which reduces capsular wrinkling [14]. So, single-piece IOLs are more widely used by the surgeons for patients with an intact lens capsule [13, 22].

### **1.5 Corneal dystrophies**

Corneal dystrophy is a non-inflammatory, bilateral, symmetric, genetic condition which results in accumulation of abnormal material in the cornea, affecting its transparency. They can be asymptomatic in some individuals, while in others can affect the vision significantly, requiring corneal transplantation. Dystrophies begin early in life, are slowly progressive, increase with age, and may not become clinically apparent until years later. These deposits result from genetic mutations that lead to transcription of aberrant proteins. Many patients with corneal dystrophies associated with deposits present with symptoms of recurrent corneal erosion or blurred vision due to either irregular astigmatism or stromal opacification.

### *DOI: http://dx.doi.org/10.5772/intechopen.104590 Surgical Interventions in Ocular Diseases*

The International Committee for Classification of Corneal Dystrophies (IC3D) developed a "new classification system for corneal dystrophies" based upon the information on phenotype, pathology and genetics. There are numerous shortcomings in the traditional corneal dystrophy classification system, which was based upon the layer of involvement of the cornea. But the drawback with this classification is that, some of the dystrophies involve more than one layer of the cornea an not limited strictly to one layer. A category number from 1 to 4 is assigned depicting the level of evidence supporting the existence of the particular dystrophy [23].

Corneal transplantation is a surgical procedure where a damaged or diseased cornea is replaced by a donor corneal tissue. Corneal dystrophies such as Reis-Bückler, Salzmann's nodular dystrophy and lattice, granular, or macular dystrophy can be treated with lamellar keratoplasty. Lamellar keratoplasty involves the removal and replacement of diseased or deformed anterior corneal tissue (epithelium, Bowman's layer, and stroma) while maintaining the host's Descemet's layer and endothelium. Lamellar keratoplasty is an endothelium sparing procedure, which significantly decreases the chances of endothelial graft rejection [24]. Also, complications like endophthalmitis, expulsive hemorrhage, glaucoma, and cataract are significantly reduced.

Penetrating keratoplasty is usually performed for endothelial decompensation and corneal edema arising from endothelial dystrophies like Fuch's endothelial dystrophy. Penetrating keratoplasty involves surgical removal of diseased or damaged cornea from the host and replacement with a full thickness donor cornea [25].

Endothelial keratoplasty is a relatively new field of corneal transplant surgery which involves the selective replacement of the recipient diseased endothelium, leaving the normal anterior surface of the cornea [26]. A modification of this procedure is DLEK (Deep Lamellar Endothelial Keratoplasty) where the incision size was reduced to 5 mm and the tissue folded in half for insertion. Another modification is DSEK (Descemet's Stripping Endothelial Keratoplasty) wherein the Descemet's membrane is stripped from the recipient and the donor tissue is placed directly on the posterior surface [27]. The visual recovery and acuity in endothelial keratoplasty is far better than in standard full thickness penetrating keratoplasty. The postoperative corneal is more regular after lamellar keratoplasty as compared to penetrating keratoplasty [28].

### **1.6 Glaucoma**

Glaucoma is an optic nerve disease with a raised intraocular pressure (IOP), with loss of ganglion cells and visual field loss.

All the treatment modalities are directed towards lowering the IOP.

Medical management included IOP lowering eyedrops and lasers. When these modalities fail to control the raising IOP, surgical options are considered.

The basic principles in the surgical management are:

1.Improve aqueous flow through the trabecular meshwork

2.Increase aqueous egress

3.Reduce aqueous production by the ciliary body.

### **2. Trabeculectomy**

It is an external filtration surgery and is considered as the gold standard in glaucoma surgery.

A small opening in the sclera is made along with removal of a portion of the meshwork is done to increase the aqueous drainage under the conjunctiva. Intraoperative mitomycin-c may also be used to improve the success rate of the procedure.

### **3. Tube shunts**

Is useful in cases of neovascular glaucoma, uveitic glaucoma, iridocorneal endothelial syndrome, fibrous ingrowth, epithelial downgrowth, history of previous vitreoretinal surgery or penetrating keratoplasty.

Few examples of tube shunts are:

### **4. Microinvasive glaucoma surgery (MIGS)**

Ideal candidates are: those with mild to moderate glaucoma, patients with poor control of IOP with topical medications and laser trabeculoplasty.

Unique features of MIGS are:

### **5. Approaches**

First approach, involves enhancing outflow across the trabecular meshwork and through Schlemm's canal. Juxtacanalicular trabecular meshwork is usually the site of maximum resistance. It can be overcome through bypassing or removing this tissue to lower IOP through increased outflow.

Bypass is achieved by placing a stent which allows aqueous to flow directly through it from the anterior chamber and into Schlemm's canal or procedures like goniotomy or trabeculotomy can be performed, where surgical incision and/or excision of trabecular meshwork is done, which improves aqueous outflow into Schlemm's canal. Alternatively, dilation of Schlemm's canal through cannulation and expansion with viscoelastic can be done to improve outflow through the normal physiologic aqueous outflow system.

Second MIGS approaches, increases the outflow via alternate pathways. The uveoscleral outflow pathway can be increased by accessing the suprachoroidal space with the placement of a microstent.

### *DOI: http://dx.doi.org/10.5772/intechopen.104590 Surgical Interventions in Ocular Diseases*

Third MIGS approach involves decreasing the aqueous production by ablation of the ciliary body, known as endocyclophotocoagulation. Here, an endoscopic laser probe is inserted through a clear corneal incision and under direct visualization ablates the ciliary body.

### **5.1 Refractive eye procedures**

Patients who have refractive errors like, myopia, hyperopia & astigmatism, would need glasses for clear vision.

For people who wish to get rid of their glasses for their day to day activities would need either one of the below procedures:

1.LASIK(laser in situ keratomileusis)

2.PRK(photorefractive keratectomy)

3.SMILE (small incision lenticule extraction)

4.Phakic intraocular lens implantation

Ideal candidates would be:

Exercise caution in patients who have thin corneas, corneal ectasia, borderline corneal topography and those with collagen vascular disorder.

LASIK: a thin corneal flap is created using, either microkeratome or femtosecond laser, then the excimer laser reshapes the underlying cornea stroma. Flap is then folded back.

PRK: rather than creating a flap, corneal epithelium is removed and then excimer laser is used to reshape the cornea. Bandage contact lens is placed for epithelium to grow back.

SMILE: femto second laser is used to create a refractive lenticule in the intrastromal pocket, which is then removed via a small incision in the cornea.

Advantages being:

### *5.1.1 Phakic intraocular lens implantation*

If a patient is not eligible for laser refractive procedure, like in high refractive errors & thin corneas, phakic lens implantation is a good alternative.

These are usually made up of collamer, acrylic, silicone.

Preoperative evaluation of the biometry and lens sizing is very important to avoid any post-operative issues like secondary glaucoma and cataract.

After a clear corneal micro incision is made, the lens is injected and placed behind the iris and infront of the crystalline lens in the sulcus.

### **6. Conclusion**

The advent of advanced technologies have revolutionized the eye care treatment. Refinement in the surgical techniques have decreased the duration of hospital stay, faster recovery and better post-operative vision quality.

Latest biometry devices have made intraocular lens power calculation more easy and predictable. Never intraocular lens also induce less aberrations, provide sharper vision and induce lesser posterior capsular opacification.

Laser refractive procedures are provide more accurate visual results and have greater safety profile.

Overall, surgeons have different technologies and machines to correct various vision related ocular conditions and patients now have the comfort to choose the best treatment for themselves.

### **Conflict of interest**

None.

### **Author details**

Hariprasad Vokuda1 \*, Srinivasa<sup>2</sup> , Roopashree Rao1 and Kinjal H. Porwal3

1 ShreeHari Netralaya, Udupi, Karnataka, India

2 Minto Eye Hospital, Bangalore Medical College and Research Institute, Bangalore, Karnataka, India

3 Bangalore Medical College and Research Institute, Bangalore, Karnataka, India

\*Address all correspondence to<EMAIL_ADDRESS>
© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Surgical Interventions in Ocular Diseases DOI: http://dx.doi.org/10.5772/intechopen.104590*

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### **Chapter 2**


**4. Discussion**

Gastritis is an inflammatory-based condition promoted by a variety of risk factors, which include stress, alcohol or drug abuse, and others; the most severe chronic form of gastritis is mainly caused by *Helicobacter pylori* infection. Unfortunately, the infection is diffused in several countries with unsustainable economic situation, and the conventional therapy against gastric inflammatory processes or for *H. pylori* eradication is not easily available.

This work investigates the anti-inflammatory and radical scavenger activities at the gastric level of eleven hydroalcoholic extracts obtained from plants widely used in Cameroon as spices and in the traditional medicine against a variety of diseases, including gastric disorders.

The study was carried out using two gastric cell models (AGS and GES-1 cells) stimulated with TNFα, which contributes to the inflammatory process in infected gastric epithelium [31]. AGS cells, a tumor gastric epithelial cell line, is a well-established in vitro model, while GES-1 cells are considered an in vitro model closer to the gastric epithelium of healthy subjects [32].

A prolonged oxidative stress may cause lipid peroxidation and DNA damages, leading to an increased risk to develop gastric cancer [33,34]; several extracts included in this study prevented H2O2-induced ROS generation in AGS and GES-1 cells, this e ffect could be explained with the presence of compounds able to counteract the excessive amount of ROS, derived from the unbalance between ROS production and endogenous antioxidant systems, acting as scavengers. The extracts displaying the highest antioxidant e ffect were those with the highest phenol content, as previously reported [25].

The investigation on the anti-inflammatory activity identified six extracts (XA, XP, DG, TT, AM, and AC) able to reduce the release and the gene expression of two NF-κB-dependent pro-inflammatory mediators, IL-8 and IL-6, which contribute to the amplification of the gastric inflammatory process [6,8,31]; the e ffect on the NF-κB pathway suggests that this transcription factor could be involved in the molecular mechanism responsible for the observed activity. In addition, the IC50s on IL-8 release in our experiments reflected in halved IL-8 mRNA level, suggesting the important contribution of the transcription, although not always statistically confirmed. The di fferent activity on the IL-8 promoter, especially evident in GES-1 cells, may be partly justified by the intervention of post-transcriptional regulatory mechanisms. The chemical analysis of the extracts has been previously reported by our group [24]; on the basis of this characterization, the hydroalcoholic extracts contain previously quantified secondary metabolites able to act as NF-κB inhibitors, such as pimaric acid in XP (8.73%), gingerol and shogaol in AM (0.7% and 2.05% respectively), chlorogenic acid and catechins, identified in some extracts [35–40]. Although further investigation is needed, these individual compounds could contribute, at least in part, to the anti-inflammatory activity displayed by the extracts. According to the literature, the anti-inflammatory e ffects could be linked to the antioxidant properties of the extracts, since it has been demonstrated that ROS are able to over-express IL-8 by activating oxidant-sensitive nuclear factors, such as NF-κB, in gastric epithelial cells [11].

Although the six extracts inhibited IL-8 release in both gastric cell models, only XP, TT, DG, and AC reduced IL-6 levels. Again, the mRNA analysis showed that all the extracts influenced the IL-6 at the transcriptional level, in particular DG, which obtained a statistically significant di fference with respect to the stimulated control. Our results allow to speculate that XA and AM do not inhibit other important transcription factors for IL-6, such as CREB, but further studies are needed to confirm this hypothesis.

NSAIDs are not used in the therapy of gastric inflammatory diseases, since they act on prostaglandin-endoperoxide synthase (cyclooxygenase) enzymes blocking also the PTGS1 (COX-1) isoform, which is involved in the protection of the gastric mucosa [14]. In this context, TT extract could be considered the most promising extract, for the ability to inhibit TNF α-induced *PTGS2* (*COX-2*) gene expression without a ffecting the *PTGS1* (*COX-1*) mRNA basal levels. Indeed, *Tetrapleura tetraptera* (TT) extract did not reduce the enzymatic activity of PTGS1 (COX-1) and PTGS2 (COX-2) isoforms in a cell-free system; however, these findings need further investigation.

In the literature, di fferent studies have demonstrated the beneficial e ffects of the fruits of this plant including antimalarial, anti-inflammatory, hypotensive, anti-insulin resistance, and antilipidemic properties [22,41,42].

This study demonstrates the antioxidant and anti-inflammatory activity, at the gastric level, of di fferent hydroalcoholic extracts from Cameroonian plants, selecting those with the most promising effects. XA, XP, TT, DG, AM, and AC are largely used and di ffused in some African countries as spices, thus making these plants interesting as functional foods, especially XP, TT, DG, and AC. Further studies are clearly needed to collect more evidence, especially for TT extract, although our findings provide a sound scientific support to the traditional use of these plants against gastric disorders. In particular, studies on the stability of the extracts in the gastric environment should reinforce the translational value of this work. Considering the order of the inhibitory concentrations (0.1–10 μg/mL) and the yields of extraction [23], it is plausible that the dietary consumption of 1–10 mg of Cameroonian spices

may achieve the bioactivity at gastric level. Thus, these products could be useful to alleviate gastric inflammation in countries where conventional therapy is not easily available.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2072-6643/12/12/3787/s1, Figure S1: E ffect of the extracts on the NF-κB driven transcription in AGS cells. Data are expressed as percentage versus the stimulated control, which is arbitrarily assigned the value 100%., Figure S2: E ffect of the extracts on the NF-κB driven transcription in GES-1 cells. Data are expressed as percentage versus the stimulated control, which is arbitrarily assigned the value 100%, Figure S3: E ffect of the extracts on the IL-8 release in AGS cells. Data are expressed as percentage versus the stimulated control, which is arbitrarily assigned the value 100%, Figure S4: E ffect of the extracts on the IL-8 release in GES-1 cells. Data are expressed as percentage versus the stimulated control, which is arbitrarily assigned the value 100%, Figure S5: E ffect of the extracts on the IL-8 promoter activity in AGS cells. Data are expressed as percentage versus the stimulated control, which is arbitrarily assigned the value 100%, Figure S6: E ffect of the extracts on the IL-8 promoter activity in GES-1 cells. Data are expressed as percentage versus the stimulated control, which is arbitrarily assigned the value 100%, Figure S7: Effect of the extracts on the IL-6 release in GES-1 cells. Data are expressed as percentage versus the stimulated control, which is arbitrarily assigned the value 100%, Table S1: List of the primers used in the study.

**Author Contributions:** Conceptualization, A.P.A.N., M.D., J.-R.K., G.A.A. and E.S.; methodology, A.P.A.N., M.F., S.P., A.M., G.M. and G.B.; software, E.S.; validation, P.M., G.B. and M.D.; formal analysis, A.P.A.N.; investigation, A.P.A.N., A.D.T., M.F., A.M., G.M., S.P.; resources, A.P.A.N., M.F., A.M., G.M., S.P.; data curation, M.D., E.S.; writing—original draft preparation, A.P.A.N., M.F. and M.D.; writing—review and editing, M.D. and P.M.; supervision, M.D., J.-R.K. and G.A.A.; project administration, E.S.; funding acquisition, M.D. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was partially funded by MIUR Progetto di Eccellenza.

**Acknowledgments:** The authors thank Dawit Kidane-Mulat, University of Texas, Austin, for providing GES-1 cells.

**Conflicts of Interest:** The authors declare no conflict of interest. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.


**2.2 The mitochondrial pathway of apoptosis (the intrinsic pathway)**

The intrinsic pathway contains the let off of cytochrome c from the mitochondria to the cytoplasm in response to cellular stress [26]. The cellular stress by the variety of factors such as DNA damage, deprivation of growth factors, defective ER, and several developmental factors activate the intrinsic pathway. In the mitochondrial pathway, the cleavage and activation of caspases begin with caspase-9, which leads to apoptosome machinery activation [19, 20]. The apoptosis proteaseactivating factor1 (APAF1) is a key molecule in the intrinsic pathway of apoptosis, besides, an important target for its pro-survival member, and scaffolding the assembled apoptosome [38]. In the Intrinsic apoptosis pathway, firstly, cytochrome c is discharged from mitochondria and enters into the cytosol, by ending with its

#### **Figure 1.**

*The caspase family proteases and apoptosis. The initial signal on the cell membrane or from the mitochondria activates the initiator caspases (caspase-2, caspase-8, and caspase-9), which act on execution caspases. The initiator caspases are produced inactively and composed of a pro-domain (containing a CARD or a death effector domain [DED]) and, a large and small subunit. On contrary, executioner caspases (caspase-3, caspase-6, and caspase-7) are activated by cleavage of the initiator caspases. Thus, dependent on initiator signaling. The active caspases including two small and large subunits.*

interaction to APAF1 [39, 40]. The cytochrome c, together with APAF1 forms the apoptosome, which leads to inactive caspase-9 monomers into active auto-process [26]. The active caspase-9, in turn, leads to activation of downstream effector caspases. Further, the mitochondria let off pro-apoptotic proteins includes apoptosis-inducing factor (AIF) and endonuclease-G [41]. Cytochrome c is only present in the mitochondrial intermembrane in healthy cells, to interact with APAF1, the apoptotic stimuli trigger the mitochondrial outer membrane (MOM) permeabilization (MOMP) [27]. Hereby, the MOMP conduce to discharge of the entire soluble proteins from mitochondrial intermembrane space to the cytosol. Additionally, rather than cytochrome c, two important pro-apoptotic proteins which are Smac and Omi, were also released meanwhile the above-mentioned procedure. These two proteins are crucial for increasing the potential of apoptosome via antagonizing the caspase inhibitor called X-linked inhibitor of apoptosis (XIAP) [26, 42]. In the lack of Smac and/or Omi, XIAP binding to caspase-9, and inhibits its catalytic activity in which also affects the caspase-3 and caspase-7 [42]. The intrinsic apoptotic pathway is regulated by the Bcl-2 family of proteins [5, 43]. The regulation of MOMP is tightly controlled by the Bcl-2 family proteins, they share BH region homology with their sequence, function, and structure. The Bcl-2 family can be sub-grouped into three categories: the pro-apoptotic proteins, Bax and Bak, play a key role for MOMP regulation; the anti-apoptotic proteins, Bcl-2, Bcl-xL, and Mcl-1, these are the blockers of MOMP; and the BH3-only proteins, Bid, Bim, Bad and Noxa, which are activators of pro-apoptotic proteins and neutralizers for Bcl2 anti-apoptotic proteins. Anti-apoptotic Bcl2 proteins control many other cellular processes such as autophagy and mitochondrial fusion [24, 44]. Bax and Bak are in charge of the loss of mitochondrial outer membrane integrity. Over their activation, they form broad oligomers, and by disturbing MOM enduing their entry into MOM. The disturbing process still unknown, but this lets off the release of entire intermembrane space proteins [45, 46]. Bax and Bak are acting on MOMP involuntarily but importantly at least one of them is needed for re-permeabilization of mitochondria. These proteins are generally being at an inactive state, and gets activated upon upstream stimuli [47–49]. The BH3-only proteins, at least two of them, Bim and active Bid activate Bax and Bak via their transient interaction [25, 50–52]. The antagonization of MOMP accrued by the Bcl2 anti-apoptotic proteins in which they bind and inhibit both Bax and Bak, also BH3-only proteins via interacting with their BH3-only domains [53]. The Bcl2 proteins are regulated both transcriptionally and posttranscriptionally. Especially, via the ubiquitin-proteasome system, the degradation of Mcl-1 involve in apoptosis due to many cellular stresses. Over DNA damage, Mcl1 ubiquitin ligase E3 (MULE) binds to Mcl1 and initiates it catalyzes [54]. Mcl1 is phosphorylated via mitogen-activated protein kinase (MAPK) upon cellular stress conditions [55]. Also, Mcl1 is degraded with growth factors stimuli such as IL3 and the deficiency of phosphoinositide 3-kinase (PI3K)-AKT signaling. This important process eases glycogen synthase kinase 3 (GSK3) from AKT inhibition. Then, GSK3 leads to phosphorylation of Mcl1 and its subsequent degradation [55, 56]. Intrinsic pathway signaling with pro-and anti-apoptotic proteins maintain many signaling processes in the important point of life and death decision. BH3-only proteins are essential upstream sensors of the mitochondrial apoptotic pathway. The regulation of several signaling pathways converge on the BH3-only proteins, and therefore, control and regulate their expression levels and activity [57, 58]. Such as the activation of Bid over cleavage by caspase-8 follow up DR ligation [59, 60]. Hereby, the Bid mediates the cross-regulation of both extrinsic and intrinsic apoptotic pathways. Also, the response to genotoxic stress can be given with Puma and Noxa, which are the direct target of p53 [61–64]. Also, the primary apoptotic factor Bim similarly can be up-regulated via forkhead transcription factor FOXO3A over

cytokine deficiency or due to ER stress to unbind the accumulated proteins [65–67]. To this end, the activity of Bad regulated via several kinases' phosphorylation including AKT, which leads to its sequestration through 14–3-3- proteins [68, 69]. Also, when Bad is released, it acts against Bcl2 anti-apoptotic proteins over growth factor deficiency and/or lacking the AKT signaling [68, 70]. It is noteworthy that MOMP is obliged the cell to death even though the caspase activation is hindered which might be the conclusion of the loss of mitochondrial function, which causes the failure of energy [26, 71]. Some cells can survive under these conditions though [26]. Nevertheless, the MOMP activation through its downstream is an important point in the regulation of caspases and might be settled. Finally, mitochondrial apoptosis can be harassed through the phosphorylation and inhibition of caspase-9 by acting downstream of MOMP [72].

#### **2.3 The extrinsic pathway of apoptosis**

The extrinsic pathway of apoptosis can be initiated through the binding of ligands to the death receptors such as tumor necrosis factor receptors (TNFRs) and Fas receptor (FasR) on the cell surface [7, 17, 73]. These receptors possess death domains at the cytosolic side, which helps in recruiting adaptor proteins such as FAS associated via death domain (FADD), and also, for some receptors, TNFRSF1A is associated via death domain (TRADD) [74, 75]. The recruitment of these adaptor proteins occurs through the interaction of death domains present in both receptors and adaptors. The death effector domains of these adaptor proteins have different upstream procaspases such as caspase-8 and caspase-10 to form a death-inducing signaling complex (DISC), which then promote activation of these caspases [17, 76]. The downstream executioner caspases such as caspase-3, caspase-6, and caspase-7 activated through their upstream caspases to execute cell death [77]. The main feature of apoptosis is the lack of systemic damage to neighboring cells during its initiation and clearance of the dead cells. This feature of apoptosis is provided by the attentive wrapping of the cell membrane around the fragmented cell by forming apoptotic bodies. The release of ATP (adenosine 5′-triphosphate) and UTP (uridine- 5′-triphosphate) from apoptotic bodies display a signal for macrophages, leads to the migration of macrophages to the apoptotic site [78]. Besides, apoptotic cells also expose the eat me signal most likely phosphatidylserine (PtdSer) on their surface, which initiates phagocytes to engulf the must-remove cells [79].


**Food Insecurity Is Associated with Mild Cognitive Impairment among Middle-Aged and Older Adults in South Africa: Findings from a Nationally Representative Survey**

**Ai Koyanagi 1,2,3,\*, Nicola Veronese 4,5, Brendon Stubbs 6,7,8, Davy Vancampfort 9,10, Andrew Stickley 11,12, Hans Oh 13, Jae Il Shin 14,15,16, Sarah Jackson 17, Lee Smith 18 and Elvira Lara 2,19**

Received: 27 February 2019; Accepted: 26 March 2019; Published: 30 March 2019

**Abstract:** There are no studies on the association between food insecurity and mild cognitive impairment (MCI). Thus, cross-sectional, community-based data on individuals aged ≥50 years from the World Health Organization's Study on Global AGEing and Adult Health (SAGE) conducted in South Africa (2007–2008) were analyzed to assess this association. The definition of MCI was based on the National Institute on Ageing-Alzheimer's Association criteria. Past 12-month food insecurity was assessed with two questions on frequency of eating less and hunger due to lack of food. Multivariable logistic regression analysis was conducted. The sample consisted of 3,672 individuals aged ≥50 years [mean (SD) age 61.4 (18.3); 56% females]. The prevalence of MCI was

8.5%, while 11.0% and 20.8% experienced moderate and severe food insecurity, respectively. After adjustment for potential confounders, moderate and severe food insecurity were associated with 2.82 (95%CI = 1.65–4.84) and 2.51 (95%CI = 1.63–3.87) times higher odds for MCI compared with no food insecurity, respectively. The OR for those aged ≥65 years with severe food insecurity was particularly high (OR = 3.87; 95%CI = 2.20–6.81). In conclusion, food insecurity was strongly associated with MCI among South African older adults. Future longitudinal research is required to assess whether addressing food insecurity may reduce risk of MCI and subsequent dementia.

**Keywords:** mild cognitive impairment; food insecurity; South Africa; epidemiology


**Author details**

Thun Itthipanichpong\* and Songthai Moonwong Department of Orthopaedics, Faculty of Medicine, Chulalongkorn University, King Chulalongkorn Memorial Hospital, Bangkok, Thailand

\*Address all correspondence to<EMAIL_ADDRESS>
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