cataract surgery cataract surgery cataract surgery, which is also called lens replacement surgery, is the removal of the natural lens (also called the "crystalline lens") of the human eye that has developed a cataract, an opaque or cloudy area. the eye's natural lens is usually replaced with an artificial intraocular lens (iol). cataract surgerycataract surgery, using a temporal approach phacoemulsification probe (in right hand) and "chopper" (in left hand)specialtyophthalmologyicd-9-cm13.19meshd002387medlineplus002957 over time, metabolic changes of the crystalline lens fibres lead to the development of a cataract, causing impairment or loss of vision. some infants are born with congenital cataracts, and environmental factors may lead to cataract formation. early symptoms may include strong glare from lights and small light sources at night, and reduced visual acuity at low light levels. during cataract surgery, the cloudy natural lens is removed, either by emulsification in place or by cutting it out. an iol is usually implanted in its place to restore useful focus. cataract surgery is generally performed by an ophthalmologist in an out-patient setting at a surgical centre or hospital. local anaesthesia is normally used; the procedure is usually quick, and causes little or no pain and minor discomfort to the patient. recovery sufficient for most daily activities usually takes place in days and full recovery about a month. well over 90% of operations are successful in restoring useful vision and there is a low complication rate. day care, high volume, minimally invasive, small incision phacoemulsification with quick post-operative recovery has become the standard of care in cataract surgery in the developed world. manual small incision cataract surgery (msics), which is considerably more economical in time, capital equipment and consumables but provides comparable results is popular in the developing world. both procedures have a low risk of serious complications. description main article: cataract magnified view of a cataract seen on examination with a slit lamp cataract surgery, also called lens replacement surgery, is the removal of the natural lens (also called the "crystalline lens") of the human eye that has developed a cataract, an opaque or cloudy area. the eye's natural lens is usually replaced with an artificial intraocular lens (iol) to restore focus within a useful range of distances. it is the definitive treatment for vision impairment due to lens opacification. a cataract is a cloudy area in the lens of the eye that causes visual impairment. cataracts usually develop slowly and can affect one or both eyes. symptoms may include faded colours, blurry or double vision, halos around lights, sensitivity to glare from bright lights, and night blindness. this may result in difficulty driving, reading, or recognizing faces. poor vision caused by cataracts may also increase the risk of falling and depression. cataracts are most commonly due to aging but may also be caused by trauma or radiation exposure, be present from birth, or may occur following eye surgery for other problems. risk factors include diabetes, longstanding use of corticosteroid medication, smoking tobacco, and extended hyperbaric oxygen therapy, prolonged exposure to sunlight, and consumption of alcohol. cataracts form when clumps of protein or yellow-brown pigment accumulate in the lens, which reduces transmission of light to the retina at the back of the eye. cataracts are diagnosed by an eye examination. cataract surgery is needed only if the cataracts are causing the person problems. early symptoms may be improved with glasses; if this does not help, cataract surgery is the only effective treatment. surgery with implants generally results in better vision and an improved quality of life. the procedure is not readily available in many countries. about 20 million people worldwide are blind due to cataracts, which cause 51% of all cases of blindness and 33% of visual impairment. they are the cause of approximately 5% of blindness in the united states, and nearly 60% of blindness in parts of africa and south america. blindness from cataracts occurs in between 10 to 40 children per 100,000 in the developing world, and between 1 and 4 children per 100,000 in the developed world. cataracts become more common with age. in the united states, cataracts occur in 68% of those over the age of 80 years. they are more common in women, and less common in hispanic and black people. contraindications contraindications to cataract surgery include cataracts that do not cause visual impairment and medical conditions that predict a high risk of unsatisfactory surgical outcomes. implantation of a posterior chamber intraocular lens (pciol) in patients younger than seven months is controversial due to rapid growth of the eyes at this age. eye growth in infants is unpredictable; an early implant is likely to result in large refractive error later in childhood. congenital cataracts may be caused by factors that make the eye more susceptible to an excessive amount of inflammation, which may be difficult to control. intraocular lenses (iols) are associated with a greater risk of visual axis opacities in this age group; aphakic optical correction in patients without using an iol is usually managed with either contact lenses or glasses. implantation of an iol in a second operation may be considered later. technique cataract surgery using a surgical microscope two main types of surgical procedures are in common use throughout the world. in phacoemulsification (phaco), the natural lens is broken into small pieces and removed by suction, and in extracapsular cataract extraction (ecce), the lens is removed from its capsule and extracted from the eye whole or a small number of substantial pieces. in most surgeries, an iol is inserted. foldable lenses are generally used for the 2–3 mm (0.08–0.12 in) phaco incision, while non-foldable lenses can be placed through the larger extracapsular incision. the small incision size used in phacoemulsification generally allows for sutureless incision closure. ecce uses a larger incision of 10–12 mm (0.39–0.47 in) and usually requires stitches; this requirement led to a variation of ecce known as manual small incision cataract surgery (msics), which does not usually need stitches. cataract surgery using intracapsular cataract extraction (icce) has been superseded by phacoemulsification and msics, and is rarely performed. ecce has largely become a contingency procedure to deal with complications during surgery. phacoemulsification is the most-commonly performed cataract procedure in the developed world. the high capital and maintenance costs of a phacoemulsification machine and of the associated disposable equipment, however, has meant ecce and msics remain the most-commonly performed procedures in developing countries. cataract surgery is commonly done as an outpatient or day care procedure, which is cheaper than hospitalisation and an overnight stay, and there is evidence day surgery has similar medical outcomes. types of surgery cataract surgery recently performed, foldable iol inserted. a small incision and very slight hemorrhage are visible to the right of the still dilated pupil. the main types of surgical technique used in cataract surgery are phacoemulsification and manual extraction. phacoemulsification involves the use of a machine with an ultrasonic handpiece equipped with a titanium or surgical steel tip which vibrates at an ultrasonic frequency—commonly 40 khz—to emulsify the lens tissue. a second instrument, which is sometimes called a "cracker" or "chopper", may be used from a side port to break the hard cataract nucleus into smaller pieces, making emulsification and the aspiration of cortical material—the soft part of the lens around the nucleus—easier. after phacoemulsification of the lens nucleus and cortical material is completed, a dual irrigation-aspiration (i-a) probe or a bimanual i-a system is used to remove the remaining peripheral cortical material. femtosecond laser-assisted cataract surgery has been reported to be safe, and may have less adverse effect on the cornea and macula than manual phacoemulsification. the laser is used to make the corneal incision, the capsulotomy and to initiate lens fragmentation, which reduces the energy requirements for phacoemulsification. it offers high precision, effective lens fragmentation at lower power levels and good optical quality, but as of 2022 has not been shown to have significant visual, refractive or safety benefit over manual phacoemulsification, and it has a higher cost. extracapsular cataract extraction (ecce), also known as manual extracapsular cataract extraction, is the removal of almost the entire natural lens in one piece, while the elastic lens capsule (posterior capsule) is left intact to allow implantation of an intraocular lens. the lens is manually removed through a 10–12 mm (0.39–0.47 in) incision in the cornea or sclera. although it requires a larger incision and the use of stitches, this method may be preferable for patients with very hard cataracts or other situations in which phacoemulsification is problematic. manual small incision cataract surgery (msics) is an evolution of ecce; the entire lens is removed from the eye through a self-sealing scleral tunnel wound. a well-constructed scleral tunnel is held closed by internal pressure, is watertight, and does not require suturing. the wound is relatively smaller than that in ecce but is still markedly larger than a phaco wound. comparative trials of msics against phaco in dense cataracts have found no difference in outcomes but msics had shorter operating times and significantly lower costs. msics has become the method of choice in the developing world because it provides high-quality outcomes with less surgically induced astigmatism than ecce, no suture-related problems, quick rehabilitation, and fewer post-operative visits. msics is easy and fast to learn for the surgeon, cost effective, simple, and applicable to almost all types of cataract. nucleus of a hypermature cataract removed by ecce intracapsular cataract extraction (icce) is the removal of the lens and the surrounding lens capsule in one piece. the procedure has a relatively high rate of complications due to the large incision required and pressure placed on the vitreous body. it has therefore been largely superseded, and is rarely performed in countries where operating microscopes and high-technology equipment are readily available. after lens removal by icce, an intraocular lens implant can be placed in either the anterior chamber or sutured into the ciliary sulcus. cryoextraction is a technique used in icce; the cataract is extracted using a cryoprobe, the refrigerated tip of which adheres to the tissue of the lens at the contact point by freezing with a cryogenic substance such as liquid nitrogen, facilitating its removal. cryoextraction may still be used for the removal of subluxated lenses. refractive lens exchange is effectively the same procedure used to replace a lens with high refractive error when other methods are not effective. there are risks in addition to cataract procedural risks. a related procedure is the implantation of phakic intraocular lenses in series with the natural lens to correct vision in cases of high refractive errors. ophthalmic viscosurgical devices main article: ophthalmic viscosurgical device] ophthalmic viscosurgical devices (ovds) are a class of clear, gel-like materials used in cataract surgery to maintain the volume and shape of the anterior chamber of the eye, and protect the intraocular tissues during the procedure. they were originally called viscoelastic substances or viscoelastics. their consistency allows surgical instruments to move through them but when there is low shear stress, they do not flow and retain their shape. ovds are available in several formulations, which may be combined or used individually as best suits the procedure. ovds are introduced into the anterior chamber at the start of the procedure and removed at the end, when they are replaced by a buffered saline solution. the tendency of cohesive ovds to adhere to themselves helps with removal. intraocular lenses main article: intraocular lens 18.5 diopter foldable intraocular lens injector for foldable intraocular lenses. the incision size for this type is 2.8mm the iol injector is inserted in the incision and aimed at the capsule the rolled up lens is ejected from the nozzle int the capsule the lens unfolds in place section diagram of the eye, showing intraocular lens implanted in the posterior lens capsule behind the iris after the removal of a cataract, an intraocular lens (iol) is usually implanted into the eye to provide refractive compensation for the lack of the natural lens. a foldable iol may be implanted through a 1.8 to 2.8 mm (0.071 to 0.110 in) incision, whereas a rigid poly(methyl methacrylate) (pmma) lens requires a larger cut. foldable iols are made of silicone, hydrophobic, or hydrophilic acrylic material of appropriate refractive power; it is folded using a holder/folder or a proprietary insertion device provided with the iol. the iol is inserted through