subjects between the ages of 30 to 49 years who received cataract surgery at st .
mary 's hospital from 1995 to 2004 ( n = 976 ) were included in this study .
patients with a history of ocular trauma , uveitis , ocular or systemic diseases other than diabetes and hypertension , congenital cataracts , and those who received combined surgeries were excluded .
the type of lens opacity , urban / rural region , and preoperative and postoperative visual acuities were analyzed .
seoul , the capital of korea , is the largest city in the country and is home to 25% of the entire korean population , was regarded as an urban region .
other cities and provinces outside of seoul , korea were considered to be rural regions . using a slit lamp biomicroscope , two ophthalmologists ( ksn and skc ) of st .
mary 's hospital , the catholic university of korea examined the anterior segment of both eyes .
the pupils of all other subjects were dilated with topical tropicamide / phenylephrine hydrochloride ( mydrin - p ; santen , osaka , japan ) eye drops until the pupil diameter was at least 7.0 mm .
nuclear opalescence and brunescence were assessed with a narrow slit beam and cortical and posterior subcapsular ( psc ) opacities were assessed with retroillumination .
lens opacity grading was conducted using the internationally recognized objective lens grading system , lens opacity classification system iii ( locs iii ) .
the locs iii is a systemic method of grading the severity of lens opacities according to photographic standards using four major characteristics : nuclear opalescence , nuclear color , cortical cataract , and psc cataract .
a cataract was defined as a locs iii score of 4 or more for nuclear opalescence or nuclear color , a locs iii score of 2 or more for a cortical cataract , and a locs iii score of 2 or more for a psc cataract .
we also analyzed distinct types of cataracts : nuclear only , cortical only , psc only , or mixed .
additionally , anterior polar ( ap ) type subcapsular opacities were evaluated because they are frequently found in this age group .
an ap opacity was defined as a subcapsular opacity at the center of the pupil seen in the non - dilated and dilated states . in our study , due to the large percentage of ap and psc opacities a mixed type lens opacity ( ap + psc ) category was created to compare the percentage of patients with cortical only or nuclear only type opacities .
the mixed type opacity was thus defined as a combination of nuclear and cortical opacities without a ap or psc opacity component .
operating procedures included either phacoemulsification or extracapsular cataract extraction with intraocular lens implantation under local anesthesia .
the cochran - armitage proportion trend test technique was used to identify changes of each parameter with the passage of time .
the quoted p - values are 2-sided and were considered to be statistically significant when calculated to be < 0.05 .
using a slit lamp biomicroscope , two ophthalmologists ( ksn and skc ) of st .
mary 's hospital , the catholic university of korea examined the anterior segment of both eyes .
the pupils of all other subjects were dilated with topical tropicamide / phenylephrine hydrochloride ( mydrin - p ; santen , osaka , japan ) eye drops until the pupil diameter was at least 7.0 mm .
nuclear opalescence and brunescence were assessed with a narrow slit beam and cortical and posterior subcapsular ( psc ) opacities were assessed with retroillumination .
lens opacity grading was conducted using the internationally recognized objective lens grading system , lens opacity classification system iii ( locs iii ) .
the locs iii is a systemic method of grading the severity of lens opacities according to photographic standards using four major characteristics : nuclear opalescence , nuclear color , cortical cataract , and psc cataract .
a cataract was defined as a locs iii score of 4 or more for nuclear opalescence or nuclear color , a locs iii score of 2 or more for a cortical cataract , and a locs iii score of 2 or more for a psc cataract .
we also analyzed distinct types of cataracts : nuclear only , cortical only , psc only , or mixed .
additionally , anterior polar ( ap ) type subcapsular opacities were evaluated because they are frequently found in this age group .
an ap opacity was defined as a subcapsular opacity at the center of the pupil seen in the non - dilated and dilated states . in our study , due to the large percentage of ap and psc opacities a mixed type lens opacity ( ap + psc ) category was created to compare the percentage of patients with cortical only or nuclear only type opacities .
the mixed type opacity was thus defined as a combination of nuclear and cortical opacities without a ap or psc opacity component .
operating procedures included either phacoemulsification or extracapsular cataract extraction with intraocular lens implantation under local anesthesia .
the cochran - armitage proportion trend test technique was used to identify changes of each parameter with the passage of time .
the quoted p - values are 2-sided and were considered to be statistically significant when calculated to be < 0.05 .
a total of 11,111 patients underwent cataract surgery in our hospital from 1995 to 2004 .
of the 11,111 patients , only 976 subjects ( 8.8% ) met the inclusion criteria .
male patients accounted for the majority of the patient population , 79.0% ( 771 / 976 ) , while female patients accounted for 21.0% ( 205 / 976 ) of the study population . in terms of home environment , 60.9% ( 594 / 976 ) of subjects were from an urban region and 39.1% ( 382 / 976 ) were from a rural region .
the proportion of adults with cataracts aged 30 to 49 years from 1995 to 2004 was 11.5% , 9.7% , 9.2% , 7.9% , 8.7% , 10.4% , 6.5% , 7.4% , 12.1% , and 5.9% , respectively in each year .
the proportion of adults with cataracts displayed a statistically significant decrease with the passage of time ( p = 0.0002 ) ( fig .
the proportion of male patinets from each year showed statistically significant decrease with the passage of time ( p = 0.0002 ) .
the proportion of total female patients from each year showed no statistically significant trend with the passage of time ( p = 0.0599 ) .
the most common lens opacities were ap opacities ( 35.7% , 348 / 976 ) and psc opacities ( 35.1% , 343 / 976 ) .
mixed ap and psc opacities ( 7.0% , 68 / 976 ) , cortical opacities ( 6.0% , 59 / 976 ) , and nuclear opacities ( 5.4% , 53 / 976 ) followed in descending order . of note ,
the mixed ap and psc opacities were more common than cortical opacities or nuclear opacities alone ( fig .
mixed nuclear and cortical type lens opacities accounted for 10.8% ( 105 / 976 ) of the study population . among the proportions of lens opacity types , the proportion of mixed ap and psc opacities showed a statistically significant decrease with the passage of time ( p < 0.0001 ) while the proportion of cortical opacities displayed a statistically significant increase with the passage of time ( p < 0.0001 ) .
the cochran - armitage test results of other lens opacities and the previously discussed elements are demonstrated in table 2 .
the percentage of subjects with a preoperative best - corrected visual acuity ( bcva ) less than 20 / 40 was 73.2% ( 714 / 976 ) .
after a postoperative period of 2 months , 92.7% ( 905 / 976 ) subjects showed a bcva of more than 20 / 40 .
the shortest follow up period was 2 months and some patients are still being followed presently .
a total of 11,111 patients underwent cataract surgery in our hospital from 1995 to 2004 .
of the 11,111 patients , only 976 subjects ( 8.8% ) met the inclusion criteria .
male patients accounted for the majority of the patient population , 79.0% ( 771 / 976 ) , while female patients accounted for 21.0% ( 205 / 976 ) of the study population . in terms of home environment , 60.9% ( 594 / 976 ) of subjects were from an urban region and 39.1% ( 382 / 976 ) were from a rural region .
the proportion of adults with cataracts aged 30 to 49 years from 1995 to 2004 was 11.5% , 9.7% , 9.2% , 7.9% , 8.7% , 10.4% , 6.5% , 7.4% , 12.1% , and 5.9% , respectively in each year .
the proportion of adults with cataracts displayed a statistically significant decrease with the passage of time ( p = 0.0002 ) ( fig .
the proportion of male patinets from each year showed statistically significant decrease with the passage of time ( p = 0.0002 ) .
the proportion of total female patients from each year showed no statistically significant trend with the passage of time ( p = 0.0599 ) .
the most common lens opacities were ap opacities ( 35.7% , 348 / 976 ) and psc opacities ( 35.1% , 343 / 976 ) .
mixed ap and psc opacities ( 7.0% , 68 / 976 ) , cortical opacities ( 6.0% , 59 / 976 ) , and nuclear opacities ( 5.4% , 53 / 976 ) followed in descending order . of note ,
the mixed ap and psc opacities were more common than cortical opacities or nuclear opacities alone ( fig .
mixed nuclear and cortical type lens opacities accounted for 10.8% ( 105 / 976 ) of the study population . among the proportions of lens opacity types , the proportion of mixed ap and psc opacities showed a statistically significant decrease with the passage of time ( p < 0.0001 ) while the proportion of cortical opacities displayed a statistically significant increase with the passage of time ( p < 0.0001 ) .
the cochran - armitage test results of other lens opacities and the previously discussed elements are demonstrated in table 2 .
the percentage of subjects with a preoperative best - corrected visual acuity ( bcva ) less than 20 / 40 was 73.2% ( 714 / 976 ) .
after a postoperative period of 2 months , 92.7% ( 905 / 976 ) subjects showed a bcva of more than 20 / 40 .
the shortest follow up period was 2 months and some patients are still being followed presently .
in this study , the percentage of subjects who underwent cataract surgery aged 30 to 49 years was 8.8% ( 976 / 11,111 ) .
this number is much less than previously mentioned in the kim study   that reported a prevalence of cataracts in patients older than 20 years old as 13.98% or the prevalence of cataracts in patients over 19 years of age from the korea national health and nutrition examination survey   that was found to be 24.1% .
although the proportion is different from the prevalence , this result suggests that age is the most important risk factor for the development of cataracts .
since there are few reports regarding the epidemiology of cataracts among adults aged 30 to 49 years , it is difficult to compare the prevalence of cataracts in korea with other countries . however , the prevalence of cataracts in patients aged 40 to 49 years old have been reported as 7.0%   and 6.5%   in two chinese studies .
considering the fact that the prevalence of cataracts is lower in younger subjects , the 8.8% of 30 to 49 years old in this study , which did include younger subjects , seems to be higher than other chinese studies .
the prevalence of cataracts among patients aged 30 to 49 years was 12.8% in the korea national health and nutrition examination survey , which is greater than the proportion found in our study .
a possible explanation for this is that all patients with cataracts may not have undergone surgery . in this study ,
male subjects made up 79.0% of the patient population and and females accounted for 21.0% , which is a noticeable male predominance of the study population .
the most common type of lens opacity was the ap opacity ( 35.7% ) , which is a rare condition outside of korea .
kim and joo   demonstrated that the prevalence of ap opacities in korea was high in comparison with other countries and was significantly higher in males . according to the study of kim et al .
, ap opacities were much more common in males ( 81.4% ) and in those younger than 40 years ( 45.4% ) in a korean population . the racial factor of koreans is considered to have affected our results such that the proportion of adults aged 30 to 49 years with cataracts was relatively higher with a predominance of ap opacities and male subjects than other races .
the ap opacity is limited to the anterior subcapsular area and the resultant lens opacity occurs in a relatively small area .
as shown by our results , ap opacities occurred mainly in males aged 30 to 49 years and caused severe vision impairment in this active population and led to heavy social and economic losses .
the ap opacity and psc opacity had greater subjective and objective effects on vision more so than other lens opacity types [ 25 - 29 ] , such that cataract surgical intervention is indicated at earlier stages .
this may be another reason why in our study , most subjects ( 70.8% ) between 30 to 49 years of age who received cataract surgeries had either an ap or psc opacity .
many studies have investigated the epidemiology of cataracts in different races and at different ages .
subjects of these studies were at least 40 years and older in singapore , china , taiwan , and australia .
these studies all showed predominance of the nuclear opacity and more females than males , which were different from the results of our study . in older subjects of various races , even in other asian races , the results were also different compared with the present study .
however , the prevalence of cataracts increased with age in all of these studies , which is consistent with our study results .
thus , it is likely that age affects the development of cataracts in all ages and races .
the overall proportion of cataracts among adults aged 30 to 49 years showed statistically significant decreases with the passage of time ( cochran - armitage test , p = 0.0002 ) . due to the wide distribution of ophthalmic services and the development of cataract surgery
, authors hypothesized that the rate of cataract surgery in this age group would increase with the passage of time .
the korean society is getting older and the proportion of young people is getting smaller as time progresses . according to the census taken by the korean statistics department the proportion of the population aged 30 to 49 years decreased to 31.16% in 2005 from 34.51% in 1995 .
one of the limitations of our study is that the subjects were not representative of the general population , but rather patients who underwent cataract surgeries .
therefore , the data may show some differences with the general population and more vision threatening lens opacity types may have been overrepresented , which may have resulted in an underestimate of nuclear or cortical opacities .
however , considering the lower prevalence of cataracts in the younger age group and only severe visual disturbances may lead to ophthalmological examination , it seems reasonable to select subjects who have undergone cataract surgery for the purpose of larger data collection .
however , nearly 40% of subjects were from a rural area , which is a considerable proportion regarding that the location of the hospital in seoul , korea . since korea is a racially homogeneous nation and data from rural areas
was substantially included , the regional differences seem to have little influenced on the study population . in conclusion , our results have revealed long - term characteristics and changes in the prevalence of cataracts among adults aged 30 to 49 years in korea over a 10-year study period .
the proportion of patients with cataracts this age group was relatively higher and had a predominance of ap and psc opacities as well as male patients in comparison with studies of senile cataracts in other races .
further studies on the assessment of the risk factors and studies based on the general population with larger sample numbers are required to substantiate these results .
 purposeto investigate the long - term characteristics of cataracts among adults aged 30 to 49 years in korean over a span of 10 years.methodssubjects between the ages of 30 to 49 years who underwent cataract surgery at st . 
 mary 's hospital from 1995 to 2004 ( n = 976 ) were included . 
 patients with a history of ocular trauma , uveitis , other ocular or systemic diseases , and congenital cataracts were excluded . 
 additional information including type of lens opacity , urban / rural region , and pre- and postoperative visual acuities were analyzed . 
 lens opacity grading was conducted using lens opacity classification system iii . 
 the cochran - armitage proportion trend test was used to analyze vision changes with the passage of time.resultsamong the patients who had undergone cataract surgeries , 8.8% ( 976 / 11,111 ) met the inclusion criteria . 
 the mean age was 41.7  5.45 years . 
 gender breakdown of the patient population included 79.0% male and 21.0% female . in terms of home environment , 
 60.9% were from an urban region and 39.1% from a rural region . 
 opacity type included anterior polar ( ap ) , posterior subcapsular ( psc ) , ap and psc , cortical , and nuclear in 35.7% , 35.1% , 7.0% , 6.0% , and 5.4% of patients , respectively . at a 2-month postoperative follow - up appointment 
 , 92.7% of patients showed a best - corrected visual acuity of more than 20 / 40.conclusionspredominance of ap and psc opacities as well as male patients was observed in this study population . 
Materials and Methods
Ocular examinations
Definitions of cataract
Operating procedure
Statistical analysis
Results
Epidemiology
Lens opacities
Others
Discussion