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K. Nagai, H. Sasaki, F. Jonasson, R. Honda, M. Kojima, Y. Sakamoto, Y. Kawakami, K. Sasaki; Who Cataract Classification System and Cataract Surgery in 12 Years. Invest. Ophthalmol. Vis. Sci. 2009;50(13):503.
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© ARVO (1962-2015); The Authors (2016-present)
The WHO cataract classification system is a useful tool for judging the timing of surgery. We studied the correlations between the three main types of cataract by WHO system and cataract surgery over 12 years in Icelanders.
Among the 1045 subjects aged over 50 yrs who joined the 1st Reykjavik Eye Study (RES) in 1996, 573 cases from 802 survivors were examined in 2008 at the 3rd RES. After excluding eyes with aphakia, pseudophakia in 1996 and poor photographed lens images in 1996 and 2008, 828 eyes of 528 cases were enrolled in this study.Lenses were evaluated under maximal mydriasis using slit-lamp biomicroscopy and documented with an anterior eye segment analysis system (EAS-1000, NIDEK). Eyes examined in 1996 were classified, by one examiner, as transparent (T), nuclear (N), cortical (C) posterior subcapsular cataract (PSC) or cortical opacity within a 3mm diameter of the pupil (CEN+) from photographed images, according to the WHO classification system. Eyes with 2 or more types were grouped as mixed type (M).
The rate of cataract surgery in group T was 6.1% (3.5% in males and 8.4% in females). By age, the rates were 2.4% in 50s, 8.1% in 60s and 22.7% in 70s at baseline. The odds ratios to 50s were 1.9 (95% CI, 1.1-3.4) for 60s and 11.0 (5.9-20.6) for 70s.By baseline type, the rates of cataract surgery were 35.6% in group C, 47.3% in group N, 75.0% in group PSC, 66.7% in group CEN(+), 19.2% in group CEN(-), and 90.9% in group M. The odds ratios of the rates of cataract surgery to transparent lenses were 5.3 (3.0-9.4) for group C, 5.3 (2.7-10.5) for group N, 40.0 (7.3-220.0) for group PSC and 89.0 (9.6-825.2) for group M.By baseline grades 1, 2 and 3, the rates were 32.6%, 40.0%, 70.0% in group C , 37.5%, 100%, 100% in group N, and 83.3%, 100%, 66.7% in group PSC, respectively.
Although the rate of cataract surgery over 12 years in eyes with transparent lenses was low in age 50s at baseline, nearly 25% of those aged in their 70s received cataract surgery within 12 years. The rate was highest in eyes with mixed type of cataract, followed by PSC and then CEN. The WHO cataract grading system is useful to predict cataract surgery.
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