Incidence, progression and risk factors of the different types of cataract in Japanese population

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Among the 1105 subjects aged over 50yrs who participated in the first Monzen Eye Study 1997-2002, 632 were reexamined five years later in 2002-2005. Incidences of the three main types of cataract increased with aging. Incidences of cortical, nuclear and posterior subcapsular cataract (PSC) were 18.9%, 3.0% and 2.0% and progression rates were 68.8%, 24.8% and 25.6% respectively. The progression rate of cortical cataract was higher in subjects aged in their 50s than those in their 60s and 70s. The five years' incidence of surgical intervention was 8.2% and was highest in subjects with mixed type of cataract, especially that with PSC at the baseline. Compared with the results of the Reykjavik Eye Study in Iceland, which was done by our group in 1996 and 2001, the prevalence, incidence and progression rate of cortical cataract was higher and those of nuclear cataract was lower in the Japanese population This study was the first to show the characteristics and natural course of the three ma … More in types of cataract in the Japanese population.The five years' change of light scattering intensities (LSIs) in the lens layers was measured using an anterior eye segment analysis system (EAS-1000, NIDEK). Although the LSIs increased with aging, the pattern of LSI changes differed by age. The increase of LSI in cortical layers was higher in subjects aged in their 50s than those in their 60s and 70s. There was no correlation between LSI in nuclear layers and age. Lenses with low LSI in nuclear layers at the baseline showed the higher increase rate of the LSIs in cortical layers. These results showed the possibility for prediction of cortical and nuclear cataract by measuring LSIs.We investigated contrast sensitivity using CAT-2000 (NEITZ) in subjects with fiber fold (FF), which is one of the subtypes of cataract presenting as parallel white lines similar to cortical opacification.. The prevalence of FF was higher in the Japanese compared with that in the Chinese population. Lenses with FF frequently had cortical cataract, however, the contrast sensitivity of FF eyes was normal if the lenses had no cortical cataract in the papillary area. Since lenses with FF are sometimes misdiagnosed as cases of cortical cataract when examined under direct illumination, it is very important for ophthalmologists to have an accurate technique of FF diagnosis and understand that they have little or no effect on visual function, including contrast sensitivity. Since the goal of this study is to show the correlation between visual function and the types and severity of lens opacities, and to establish guidelines for identifying proper candidates for cataract surgery, further investigation should be done especially regarding visual function of eyes with mixed types of cataract. Less