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      Racial Differences of Lens Transparency Properties with Aging and Prevalence of Age-Related Cataract Applying a WHO Classification System

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          Purpose: To investigate racial differences of lens transparency properties and the prevalence of lens opacification by age. Methods: Lenses of randomly selected Asian (1,038 Japanese and 517 Singaporeans) and Caucasian (1,045 Icelanders) subjects were evaluated for their lens transparency property (LTP). The prevalence of lens opacification was determined with a newly proposed WHO cataract classification system. Results: LTP increased with aging for all nationalities. Light scattering intensity was significantly higher in the Singaporeans followed by the Icelandic subjects. The prevalence of cortical opacification in Singaporeans was significantly higher than those of the other nationalities up to the age of 60, and the prevalence in Asians was significantly higher than that in Caucasians aged 60–69. Cortical opacification was more prevalent than the other types for both Japanese and Icelanders in their 50s, 60s and 70s. Regarding the central optical zone, the prevalence in the Singaporeans was significantly higher than in the other two groups in their 50s and 60s. The prevalence of nuclear opacification in Singaporeans was markedly higher than those of the two other groups for all ages. Subcapsular cataract was the least prevalent type for all age groups and nationalities; however, the highest prevalence was observed in Singaporeans. Conclusions: Lens transparency decreased with age in the Singaporeans more markedly than in the other two groups. The high prevalence of nuclear opacification in Singaporeans is considered to be due to environmental rather than race-specific factors.

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          Changes in Light Scattering Intensity of the Transparent Lenses of Subjects Selected from Population-Based Surveys Depending on Age: Analysis through Scheimpflug Images

          The physiological ageing changes of decreasing lens transparency were objectively evaluated in a total of 1,040 eyes selected from 1,685 individuals who were the subjects of population-based cataract epidemiological surveys performed in three climatically different survey fields in Japan. The lens transparency changes were evaluated from the light scattering intensity on thirteen different lens layers seen in slit images taken by the latest type of Scheimpflug camera. The mean percentage prevalence of cataracts in all the epidemiological survey subjects including grading from I to III, which was also judged objectively through documented images, was 64.6% in the Noto subjects, 46.6% in the Hokkaido subjects and 38.0% in the Okinawa subjects. The lens transparency at all of the measuring points decreased with ageing. The above changes, seen in the lenses of subjects in their 40s to 60s, were obviously more prominent compared with those seen in subjects in their 40s. Although there were some differences in transparency decrease with ageing among the subjects of the three areas, the authors tentatively propose to show the data obtained from the Noto subjects as representative of Japanese individuals. Lens transparency changes on each lens layer showed characteristic ageing changes and those of the representative four layers showed an exponential decrease in transparency. The decreasing ratio might accelerate from age as early as the mid-40s.
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            An Index for Human Lens Transparency Related to Age and Lens Layer: Comparison between Normal Volunteers and Diabetic Patients with Still Clear Lenses

            Objective: The light scattering intensity of normal, clear lenses varies with age and with the localization within the lens. Realizing the biometry of single lens areas together with their relevant light scattering intensity one should be able to calculate an index to express the lens transparency properties of normal human lenses in dependence on age. Performing the same procedure in cases of diabetic patients with still clear lenses it should become possible to obtain an index for the lens transparency properties of lenses under the ‘risk factor’ diabetes. Methods: 748 eyes with transparent lenses in 383 healthy individuals and 134 eyes with clear lenses in 70 subjects with diabetes were examined. Scheimpflug slit images of the lens were documented by a Nidek EAS-1000 instrument. Biometry for measuring the distance of the single lens layers from the anterior capsule and densitometry for determining the light scattering intensity of six defined lens layers along the (theoretical) optical axis were performed. The index of the lens transparency properties was calculated using the light scattering intensity of a defined lens layer and its distance from the anterior capsule. Results: Lens thickness and light scattering intensities increased linearly with increasing age in the normal population as well as in the diabetic patients. The densitogram pattern of the light scattering intensities in the defined representative six points was similar in both populations, but in the diabetic group the lens thickness was larger and the light scattering intensities were higher at all ages. Conclusion: The index of lens transparency properties calculated with the light scattering intensities of a certain lens area and its distance from the anterior capsule is a useful measure of lens clarity in dependence on age. ‘Clear’ lenses of the diabetic population show significantly higher indices for the lens transparency properties in all age groups.
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              Classification System for Cataracts

              A cataract classification and grading system for the main purpose of cataract epidemiological studies is proposed by the Japanese Cooperative Cataract Epidemiology Study Group. Cataractous types are classified principally into cortical, nuclear and subcapsular opacities. Stages of cataract advancement are classified into grade I (early stage), grade II (moderate stage) and grade III (advanced stage). Regarding cortical opacities an opacified area obtained from red-reflex images is utilized for grading judgment. Nuclear opacity grading is based on the intensity of scattering at the nucleus. Grading of subcapsular opacities is judged from their extension in the three different pupillary areas. To help grading judgments, standard pictures of cortical and nuclear cataracts are provided. Gradings of lens coloration are divided into pale yellow (grade I), yellow (II), brownish yellow (III) and brown including reddish and black brown (IV). A recording chart is also provided.

                Author and article information

                Ophthalmic Res
                Ophthalmic Research
                S. Karger AG
                December 2004
                23 December 2004
                : 36
                : 6
                : 332-340
                aDepartment of Ophthalmology, Kanazawa Medical University, Uchinada, Japan; bDepartment of Ophthalmology, Iceland University, Reykjavik, Iceland; cSchepens Retina Association Foundation, Boston, Mass., USA
                81636 Ophthalmic Res 2004;36:332–340
                © 2004 S. Karger AG, Basel

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                Figures: 4, Tables: 8, References: 15, Pages: 9
                Original Paper


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