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For the past 10 years, the authors have performed cataract epidemiological surveys in several places. All of them were principally population based and applied new types of photodocumentation systems which were developed by our department. The survey places in Japan were Noto, our main survey field located in the centre of the main island of Japan, one village in the subtropical island of Okinawa, a village in the northern island of Hokkaido and one village (Bukittinggi) in West-Sumatra, Indonesia, very close to the equator. The survey methods applied including an interview and ophthalmological examinations, were almost identical in each place and the authors believe that the quality of the examinations was at high level. The cataract classification and grading systems applied were those established by the Japanese Co-operative Cataract Epidemiology Study Group. At present, no significant prominent difference of cataract prevalence and distribution of cataract types have been found in the three Japan survey places. The distribution of cataract types in the Indonesian subjects however, was different from the Japanese subjects. The lens transparency ratio in the Noto survey was quite similar to that of a Dutch study. From photographic images of both opaque and transparent lenses much objective information which be cannot detected through naked eye observation is obtainable. Furthermore, data obtained from the images are comparable because of their objectivity. Although the methodology seems to be rather sophisticated and is costly, the above advantages make it an important asset in this type of cataract research. For example, lens transparency changes with ageing can be indicated quantitatively from image analysis data.(ABSTRACT TRUNCATED AT 250 WORDS)
For the past 10 years, the authors have performed cataract epidemiological surveys in several places. All of them were principally population based and applied new types of photodocumentation systems which were developed by our department. The survey places in Japan were Noto, our main survey field located in the centre of the main island of Japan, one village in the subtropical island of Okinawa, a village in the northern island of Hokkaido and one village (Bukittinggi) in West-Sumatra, Indonesia, very close to the equator. The survey methods applied including an interview and ophthalmological examinations, were almost identical in each place and the authors believe that the quality of the examinations was at high level. The cataract classification and grading systems applied were those established by the Japanese Co-operative Cataract Epidemiology Study Group. At present, no significant prominent difference of cataract prevalence and distribution of cataract types have been found in the three Japan survey places. The distribution of cataract types in the Indonesian subjects however, was different from the Japanese subjects. The lens transparency ratio in the Noto survey was quite similar to that of a Dutch study. From photographic images of both opaque and transparent lenses much objective information which be cannot detected through naked eye observation is obtainable. Furthermore, data obtained from the images are comparable because of their objectivity. Although the methodology seems to be rather sophisticated and is costly, the above advantages make it an important asset in this type of cataract research. For example, lens transparency changes with ageing can be indicated quantitatively from image analysis data.(ABSTRACT TRUNCATED AT 250 WORDS)
It is known that fluorescence, much of it caused by UVA light excitation, increases in the aging human lens, resulting in loss of sharp vision. This study used an in vivo animal model to investigate UVA-excited fluorescence in the rabbit lens, which contains a high level of the UVA chromophore NADH, existing both free and bound to λ-crystallin. Also, the ability of a Class I (senofilcon A) soft contact lens to protect against UVA-induced effects on the rabbit lens was tested. Rabbit eyes were irradiated with UVA light in vivo (100 mW/cm2 on the cornea) for 1 hour using monochromatic 365 nm light. Irradiation was conducted in the presence of either a senofilcon A contact lens, a minimally UV-absorbing lotrafilcon A contact lens, or no contact lens at all. Eyes irradiated without a contact lens showed blue 365 nm-excited fluorescence initially, but this changed to intense yellow fluorescence after 1 hour. Isolated, previously irradiated lenses exhibited yellow fluorescence originating from the lens nucleus when viewed under 365 nm light, but showed normal blue fluorescence arising from the cortex. Previously irradiated lenses also exhibited a faint yellow color when observed under visible light. The senofilcon A contact lens protected completely against the UVA-induced effects on fluorescence and lens yellowing, whereas the lotrafilcon A lens showed no protection. The UVA-exposure also produced a 53% loss of total NADH (free plus bound) in the lens nucleus, with only a 13% drop in the anterior cortex. NADH loss in the nucleus was completely prevented with use of a senofilcon A contact lens, but no significant protection was observed with a lotrafilcon A lens. Overall, the senofilcon A lens provided an average of 67% protection against UVA-induced loss of four pyridine nucleotides in four different regions of the lens. HPLC analysis with fluorescence detection indicated a nearly six-fold increase in 365 nm-excited yellow fluorescence arising from lens nuclear λ-crystallin after the in vivo UVA exposure. It is concluded that UVA-induced loss of free NADH (which fluoresces blue) may have allowed the natural yellow fluorescence of λ-crystallin and other proteins in the lens nucleus to become visible. Increased fluorescence exhibited by UVA-exposed λ-crystallin may have been the result of a UVA-induced change in the conformation of the protein occurring during the initial UVA-exposure in vivo. The results demonstrate the greater susceptibility of the lens nucleus to UVA-induced stress, and may relate to the formation of human nuclear cataract. The senofilcon A contact lens was shown to be beneficial in protecting the rabbit lens against effects of UVA light, including changes in fluorescence, increased yellowing and loss of pyridine nucleotides.
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