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RR Ansari, FJ Giblin, JF King, VR Leverenz, L- R Lin; In Vivo Static and Dynamic Light Scattering (DLS) Measurements in Lenses of Hyperbaric Oxygen (HBO)-treated Guinea Pigs Indicate Increased Scattering and Protein Size . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2358.
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Purpose:To monitor early changes in lens proteins non-invasively and quantitatively in a model for nuclear cataract. It was shown previously that human patients treated for up to 400 hours with hyperbaric oxygen (HBO) developed nuclear cataracts (Palmquist et al., 1984). We have treated guinea pigs with HBO for up to 200 hours to induce an increased level of nuclear light scattering in their lenses. We investigated the possible contribution of an O2-induced increase in lens protein size (aggregate formation) to the observed scatter. Method:Guinea pigs, initially 18 months old, were treated for up to 86 times with HBO (2.5 atm 100% O2, 2.5 h, 3x per week). Aged-matched untreated animals were used as controls. The eyes of the animals were analyzed in vivo using an integrated static and DLS fiber optic probe at 60, 67 and 83 HBO treatments (5-7 months of treatment). In vivo static light scattering (SLS) scans were made at 0.01 mm/sec to obtain the level of scatter along the optical axis of the eye. DLS measurements were made at intervals of 0.1mm along the 5mm visual axis from the anterior to the posterior capsules. Each measurement was completed in 5 seconds at a laser (l=670 nm) power of 50mW. Other complementary methods employed in this study include periodic monitoring of the animals with slit-lamp bio-microscopy and photographic observations with a sharp laser beam out of the DLS probe passing through the excised lenses. Result:The SLS scans were able to clearly indicate the anatomy and the structure within the guinea pig eye including the cornea, aqueous, the different regions of the lens, and the vitreous. Lenses from control animals typically showed a low level of scatter throughout the lens, with a slightly elevated level in the nuclear region. Lenses from experimental animals typically showed an increased level of scatter throughout the lens, particularly in the nucleus. At this time, DLS analyses have been completed only for 60 HBO-treatments and only in the center of the lens. Control lenses showed a single group of proteins with a mean diameter of about 40 nm. Experimental lenses showed two groups of proteins having mean diameters of 400 and 4,000 nm. DLS data for 67 and 83 HBO treatments, measured at 50 individual points across each lens, are currently being analyzed. Conclusion:O2-induced aggregation of lens proteins contributes to increased nuclear light scattering in lenses of HBO-treated guinea pigs. In vivo DLS and the HBO/guinea pig model are useful for studying mechanisms of aging in the lens.
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