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J.G. Sivak, T. German, K.L. Moran, V. Bantseev, C. Balian; Chromatic Aberration of the Lens Measured In Vitro . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3496.
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Purpose: The exaggerated chromatic dispersion of the lens is thought to be a primary cause for the fact that human longitudinal chromatic aberration is greater than that calculated from model eye values. To measure lens chromatic aberration directly, a new scanning laser system, incorporating both a short wavelength diode laser (gallium-nitride, 417.5nm) as well as a superimposed helium-neon laser (632 nm) has been developed. Methods: A mirror reflects the red or blue laser up through the cultured lens and a positioning motor moves the laser in defined steps across the lens. A digital camera captures the position and slope of the refracted laser beam at each step and the data is used to calculate back vertex distance focal length. Bovine and rat lenses were placed in cells of glass and silicon rubber, so that both lens surfaces are bathed in culture medium while the lens is suspended equatorially on a beveled washer. A series of laser beams were passed through each lens at increments of 0.50 mm for bovine and 0.18 mm for rats, to provide a measure of spherical aberration for each wavelength. Results: The results indicate a difference of back vertex focal length (blue and red) of about 3 mm for adult bovine lenses and about 0.4 mm for 12 week old rat lenses These differences are consistent across the lens, indicating that spherical aberration is not affected by wavelength. . The rat data included a group which has spontaneous diabetes. Diabetic lens damage, measured as focal length variability, amounted to 0.0884 mm for the red laser and 0.0920 mm for the blue laser (n=9). These values compare to 0.0880 and 0.0572 mm for control lenses. Conclusions: 1) Lens chromatic aberration is substantial and can be measured in vitro. 2) Blue wavelengths are more sensitive indicators of lens damage in lens culture research.
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