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C. Okamoto, Y. Ishii, T. Oshika, T. Samejima, K. Miyata, Y. Hirohara, T. Mihashi; Wavefront Aberration and Letter Contrast Sensitivity in Keratoconus . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2537.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: It has been reported that eyes with keratoconus have significantly larger amount of coma and spherical aberrations than the normal subjects. However, the relation between increases in higher order aberration and visual functional has not been studied. We assessed the influence of ocular wavefront aberrations on contrast sensitivity in patients with keratoconus. Methods: Subjects were 22 eyes of 14 patients with keratoconus (age 30.5 ± 8.4 years, means ± SD) and 26 eyes of 13 normal controls (29.2 ± 6.7 years). Eyes with keratoconus were positive with the keratoconus screening test of the placido disk videokeratography (TMS-2, Computed Anatomy Inc., New York, NY). The wavefront aberrations of the eye were measured for 4- and 6-mm pupils using the Hartmann-Shack wavefront analyzer (Topcon KR-9000PW). The letter contrast sensitivity was examined under spectacle correction using CSV1000LV contrast charts (Vector Vision). Results: Results for a 4-mm pupil are first presented. Eyes with keratoconus showed significantly larger values than the normal controls for coma (0.569 ± 0.322 vs. 0.096 ± 0.048, p<0.001, unpaired t-test) and spherical (0.183 ± 0.079 vs. 0.064 ± 0.019, p<0.001) aberrations. The letter contrast sensitivity was significantly worse in patients with keratoconus than in normal controls (17.4 ± 3.8 vs. 21.8 ± 1.4, p<0.001). When analyzed in all 48 eyes, the letter contrast sensitivity had significant negative correlations with coma (Pearson r=-0.808, p<0.001) and spherical (r=-0.695, p<0.001) aberrations. In 22 eyes with keratoconus, the letter contrast sensitivity displayed a significant correlation with coma aberration (r=-0.671, p=0.001), but not with spherical aberration (r=-0.389, p=0.090). Similar results were obtained for a 6-mm pupil. Conclusions: In eyes with keratoconus, letter contrast sensitivity is reduced due to the increases in higher order wavefront aberrations, especially coma aberration.
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