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V. Fernandez–Sanchez, F. Lara, M.E. Ponce, N. Lopez–Gil; Effect of trefoil and coma induced by contact lenses on human vision . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2846.
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Purpose: Typical values of trefoil and coma in visually–normal individuals are 0.1 microns (for a 5–mm pupil), but can be over ten times this value in eyes with pathologies such as keratoconus or penetrating keratoplasty. We study the real effect that these high–order aberrations have on vision. Methods: We evaluated ocular aberrations and visual performances in 11 young visually–normal adults. Soft contact lenses (CLs) were used that induced normal values (0.1–0.2 microns) or pathological values (1.2 microns) of both, trefoil and coma. Aberration measurements were obtained for a pupil diameter of 5 mm, under cycloplegia. The residual sphere and cylinder induced by each CL was corrected with spectacle trial lenses in order to avoid extra aberrations generated by decentrations and rotations of each CL. Measures of high– (HCVA) and low– (LCVA) contrast visual acuity as well as contrast sensitivity (CS) were made with each CL. Results: We found a significant (p<0.05) loss of 0.20 and 0.39 logMAR in the HCVA and LCVA tests, respectively, for the higher values (pathological values) of coma and trefoil. However, the losses with the other four CLs (normal values) were less than 0.05 logMAR and were not significant. Visual performance did not differ significantly between coma and trefoil conditions. CS was also reduced significantly for pathological values of aberrations, but not in the case of normal values of the two aberrations induced. Conclusions:Normal values of trefoil and coma found in the population do not lead to significant decrements in visual performances. However, in those cases where these aberrations are clearly elevated, such as in some corneal pathologies, their effects are relevant and should be corrected.
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