Peripheral ocular aberrations in mild and moderate keratoconus.

PURPOSE To investigate the influence of keratoconus on peripheral ocular aberrations. METHODS Aberrations in seven mild and five moderate keratoconics were determined over a 42° horizontal × 32° vertical visual field, with a modified aberrometer. Control data were obtained from an emmetropic group. RESULTS Most aberrations in the keratoconics showed field dependence, predominately along the vertical meridian. Mean spherical equivalent M, oblique astigmatism J(45), and regular astigmatism J(180) refraction components and total root mean square aberrations (excluding defocus) had high magnitudes in the inferior visual field. The rates of change of aberrations were higher in the moderate than in the mild keratoconics. Coma was the dominant peripheral higher-order aberration in both the emmetropes and the keratoconics; for the latter, it had high magnitudes in the center and periphery of the visual field. CONCLUSIONS Greater rates of change in aberrations across the visual field occurred in the keratoconus groups than in the emmetropic control group. The moderate keratoconics had more rapid changes in, and higher magnitudes of, aberrations across the visual field than did the mild keratoconics. The dominant higher-order aberration for the keratoconics across the visual field was vertical coma.