Higher order aberrations across the horizontal visual field.

The relationship between higher order aberrations and position in the horizontal visual field is investigated in normal and refractive corneal surgery subjects. Individual aberration coefficients are obtained from two studies using five untreated subjects and two myopic subjects following conventional laser assisted in situ keratomileusis (LASIK) surgery. Measurements are made out to 40 deg in the temporal and nasal visual fields. For the untreated subjects, horizontal coma is linearly influenced by position, and spherical aberration and secondary astigmatism are influenced quadratically by position (45 subjects). For the myopic LASIK subjects, the horizontal coma is opposite in sign from that for unoperated eyes at similar visual field positions, and this can be attributable largely to anterior corneal asphericity. Again, both spherical aberration and secondary astigmatism are influenced quadratically by position. To summarize, horizontal coma, spherical aberration, and secondary astigmatism change systemically across the horizontal visual field, and corneal asphericity has a major influence on the rate of change of coma and its sign.