Effect of optic aberrations, caused by ablation pattern decentration after laser vision correction, on visual acuity

The aim of this work was to study the effects of subclinical ablation pattern decentration on the quality of vision after photorefractive laser surgery. Optical high order spherical and coma-like aberrations of 30 eyes were evaluated before, 1 and 3 months after photorefractive surgery (PRK and LASIK). Relationship between the size and shape of the light spot on the retina during transmission of paraxial beams through the eye and the ablation zone decentrations was estimated. The results are presented for pupil diameters of 1 and 6 mm both at the center of the retina along the optical axis and at a distance of 0.5 mm from the center. Decentration of ablation zone by less than 1 mm makes the principal contribution to induction of higher order aberrations. The relative increase factor is 3.9 and 5.1 for the coma-like and spherical aberrations, respectively. At such decentrations spatial resolution of the eye decreases as the pupil size increases, which is most pronounced even at a slight distance from the visual axis but inside the fovea.