Changes in contrast sensitivity function and ocular higher order aberration by conventional myopic photorefractive keratectomy.

PURPOSE

To evaluate the relation between induced changes in ocular higher order aberrations and changes in the contrast sensitivity function in patients undergoing excimer laser photorefractive keratectomy (PRK).

METHODS

Myopic PRK using excimer laser was performed in 31 patients (56 eyes). The preoperative refractive error was -6.2 +/- 2.9 diopters. Before and 1 month after surgery, we measured the ocular higher order aberrations for a 4-mm pupil, and three indices of contrast sensitivity function. From the data collected, the area under the log contrast sensitivity function (AULCSF) was calculated.

RESULTS

PRK significantly reduced AULCSF (P = 0.004), low-contrast visual acuity (P = 0.004), and letter-contrast sensitivity (P = 0.013). Coma-like (P < 0.001) and spherical-like (P < 0.001) aberrations were significantly increased by surgery. The change in AULCSF by surgery significantly correlated with the change in coma-like (r = -0.468, P < 0.001) and spherical-like (r = -0.291, P = 0.033) aberrations. The change in low-contrast visual acuity by PRK significantly correlated with the change in coma-like aberration (r = 0.599, P < 0.007), but not with change in spherical-like aberrations (r = 0.136, P = 0.326). There were significant correlations between changes in letter-contrast sensitivity and changes in coma-like (r = -0.450, P < 0.001) and spherical-like (r = -0.255, P = 0.048) aberrations.

CONCLUSIONS

PRK significantly increases ocular higher order aberrations, which compromise contrast sensitivity function after surgery.