Effect of Tear Film Break-up on Higher Order Aberrations of the Anterior Cornea in Normal, Dry, and Post-LASIK Eyes

Abstract

To evaluate the effects of tear film breakup on higher order aberrations of the anterior cornea in normal, dry, and post-LASIK eyes. In a prospective study, 120 eyes (120 subjects) comprised three groups: post-LASIK eyes, dry eyes, and normal eyes. Tear film break-up time (BUT) was measured by fluorescein dye under slit-lamp microscopy. Corneal topographies were measured by videokeratography immediately after the following times: post-blink, 1/2 BUT, BUT, and after normal saline application. VOL-Pro software processed topographies to obtain and analyze higher order aberrations (3rd through 6th orders over 6 mm) of the anterior comeal surface. The measurement time scale was set by the BUT: significantly less for dry eyes (8.3 +/- 3.4 seconds) than post-LASIK eyes (11.3 +/- 5.1 seconds) or normal eyes (10.3 +/- 5.6 seconds). Normal and dry eye subjects showed a pattern of significant increase of aberrations from post-blink through BUT and decrease of aberrations after saline addition in coma, trefoil, and 3rd through 6th order aberrations. Post-LASIK eyes exhibited no significant difference between phases. Disruption of the tear film increases anterior corneal higher order aberrations in normal eyes and more rapidly in dry eyes. The increase in aberrations caused by conventional LASIK is greater than that of tear film-related effects.