Corneal aberrations and its effect on contrast sensitivity after wavefront-guided and wavefront-optimized refractive surgeries

Abstract

Purpose: To evaluate the changes in corneal aberrations following wavefront-guided (WFG) and wavefront-optimized (WFO) refractive surgeries and determine the effect of postoperative corneal aberrations on contrast sensitivity.

Methods: In a prospective study, active duty U.S. military service members with mean age 30.1±6.1 years and refractive error -3.74±1.40 diopters (D) undergoing either PRK or LASIK were randomized to receive either WFG (n=51) or WFO (n=56) treatment. WFG treatment was performed using the VISX CustomVue STAR S4 IR and WFO with Wavelight Allegretto Wave Eye excimer laser system. Corneal aberrometry parameters were analyzed using the Oculus Pentacam system. The root mean square (RMS) of spherical aberration (SA), higher order aberrations (HOA) and total aberrations (TA) were calculated for a pupil diameter of 6.0 mm. Contrast threshold was measured preoperatively with correction and postoperatively without correction using the Metropsis Visual Stimulus Generation Device at five different spatial frequencies and area under the log contrast sensitivity function (AULCSF) was calculated. Paired sample t-test was used to compare pre- and postoperative changes. Linear regression analysis was used to explore the effect of corneal aberrations and treatment performed on contrast sensitivity.

Results: Corneal SA and HOA significantly increased at 6 months following either WFG or WFO refractive surgery. The mean difference in SA was 0.47 µm, P<0.01 and HOA was 0.54 µm, P<0.01 in WFG group while the mean difference in SA was 0.54 µm, P<0.01 and HOA was 0.46 µm in the WFO group. TA did not change significantly after either treatment (P>0.22). The AULCSF did not change significantly 6 months after either WFG or WFO refractive surgery (P>0.42). The changes in corneal SA, HOA and TA as well as the surgery performed were not significantly associated with the changes in AULCSF (P=0.08).

Conclusions: Both WFG and WFO refractive surgeries significantly induce changes in corneal spherical aberration and higher order aberrations but not in contrast sensitivity function. Corneal aberrations induced by WFG and WFO refractive surgeries appear to have no significant effect on postoperative contrast sensitivity.