Visual acuity and macular sensitivity in myopic eyes before and after laser in situ keratomileusis

PURPOSE. To evaluate the changes in visual acuity (VA) and in macular sensitivity in myopic eyes subjected to laser in situ keratomileusis (LASIK) refractive surgery. METHODS. In 38 myopic eyes, VA by Snellen's table and macular sensitivity by scanning laser ophthalmoscope (SLO) microperimetry were assessed before and after 24 weeks after LASIK surgery. The myopic eyes were divided into three age-matched groups: Group A = from -5 diopters (D) to -7 D and normal SLO-macular sensitivity (15 eyes); Group B = from -8 D to -16 D and normal SLO-macular sensitivity (9 eyes); and Group C = from -8 D to -16 D and abnormal SLO-macular sensitivity. RESULTS. In Group A and B eyes, at the first week after LASIK surgery, we observed a significant (analysis of variance, p < 0.01) reduction in VA and SLO-macular sensitivity with respect to baseline values, while after 12 and 24 weeks no differences (p > 0.01) were found when compared to baseline. In Group C patients, at 1 and 4 weeks after surgical treatment, we observed a significant (p < 0.01) reduction in VA and SLO-macular sensitivity with respect to baseline values. At 12 and 24 weeks the values of VA were reduced, but not significantly (p > 0.01), while values of SLO-macular sensitivity were still significantly (p < 0.01) reduced. CONCLUSIONS. LASIK could induce a reduction in VA and SLO-macular sensitivity in all myopic eyes during the 4 weeks following the surgery. This reduction is still present after 24 weeks only in eyes with the highest preoperative degree of myopia combined with the greatest reduction in macular sensitivity.