Visual acuity in the early course following photorefractive keratectomy for myopia

Background Photorefractive keratectomy (PRK) using the excimer laser is an accepted surgical technique for correction of myopic refraction errors in c ase of spectacle or contact lens incompatibility. The purpose of this study was to assess the development of uncorrected (UVA) and best-corrected visu al acuity (CVA) in the early course following PRK. Patients and Methods 48 eyes of 29 patients that underwent myopic photorefr active keratectomy using 193 nm excimer laser (MEL 60, Aesculap-Meditec) we re included in this study. The mean preoperative spherical equivalent was - 5.3 +/- 2.4 diopters (D) (range -1.75 to -9.5 D). Pre-, intra- and postoper ative treatment was standardized. The median time interval to complete epit helial closure was 2 days. According to their spherical equivalent, patient s were divided in two groups: group 1 with myopia less than or equal to 6 D (n = 28), group 2 with myopia more than 6 D (n = 20). Examination of UVA a nd CVA were performed preoperatively and on days 3, 7 as well as 1 month, 3 and 6 months postoperatively. Results On day 3 after surgery UVA was 0.43 +/- 0.21 for group 1 with myopi a less than or equal to 6 D, and 0.36 +/- 0.14 for group 2 with myopia more than 6 D. The UVA was stable after 3 months (0.92 +/- 0.29 and 0.66 +/- 0. 20, respectively), the CVA was stable after 1 month (1.04 +/- 0.18 and 0.86 +/- 0.19, respectively). After surgery, the UVA increased by + 0.73 +/- 0. 25, whereas the CVA increased by + 0.05 +/- 0.10 for the whole group. The d ifference comparing pre- and postoperative UVA was significantly higher in group1 (0.81 +/- 0.22) than in group 2 (0.60 +/- 0.26) (p = 0.002). However , postoperative CVA values were not significantly different from preoperati ve values in both groups after 6 months (p = 0.3). Conclusion Useful uncorrected visual acuity is normally achieved at day 3 a fter PRK in eyes with mild to moderate myopia. With higher degrees of myopi a the uncorrected visual acuity does increase slower towards a lower level. One of the reasons for this phenomenon might be a significant regression o f the refractive effects during the first half year after surgery.