Purpose: To prospectively evaluate the safety, efficacy, and visual performance of excimer laser enhancement following photoastigmatic refractive keratectomy (PARK) with the Summit Apex Plus.
Setting: Stanford University School of Medicine Eye Laser Clinic, Stanford, California, USA.
Methods: As part of a Food and Drug Administration clinical trial, 93 eyes of 56 patients with a mean spherical equivalent (SE) of -4.98 diopters (D) +/- 1.80 (SD) (range -1.75 to -8.50 D) had PARK for compound myopic astigmatism using the Summit Apex Plus excimer laser and a poly(methyl methacrylate) erodible mask. Seventeen eyes with a mean SE of -2.08 +/- 0.76 D required excimer laser refractive keratectomy for residual spherical myopia or compound myopic astigmatism. Patients were prospectively followed 1, 3, 6, 9, and 12+ months after the enhancement procedure. Primary outcome variables included uncorrected visual acuity (UCVA), refraction, vector analysis, best spectacle-corrected visual acuity (BSCVA) under standard ambient conditions (photopic, scotopic, and glare), corneal clarity, and contrast sensitivity function curve under photopic and scotopic conditions.
Results: At the last postoperative visit, the mean sphere had been corrected 82% to a residual of -0.29 +/- 1.23 D and mean SE had been corrected 65% to a residual of -0.74 +/- 1.27 D. Eighty-two percent of eyes were within +/-1.0 D of attempted correction. Eighty-eight percent had a UCVA of 20/40 or better. Vector analysis demonstrated a difference vector of within +/-1.0 D in 75% of eyes that had PARK retreatment. There was no significant loss in the contrast sensitivity curve. Late regression associated with corneal haze and loss of BSCVA occurred in 2 eyes (11.7%).
Conclusions: Retreatment following PARK for compound myopic astigmatism results in effective reduction in residual spherical myopia and compound myopic astigmatism. An improvement in UCVA without loss of contrast sensitivity can be expected in most eyes. However, regression, corneal haze, and loss of BSCVA may occur. Further studies are indicated to predict risk factors for these complications.