Hyperopic photorefractive keratectomy with the erodible mask and Axicon system: Two year follow-up

Purpose: To evaluate efficacy and long-term stability of hyperopic photoref ractive keratectomy (H-PRK) using the erodible mask and Axicon system. Setting: Department of Ophthalmology, St. Thomas' Hospital, London, England . Methods: Forty-three patients (43 eyes), with a mean preoperative refractio n (spherical equivalent) of +4.54 diopters (D) (range +1.75 to +7.50 D), we re treated using an Apex Plus(R) excimer laser (Summit Technology). This us es an erodible mask to ablate a 6.50 mm diameter hyperopic correction and a n Axicon to fashion a 1.50 mm blend zone around the correction. The overall ablation diameter was 9.50 mm. Follow-up was 2 years. Results: At 2 years, the mean manifest refraction was +0.16 D (range +4.125 to -4.000 D), with the induced correction appearing stable after 9 months. Based on the Munnerlyn algorithm, predictability was acceptable for correc tions up to +4.50 D, with 68% of eyes within +/-1.00 D of the predicted cor rection. It was poorer for +6.00 D corrections, with 33% of eyes within +/- 1.00 D of that expected. Patient satisfaction was high. Forty eyes (93%) ha d an improvement in uncorrected near visual acuity and 37 (86%), an improve ment in uncorrected distance acuity. A peripheral ring of haze. 6.5 mm in d iameter, appeared in all eyes 1 month postoperatively. Its intensity was ma ximal at 3 to 9 months and then diminished over time. There were no signifi cant differences in measurements of the central corneal transparency at 12 and 24 months and those preoperatively. Measurements of flicker contrast se nsitivity, forward light scatter (glare), and scotopic halos showed no sign ificant differences between preoperative values and those measured after 6 months. Conclusions: Achieved H-PRK corrections with the erodible mask and Axicon s ystem agreed closely with the Munnerlyn algorithm, with refractive stabilit y after 9 months. Predictability was acceptable for corrections up to +4.50 D. Axial corneal transparency was not compromised and visual performance, in terms of best spectacle-corrected visual acuity, forward light scatter, and night halos, was not impaired. (C) Cataract Refract Surg 2000; 26:524-5 35 (C) 2000 ASCRS and ESCRS.