Photorefractive Keratectomy in the Management of High Myopic Defects . Tissue–Saving vs Planoscan

Abstract

Purpose: : To evaluate the efficacy, safety and predictability of photorefractive keratectomy (PRK) with the Technolas laser 217 z100 Baush&Lomb (algorithm Zyoptix Tissue Saving) in the treatment of high myopic refractive defects in patients with thin corneas.

Methods: : The authors report the results during a 10 month follow–up period of 16 eyes treated with the Zyoptix Tissue Saving algorithm for high myopic refractive defects with and without astigmatism in patients with thin corneas and a scotopic pupillary diameter greater than 6.5. For each patient the pre– and postoperative Uncorrected Visual Acuity (UCVA) and Best–Corrected Visual Acuity (BCVA) was graded after 1, 3, 6, and 10 months.

Results: : The mean age of the patients was 35.9 (range 22–54). The treated eyes were 28. Average saving of corneal tissue was 24% with very good refractive results compared to Planoscan treatment. This algorithm reduced the superior order aberrations by means of a laser ablation profile based on Hartmann–Shack Zywave aberrometry and the Munnerlin formula consenting an ablation of a wider optic zone with saving of corneal tissue. The treatment considered the possibility of a different typology of ablation according to the characteristics of each patient; Planoscan Zyoptix personalized Tissue Saving. The uncorrected post–operative visual acuity in each patient was never less than pre–operative values. In the first month after treatment we found a hypermetropic shift varying from + 0.75 to + 2 diopters (D) in the patients with myopia and myopic astigmatism. The patients had been informed about this transitory hypercorrections and the possible risks and benefits of treatment.

Conclusions: : The authors believe that photorefractive keratectomy is a valid approach to refractive surgery in patients with high refractive errors and thin corneas. However, further study, with a greater number of patients and longer follow–up, is necessary to confirm these results.

Keywords: cornea: epithelium • refractive surgery: PRK • refractive surgery: PRK