Photorefractive keratectomy in eyes with atypical topography

Abstract

Laser correction of refractive errors is one of the most effective surgical procedures today. Even so, the selection of patients who will have the outcomes they expect remains a major challenge. Corneal ectasia, a frustrating problem that can occur naturally with diseases such as keratoconus, has also been reported after refractive surgery. This review addresses the issues surrounding the use of surface refractive surgery in patients who may have atypical topography, which is a risk factor for ectasia. At present, available tests for predicting future corneal stability can give false positives and false negatives. Although the technology for treating irregular corneal astigmatism has improved, results in eyes with irregular astigmatism are less predictable than in eyes with regular astigmatism, even when wavefront- and topography-driven treatments are used. An increased risk for corneal instability may be associated with laser vision correction (LVC), although instability is generally thought to be less of a risk with surface ablation or photorefractive keratectomy than with laser in situ keratomileusis. Surface LVC has shown good success in improving uncorrected distance visual acuity with a relatively low rate of complications, even in eyes with topographic irregularities.

Reasons for Not Performing LASIK in Refractive Surgery Candidates in Yemen

“…This is similar to a study in India, which cited the same most common reasons for rejection of LASIK (20), and Table III compares their results with this study. Patients with thin corneas and normal corneal topography and refraction less than -5.00 D of myopia or thick cornea with mild suspicious corneal topographies were advised to have PRK (29). Patients with thin corneas and higher refractive errors and cases with >5% Klyce-Maeda KCI using the TMS-2 regardless of their refractive error were advised to have phakic intraocular lens implantation (30).…”

Reasons for not performing keratorefractive surgery in patients seeking refractive surgery in a hospital-based cohort in "Yemen"

“…Pachymetry is an important test and is an indicator of corneal health, but varies widely in different ethnic populations 22. Patients with thin corneas, normal corneal topography and refraction less than -5.00 Diopters of myopia or thick cornea with mild atypical corneal topographies were advised to have PRK 23. Patients with thin corneas and higher refractive errors and cases with >5% Klyce-Maeda KCI using the TMS-2, regardless of their refractive error, were advised to have phakic intraocular lens implantation 24.…”

PRK em olhos com topografia atípica e pentacam normal

“…A study by Silva Filho et al reported that preoperative topographic irregularities may predict the loss of corrected visual acuity in the postoperative period (20) . On the other hand, refractive surgery with high success rates and minimal adverse effects in patients with atypical or irregular topography has already been described in the literature (21,22) . A recent study reports the use of LASIK in eyes with suspected keratoconus on topography but confirmed as normal through epithelial thickness mapping with digital high frequency ultrasound (Artemis VHF, ArcScan Inc.); the patients were followed up for one year without developing ectasia (23) .…”