Abstract
Is it possible to obtain good results in myopia of 2 or fewer diopters (D) with transepithelial photorefractive keratectomy (TransPRK) changing the optical zone and epithelium thickness? We retrospectively analyzed two groups of 296 eyes with a minimum follow-up of 4 months. Group A had 2 or less D, treated with an optical zone (OZ) 0.2 mm bigger than recommended, and a central epithelium thickness of 60 microns, and group B had 2 D to 5 D, with the recommended optical zone, and a 55-micron epithelium ablation at the center. The outcomes were not different between the two myopic ranges; the postop uncorrected distance visual acuity was 20/20 ± 4 in both groups (p = 0.2), which was −0.3 ± 0.8 lines worse than the preoperative corrected distance visual acuity in both groups (p = 0.5). The safety of the treatments resulted in a change of 0.0 ± 0.7 lines in the low myopia group, versus a gain of +0.1 ± 0.8 lines in the moderate myopia group (p = 0.1). The deviation from the intended target was −0.04 ± 0.33 D in the low myopia group and +0.07 ± 0.32 D in the moderate myopia group (p < 0.0001); the postoperative spherical equivalent was 0.00 ± 0.33 D in the low myopia group and +0.10 ± 0.31 D in the moderate myopia group (p < 0.0001). The postop refractive astigmatism was 0.32 ± 0.16 D in both groups (p = 0.5). In conclusion, the refractive and visual outcomes after TransPRK are comparable in low myopia changing the optical zone and epithelium thickness versus moderate myopia with standard optical zone and epithelium thickness.
Highlights
Transepithelial photorefractive keratectomy (TransPRK) using the AMARIS laser platform (Schwind eye-tech-solutions, Kleinostheim, Germany) is a one-step surface ablation consisting of a reverse aspheric photorefractive keratectomy (PRK) followed by a phototherapeutic keratectomy (PTK) to complete the stromal ablation [1,2]
The PTK of the epithelium is standardized by the software of the laser system, with an aspherical profile of 55 μm ablation at the center and 65 μm at the 4 mm periphery [3]
In cases where the epithelium is thicker than the applied epithelial ablation profile, the resulting effective optical zone (OZ) will be reduced
Summary
Transepithelial photorefractive keratectomy (TransPRK) using the AMARIS laser platform (Schwind eye-tech-solutions, Kleinostheim, Germany) is a one-step surface ablation consisting of a reverse aspheric photorefractive keratectomy (PRK) followed by a phototherapeutic keratectomy (PTK) to complete the stromal ablation [1,2]. The PTK of the epithelium is standardized by the software of the laser system, with an aspherical profile of 55 μm ablation at the center and 65 μm at the 4 mm periphery [3]. In that theoretical work [4], the authors described potential refractive deviations and the outcomes if the epithelium is thinner or thicker than that given by the default algorithm of the software, which was 55 μm at the center. In the cases that the actual epithelium was thicker than what is assumed in the model, the effects in the reduction in the achieved OZ (respect to the planned OZ) are smaller for higher refractive corrections or larger OZs. The larger the planned refractive correction, the less of a difference between the planned OZ and achieved OZ, and as with higher corrections or larger OZs, we get deeper ablation depths
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