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Introduction
Among the refractive surgery treatments, laser-mediated corneal epithelial removal, known as transepithelial photorefractive keratectomy (TransPRK), was performed in the 1990s (1). Since then, the epithelium has been removed using excimer laser photo therapeutic keratectomy followed by refractive ablation of the stroma (two-step approach). The two-step technique was not widely used due to the long intervention time, the uneven epithelial removal and treatment inaccuracy (2,3).
More recently, with the development of the newer generation of faster lasers and improved ablation algorithms, a single-step treatment TransPRK was developed on the Schwind Amaris platform (Schwind eye-tech-solutions GmbH). This one-step approach allows for simultaneous ablation of the epithelium and the stroma with little trauma to the eye. Studies using high-frequency digital ultrasonography have demonstrated that the corneal epithelium does not have a uniform thickness (4). The single-step ablation profile was generated from the literature targets of 55 µm centrally and 65 µm peripherally, using theoretical simulations for the scope of ablation optical zone (OZ) (2).
Several studies have determined increased higher-order wavefront aberrations (HOAs) after corneal refractive surgery, including PRK (5–7). However, to date, only a few studies have reported on HOAs associated with single-step TransPRK in myopia. Adib-Moghaddam et al (8) indicated that corneal spherical, coma and trefoil aberrations were significantly improved at 18 months after single-step TransPRK. Other studies comparing TransPRK with alcohol-assisted PRK indicated that the differences between the pre- and post-operative HOAs of the same type of surgery were not significant (9,10). The present study evaluated the changes of corneal HOAs after TransPRK in myopia and the association between post-operative changes in HOAs and pre-operative mean spherical equivalent refraction (MSER), astigmatism and central corneal ablation depth (CCAD). HOAs in the eye are closely linked to visual quality after refractive surgery. The present study investigated the changes in post-operative corneal HOAs and the correlation between changes in HOA and the pre-operative diopter (D). It is important to predict post-operative corneal HOA changes and visual quality.
Materials and methods
Patient population and study design
The present retrospective study included 80 eyes of 80 patients with myopia who underwent single-step TransPRK between June 2015 and July 2017 at the Department of Ophthalmology of Peking University International Hospital (Beijing, China).
The inclusion criteria were as follows: Age >18...