Authors: Hou Jie, Wang Yan, Lei Yulin, Zheng Xiuyun, Zhang Ying
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Corneal epithelial remodeling will happen after laser refractive surgery, But there have been few studies to evaluate the changes of the corneal epithelial thickness after integrated transepithelial photorefractive keratectomy (TransPRK).
This study was to evaluate the changes in epithelial thickness profile within the optical zone and its related factors following TransPRK for myopia.
In this retrospective non-randomized controlled study, forty-three patients (43 eyes) who underwent TransPRK with the spherical equivalent refraction -1.25 to -6.25 D from August 2014 to May 2015 in Jinan Mingshui Eye Hospital were included under the informed consent.Epithelial thickness was measured using spectral-domain optical coherence tomography in different corneal zones (central, 2 mm; paracentral, 2-5 mm, and mid-peripheral, 5-6 mm) preoperatively at 1 week and 1, 3, and 6 months postoperatively.Correlations between epithelial thickness changes and the amount of correction, optical zone, and Q-value changes (ΔQ) were analyzed 6 months postoperatively.
The mean epithelial thickness in the central zone were (53.97±4.33), (51.03±4.11), (55.14±5.46) and (56.68±5.09)μm at 1 week, 1 month, 3 months and 6 months after surgery, respectively.The epithelium were thicker at 3 months and 6 months after surgery compared to preoperative measurements ([52.37±3.42]μm), with significant differences between them (both at P<0.05). Compared to preoperative values, the epithelial thickness at 6 months after surgery was (3.69±4.23), (5.19±3.88) and (6.23±3.91)μm thicker in the center, paracenter, and mid-periphery zone, respectively, with significant differences between them (all at P<0.01). Epithelial thickness was positively correlated with programmed spherial equivalent correction and ΔQ (all at P<0.05). A significant positive relationship was observed between epithelial thickening and ablation depth paracentrally and mid-peripherally(r=0.380, 0.383; both at P<0.05). Significantly negative relationships were observed between epithelial thickening and optical zone at the center, paracenter, and mid-periphery, respectively(r=0.405, 0.485, 0.384; all at P<0.05). No correlation between epithelial thickness change and ablation depth at the central zone was detected (P>0.05).
The epithelial thickness shows a lenticular change with more thickening mid-Peripherally after TransPRK, which results in increased oblateness postoperatively.Epithelial remodeling may modify the profile after surface ablation.