PURPOSE: To determine the effect of patient age, postoperative time, ablation zone diameter and depth, attempted correction, and corneal topography on postoperative corneal epithelial thickness after photorefractive keratectomy (PRK). SETTING: Private clinic and university hospital, Stockholm, Sweden. METHODS: This retrospective, unmasked study comprised 136 myopic patients treated unilaterally with PRK. Seventy eyes had been treated with the Summit excimer laser 27 months +/- 7 (SD) earlier using ablation zone diameters of 4.1 to 5.0 mm. Sixty-six eyes had been treated with the VISX excimer laser 6 +/- 3 months earlier using a 6.0 mm zone diameter. The untreated fellow eyes served as controls. Epithelial thickness was measured at a standardized central corneal area with a modified optical pachymeter, and corneal topography was determined using computerized videokeratoscopy. RESULTS: In the Summit group, the epithelial layer in the PRK eyes was 12.0 microns (21%) thicker than in the control eyes (P < .001; 95% confidence interval [CI] 9.35 to 14.3 microns). This thickness differential correlated significantly with increased ablation depth and attempted correction. In the VISX group, the epithelium in the treated eyes was 7.0 microns (7%) thinner (P = .0009; 95% CI -1.9 to -6.7 microns) and thickness did not correlate with ablation depth or attempted correction. There was no correlation between epithelial hyperplasia and patient age or postoperative follow-up. With the laser groups combined, epithelial hyperplasia was greater with smaller zone sizes and a greater rate of change in power at the edge of the ablation zone. CONCLUSION: The factors associated with an increase in epithelial thickness were small ablation zones, greater attempted corrections, and deeper ablations. Larger, smoother ablation profiles may result in less epithelial hyperplasia.
PURPOSE: To determine the effect of patient age, postoperative time, ablation zone diameter and depth, attempted correction, and corneal topography on postoperative corneal epithelial thickness after photorefractive keratectomy (PRK). SETTING: Private clinic and university hospital, Stockholm, Sweden. METHODS: This retrospective, unmasked study comprised 136 myopic patients treated unilaterally with PRK. Seventy eyes had been treated with the Summit excimer laser 27 months +/- 7 (SD) earlier using ablation zone diameters of 4.1 to 5.0 mm. Sixty-six eyes had been treated with the VISX excimer laser 6 +/- 3 months earlier using a 6.0 mm zone diameter. The untreated fellow eyes served as controls. Epithelial thickness was measured at a standardized central corneal area with a modified optical pachymeter, and corneal topography was determined using computerized videokeratoscopy. RESULTS: In the Summit group, the epithelial layer in the PRK eyes was 12.0 microns (21%) thicker than in the control eyes (P < .001; 95% confidence interval [CI] 9.35 to 14.3 microns). This thickness differential correlated significantly with increased ablation depth and attempted correction. In the VISX group, the epithelium in the treated eyes was 7.0 microns (7%) thinner (P = .0009; 95% CI -1.9 to -6.7 microns) and thickness did not correlate with ablation depth or attempted correction. There was no correlation between epithelial hyperplasia and patient age or postoperative follow-up. With the laser groups combined, epithelial hyperplasia was greater with smaller zone sizes and a greater rate of change in power at the edge of the ablation zone. CONCLUSION: The factors associated with an increase in epithelial thickness were small ablation zones, greater attempted corrections, and deeper ablations. Larger, smoother ablation profiles may result in less epithelial hyperplasia.
Authors: Dan Z Reinstein; Sabong Srivannaboon; Marine Gobbe; Timothy J Archer; Ronald H Silverman; Hugo Sutton; D Jackson Coleman Journal: J Refract Surg Date: 2009-05 Impact factor: 3.573
Authors: Jaganmohan R Jangamreddy; Michel K C Haagdorens; M Mirazul Islam; Philip Lewis; Ayan Samanta; Per Fagerholm; Aneta Liszka; Monika K Ljunggren; Oleksiy Buznyk; Emilio I Alarcon; Nadia Zakaria; Keith M Meek; May Griffith Journal: Acta Biomater Date: 2018-01-31 Impact factor: 8.947