Visual, refractive and topographic 3-year effectiveness of the modifiedcretan protocol in treatment of progressive keratoconus

Visual, Refractive and Topographic 3-Year Effectiveness of The Modified Cretan Protocol In Treatment Of Progressive Keratoconus Purpose: To compare the 3-year refractive, visual, topographical and aberometric results of accelerated corneal collagen cross-linking (CXL) treatment after mechanical epithelial debridement and transepithelial phototherapeutic keratectomy (PTK) epithelial ablation in patients with progressive keratoconus (CC). Methods: 92 mechanical epithelial debridement + CXL (Group-1), 59 PTK epithelial ablation + CXL (Group-2) patients were included in this retrospective study. Eyes that had accelerated CXL after mechanical (Group-1) or transepithelial PTK (Group-2) epithelial removal were evaluated preoperatively and 6, 12, 24, and 36 months postoperatively. The uncorrected (UDVA) and best corrected distance visual acuitie (BCVA) levels, spherical equivalent (SE), manifest astigmatism, and corneal tomographic and aberrometric parameters were assessed. Results: 151 eyes of 110 consecutive CC patients were included in this study; In group-1, 92 eyes of 70 patients and 59 eyes of 40 patients in group-2 were evaluated. Preoperative UDVA, BCVA, SE, refractive astigmatism, keratometry (K-1, K-2), maksimum K (Kmaks), K-mean values were similar between the groupswithout any significant difference (p>0.05). In both groups the increase in the mean UDVA and BCVA were found statistically significant at 36 months postoperatively. (group-1; p=0.002, p=0.002, respectively; group-2; p<0.001, p=0.003 respectively). The increase in UCVA at 3 years was found to be significantly higher in group-2 than in group-1 (p = 0.018). In both groups, the decrease in refractive astigmatism values were statistically significant (Group-1, p=0.013; Group-2, p <0.001, respectively) and there was no significant difference between the groups at the end of 36 months. (p=0.094) K1, K2, K maks and K-mean decreased in both groups at the end of 36 months compared to baseline and the decrease in group-2 was significantly higher (for all values, p<0.05). Coma and spherical aberation, which were similar for both groups at the beginning, were significantly lower in group-2 at the end of 36 months (Coma p <0.001; Spherical v aberration p <0.001). Another objective parameter, Point Spread Function (PSF) was significantly higher in group-2 when compared to group-1 at 36-months follow-up. (p<0.001) No complications were observed in either group. Conclusions: In the early and late periods visual, refractive, topographic and aberrometric outcomes of transepithelial PTK ablation were better than those of mechanical epithelium removal associated with accelerated CXL in patients with keratoconus. The choice of PTK method to remove the corneal epithelium is effective and reliable when applying CXL treatment in progressive keratoconus patients. Key Words: Phototherapeutic keratectomy, Collagen cross-linking, Keratoconus