Corneal Haze and Densitometry in Keratoconus after Collagen Cross-Linking by Three Different Protocols

Purpose: To evaluate postoperative corneal haze and corneal densitometry following three different corneal cross-linking (CXL) protocols; standard, accelerated, and trans-epithelial (TE). Methods: The study recniited 104 eyes (53 patients) with progressive keratoconus divided into three groups: Group I were subjected to standard CXL, Group II to TE-CXL, and Group III to accelerated CXL (A-CXL) (10 mW/cm(2) for 9 min). Subjective and objective corneal haze measures were evaluated before and 3, 6, and 12 months post-CXL using slit-lamp biomicroscopy and Pentacam Sheimpflug camera. Results: There was a significant difference in corneal densitometry between the three groups at 3 and 6 months post-CXL (P < 0.0001). By the 12th month, a significant statistical difference was observed only in zones (0-2 mm) and (2-6 mm) in both the anterior and the central layers. In Group I, the densitometry value of the preoperative anterior stromal layer (anterior 120 mu m) was 19.42 +/- 1.81. Then, it peaked at 23.12 +/- 1.21 at 3 months (P < 0.0001), reached 19.82 +/- 1.19 at 6 months (P = 0.007), and decreased to 19.33 +/- 3.23 (P > 0.05) at 12 months. In Group II, the preoperative densitometry value of the anterior layer was 19.41 +/- 1.21, peaked at 19.72 +/- 1.12 at 3 months (P = 0.02), reached 19.04 +/- 1.18 at 6 months (P = 0.052), and increased to 19.13 +/- 1.37 at 12 months (P = 0.84). In Group III, the preoperative densitometry value of the anterior stromal layer was 19.53 +/- 2.23. Then, it peaked at 24.80 +/- 1.08 at 3 months (P < 0.0001), decreased to 21.75 +/- 1.11 at 6 months (P < 0.0001), and reached 19.77 +/- 2.26 at 12 months (P = 0.047). There was no significant correlation between the visual acuity changes and the total conical densitometry. Conclusion: The TE-CXL group showed a better and earlier recovery from the haze, while the A-CXL group showed a delay in recovering and persistent increased corneal densitometry, mainly in the anterior 120 mu.