Epithelial and Stromal Remodeling After Corneal Collagen Cross-linking Evaluated by Spectral-Domain OCT

PURPOSE: To evaluate changes in corneal epithelial and stromal thickness after corneal collagen cross-linking (CXL) in eyes with keratoconus and postoperative corneal ectasia using spectral-domain optical coherence tomography (SD-OCT). METHODS: Anterior segment SD-OCT (RTVue-100; Optovue, Inc., Fremont, CA) was used to compare regional corneal epithelial and stromal thickness in eyes with keratoconus and ectasia before CXL and 1 and 3 months after CXL. The anterior surface of the cornea, epithelium-Bowman's layer interface, and posterior reflective surface were used as anatomical landmarks to measure epithelial and stromal thickness, respectively. Regional thickness was assessed centrally and at 21 points 0.5 mm apart across the central 6 mm of the corneal vertex in the horizontal and vertical meridians. RESULTS: Thirty-one eyes from 30 patients were evaluated, including 17 eyes (17 patients) with keratoconus and 14 eyes (13 patients) with ectasia. Preoperatively, a highly irregular epithelial thickness profile and distribution was observed in both groups. After CXL, epithelial thickness was significantly thinner 2.5 and 2 mm below and 1.5 mm above the corneal apex (49.26 +/- 5.69 mu m; range: 43 to 62 mu m), and 2.5 and 1 mm nasal and 2 mm temporal to the corneal apex (46.66 +/- 4.53 mu m; range: 39 to 57 mu m) compared to preoperative values (P < .05 for all measurements). Epithelial thickness standard deviations were significantly lower (by 3 to 6 mu m) 3 months after CXL, compared to ranges before CXL in both the vertical and horizontal meridians for keratoconus and ectasia (P = .048). No significant differences were found between epithelial remodeling in keratoconus and corneal ectasia (P = .98). No significant or consistent stromal changes were found for either group. CONCLUSIONS: Significant epithelial remodeling occurs after CXL in eyes with keratoconus and corneal ectasia, creating a similar, more regularized thickness profile in all meridians in the early postoperative period. This pattern of remodeling may facilitate interpretation of corneal curvature and thickness changes after CXL and may be related to visual acuity after CXL.