Comparison of the Central and Peripheral Corneal Stromal Demarcation Line Depth in Conventional Versus Accelerated Collagen Cross-Linking

Purpose:To compare the stromal demarcation line depth at the corneal center and its periphery in conventional versus accelerated collagen cross-linking (CXL).Methods:Patients with keratoconus who received either conventional 30-minute CXL with 3.0 mW/cm(2) irradiation intensity (group 1) or accelerated 10-minute CXL with 9.0 mW/cm(2) irradiation intensity (group 2) were included. The stromal demarcation line at the corneal center and 3-mm periphery measured at the first postoperative month using anterior segment optical coherence tomography were compared.Results:Thirty-three patients were included (18 in group 1, 15 in group 2) in this study. The mean demarcation line depth at center was 295 62 m in group 1 and 203 +/- 45 m in group 2 (P < 0.001). The mean depths at 3-mm periphery (nasal, temporal, superior, and inferior) in group 1 were 260 +/- 64 m, 269 +/- 44 m, 232 +/- 46 m, and 242 +/- 66 m, respectively. The corresponding measurements in group 2 were 204 +/- 62 m, 201 +/- 55 m, 196 +/- 68 m, and 189 +/- 53 m. Apart from the superior peripheral cornea (P = 0.064), the demarcation line depth measured at other peripheral regions was deeper in group 1 compared to that of group 2 (P < 0.015). The peripheral demarcation line depth was significantly shallower than observed in the central line depth for group 1 (P = 0.001), but not for group 2 (P = 0.177).Conclusions:The stromal demarcation line depth was shallower after accelerated CXL compared to that of conventional CXL at the corneal center and its periphery. The volume of cross-linked stroma appears to be larger after conventional CXL compared to its accelerated counterparts.