Comparison of the Central and Peripheral Corneal Stromal Demarcation Line Depth in Conventional Versus Accelerated...

To compare the stromal demarcation line depth at the corneal center and its periphery in conventional versus accelerated collagen cross-linking (CXL).

Patients with keratoconus who received either conventional 30-minute CXL with 3.0 mW/cm² irradiation intensity (group 1) or accelerated 10-minute CXL with 9.0 mW/cm² 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.

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 μm in group 1 and 203 ± 45 μm in group 2 (P < 0.001). The mean depths at 3-mm periphery (nasal, temporal, superior, and inferior) in group 1 were 260 ± 64 μm, 269 ± 44 μm, 232 ± 46 μm, and 242 ± 66 μm, respectively. The corresponding measurements in group 2 were 204 ± 62 μm, 201 ± 55 μm, 196 ± 68 μm, and 189 ± 53 μm. 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).

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.