Safety and Efficacy of Epithelial Island Crosslinking in Keratoconus with Thinnest Pachymetry Less Than 400µ

Purpose: To evaluate the efficacy and safety of epithelial-island crosslinking (EI-CXL) in keratoconus with corneas thinner than 400 µm.

Methods: Twenty-six patients (30 eyes) underwent EI-CXL (preserving the epithelium over the thinnest area), using standard protocol (3 mW/cm for 30 min). Uncorrected and best spectacle-corrected distance visual acuity (UCDVA, BCDVA), manifest refractive spherical equivalent (SEQ), mean simulated keratometry (Kmean), maximum keratometry (Kmax), and thinnest corneal thickness (TCT) were determined preoperatively and at 1, 3, 6, and 12 months following CXL. Endothelial cell count (ECC) was determined preoperatively and at 6 months. Anterior segment optical coherence tomography (AS-OCT) was done at 1 month to determine the depth of the corneal stromal demarcation line (DL).

Results: After 1 year, mean UCDVA improved from 1.29 preoperatively to 1.17 ( = 0.001) and BCDVA from 0.62 to 0.57 ( = 0.011). Mean manifest SEQ decreased from -7.63 to-7.32D ( = 0.001). Mean Kmean decreased from 54.92 to 54.81D ( = 0.045), and Kmax from 67.60 to 67.42D ( = 0.072), and mean TCT changed minimally from 377.17 to 375.30 µ ( = 0.11). The mean ECC decreased from 2329 to 2268 cells/mm (2.6% decrease, < 0.001). AS-OCT showed a DL in 29 out of 30 eyes at an average depth of 215.9 µ under the spared epithelium, and 299.9 µ in the de-epithelialized cornea.

Conclusion: EI-CXL halted keratoconus progression over a 1-year period. This was associated with statistically significant endothelial loss, but less than seen with conventional epi-off CXL in thinner corneas.