Safety and Efficacy of Epithelial Island Crosslinking in Keratoconus with Thinnest Pachymetry less than 400µ

Abstract

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/cm² 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 (P = 0.001) and BCDVA from 0.62 to 0.57 (P = 0.011). Mean manifest SEQ decreased from -7.63 to-7.32D (P = 0.001). Mean Kmean decreased from 54.92 to 54.81D (P = 0.045), and Kmax from 67.60 to 67.42D (P = 0.072), and mean TCT changed minimally from 377.17 to 375.30 µ (P = 0.11). The mean ECC decreased from 2329 to 2268 cells/mm² (2.6% decrease, P < 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.

Keywords: Customized epithelial debridement; demarcation line; epithelial island crosslinking; keratoconus; pachymetry.

Figure 1

Preoperative tomography with millimeter scale (red circle represents the epithelial Island, blue circle represents the pupillary area)

Figure 2

(a) Figure showing the surgeon's view of the left eye. The epithelial island is slightly below and temporal to the pupil. (b) Figure showing the same eye as Figure 2a, with an overlay (blue circle) indicating the boundaries of the pithelial island, and another (red circle), indicating the peripheral boundary of the debrided epithelium. The area of debrided epithelium is soaked with riboflavin

Figure 3

Bar chart showing depth of demarcation line under epithelialized and non-epithelialized areas

Figure 4

Anterior segment optical coherence tomography showing demarcation line 288 µm under spared epithelium and 380 µm under peripheral cornea