LAUSR

PURPOSE To determine whether corneal cross-linking with individualized fluence ("sub400 protocol") is able to stop keratoconus progression in ultra-thin corneas with 12-month follow-up. DESIGN Retrospective, interventional case series. METHODS Thirty-nine eyes with progressive keratoconus and corneal stromal thicknesses from 214-398 μm at the time of UV-irradiation were enrolled. After epithelium removal, UV-irradiation was performed at 3mW/cm2 with irradiation times individually adapted to stromal thickness. Pre- and postoperative examinations included CDVA, refraction, Scheimpflug and AS-OCT imaging up to 12 months after CXL. Outcome measures were arrest of keratoconus progression at 12-months postoperatively and stromal demarcation line (DL) depth. RESULTS Thirty-five eyes (90%) showed tomographical stability at 12 months after surgery. No eyes showed signs of endothelial decompensation. A significant correlation was found between DL-depth and irradiation time (r=+0.448, p=0.004) but not between DL-depth and change in Kmax (r=-0.215, p=0.189). On average, there was a significant change (p<0.05) in thinnest stromal thickness (-14.5±21.7μm), Kmax (-2.06±3.66D) and densitometry (+2.00±2.07GSU). No significant changes were found in CDVA (p=0.611), sphere (p=0.077) or cylinder (p=0.915). CONCLUSIONS The "sub400" individualized fluence CXL protocol standardizes the treatment in ultra-thin corneas and halted keratoconus progression with a success rate of 90% at 12 months. The sub400 protocol allows for the treatment of corneas as thin as 214μm of corneal stroma, markedly extending treatment range. The demarcation line depth did not predict treatment outcome. Hence, the depth is unlikely related to the extent of CXL-induced corneal stiffening but rather to the extent of CXL-induced microstructural changes and wound healing.