Intraoperative corneal thickness measurement by optical coherence tomography in keratoconic patients undergoing corneal collagen cross-linking

Purpose: To assess intraoperative variation of corneal thinnest point in keratoconic patients undergoing riboflavin/ultraviolet type A (UV-A) cross-linking treatment using noncontact time-domain optical pachymetry. • Design: Prospective, noncomparative interventional study. • Methods: Ten patients underwent epithelium-off riboflavin/UV-A corneal cross-linking at Siena University Hospital; corneal thickness was measured using optical coherence tomography at the following times: preoperatively with epithelium on; after removal of a 9-mm-diameter disc of epithelium; immediately after instillation of 2 drops of riboflavin 0.1%-dextran T 500 20% solution; after repeated instillation of riboflavin 0.1%-dextran T 500 20% solution every 2.5 minutes, at 10, 20, and 30 minutes of soaking time; at the end of the treatment after 30 minutes of UV-A exposure with the riboflavin biofilm in situ; and finally after washing the riboflavin biofilm. • Results: The most significant decrease in thinnest point measurement was detected meanly in the first 10 minutes of corneal soaking. In this interval, the minimum recommended in various studies, a mean reduction of -79.28 μm (-17.61% of initial thinnest point value after removal of the epithelium) was recorded. No adverse events were recorded. • Conclusions: The study demonstrates a statistically significant intraoperative reduction in corneal thinnest point value during epithelium-off cross-linking procedure using standard riboflavin 0.1%-dextran 20% solutions. Intraoperative optical pachymetry evaluation during cross-linking should be recommended before starting UV-A irradiation, and if a thickness under 380 μm is detected, the stroma should be reexpanded with hypotonic dextran-free riboflavin solutions.