Revisiting corneal collagen crossliniking (CXL) safety: Evaluation of the effect of ultraviolet‐A (UVA) radiation on the retina with multifocal electroretinogram (mf‐ERG) and optical coherence tomography (OCT)

Purpose The evaluation of the effect of UVA radiation on the photoreceptors after CXL. Methods Seventeen eyes of 17 patients with keratoconus (n=15), pellucid marginal degeneration (n=1) and post‐LASIK ectasia (n=1), underwent CXL (Dresden protocol). The patients were examined preoperatively, at 2 and 6 weeks postoperatively with mf‐ERG and OCT. The P1 amplitude of the photoreceptor response was documented in 4 concentric rings, with ring 1 (R1) representing the foveal response and rings 2–4 (R2‐R4) corresponding to the successive annuli of stimulation. Uncorrected (UDVA) and corrected distance visual acuity (CDVA), corneal densitometry and central retinal thickness were also recorded. Results The preoperative mean values of P1 amplitudes for the 4 rings were R1=109.96±28.96 nV/deg2, R2=49.8±14.46, R3=29.85±8.9 and R4=19.33±6.3. At 2 weeks after CXL these values were R1=77.54±24.47, R2=36.55±12.53, R3=21.53±7.71 and R4=15.3±6.13, showing a statistically significant reduction for all rings (P.05). Corneal densitometry increased to statistically significant level at 2 (P