Changes in the Morphology and Function of the Sub-basal Corneal Nerve Plexus after Accelerated Corneal Cross-Linking: A One-Year Follow-Up Study

Observe the recovery of nerve morphology and function in the sub-basal corneal plexus before and one year after accelerated corneal cross-linking surgery. This study included 34 patients (47 eyes) with progressive keratoconus who underwent accelerated corneal cross-linking. Evaluations were performed preoperatively and at 1, 3, 6, and 12 months postoperatively using Pentacam topography, Cochet-Bonnet esthesiometer, and in vivo confocal microscopy. At least 3 in vivo confocal microscopy images from one eye of each keratoconus patient were selected for analysis. The nerve fiber density, nerve branch density, nerve fiber length, and nerve fiber width of the central cornea were quantified using ACCMetrics software. The sub-basal corneal plexus tortuosity was quantified by measuring the amplitude of the curves and the area under the curve formed by the main nerve fiber. Central corneal sensitivity significantly decreased at 1 and 3 months post- accelerated corneal cross-linking (P < 0.001) but returned to preoperative levels by 6 months. No significant sensitivity decreased was noted in superior, nasal, and temporal regions at all follow-up time points. The nerve branch density, nerve fiber length and nerve fiber width were significantly reduced at 1, 3 and 6 months (P ≤0.022) but returned to normal levels at 1 year (P = 0.348, P = 0.087). The nerve fiber density, amplitudes and area under the curves remained significantly reduced at 1 year (P ≤ 0.041). Corneal sensitivity in the central region fully recovered by 6 months post- accelerated corneal cross-linking, while sub-basal corneal plexus recovery was slightly delayed. By 1 year, the nerve fiber density, and nerve tortuosity remained reduced. This indicates the need for ongoing monitoring of sub-basal corneal plexus status to ensure long-term safety.