Role of corneal collagen cross-linking in pseudophakic bullous keratopathy: a clinicopathological study.

OBJECTIVE To evaluate the clinical and histopathologic changes induced by collagen cross-linking (CXL) in pseudophakic bullous keratopathy (PBK). DESIGN Randomized, prospective, interventional study. PARTICIPANTS Twenty-four patients with PBK were included in the study. METHODS Twenty-four patients with PBK underwent CXL followed by keratoplasty at 1 or 3 months. Twelve patients underwent penetrating keratoplasty 1 month after CXL (group A) and the remaining 12 patients underwent penetrating keratoplasty 3 months after CXL (group B). The main outcome measures were assessed at 1 week and 1 month for all patients and at 3 months for 12 patients only. The corneal buttons underwent histopathologic and immunofluorescence evaluation. MAIN OUTCOME MEASURES Visual acuity, ocular discomfort (tearing, redness, pain), corneal haze, central corneal thickness, histopathologic evaluation, and immunofluorescent microscopy. RESULTS Mean visual acuity showed a significant improvement after CXL, from 1.925 ± 0.173 before surgery to 1.75±0.296 at 1 month after surgery (P = 0.010), but deteriorated to 1.81 ± 0.23 at 3 months. Symptomatic relief after CXL was at a maximum at 1 month, with a worsening trend at 3 months. Eighteen patients showed a reduction in corneal haze 1 month after CXL. The effect was maintained in 9 of 12 patients at 3 months. The mean central corneal thickness decreased significantly from 846.46 ± 88.741 to 781.0 ± 98.788 μm at 1 month (P<0.01) after CXL, but increased to 805.08±136.06 μm at 3 months. Immunofluorescence microscopy revealed anterior stromal compaction in 7 of 12 patients (58.3%) in group A and in 5 of 12 patients (41.6%) in group B. Staining of keratocyte nuclei with 4',6-diaminido-2-phenylindole dihydrochloride (Molecular Probes, Carlsband, CA) revealed a relative uniform distribution throughout the stroma. CONCLUSIONS Collagen cross-linking causes symptomatic relief and a decrease in central corneal thickness and anterior stromal compaction in PBK. However, the effect decreases with time and depends on disease severity.