The persistence of pain relief after corneal crosslinking in mild bullous keratopathy eyes

Abstract

Purpose : Crosslinking (CXL) corneal collagen to edematous corneal stroma effectively reduces central corneal thickness and relieves pain. The prospective observational case study was to examine the persistence of pain relief of bullous keratopathy (BK) up to 1 year after CXL treatment and to observe the stroma using in vivo confocal microscopy.

Methods : Eleven eyes from 11 patients who underwent consecutive CXL treatments for BK between September 2011 and December 2013 were followed up over the course of one year. The mean patient age was 78.6 ±12.0 (SD) years. The best-corrected visual acuity (BCVA), intraocular pressure (IOP), and corneal thickness were examined before treatment, as well as 1 week and 1, 3, 6, and 12 months after treatment. The intensity and frequency of pain were scaled from 0 (minimum) to 10 (maximum). At 12 months after CXL treatment, the corneal stroma at depths of 100 and 200 μm was observed via confocal microscopy, and the densities of keratocytes (cell/mm²) and nerve fibers (mm/mm²) were calculated.

Results : The BCVA after treatment did not significantly improve from that before treatment (P=0.996, Kruskal-Wallis test). In the CCT, there was no significant change at any examination point (P=0.52). The mean pain intensity score was 6.27 (range: 0-9) before treatment and significantly decreased after treatment (P<0.01): the score at 12 months was 1.80 (range: 0-6; P<0.01). The mean pain frequency score was 5.45 (range: 0-10) before treatment and significantly decreased after treatment (P<0.05): the score at 12 months was 1.27 (range: 0-5; P<0.01). Confocal microscopy observations showed keratocytes and nerve fibers were rarely observed at 12 months after CXL. At a depth of 100 μm, the gross keratocyte and nerve fiber densities for all images were 5.1 cells/mm² and zero, respectively. At a depth of 200 μm, the gross densities were 2.9 cells/mm² and 0.21 mm/mm², respectively.

Conclusions : CXL effectively relieved the intensity and frequency of BK pain for at least 1 year after treatment. In vivo confocal microscopic observation and a lack of change in CCT demonstrated that the persistence of pain relief was attributable to the inadequate regeneration of nerve fibers in the corneal stroma.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.