Release of Calcitonin Gene-Related Peptide in Tears After Excimer Laser Photorefractive Keratectomy

BACKGROUND: Sensory nerves known to affect corneal healing are damaged to a variable degree after photorefractive keratectomy (PRK). To search for nerve-bound factors involved in corneal healing, we monitored tear fluid calcitonin gene-related peptide (CGRP) levels of six human eyes undergoing PRK. METHODS: CGRP concentrations were determined using an immunoassay. RESULTS: Normal human tear fluid contains CGRP. The mean CGRP concentration was slightly increased postoperatively, despite a marked tear fluid hypersecretion. Consequently, an almost ten-fold increase in release of CGRP in tears was observed on days 1 and 2 after PRK. Values measured on day 7 had returned to a normal level. CONCLUSION: The observed postoperative increase in release of CGRP in tears may have an impact on the healing of PRK wounds. Extensive neural damage following deep photoablations may impair healing and should probably be avoided.