Effectiveness of Nerve growth factor treatment on corneal innervation following photorefractive keratectomy

Abstract

Abstract: : Purpose:We investigated the effectiveness of Nerve growth factor (NGF) eye drops on corneal reinnervation after photorefractive keratectomy (PRK) in humans Methods:Twenty eyes (10 patients) who had undergone standard flying–spot PRK to correct myopia from –7.0 D to –10.0 D were evaluated. Patients received either NGF eye drops (100 ug/ml in BSS solution) or BSS alone, according to a double masked randomized study. Patients received TID eye drops regimen for three months. Clinical signs and symptoms, and additional tests including corneal confocal microscopy and tear film evaluation were performed at baseline, at day 1, 2, weekly for 1 month and monthly up to 3 months after discontinuation of treatment. Central corneas were scanned throughout their full thicknesses by confocal microscopy before and at follow–up visits after PRK by means of a scanning slit confocal microscope (Confoscan 3.0, Nidek Technologies, Italy), equipped with an Achroplan (Zeiss, Germany) non–applanating 40X immersion objective lens providing 1000X magnification. Nerve fibers were identified as bright, well–defined, linear structures, and the presence of visible fibers was graded as average from four to eight scans per eye per visit in order to investigate the distribution and morphology of corneal regenerating nerves in the sub–basal and sub–epithelial region. Non parametric statistical analysis was performed at each time point of the follow up. Results:A significant improvement of corneal reinnervation score for both subepithelial and subbasal fibers was detected as early as 21 days in the NGF treated eyes, and persisted until 1 months of follow up after discontinuation of treatment (p<0.05). A significant improvement of Schirmer test values was observed at day 14 (28.2±4.8 vs. 23.1±5.2 mm/5min.; p<0.05) and 21 23.6±6.1 vs. 17.1±5.9 mm/5min.; p<0.05) following surgery. No significant differences were observed in signs and symptoms at any time point of the study. None of the patients presented complications, side effects or wound–healing anomalies during the entire follow–up. Conclusions:NGF induces a prompt recovery of corneal nerves associated with an increase of tear production as early as 2 weeks following PRK.

Keywords: cornea: clinical science • nerve fiber layer • cornea: clinical science