Corneal morphology and sensitivity changes induced by the long-term application of topical prostaglandin analogs

Abstract

Objective To evaluate the corneal morphology and corneal mechanical sensitivity in patients under long-term prostaglandin analog treatment.Methods A cross-sectional case-control study was performed in the Eye and ENT Hospital of Fudan University from August 2011 to April 2012.A total of 20 patients with bilateral primary open-angle glaucoma were enrolled,including 10 patients treated with prostaglandin eye drops for at least one year with an unchanged prescription during the final 6 months (group A),and 10 untreated patients (group B).Corneal sensitivity was assessed using the Cochet & Bonnet esthesiometer.Corneal morphology was examined with an in vivo confocal microscope.A two-eye design model was used to evaluate the differences between the two groups.A Spearman correlation coefficient was used to analyze the relationship between corneal sensitivity and corneal subbasal cells.Results The corneal basal epithelial cell density of group A was significantly higher than that of group B (7 009±638 cells/mm2 vs.6 745±482 cells/mm2; F=5.22,P＜0.05).Results were similar for the tortuosity of corneal subbasal nerves (1.71±0.46 vs.1.42±0.43;F=7.29,P＜0.05) and the grade for activated keratocytes (2.35±0.81 vs.1.25±0.44; F=59.67,P＜0.01).In contrast,the branches of the corneal subbasal nerves (17.44±2.56 mm/nm2 vs.19.54±5.02 mm/mm2;F=8.22,P＜0.05) and corneal sensitivity (54.25±6.74 mm vs.59.50±1.54 mm; F=12.08,P＜0.01) were significantly reduced in group A.The corneal endothelium did not present any morphological abnormalities.The reduced corneal sensitivity positively correlated with the density of the corneal subbasal nerves (r=0.379,P＜0.05).No correlations were found between corneal sensitivity and other factors such as tortuosity,reflectivity of subbasal nerves,the density of Langerhans ceils or inflammatory cells.Conclusion Significant morphological alterations in the cornea were found in glaucomatous patients with chronic prostaglandin analog treatment,except for endothelium cells.Corneal sensitivity was reduced,which correlated with a decreased density in corneal subbasal nerves. Key words: Microscopy,confocal; Preservatives,pharmaceutical; Glaucoma; Comea