Effects of benoxinate hydrochloride 0.4% on the morphological appearance of the cornea using confocal microscopy

PURPOSE: To investigate whether benoxinate hydrochloride 0.4% used to make confocal microscopy more comfortable alters the morphology of the cornea as viewed with the confocal microscope. METHODS: Confocal microscopy was performed on both eyes of 10 subjects prior to instillation of either topical anaesthetic or non-preserved sterile saline, on two randomly ordered occasions. Images of all corneal layers were analysed quantitatively and qualitatively in a masked fashion. RESULTS: The images were similar in appearance in 5/10 subjects, there was greater clarity when anaesthetic was instilled in 4/10 subjects, and in the remaining subject there was greater clarity when saline was used. Anaesthetic had no influence on anterior keratocyte density (AKD), posterior keratocyte density (PKD) or endothelial cell density (ECD). CONCLUSIONS: Local anaesthetic does not affect corneal morphology as imaged using the confocal microscope. However, failure to use anaesthetic may lead to a degradation of image quality due to patient discomfort and excessive eye movements