Impact of general anesthesia on feline aqueous tear production and the feline corneal epithelium

ObjectivesThe aim of the present study was to identify the prevalence of corneal injury in cats undergoing general anesthesia (GA) while receiving prophylactic ocular lubrication, identify risk factors for corneal injury and quantify the effect of GA on tear production in cats.MethodsA total of 42 cats undergoing GA for non-ophthalmic procedures were included. Before GA, an ocular examination including a Schirmer tear test-1 (STT-1) and fluorescein stain (FS) was performed. Prophylactic lubrication was administered at the time of anesthetic induction and repeated every 15 mins until extubation. At 1 h after extubation, STT-1 and FS were performed and repeated hourly for 4 h. A Shapiro-Wilk test and paired <i>t</i>-test compared STT-1 results before and after GA. Logistic regression was used to analyze corneal injury and possible risk factors for corneal injury.ResultsNo cats developed FS uptake consistent with corneal ulceration. In total, 14 cats and 23 (27.4%) eyes developed corneal erosion at all time points. There was a significant decrease in tear production at all four time points after GA. Pre-medication opioid choice and corneal exposure were identified as significant risk factors for corneal injury.Conclusions and relevanceCorneal ulceration did not develop after GA in this study. There was a significant decrease in tear production in cats for at least 4 h after GA. Cats appear to have a higher prevalence of corneal injury after GA compared with dogs. Frequent eye lubrication is recommended for feline patients during and after GA.