Di Palma, Cristina (2024) Lesioni corneali e valutazione quali-quantitativa del film lacrimale del cane in corso di anestesia generale: confronto tra due diversi trattamenti topici di protezione corneale. [Tesi di dottorato]

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Background: Corneal abrasions are the most common ocular complication in humans during general anesthesia (GA) for non-ophthalmic surgery. Anesthesia induced corneal lesions have also been reported in dogs (Dawson & Sanchez, 2016), cats (Madruga et al., 2023) and horses (Scarabelli et al., 2018). Objective: To determinate the incidence of corneal lesions and evaluate the quality and production rate of the precorneal tear film in dogs receiving two different ocular treatments during general anesthesia (GA) for non-ophthalmic surgery: 0,25% hyaluronic acid lubricant drops or topical 2% pilocarpine instillation. Study design: blinded, prospective, randomized, clinical trial. Materials and Methods: An ophthalmological examination (slit-lamp biomicroscopy, Schirmer Tear Test-1 (STT-1), tear film BUT, fluorescein and lissamine green staining, tear osmolarity using I-Pen osmometer) was performed before preanesthetic medication in dogs undergoing elective surgery. Only dogs without a pre-existing eye disease were included in the study. Dogs were randomly allocated to receive topical ocular treatment during GA, 0,25% hyaluronic acid (GH) lubricants or 2% pilocarpine (GP). STT-1 was performed immediately after intubation (T-int) and every hour afterwards, until the end of anesthesia, just before instillation of one drop of the assigned treatment according to randomization (T-1h, T-2h). The same ophthalmologist, blind to the treatment, performed the complete ophthalmological examination after extubation (T-est) and 24 hours after surgery (T-24h). Results: Thirty dogs (60 eyes) were enrolled in the study. STT-1 values showed an immediate decrease in both groups immediately after intubation, but group P showed a rapid increase in tear production immediately after topical administration with a significant difference between the groups at T-1h, T-2h and T-est. No statistically significant differences were observed between the two groups for the other values (BUT - IOP - OSM). There was no corneal ulceration in either group, while 11.7% of eyes presented superficial de-epithelialization at T-est and 15% at T.24h. There were no statistically significant differences between the two groups regarding the presence of corneal abrasions. Conclusions: The tested topical eye treatments prevent corneal ulcers. According to medical literature, several prophylactic strategies can prevent exposure keratopathy by using lubricant eye drop formulations during GA (Grixti et al., 2013). The new pilocarpine protocol tested in our study increased the tear production but did not eliminate corneal complications in GA. In our study, tear osmolarity did not change after the exposure keratopathy associated with GA.

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