Retrobulbar neurolytic ethanol injection for the treatment of end-stage canine glaucoma
Enders, Andrew Michael
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Background: Glaucoma is a chronic ocular disease of both dogs and humans that results in blindness and ocular discomfort. Most commonly, end-stage glaucomatous eyes in dogs are enucleated to provide comfort. This intervention requires significant financial investment, general anesthesia, and has a psychological impact on some owners. Retrobulbar neurolytic injections are used in humans to provide immediate and long-acting pain relief, while simultaneously preserving the globe. Objectives: To determine the safety and efficacy of retrobulbar neurolytic ethanol injection in canine eyes with end-stage glaucoma. Animals: 16 client-owned dogs (19 eyes) diagnosed with end-stage glaucoma. Methods: All eyes underwent an ophthalmic examination, including Schirmer Tear Testing (STT), intraocular pressure (IOP) measurement, corneal touch threshold (CTT), anterior and posterior segment examination, and fluorescein staining. Subjects were sedated and administered a retrobulbar block with bupivacaine, followed by retrobulbar injection of ethanol or saline solution. At specified time points after the procedure, clients assessed their pet's comfort and side effects of the injections via survey. Subjects returned for enucleation. Owner perceived comfort after the enucleation was assessed at identical post-procedure time points and compared to that achieved with retrobulbar ethanol injection or control solution. Overall client satisfaction with each procedure, as well as the effects of retrobulbar ethanol injection on STT, IOP, CTT, and histological changes in retrobulbar tissues were investigated. Results: Retrobulbar neurolytic ethanol injections did not signficiantly improve owner perceived comfort compared to control group treatment or provide more comfort than enucleation. Retrobulbar ethanol injections did not signficantly lower IOP, but did significantly elevate CTT. There was a trend towards lower STT in eyes receiving retrobulbar ethanol injections. Retrobulbar ethanol injections were safe, well tolerated, and no differences in client satisfaction with particpation in the study were noted in either injection group. Histologically, globes in the treatment group displayed significantly greater inflammation and fibrosis; retrobublar tissue samples were not significantly different between control and treatment groups with regard to inflammation or fibrosis. Conclusions and Clinical Importance: Retrobulbar neurolytic ethanol injections were not determined to be an effective globe-sparing alternative treatment to provide analgesia for end-stage canine glaucoma. Enucleation remains an effective way to provide comfort to dogs with elevated IOP.
- Masters Theses