Retrospective study of treatment outcomes and complications of cyclocryotherapy in 58 glaucoma-affected dogs from 2018 to 2023

Background and Aim: Glaucoma is a neurodegenerative disease characterized by elevated intraocular pressure (IOP) and can lead to irreversible blindness in dogs. Cyclocryotherapy, a cyclodestructive surgical technique, reduces IOP by damaging the ciliary body epithelium to decrease aqueous humor production. Limited data exist on its clinical outcomes and complications in canine patients. This study aimed to evaluate the efficacy and post-operative complications of cyclocryotherapy in dogs with primary and secondary glaucoma. Materials and Methods: A retrospective analysis was conducted on the medical records of 73 eyes from 58 dogs treated with cyclocryotherapy at Kasetsart University Veterinary Teaching Hospital (2018–2023). The procedure involved applying a double cycle of freezing and thawing using a cryoprobe on 8–10 scleral sites. Evaluations occurred at weeks 1 and 2, then at 1, 3, and 6 months post-operatively. Data collected included IOP, anti-glaucoma medication use, post-operative complications, and vision status. Statistical analyses involved paired t-tests, Chi-square tests, and repeated measures analysis of variance. Results: Primary glaucoma was present in 40 eyes (54.79%) and secondary glaucoma in 33 eyes (45.21%). Mean pre-operative IOP for primary and secondary glaucoma was 42 ± 36 mmHg and 50.7 ± 14.5 mmHg, respectively, significantly decreasing to 18.3 ± 12.84 mmHg and 14.42 ± 12.06 mmHg at the final follow-up (p < 0.001). The success rate was 83.56%, with 92.30% of eyes preserving vision. Post-operative complications occurred in 50% of cases, primarily conjunctivitis (28.76%). The frequency of anti-glaucoma medication use significantly decreased in both groups (p < 0.001). Conclusion: Cyclocryotherapy effectively manages canine glaucoma, significantly reducing IOP and medication dependence while preserving vision in most cases. Although complications were noted, they were generally manageable. Prospective studies are recommended to refine treatment protocols and validate these findings. Keywords: cyclocryotherapy, dogs, glaucoma, intraocular pressure, veterinary ophthalmology.