Factors Influencing the Incidence and Onset of Primary Angle-Closure Glaucoma in the Unaffected Eye of Dogs.

Objective: To determine factors that may affect the onset of glaucoma in the unaffected, contralateral eye of dogs with primary angle-closure glaucoma (PACG).

Methods: One hundred and seventeen dogs unilaterally affected by PACG. Methods: Multicenter retrospective study. Patient factors, examination findings, prophylactic treatments, and treatment failure dates were recorded. Treatment failure was defined as glaucoma onset in the contralateral eye (IOP > 25 mmHg); death prior to a second diagnosis was treated as a competing risk. Cumulative incidence plots and Cox proportional hazard models were used to visualize and test for associations between baseline characteristics and time to treatment failure.

Results: Mean age at first diagnosis was 8.3 years and 69.2% were female. Within 5 years, 70.9% of dogs with unilateral PACG developed glaucoma in the contralateral eye. Median time to treatment failure was 2.15 years. The most common purebred dogs were the Cocker Spaniel, Basset Hound, and Shih Tzu. Dogs with an initial diagnosis in the left eye had a 1.8-fold increased risk of treatment failure of the right eye. Time to treatment failure was not different between dogs receiving prophylactic topical carbonic anhydrase inhibitors versus beta-blockers, nor in dogs receiving versus not receiving topical corticosteroids.

Conclusions: No treatment regimen was found to be superior to another for PACG prophylaxis. Future prospective studies are warranted to investigate complementary glaucoma management strategies.