Abstract
Purpose: :
Some dog breeds have a high incidence of hereditary visual diseases, in particular, cataracts and retinal degeneration (DHR). The electrorretinography (ERGs) is a reliable diagnostic method for analyzing the retinal function. Because of the association between these two diseases, it is necessary to assess the retinal function before cataract surgery, in order to predict the possibility of post-surgical visual recovery. The objective of this work was to characterize the population of dogs with cataracts according to breed, age and the presence of DHR in Buenos Aires (BA), as well as to determine the probability that dogs with cataracts have DHR according to breed and age.
Methods: :
Dogs with bilateral cataracts (312 animals) were analyzed by ERGs. The animals showed not unilateral alterations of the pupil reflex, or other apparent condition of the eyeball (uveitis, glaucoma, or retinal detachment). Patients were categorized in: English Cocker Spaniel, Poodle, Fox terrier, and others breeds; according to the age in: young 0-3; adult 4-7, and wearers > 8 years, and according to the ERGs in: null, subnormal, and normal. Estimated percentages of patients with DHR according to breed and age and the likelihood (odds) for the disease according to the breed, and age of the patient with cataract procedure was calculated by PROC LOGISTIC, SAS, version 9.1.3 (SAS Institute Inc., Cary, NC, USA).
Results: :
Forty percent of dogs (123) were DHR positive, 59.8 % were Cocker, 41.5% poodles, 23.% Fox terriers and 18.4% of other breeds presented anomalous ERGs. On the other hand, 46.7% of the wearers, 40.2 % of adults and 7.9 % of young dogs showed a pathological ERG. For the Cockers the likelihood of DHR was 2.66 (confidence interval (CI): 1.71-4.14; p < 0.001), for the Poodle 1.57 (IC: 1, 01-2, 45, p < 0,05), while for Fox terrier the presence or absence of DHR was similar, with an estimated probability of 0.59 (IC: 0, 26-1, 31). For other breeds, the likelihood of DHR was 0.41 (0, 24-0, 68, p < 0.001). The probabilities estimated for each age group were 2.55 (IC: 1, 57-4, 15, p < 0.001); 1.50 (IC: 0, 2-92, 45) and 0.26 (IC: 0, 11-0, 59, p < 0.01) for the wearers, adults and youths, respectively.
Conclusions: :
These results confirm a high prevalence of DHR in patients (Poodles and Cockers) with cataract in BA, as well as those over the age of 4 years of age. Through the analysis of probability, it can be concluded that belonging to the Cocker and Poodle breed in BA is a risk factor for the development of DHR in dogs with cataracts, while to for Fox terrier this association was not evident. In other breeds, the possibility of submitting a retinopathy (protection factor) is minimal. Also, older suffering from cataract patient, there is an increased risk of DHR.