Incidence of Juvenile Cataract in 213 Labrador Retrievers in Hokkaido Guide Dog for the Blind Association

Abstract

A guide dog is a dog that has been trained to guide people with blindness or impaired vision. Obviously, a guide dog should have no ocular abnormality that could lead to vision loss or visual impairment such as cataract. This study aimed to determine the incidence of juvenile cataract in Labrador Retrievers that were receiving guide dog training in order to control the incidence of cataracts as well as to revise the breeding plan. A total of 213 trainee Labrador Retrievers underwent complete ophthalmic evaluations comprising menace response, pupillary light reflex, tonometry, and slit-lamp biomicroscopy. Age, gender, position of cataract in the lens, and familial relation were determined for each dog. Juvenile cataracts were detected in 17 eyes of 12 dogs. The incidence rate was 5.63%, and the mean age at detection was 1.24 ± 0.24 years. In 11 of 12 dogs, the cataracts were located in the posterior part of the lens. With respect to familial relations among the dogs with cataract, 2 dogs belonged to the same litter (group A), 2 groups (groups B and C) were from the each same father and 3 groups (groups A, D and E) were from the each same mother. In this study, the incidence rate of cataract in Labrador Retrievers was found to be higher than that in the control population reported previously. Thus, our results proved the prevalence of cataract in Labrador Retrievers. However, the incidence of cataracts in this study was slightly lower than the rate documented in previous reports in UK and The Netherlands. This underestimation of the incidence could be because we examined only juvenile Labrador Retrievers and we did not detect late-onset cataract. To confirm the incidence of cataract, our cases could be used as preliminary data for a bigger study in future. Further, in our study, most cataracts were located in the posterior part of the lens, as stated by a previous study with Labrador Retrievers. Further, we also noted a significant familial relation with respect to the incidence of cataract formation. The results of this study indicate that genetic factor is strongly related to the development of cataract, and suggest excluding all Labrador Retrievers with cataract from breeding for guide dogs. This study is still in progress, and preliminary research is needed to revise the breeding plan in order to control the incidence of cataracts in guide dogs.