Vision Loss in Golden Retriever Pigmentary Uveitis

Golden Retriever Pigmentary Uveitis (GRPU) is an inflammatory disease of the eye recognized in Golden Retrievers throughout the United States and Canada. Clinical signs include excessive pigment on the iris, protein or fibrinous material in the anterior chamber of the eye, low intra-ocular pressure, and conjunctivitis. The definitive sign required for a diagnosis of GRPU is radial pigment on the anterior lens capsule (front of the lens). (See Diagnostic Criteria for Golden Retriever Pigmentary Uveitis.) This progressive disease often leads to glaucoma and vision loss and appears later in life, affecting dogs at an average age of 8.5 years. While GRPU is a heritable disease, the pattern of inheritance and underlying genetic cause(s) remain unknown.

To better understand and control this disease, the AKC Canine Health Foundation (CHF) is collaborating with the Golden Retriever Club of America (GRCA), the Golden Retriever Foundation® (GRF), and Dr. Wendy Townsend, a veterinary ophthalmologist at Purdue University (CHF Grant 02569-MOU: Development of a Polygenic Risk Model for Pigmentary Uveitis in Golden Retrievers). Previous studies have reported the incidence of vision loss in affected eyes within one year of diagnosis at 50%. This vision loss is most often due to glaucoma. Dr. Townsend studied affected dogs over time to determine the incidence of vision loss, the risk factors for developing glaucoma, and the effect of treatment on disease progression. She performed two examinations at least six months apart on 29 Golden Retrievers with pigmentary uveitis between 2011-2018. The results were recently published in Veterinary Ophthalmology¹ and provide valuable information on the progression of this unique disease.

Incidence of vision loss -
Unlike previous reports, only 20% of the eyes in this population had vision loss and only 4 out of 29 dogs studied were completely blind. Similar to previous studies, the main cause of vision loss in this population was glaucoma. However, glaucoma took longer to develop than previously reported, with an average of 3.8 years in this population. The different results could be due to the fact that the dogs in this study were diagnosed and began treatment earlier than those in previous reports. Since this was an observational study, additional data collection is needed to better define the progression of GRPU.

Risk factors for glaucoma –
Fibrinous material in the anterior chamber of the eye and posterior synechia (a condition where the iris sticks to the lens sitting behind it) were significant risk factors for development of glaucoma. Iris cysts are often associated with GRPU, but the number of such cysts seen on clinical examination was NOT significantly associated with the development of glaucoma in this population.

Effects of Treatment –
A GRPU scoring system was developed based on the degree of radial pigment seen on the anterior lens capsule, the degree of posterior synechia, the presence/absence of fibrinous material, and the presence/absence of glaucoma. (See Table 1 in the Veterinary Ophthalmology publication for full details of the GRPU score.) While dogs were treated with a variety of medications and eye health supplements, the mainstay of treatment for GRPU is topical steroids or non-steroidal anti-inflammatories (NSAIDs). There was no significant difference in the change in GRPU score over time between dogs treated with these two medication types, indicating that neither is superior over the other at slowing the progression of disease. In fact, time was the biggest risk factor for a worsening GRPU score. The longer an eye was affected, the higher its GRPU score, confirming the progressive nature of this disease.

These results provide valuable information indicating that early diagnosis and initiation of treatment are critical to preserve vision in Golden Retrievers affected by pigmentary uveitis. Annual examination by a board-certified veterinary ophthalmologist is recommended for all Golden Retrievers. Additional study is underway to identify the genes that contribute to disease development. This research demonstrates the value of collaboration to improve the health and well-being of all dogs. Learn more about CHF’s research to improve canine health at akcchf.org.

References:

1. Jost, H. E., Townsend, W. M., Moore, G. E., & Liang, S. (2020). Golden retriever pigmentary uveitis: Vision loss, risk factors for glaucoma, and effect of treatment on disease progression. Veterinary Ophthalmology. https://doi.org/10.1111/vop.12841