Research Aims to Unravel Glaucoma Mysteries in Companion Animals
In an attempt to unravel the mystery of primary and secondary glaucoma in dogs and cats, Cheryl Cullen, DVM, MS, DACVO, began a study on 50 enucleated eyes in August 2003. Cullen acknowledges that more research is needed, but believes that her work may lead to new treatment modalities.
“There is so much about glaucoma that we don’t understand,” said Cullen, who published her findings, including data about why aspirin-like drugs are an effective treatment, in the September 2004 issue of Veterinary Ophthalmology. She will continue her research on ferrets, whose eyes closely resemble those of dogs, in March 2005 at Guelph University.
Cullen estimates that about 0.89 percent of all dogs will get glaucoma and, as a result, go blind. Most dogs are diagnosed with the disease at eight years of age. Glaucoma often starts in one eye and travels to the other, blinding a dog within three days, she said. Symptoms include cloudy eyes that may show signs of tearing, a red sclera and vision impairment. The condition is painful, but animals frequently mask signs of pain, Cullen added.
In her study, Cullen compared infected eyes with normal eyes that were sectioned into 5 micrometers and stained with antibodies. She compared stains to gauge how tissue reacted to different treatment. “Our findings have spawned more research and helped us discern why [certain] treatments are effective,” Cullen added.
Treatment is usually handled by specialists, but veterinarians play what Cullen described as a critical role in the process. “We are completely dependent on general practitioners for the diagnosis and emergency treatment,” she said.
Several breeds, including American Cocker spaniels and Basset hounds, are predisposed to glaucoma. In cats, the disease is not breed specific, and age of onset varies depending on the cause, which is hard to pin down, Cullen added.
Treatment options include medical management and surgery, though a medical approach often is pricey and does not offer a long-term solution, Cullen said. The three existing medications are borrowed from the human field. Doing laser surgery or implanting shunts in the eye are two alternatives to medication, though both procedures last only about two years, Cullen said.
“Regardless of surgery, primary glaucoma returns and both eyes will be affected,” Cullen added. “That’s what’s so frustrating. You have a client come in and you can see the road ahead because you’ve been there, and you just wish there was something else you could do.”