Retinoblastoma is a form of cancer that starts in the retina. The condition is rare in dogs but has similar symptoms to retinoblastoma in humans.
This type of eye cancer occurs infrequently because it is autosomal recessive meaning the mutation that starts the tumor in the retina must be passed onto the dog by both parents. If only one parent passes on the gene, the dog will not develop retinoblastoma but could pass the gene on to its offspring. The first identified case of retinoblastoma in a nonhuman animal was documented in 1997 by researchers in the Archives of Ophthalmology journal.
The researchers who documented the first case noted that the symptoms were similar in the dog to those seen in affected humans. For example, an early sign of the condition can sometimes be seen in photographs. If a dog or person's pupil appears white in a flash photograph, this can indicate retinoblastoma. Other symptoms include vision problems, eye swelling and blood in the front chamber of the retina.
Diagnosis & Treatment
If you suspect your dog may have retinoblastoma, the first step to a diagnosis is for your veterinarian to examine the back of the dog’s eyes using an ophthalmoscope. In many cases, dogs with this condition will have hemorrhaging in the back of the affected eye. Your vet also will run tests to rule out other eye conditions, such as glaucoma.
Once diagnosed, your veterinarian will want to determine if the cancer has spread into the central nervous system. He or she may use a CT scan or an MRI scan to look for signs of tumors outside of the retina. As with humans, retinoblastoma treatment could involve radiation and/or chemotherapy to shrink the tumor and stop it from spreading. The eye also could be surgically removed.