Dr. Tofflemire,

My pet, Maddie, has a brown thing in one of her eyes.  My vet says it could be a mass.  Do you have insight?


Hi Wayne,

While “mass” could denote many different possibilities, Maddie’s mass appears to be a uveal cyst. Uveal cysts are benign, fluid-filled structures with variable degrees of pigmentation. They can be free-floating or stuck in position within the eye.

Uveal cysts are commonly incidental findings in dogs, with typically little effect on the vision or function of the eye. However, some dogs may experience vision deficits if uveal cysts are large or numerous enough to obstruct the pupil. In these cases, deflation of the cysts may be performed.

Importantly, there are certain breeds of dogs such as Golden Retrievers, Great Danes, and American Bulldogs––where uveal cysts are linked to glaucoma and/or uveitis. I highly recommend consulting with an ophthalmologist for uveal cysts in these breeds.

Finally, uveal cysts also occur in other species. Horses, in particular, will often spook with uveal cysts, presumably as a result of unexpected shadowing when the cyst moves. Like dogs, deflation of the cysts is often helpful in these cases.   

-Dr. Tofflemire