The following is from the Albuquerque Journal:
Q: I have friends that have macular degeneration. One is legally blind. I have read internet articles telling that cats can carry the parasite Toxoplasma gondii.
One of them states that toxoplasmosis is the most common cause of eye inflammation in the world. Could this be causing the eye problems that our long-term cat owner friends have?
Dr. Nichol: Toxoplasmosis is a zoonotic disease, meaning that it is transmissible between animals and humans. It’s caused by a single-celled protozoan parasite that can infect any warm-blooded mammal but cats are its definitive host.
I sent your question to human ophthalmologist Dr. Jesse Swift.
The good doctor’s comments: “Toxoplasmosis is a common parasite that usually does not affect healthy individuals. It can, however, affect those that are immunosuppressed due to cancer treatment, HIV/AIDS, or other reasons. It can also affect the fetus in a pregnant woman. The children that contract congenital toxoplasmosis can develop hearing loss, mental disability, and blindness. In fact, toxoplasmosis is a leading cause of blindness especially in underdeveloped countries. It is also a leading cause of uveitis or eye inflammation in both children and adults. In those that are immunosuppressed it can cause life threatening encephalitis.”
Another human ophthalmologist, Dr. Stephen Saxe, was also kind enough to weigh in. “Toxoplasmosis and age-related macular degeneration are both diseases that can affect the retina and the macula (the anatomical visual center of the retina). They both can cause inflammation and scarring in the retina. However, toxoplasmosis and age-related macular degeneration are two separate diseases caused by two completely different mechanisms.”