Eye Care for Pets

Just like in humans, maintaining our pets’ visual needs is an important aspect of their overall health and well being. A board-certified veterinary ophthalmologist from Cummings School of Veterinary Medicine recently addressed some frequently asked questions about eye care for pets.

When does my pet need an eye exam?

Pets should be examined by a veterinarian if you notice signs of eye discomfort (squinting or tearing), changes in eye color (redness or cloudiness) or changes in vision. Many common eye conditions can be successfully diagnosed and treated by your family veterinarian. However, some cases may benefit from a referral to a boarded veterinary ophthalmologist for further diagnostic testing, medical treatment, or surgery. Veterinary ophthalmologists work closely alongside your family vet to ensure your pet receives the best care.

Annual eye exams for working animals like service dogs can help catch problems early. Screening eye exams can be scheduled prior to breeding in dogs. Performing a pre-emptive eye exam in these cases can help decrease the frequency of heritable eye diseases in a given breed.

Finally, another common reason to schedule an eye exam is for an equine prepurchase exam. A prepurchase exam can assess the overall eye health and functional vision of a horse prior to an ownership change.

Is my pet color blind?
Animals are not color blind, but they do not see colors in the same way that people do. Most humans have three types of retinal cells called cone photoreceptors (commonly called red, green, and blue cones). These cones work together to create the color combinations we see. Dogs, cats, and horses only have two types of cones, so they can’t see as many different colors. Dogs¹ and cats² have color vision similar (but not identical) to that of a person with red-green color vision deficiency—they see red and green as similar colors. Horses’ color vision is different and they likely see orange and blue as similar colors, but this doesn’t mean orange or blue objects are invisible to them.³ Color is only one component of vision, and there are other important factors such as the lighting conditions, motion detection, and acuity.

Can my dog recognize me by sight?
In short, yes, your dog can recognize you by sight under the right conditions.⁴ However, keep in mind dogs perceive the world differently than we do. A normal dog’s visual acuity (sharpness of vision) is only around 20/75, where normal vision for people is 20/20.⁵ Dogs’ brains also respond more strongly to images of other dogs, rather than to humans.⁶

Dogs can also recognize their owners using senses other than vision. They have a highly developed sense of smell and show positive brain associations when smelling people they know.⁷ Dogs also hear better than people can, and they can distinguish their owner’s voice from the voices of strangers.⁸ So don’t worry if your dog doesn’t always seem to recognize you from a distance* but is still happy to greet you once you come closer. They can’t see as well as you can, but they still know and love you!

My vet prescribed eye drops. When can I stop giving them?
It depends! Some eye conditions are temporary and may need eye drop treatments for a certain period of time before they can be safely stopped. Other eye conditions are lifelong and require daily eye drop medications indefinitely. If eye drops are stopped in these cases, the condition may worsen or relapse. It is safest to check with your vet before starting or stopping any medications. Frequently, a follow-up exam is needed to ensure it is okay to stop them completely.

How long are eye drop bottles good for after they’ve been opened?
This also depends. Most commercial eye drop bottles contain preservatives, which help prevent the growth of bacteria or fungi while the bottle is in use. If used and stored correctly, they can be used until the expiration date is reached or for the time indicated by the manufacturer. Some manufacturers recommend throwing away the bottle 28 days after opening to minimize the risk of contamination. Bottles that are preservative-free must be thrown away much more quickly.

Good practices for handling and storing eye drops will keep them safe and effective. Keep the eye drops as clean as possible. The medication cap should be replaced as soon as you are done using the bottle. Avoid touching the tip of the bottle—this includes avoiding your pet’s hair or eyelashes and your hands. Most eye drops should be stored in a cool, dry place away from direct sunlight, but others need to be stored in the fridge. If the bottle has been chewed on, has been left all day in a hot car, or is past the expiration date, it’s best to throw the bottle away and get a new one.

Certified by the American College of Veterinary Ophthalmologists, Dr. Vanessa Yang is an assistant professor of veterinary ophthalmology in the Department of Clinical Sciences at Cummings School of Veterinary Medicine. 

References

1. Siniscalchi M, d’Ingeo S, Fornelli S, Quaranta A. Are dogs red–green colour blind? R. Soc. Open sci. 4:170869. http://dx.doi.org/10.1098/rsos.170869
2. Clark DL, Clark RA. Neutral point testing of color vision in the domestic cat, Exp Eye Res 153:23-26, 2016.
3. Carrol J, et al. Photopigment basis for dichromatic color vision in the horse. J Vis Sci 1(2):2, 2001.
4. Mongillo P, et al. Recognition of human faces by dogs (Canis familiaris) requires visibility of head contour. Animal Cognition 20,881-890, 2017.
5. Maggs DL, Miller PE, Ofri R. Slatter’s Fundamentals of Veterinary Ophthalmology, 6^th Ed. St. Louis, Missouri. Elsevier, 2018.
6. Bunford N, et al. Comparative brain imaging reveals analogous and divergent patterns of species and face sensitivity in humans and dogs. J Neurosci 40(43):8396-8408, 2020.
7. Berns GS, Brooks AM, Spivak M. Scent of the familiar: An fMRI study of canine brain responses to familiar and unfamiliar human and dog odors. Behav Process 110:37-46, 2015.
8. Gábor A, et al. The acoustic basis of human voice identity processing in dogs. Animal Cognition 25:905-916, 2022.

* If you notice a decrease in vision over time, please consult a veterinarian.