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We received a call the other day because the owner was concerned that her cat’s pupils were different sizes. First thing to consider is how long has this occurred. Many cats have eyes that are slightly different in size. The key word is slightly.
She sent me an email with a photo. The difference was dramatic with one pupil being very small and the other large. This was a very recent and quickly forming symptom. We made an appointment so he could be receive a thorough physical examine. When I have a situation like this one, I always examine everything else prior to the reason for the visit. In this case, everything but the eyes was with in normal limits.
My first thought was Horner’s syndrome, but it was lacking one classical sign. The side of the small pupil did not have a raise third eyelid. Horner’s can be cause by 5 different things, and I thought that maybe this was an unusual presentation.
As with the physical exam, a thorough ocular exam is essential. Both eyes were examined with an ophthalmoscope to get a better look. A Schirmer tear test was performed to look for inadequate tear production. A blood pressure was taken since hypertension can cause vision issues. Numbing drops were applied to the eyes and the ocular pressures were taken. To our surprise, the eye with the smaller pupil was the normal one. The eye with the larger pupil had glaucoma. The pressure in the larger pupil measured 50 mmHg and the small one 15 mmHg. 20 mmHg is considered the higher end of normal and if there is a difference of 10% pressure in the eyes that is significant.
Glaucoma is not common in cats and can be painful. Furthermore it can result in blindness. Fortunately, eye drops brought the pressure under control and he is doing well. Without quick action, the disease can result in having to remove the eye. When things seem unusual with your cat, quick action can result in control of a bad situation. You should always feel comfortable in contacting your veterinarian for advice.
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