This week’s “Case of the Week,” deals with a little miniature pinscher mix named Chestnut. Chestnut presented to the Animal Care Center in Plainfield for routine vaccinations and a physical exam. During the examination, Chestnut’s owner reported that Chestnut’s left eye had been looking red recently. Upon further examination of Chestnut’s eye, there was a considerable amount of redness in the eye (called conjunctivitis), as well as a dilated pupil. A simple test was performed that allows the veterinarian to determine if Chestnut could see out of his left eye. It is called a menace response test. In this type of test, the veterinarian slowly pushes his or her hand towards the patient’s eye that is being tested. The response that the patient gives is then noted. Just as with people, if the patient can see the hand coming towards their face, they will flinch and blink the eye. This lets the veterinarian know that the patient can see. In Chestnut’s case, no response was noted, thus giving evidence that Chestnut was blind in his left eye.
Any time an eyeball is red or irritated, it is recommended to check the pressure within the eye in question. A tool called a tonometer is used to check the internal pressure within the eye. This pressure is called, “intraocular pressure.” When people go to the eye doctor, the “puff of air” into your eye, measures the same thing. When the pressures were measured in Chestnut’s eye, the pressure in the left eye was nearly four times the normal value! When pressures within the eye are increased, this is called, glaucoma.
Glaucoma can either be a primary problem or a secondary problem. In Chestnut’s case, his glaucoma was secondary to a lens luxation. Chestnut’s lens within his eye, which helps to focus his vision, had fallen out of place and was blocking the natural flow of fluid within the eye, thus leading to a backup of fluid (called aqueous humor). This excess fluid is what causes the increased pressure within the eye. In addition to blindness, glaucoma can cause chronic pain similar to a terrible headache.
Since Chestnut had lost vision in the left eye and the eye was only a source of constant discomfort, it was decided that the best course of action would be to remove the left eye. While it can be difficult to come to the realization that Chestnut would be better off having his eye removed, removing the blind and painful eye would make him feel so much better. Chestnut underwent a procedure called an enucleation, or removal of the eye. Chestnut went home the same day and had his sutures removed 14 days later. He recovered well and is doing much better today without the constant source of pain! From now on, we will continue to check the pressures in Chestnut’s right eye to ensure that the pressures remain within normal limits. With primary glaucoma, if one eye is affected, there is about a 50% chance the other eye can develop increased pressures too. We suspect that Chestnut’s glaucoma was secondary, so the likelihood of Chestnut’s right eye becoming affected is low.