Let’s know about Anisocoria in dogs. The anatomy of a dog’s eye is very similar to the anatomy of a human eye in that both have a sclera (the white part), irises (the colored part), and pupils (the dark opening in the center of the iris). Like ours, a dog’s pupils allow light to pass through the eyes and retina. In a normal, healthy eye, both pupils will constrict in high light and dilate in low light. So what does it mean if your dog’s pupils are two different sizes?
What is Anisocoria?
Anisocoria, while a mouth, is the medical term for pupils when there are two different sizes of pupils. Anisocoria, in itself, is not a disease but a symptom of an underlying condition. There are many reasons why your dog has pupils that have different sizes.
- corneal ulcer/injury
- A brain or neurological disorder affecting specific nerves running to your dog’s eye (i). Horner’s syndrome)
- Glaucoma (a pressure buildup within the eye in the affected eye and dilated)
- there is a decline in iris tissue that can occur with aging
- head trauma
- exposure to chemicals or toxins
Depending on the underlying cause you may not notice any other symptoms or you may see differences, in ocular symptoms. Dogs with anisocoria may also have sclerosis, a cloudy or blue-tinged cornea (outermost layer of the eye), eye discharge, a droopy eyelid, a squinting eye, or rubbing/pawing on the affected eye. Your dog may also be less active than usual. Regardless of the cause, if your dog’s anisocoria has a sudden onset it is an emergency that requires immediate veterinary care. Failure to get your dog’s care promptly can permanently damage your dog’s vision in the affected eye.
Diagnosing the Cause of Your Dog’s Anisocoria
Most eye workups will begin with three basic tests: a Schirmer tear test, a fluorescein stain, and an intraocular pressure test. A Schirmer tear test will check the ability of your dog’s eyes to make tears. some disease processes there that will stop tear production. Your dog’s eyes will actually try to compensate but instead of tears, they may produce a thick, sticky discharge. All this to say, you might think that your dog only has funky tears when in reality they lack them! Staining the eye with fluorescein dye can brighten up any ulcers on your dog’s cornea. The stain will collect itself into the ulcer so that, even when the excess stain is out of the eye, the stain will still fluoresce under dark light. Checking your dog’s intraocular pressures can check for glaucoma as well as uveitis. If your dog has glaucoma in one or both eyes, it will have higher than normal pressures. If your dog has Uveitis in one or both eyes, it will have lower-than-normal pressure. Rest assured, If the standard three eye tests do not reveal anything out of the norm, your vet may want to perform more specific tests. Gentle scrape samples of your dog’s conjunctiva may be sent for histopathology to an external laboratory, where a veterinary specialist will look at the samples under a microscope. This allows them to determine if any abnormal cells are present which may indicate a benign (or malignant) growth. Your vet can check a blood panel to rule out any systemic diseases. They may also want your dog to be seen by a skull radiograph, an MRI, or even a veterinary ophthalmologist.
Treating Your Dog’s Anisocoria
The best way to treat your dog’s anisocoria depends entirely on the cause of your dog’s anisocoria. Specific treatment will be based on the specific disease. If your dog’s anisocoria is triggered by a chemical or toxic exposure, removing the substance may reverse the anisocoria. Some causes, such as Kirner’s syndrome, are self-limiting and anisocoria may resolve on its own. For still other reasons, such as degenerative conditions, your dog’s anisocoria may never get better. Some causes of anisocoria may also require long-term medication. If your dog’s vision is affected because of their anisocoria their vision does not return to normal. Regardless of the cause of your dog’s anisocoria, seeking immediate veterinary attention is important to your dog’s vision and eye health. Whether you see an emergency veterinarian or your regular vet, they can help you figure out what is causing your dog’s troubled eye symptoms and how best to deal with the problem.