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In dogs and cats, blindness, or the inability to see, can be quite distressing for both the pet and their owner. This can be especially upsetting when blindness comes on suddenly. Symptoms of blindness can include walking into walls or furniture, confusion, or reluctance to move around. In some cases, the eyes may appear different than they usually do, such as abnormal redness, enlarged pupils, white pupils, or a swollen appearance. Blindness can be due to issues with the eyeball itself (also known as the globe), the pupil (the black, center part of the eye), the iris (the colored part of the eye), the lens (a structure behind the pupil that allows the eye to focus), the optic nerve or disk (which attaches to the back of the eye, connecting the eye to the brain), or the cornea (the clear layer over the eye that covers the pupil and iris). If you think your pet has gone blind, or is experiencing difficulty seeing, contact your veterinarian as soon as you can. In some cases, immediate treatment may lead to your pet’s vision returning. Below or some common causes of sudden blindness in dogs and cats.
Trauma
If your pet was recently hit by a car, scratched or hit in the face, or involved in a fire, the damage could have caused you pet to become blind. Sometimes this is due to damage to the brain or nerves, which may or may not be reversible. Other times, the eyes themselves can be affected, such as damage to the eyeball or cornea.
Infection
Certain infections which can affect the entire body (systemic infections), such as toxoplasmosis or blastomycosis, can cause sudden blindness. Your pet will likely be showing numerous symptoms other than those directly related to the eyes in these cases. Infections of the eye itself, such as corneal ulcers, may also cause blindness. Eye infections can manifest in various ways, including conjunctivitis in dogs which may cause redness and discharge but typically doesn't lead to blindness. Corneal ulcers, which are caused by an infection in the cornea, may cause your pet to squint, have runny eyes, or have a red appearance to one or both eyes.
Inflammation
Uveitis is a somewhat common eye issue that might cause sudden blindness. This disease results in inflammation within the middle layer of the eye. Squinting and redness of the eyes are common symptoms. Uveitis usually occurs because of other diseases or disorders of the body or eye and so you may notice other symptoms as well.
Cancer
Unfortunately, sudden blindness can be caused by certain cancers. Brain tumors, nerve tumors, or cancers within or near the eye can sometimes cause blindness. Eye swelling can be a symptom, but not always. Confusion, seizures, or unusual behavior may be other symptoms of a brain tumor, but again, this is not always the case. Blindness may be the only symptom.
Glaucoma
Glaucoma is high pressure within the eye (elevated intraocular pressure). Glaucoma may occur in one eye, then the other, or it can affect both eyes at the same time. Eye swelling, redness, and squinting may be symptoms other than blindness.
Retinal detachment
The retina, which is the inner layer of cells at the back of the eye and contains the optic nerve, helps process light. When this layer of cells partially or fully detaches from the back of the eye, blindness can occur. The eye is often still situated normally in the eye socket unless retinal detachment was caused by trauma. In cats, retinal detachment is commonly due to elevated blood pressure (also known as hypertension). Retinal detachment may have no symptoms other than sudden blindness, although you may notice that your pet’s pupils stay dilated or enlarged.
Neurologic diseases
Certain diseases within the brain or nerves can cause sudden blindness. Often other symptoms will be present, such as walking in circles, seizures, or unusual behavior.
Toxins/Medications
Certain medications, if overdosed, can cause blindness (eg, ivermectin). Certain household products can also cause blindness in pets, such as ethylene glycol (antifreeze). Generally, if a pet is experiencing a toxic dose of a medication or has gotten into something like antifreeze, he or she will be showing other symptoms as well as blindness.
Cataracts
Cataracts cause the normally clear, invisible lens to become cloudy or white. It may appear as though the pupil has actually turned white. This type of discoloration of the lens makes vision difficult and if the cataract is severe enough, will cause blindness. Cataracts can sometimes be due to age or genetics. A common medical condition that causes cataracts is diabetes mellitus. Drinking, urinating, and eating significantly more than usual are other common symptoms of diabetes. In addition to blindness, cataracts may also result in glaucoma or uveitis. Cataracts can be surgically removed when medically necessary.
Idiopathic
Sometimes the cause for blindness cannot be identified. An example of this is sudden acquired retinal degeneration syndrome (SARDS) in dogs. A pet may suddenly become permanently blind with no cause and no cure. While this is rare, this can happen in some pets.
The good news is that not all causes of blindness result in permanent loss of sight. Your veterinarian will be able to help you identify what is going on with your pet and provide you with advice and treatment options if available. Always call your veterinarian if you are suspicious of vision loss because prompt medical treatment will, at the very least, prevent major discomfort in your pet, and keep them as happy and healthy as possible.