A red, tearing eye can indicate a serious issue for your pet, while other problematic eye conditions cause no signs except rapid onset blindness. Our Family Pet Care team provides information about common canine and feline eye disorders.

Normal pet eye anatomy

Learning about normal eye anatomy is helpful to better understand conditions that can affect your pet’s vision. Important ocular anatomic structures include:

  • Cornea — The cornea is the clear, dome-shaped structure that covers the front of the eye. The cornea’s main function is to focus light into the eye. 
  • Conjunctiva — The conjunctiva is a thin mucous membrane that covers the inside of the eyelid and the sclera (i.e., white of the eye).
  • Iris — The iris is the colored part of the eye that controls the amount of light that passes through the pupil.
  • Pupil — The pupil is the black opening in the middle of the iris. Pupil size changes in response to light.
  • Lens — The lens is a transparent biconvex structure that focuses light rays onto the retina.
  • Retina — The retina is the light-sensitive tissue layer at the back of the eye. The lens focuses images onto the retina, and the retina converts these images to electric signals that are sent along the optic nerve to the brain.

Common canine eye disorders

Many conditions can affect your dog’s eyes. Common canine eye disorders include:

  • Keratoconjunctivitis sicca (KCS) — KCS (i.e., dry eye) is a tear-production deficiency that prevents adequate corneal hydration, causing the eyes to become inflamed. If left untreated, corneal ulcers and scarring can occur, affecting your dog’s eyesight. KCS is most commonly caused by an immune-mediated disorder that damages the tear-producing glands, but the condition can also result from viral infection, hypothyroidism, nerve damage secondary to inner ear infection, and in response to certain medications. While any dog can develop KCS, certain breeds, such as English bulldogs, cocker spaniels, West Highland terriers, Lhasa apsos, and pugs, are at increased risk. Our Family Pet Care team measures your dog’s tear production using a special paper strip (i.e., Schirmer tear test). KCS treatment involves tear-production stimulating medications as well as artificial tears and ointments to lubricate the cornea. In some cases, pain medications may be necessary to alleviate your dog’s eye discomfort, and if corneal ulcers are present, we will likely prescribe topical antimicrobials to prevent infection.
  • Entropion — Entropion is a condition that causes the eyelid to roll inward, allowing the eyelid hair to rub the cornea, creating irritation and potentially corneal ulcers. Signs include squinting, tearing, redness, and rubbing at the eyes. Entropion is most commonly seen in Labrador retrievers, Shar-peis, chow chows, rottweilers, and bulldogs. In some cases, puppies outgrow the condition, but they need temporary corrective sutures placed to protect their eyes until they grow into their skin. When adult dogs are affected, surgery is necessary to correct the entropion.
  • Cherry eye —  A cherry eye occurs when the third eyelid’s tear gland prolapses, forming a red bump in the inner corner of the dog’s eye. The condition is most common in flat-faced (i.e., brachycephalic) breeds, such as pugs and English bulldogs, and giant dog breeds with droopy eyelids such as Bullmastiffs and Newfoundlands. Cherry eye can inflame the eye and lead to low tear production. In mild cases, anti-inflammatory eye drops may correct the problem, but usually surgery is necessary to reposition the prolapsed gland. Recurrence is possible after surgery.
  • Sudden acquired retinal degeneration syndrome (SARDS) — SARDS results in rapid onset blindness. The condition typically affects dogs older than 6 years of age and can occur in any breed. Most dogs are seemingly fine one day and unable to see the next. An electroretinogram (ERG) is needed to assess retinal function and diagnose SARDS, because the eyes appear normal. SARDS cause is unknown, but the condition may be associated with Cushing’s disease. While no SARDS treatment is available, the condition is not painful, and most dogs adjust to vision loss quickly.

Common feline eye disorders

Conditions, such as KCS, cherry eye, and entropion, can affect cats, but these disorders aren’t as common in felines as they are in dogs. Common feline eye disorders include:

  • Conjunctivitis — Conjunctivitis is conjunctival inflammation that leads to eye irritation, redness, and discharge. In cats, the condition is most often caused by feline herpesvirus (FHV) but can also be caused by bacterial infections such as chlamydiosis and mycoplasma. Most cats are exposed to FHV at some point in their lives, and 80% of exposed cats harbor the virus in nerve tissue. Of these, 45% can develop recurrent disease, typically when they are stressed. Treatment for FHV conjunctivitis typically involves topical antiviral eye medications to control the flare-up and potentially antibiotic eye medications to address secondary bacterial infections. Antibiotic treatment is usually effective to resolve bacterial conjunctivitis.
  • Eosinophilic keratitis — Eosinophilic keratitis is a chronic inflammatory corneal disease caused by eosinophils (i.e., a white blood cell type) invading the cornea. The inflammation can also spread to the conjunctival tissue. The cause is unknown but is suspected to be related to FHV. Cats with eosinophilic keratitis have raised pink, tan, white, or grey lesions on their corneal surface, affecting one or both eyes. Affected cats typically squint and have a thick ocular discharge. Potential treatment options for eosinophilic keratitis include topical steroids, nonsteroidal anti-inflammatories (NSAIDs), immune modulating agents, anti-virals, and antibiotics to control secondary corneal ulcerations. Oral medications may also be helpful. 
  • Corneal sequestrum — A corneal sequestrum is dead corneal tissue that appears as a black spot on the corneal surface. Affected cats usually exhibit excessive tearing and squinting. The condition is thought to be associated with FHV. The black spot’s surgical removal is necessary to resolve the problem, and our team will refer you to a veterinary ophthalmologist if your cat is affected.
  • Feline anterior uveitis — Anterior uveitis is inflammation inside the front of the eye. The most common causes include feline leukemia virus (FeLV), feline infectious peritonitis (FIP), feline immunodeficiency virus (FIV), toxoplasmosis, cryptococcus, and certain cancers. Affected cats have painful red eyes that appear cloudy. Treatment depends on the underlying cause.

If your pet’s eyes are red or tearing or if you are concerned about their vision, contact our Family Pet Care team to perform your dog’s or cat’s thorough ophthalmic exam.