Occasional eye redness in dogs is often nothing to worry about, and may be caused by household irritants, a mild allergy, or breed-specific appearance (i.e., droopy lower lids in Basset hounds). Inflammation of the pinkish tissues lining your dog’s eyelids and sclera (i.e., conjunctivitis) commonly causes mild redness and discharge in young or allergic dogs, and can usually be diagnosed and managed by your primary veterinarian. 

Severe redness in one or both eyes, redness that persists despite treatment, or redness accompanied by squinting and pain may have a more sinister cause and should be evaluated by our Envision More Veterinary Ophthalmology team. Here are the top five eye redness causes that require specialist examination and treatment.

#1: Corneal ulcers in dogs

The cornea is the clear “window” covering the iris and pupil. The cornea has several layers, and a superficial corneal ulcer occurs when the top layer is abraded or eroded away, leaving a shallow surface wound. Corneal ulcers can be caused by injury, underlying eye disorders, and normal or abnormal hairs rubbing on the eye, or may be spontaneous and age-related. Dogs with a corneal ulcer usually have a red, squinty, watery eye. 

Most superficial ulcers heal in a few days when treated with antibiotic eye drops to prevent infection. If the ulcer becomes infected, bacteria can penetrate deeper into the corneal layers and create a divot or rupture the eye completely. Deeper ulcers are more serious, and require prompt, aggressive medical treatment to prevent vision or eye loss. Specialized grafting surgery, which fills in the deep divot with donor cornea or the pet’s own tissues, can prevent eye rupture and save vision for many pets. 

#2: Keratoconjunctivitis sicca in dogs

Dogs with keratoconjunctivitis (KCS), which is the medical term for dry eye, cannot make enough tears to lubricate their eye surface, or their tear film evaporates too quickly. Tears carry nutrients, protect the eye surface, and determine the balance of bad and good bacteria. Pets with dry eye experience increased thick, goopy discharge, and red, cloudy, or pigmented color changes from chronic surface inflammation. Left untreated, these inflammatory changes lead to scarring that can permanently blur the pet’s vision.

Most cases respond well to topical medications (i.e., typically, tacrolimus or cyclosporine) that stimulate tear production. Dogs will need lifelong medical treatment, which only manages the condition, and does not provide a permanent cure. If medications are not effective, surgery that reroutes saliva onto the eyes can provide some relief. Saliva contains calcium and other minerals that can deposit onto the eyes, so this solution isn’t perfect.

#3: Uveitis in dogs

Uveitis, which describes inflammation in the interior, front eye structures, can cause tissues in the eye to stick together, resulting in an abnormal pupil shape, or they can block fluid drainage and lead to pressure buildup (i.e., glaucoma). High eye pressures damage the optic nerve and may lead to blindness in hours or days. An eye with uveitis may appear red and cloudy, and the iris may change color or appear fluffy and swollen.

Uveitis is often a sign of underlying, systemic disease (e.g., infection, cancer), so treatment is focused on reducing eye inflammation, preventing glaucoma, and finding and treating the underlying cause. Blood and urine tests look for common infections, and X-rays or ultrasound can help diagnose cancer. If cancer and infection are ruled out, a local immune system overreaction, which steroids can help suppress, is the likely cause.

#4: Glaucoma in dogs

Glaucoma in dogs is, for lack of a better term, a huge bummer. The eye is always producing fluid, which drains through tiny openings near the iris, but when the fluid cannot drain and inside eye pressure increases, glaucoma results. The increased pressure is painful, and the optic nerve is damaged, leading to vision loss.

Glaucoma may be primary or secondary. Primary glaucoma results from abnormally formed drains and usually occurs in middle or older age, starting in one eye and progressing to the other. Secondary glaucoma is usually the result of chronic inflammation that clogs up and scars the drains after eye surgery, eye trauma, or uveitis. Signs include eye redness, squinting or rubbing at the eye, and a cloudy cornea. 

Most dog owners don’t notice primary glaucoma signs until the dog has already lost vision in the first eye. Primary glaucoma treatment is aimed at providing comfort and delaying vision loss in the remaining eye:

  • Removal — A blind, painful eye is best removed, but other procedures can help if surgery is not an option.
  • Medication — Medications can control pressure and help preserve vision for months or years, but eventually stop working.
  • Surgery — Surgery to reduce fluid production or open the drains has varying success, but may be an option for some dogs.
  • Secondary glaucoma — Treatment for secondary glaucoma is similar.

Eventually, many dogs with glaucoma go completely blind, but ophthalmologic treatment can delay vision loss and ensure your dog’s comfort.

#5: Eye trauma in dogs

Eye trauma can occur from an accident, a fall, a crushing dog bite, or being hit with an object like a tennis ball or stick. Trauma can cause bleeding inside the eye, corneal injuries, eye rupture, severe uveitis, or glaucoma, or can pop the eye out of the socket (i.e., proptosis). Traumatic eye injuries can result in vision loss, so your dog needs immediate treatment to address pain, prevent infection, and provide the best chance for a full recovery. Seek emergency care if your dog sustained head or eye trauma.

Red eyes can signal ocular irritation, disease, or trauma. Our Envision More Veterinary Ophthalmology team uses advanced, specialized equipment to quickly diagnose and treat your pet’s eye problems. Call us immediately to schedule a visit for your dog with a red eye, or if you notice any other eye or vision changes.