Corneal ulcers in dogs can be painful and may lead to blindness if they are severe or left untreated. In this post, our South Florida vets define this condition and discuss signs, diagnosis, treatment and prevention options.
What is the cornea?
Similar to a clear windowpane, the cornea is a transparent, shiny, nerve-rich membrane that makes up the front of the eyeball (outer layer of the eye). It protects the inner structure (the pupil, iris, and aqueous humor) of the eye. A dog's cornea is about half as thick as a dime.
The three layers of the cornea are comprised of highly specialized skin cells and include the:
Epithelium
Considered the "skin of the eye", the epithelium is a very thin layer of cells on the top surface of the cornea. A corneal ulcer appears when the epithelium is missing, and the cornea's nerves become irritated.
Stroma
The stroma is the middle layer of the cornea. It is the thickest of the three layers and is the main supportive tissue, making up 90% of the cornea's thickness.
Descemet's Membrane
The deepest layer of the cornea is very thin. The aqueous humor a clear fluid that fills the inner chamber of the eye and is located is on the other side of Descemet's membrane.
What is a corneal ulcer and how does it affect my dog?
A corneal ulcer (medically referred to as ulcerative keratitis) is a painful wound or abrasion on the cornea's surface that causes swelling and inflammation.
There are four types of corneal ulcers, which can range in severity from superficial to deep, depending on which layers of the cornea are injured:
Superficial Corneal Ulcer
A much less serious injury, a superficial corneal ulcer involves only the surface epithelium. It will still require veterinary care.
Stromal Ulcers
Stromal ulcers affect the cornea stroma and can be much more threatening to the eye and your dog's comfort. Because the stroma is laced with nerves, damage to this layer of the cornea can cause significant pain for your dog. Stromal ulcers take longer to heal than superficial corneal abrasions.
Deep Corneal Ulcer & Perforations
A deep corneal ulcer (descemetocele) is typically a sign of bacterial infection and begins to involve the corneal stroma. The bacteria release substances that degrade the corneal stroma, causing the ulcer to progress deeper.
If the ulcer extends to the deepest level (the Descemet's membrane), this is referred to as a descemetocele and is considered a veterinary emergency as it can cause the eye to rupture. Corneal perforations occur when the ulcer extends completely through the Descemet's membrane and are just as urgent.
If the Descemet's membrane ruptures, the eye's fluid leaks out and can potentially lead to irreparable, blinding damage to the eye.
Indolent Ulcers
Also referred to as spontaneous corneal epithelial defects (SCCEDs), these non-healing ulcers are typically caused by trauma. More common in older dogs around eight or nine years of age, indolent ulcer is superficial but can sometimes become infected and affect the stroma.
With this type of ulcer, improper healing can be the culprit; the epithelium may be loosely attached to the underlying stroma.
Corneal ulcers can affect dogs in different ways depending on the severity of the condition. While a surface-layer abrasion may not seem to make much difference to the dog or their ability to see and get around, deeper abrasions can be painful and be more likely to affect a dog's vision.
Though trauma to the eye is always assumed to be painful, this may not always be the case with every corneal ulcer. Unfortunately, some corneal ulcers can be painful. Abrasions that progress deeper than the corneal epithelium can be extremely uncomfortable for your dog.
What are common signs of corneal ulcers?
Common signs and symptoms of this condition include:
- Excessive blinking
- Pawing or rubbing at the eye
- Tearing or watery eyes
- Redness
- Holding the eye closed
- Sensitivity to light
- Discharge from the eye
- Ocular discomfort
- Film development over the eye
Dogs will usually show clear signs of an eye injury or problem during the first few days after the trauma occurs.
Corneal ulcers can be slow to heal depending on the depth of the trauma. If you suspect your dog has experienced any type of eye injury or trauma, bring them to your vet right away for emergency care, as early detection and diagnosis are key to positive outcomes and may prevent blindness, vision loss, and other complications. Your veterinarian may refer you to our veterinary ophthalmologists for advanced diagnosis and treatment if required.
What causes corneal ulcers?
Corneal ulcers can appear for several reasons. Most ulcers in dogs develop due to:
- Trauma (the eye being scratched by heavy vegetation or a thorn while your dog is playing or during a fight with another animal)
- Dry eye
- Illness or disease
- Chemical burns
- Eyelid anomalies (eyelid rolling or inability to close the eyelids)
- Irritating substances like dust, debris, or shampoo
- Bacteria or eye infection (less common)
- Facial nerve paralysis that affects eyelid movement
- Primary abnormalities of the cornea like spontaneous chronic corneal epithelial defects (SCCED)
More serious injuries to the cornea can happen due to lacerations from a cat's scratch or sharp object.
Corneal ulcers are also common in certain breeds or dogs with underlying diseases like:
- Brachycephalic (flat-faced) breeds with shorter noses and prominent eyes, such as Boston terriers, pugs, shih tzus, boxers, and bulldogs
- Dry eye, which develops when decreased production of tears leads to drying of the corneal surface
How will a vet diagnose a corneal ulcer?
All three layers of the cornea are clear, so a veterinary ophthalmologist will need to examine them under a microscope using a specialized stain (fluorescein). When the stain is placed on the eye, the dye will adhere to the ulcer and produce a green fluorescence that identifies the ulcer's presence.
How is a corneal ulcer treated?
Treatment for your dog's corneal ulcer will depend on its type. Simple, superficial corneal ulcers will heal on their own within 3-10 days depending on the size of the ulcer. Your vet will likely prescribe medications to relieve discomfort and prevent infection.
Some corneal ulcers will need to be treated with:
- Antibiotic eye drops
- Topical antibiotic ointments
- Eyedrops with a pain reliever
- Injectable medications
For more serious cases of corneal ulcers, more intensive treatment is required to prevent the depth of the ulcer from progressing. In severe cases, your vet may refer you to a veterinary ophthalmologist for corneal surgery. During the procedure, a graft may be placed on the ulcer to stabilize the cornea, preserve the eye, and prevent the eye from rupturing. Another option is corneal diamond burr debridement surgery, which gently removes the damaged corneal tissue to promote proper healing.
You may need to administer multiple eye drops or injectable medications several times a day as your dog recovers, as well as pain and anti-inflammatory medications by mouth.
Following surgery, your dog will need to wear an E-collar (Elizabethan cone) to protect the eye as it heals, since scratching at the eye can delay and complicate healing. Your dog should also wear a protective eye covering recommended by your vet or veterinary ophthalmologist to protect the cornea as it heals.
Followup Care & Prognosis
If your dog has developed a corneal ulcer, the prognosis will depend on the type of ulcer, whether any complications have occurred, and individual factors like your dog's health status. Dogs with corneal ulcers that are properly treated almost always maintain their vision.
Serious complications like vision loss and the need for eye removal surgery (enucleation) are more common if the condition is left untreated, improper healing occurs, or deep corneal ulcers or perforations have occurred.
During the healing process, a scar on the surface of the cornea that develops during the healing process can lead to corneal opacity, which makes part of the eye appear as if it has clouded over. This also makes it impossible for light to properly reach the optic nerve. Therefore, your dog's visual opacity can be affected. In some cases, the right treatments during the healing process can help prevent heavy scar formation.
Corneal opacity caused by scarring after an ulcer should not be confused with corneal dystrophy, which also causes opacity. However, corneal dystrophy is the result of a genetic malfunction that interferes with how a dog's body metabolizes fat. Fatty deposits collect in the eye and cause similar cloudiness that impedes visual capacity over time.
When it comes to treating corneal ulcers in dogs, follow-up appointments with your vet or veterinary ophthalmologist are critical to determine whether the ulcer has completely healed. Simple, superficial corneal ulcers should heal within one or two weeks or less. However, these ulcers may heal more slowly in some cases, depending on your dog's health status.
If your dog's ulcer does not heal or show signs of healing within this timeframe, an underlying condition (dry eye, abnormally directed eyelashes, entropion, etc.) may be complicating the healing process.
Chronic, non-healing (indolent) ulcers are very common in older dogs and require additional procedures like diamond burr debridement to support and facilitate healing. If your dog's corneal ulcer is not healing properly and an inciting cause cannot be identified, further specialty care provided by a veterinary ophthalmologist may be required.
How can I prevent my dog from developing corneal ulcers?
Our veterinary ophthalmologists recommend taking the following precautions to prevent corneal ulcers:
- Carefully monitoring short-nosed dogs during play or physical activity to protect their eyes from trauma, particularly watching for low-hanging hedges, thorns, sharp table corners, etc.
- Preventing your dog from playing roughly with other dogs or animals
- Keeping your dog separate from cats if they do not get along with felines, as cat scratches are a common cause of eye ulcers in dogs
- Making an appointment with your vet or veterinary ophthalmologist as soon as possible if you notice any problems with your dog's eye, so conditions and injuries can be detected and treated early
Veterinary Ophthalmology at Animal Eye Guys
Dogs can develop minor or severe eye conditions that may cause pain and discomfort, and impact their vision. While some of these are age-related, others may be injuries, diseases, or genetic problems.
No matter the issue, a veterinarian or veterinary ophthalmologist should promptly assess any signs of discomfort or loss of sight. Early detection, diagnosis, and treatment are important to ensuring the best possible outcome for your dog's health.
Depending on the cause and unique circumstances surrounding your dog's vision loss, one of our board-certified veterinary ophthalmologists may recommend eye (ocular) surgery to treat the condition or disease, or to repair an injury sustained through trauma.
We understand that the idea of bringing your pet in for surgery can be daunting. Please rest assured that we recommend surgery only when it is in your four-legged companion's best interests.
If your dog is experiencing signs of symptoms of vision loss or an eye disease, request an appointment at any of our clinic's locations in South Florida.
Note: Animal Eye Guys specializes in treating eye conditions and illnesses. The advice provided in this post is intended for informational purposes and does not constitute medical or behavioral advice regarding pets. Please make an appointment with your vet for an accurate diagnosis of your pet's condition.