This is not just redness. This is an open wound on the eye.
A corneal ulcer is exactly that, a break in the surface of the cornea, the clear protective layer at the front of the eye. When that surface is breached, the sensitive nerve-rich tissue beneath it is exposed. The result is intense, immediate pain. And unlike a wound on the skin, a wound on the eye cannot be covered, rested, or left to heal quietly on its own without serious risk of catastrophic consequences.
Corneal ulcers can progress from a superficial scratch to a deep crater in a matter of days. A deep ulcer can perforate the eye entirely. That is not a hypothetical worst case. It is a documented outcome of untreated or inadequately managed ulcers, and it can happen faster than most owners expect.
This is one of the most painful conditions a dog can experience. It is also one of the most time-sensitive.
What is an Eye Ulcer in Dogs?
The cornea is the clear, dome-shaped outer surface of the eye. It has multiple layers, and its outermost layer, the epithelium, acts as a physical and biological barrier protecting the deeper, more vulnerable structures beneath it. When this barrier is damaged, whether by a scratch, a foreign object, an infection, or an underlying condition, the result is a corneal ulcer.
An ulcer is essentially an erosion. The surface tissue has been worn away or destroyed, leaving an open sore. In the cornea, where the density of pain-sensing nerve fibres is among the highest in the body, even a small ulcer produces disproportionate pain. This is why a dog with a corneal ulcer will squint intensely, avoid light, and paw at the eye repeatedly, not because it is being dramatic, but because the pain is genuinely severe.
Types of Corneal Ulcers
Understanding the depth of an ulcer is central to understanding how serious the situation is.
Superficial ulcers affect only the outermost epithelial layer of the cornea. With prompt and appropriate treatment, these heal relatively quickly, typically within five to seven days, without permanent damage to vision or the eye structure.
Stromal ulcers penetrate deeper into the cornea, reaching the stroma, the thick middle layer that gives the cornea its strength. These are more serious, heal more slowly, and carry a higher risk of complications, including infection and scarring.
Descemetoceles are ulcers that have eroded through almost the entire corneal thickness, leaving only the thin innermost membrane, Descemet’s membrane, intact. These are surgical emergencies. The membrane is extremely fragile, and perforation can occur at any moment.
Perforating ulcers have already penetrated the full thickness of the cornea. The interior of the eye is exposed. This represents the most severe outcome and requires emergency surgical intervention to have any chance of saving the eye.
Symptoms of Eye Ulcers in Dogs
The symptoms of a corneal ulcer are driven almost entirely by pain and the body’s inflammatory response to the injury. They are hard to miss once you know what to look for.
Pain Signs
- Intense, persistent squinting, often with the eye held partially or fully closed
- Strong sensitivity to light, with the dog turning away from bright environments
- A tense or guarded expression around the affected eye
The squinting associated with a corneal ulcer is not mild. A dog with a significant ulcer will often keep the affected eye nearly shut and become distressed if the area is approached. Pain of this intensity warrants emergency veterinary attention, not monitoring.
Visible Signs
- Visible redness of the white of the eye and the tissue surrounding the cornea
- Increased tearing, with tears running down the face
- In ulcers involving deeper tissue, visible cloudiness or a dull, hazy appearance to the corneal surface
Discharge
- Clear to mildly cloudy discharge in simple ulcers
- Yellow or green discharge indicating secondary bacterial infection, which is a serious complicating factor that requires immediate antibiotic treatment
Behavioural Signs
- Persistent pawing at the eye or rubbing the face against furniture and carpet
- Reluctance to be touched around the head
- Reduced activity and appetite, reflecting the level of discomfort
A dog repeatedly pawing at its eye is a dog in significant pain. It is also a dog at risk of worsening the injury with every contact, making it critical to prevent self-trauma with a properly fitted cone until veterinary assessment is completed.
Severe Signs
- Visible cloudiness or a white, opaque area on the corneal surface indicating deep tissue involvement or infection
- A visible indentation or depression in the corneal surface in deep stromal ulcers
- A dark, protruding area on the cornea, which may indicate iris tissue bulging through a perforation
- Swelling of the tissues around the eye
Any of these signs indicates a veterinary emergency. The eye is at immediate risk of rupture or has already ruptured, and every hour without surgical intervention worsens the prognosis for saving it.
Causes of Eye Ulcers in Dogs
Trauma
Trauma is the most common cause of corneal ulcers in dogs. Scratches from cat claws, contact with rough vegetation, foreign bodies including grass seeds and grit, blunt impact, and even vigorous rubbing against a rough surface can all damage the corneal epithelium. Traumatic ulcers tend to be straightforward in diagnosis because there is often a clear triggering event.
Eyelid and Eyelash Abnormalities
Structural problems involving the eyelids are a significant and often underappreciated cause of corneal ulcers. When eyelashes grow in an abnormal direction and contact the corneal surface with every blink, the cumulative friction causes progressive epithelial damage. This condition, called distichiasis, and the related condition of ectopic cilia, create a persistent source of corneal trauma that will continue to cause ulcers unless the underlying eyelash problem is addressed. Our detailed guide on eyelash causing eye injury covers this in full.
Entropion, where the eyelid rolls inward and the lid margin continuously contacts the corneal surface, is another structural cause of ulcers, particularly in breeds with prominent skin folds around the face.
Dry Eye
Keratoconjunctivitis sicca, or dry eye, is a condition where tear production is insufficient to keep the corneal surface adequately lubricated. The cornea depends on the tear film not only for moisture but for oxygen and nutrition. When tear production falls below the required level, the corneal surface becomes fragile and prone to erosion. Dry eye is one of the most common underlying causes of recurrent corneal ulcers, and treating the ulcer without managing the dry eye will lead to repeated recurrence.
Infections
While infections are more commonly a complicating factor of an existing ulcer rather than the primary cause, certain viral infections, including canine herpesvirus, can directly attack the corneal epithelium. Bacterial infections frequently superimpose on traumatic or dry eye ulcers and can dramatically accelerate the depth and speed of progression. Fungal ulcers, though less common, are particularly aggressive. For context on conditions that affect the cornea beyond ulceration, our guide on corneal diseases in dogs covers the broader spectrum of corneal pathology.
Chemical Irritation
Shampoo or soap entering the eye during bathing, exposure to cleaning products, or contact with toxic plants or chemicals can cause chemical burns to the corneal surface. These injuries can range from mild epithelial erosion to severe deep burns, depending on the substance involved and the duration of contact.
Related Videos
Diagnosis of Eye Ulcers in Dogs
Ophthalmic Examination
The veterinarian will begin with a thorough examination of the eye, including the eyelids, eyelashes, conjunctiva, and corneal surface. Even without special staining, deep ulcers may be visible as areas of cloudiness, depression, or opacity on the cornea.
Fluorescein Staining
Fluorescein staining is the definitive diagnostic tool for corneal ulcers and is a standard part of any eye examination where ulceration is suspected. A small amount of orange dye is applied to the eye surface. Under a specific wavelength of blue light, any area where the corneal epithelium has been breached glows bright green because the dye adheres to the exposed stromal tissue beneath. This test identifies the presence of an ulcer, its location, and provides a basic assessment of its size and shape.
Fluorescein staining is also critical before initiating any treatment, because corticosteroid eye drops, commonly used for other eye conditions, are absolutely contraindicated in the presence of a corneal ulcer and can cause catastrophic deepening of the wound if applied incorrectly.
Identifying the Underlying Cause
Treating the ulcer without identifying why it occurred leads to recurrence. The examination should include assessment of tear production using the Schirmer tear test, evaluation of the eyelids and eyelashes for structural abnormalities, assessment for signs of infection, and, where indicated, consideration of systemic disease. In dogs with excessive tearing dogs preceding the ulcer, underlying nasolacrimal duct problems or chronic surface irritation may be contributing factors worth investigating.
Treatment of Eye Ulcers in Dogs
Treatment must be started immediately. There is no safe window for observation.
Antibiotic Eye Drops
Antibiotic eye drops or ointment are the foundation of treatment for virtually all corneal ulcers, both to treat any existing bacterial infection and to prevent secondary infection from taking hold in the exposed tissue. The choice of antibiotic is based on the severity of the ulcer and, where indicated, culture and sensitivity results. Frequency of application, often every two to four hours in the initial stages, is critical for effectiveness.
Pain Relief
Pain management is not optional. Corneal ulcers are intensely painful, and a dog that is in significant discomfort is also more likely to paw at the eye and worsen the injury. Systemic pain relief is prescribed alongside topical treatment to ensure the dog is comfortable enough to rest and allow healing to begin.
Atropine Eye Drops
Atropine is used in moderate to severe ulcers to relax the ciliary muscle and dilate the pupil. This reduces the painful spasm that occurs when the ciliary body contracts in response to corneal irritation and helps prevent the development of secondary uveitis, which can complicate deep ulcers. Atropine use requires veterinary guidance as it is not appropriate in all cases.
Lubricating Eye Drops
In cases where dry eye is a contributing factor, artificial tear supplementation is essential. Lubricants reduce friction on the healing corneal surface and support the environment needed for epithelial regeneration.
Protective Cone
A correctly fitted Elizabethan collar is essential throughout the treatment period. A dog pawing at or rubbing an already ulcerated eye can deepen the ulcer, introduce infection, or trigger perforation in a matter of seconds. The cone is not optional.
Surgical Intervention for Deep Ulcers
Stromal ulcers that are not responding to medical management, descemetoceles, and perforating ulcers require surgical treatment. Options include conjunctival grafting, where tissue from the conjunctiva is used to provide structural support and blood supply to the healing cornea, corneoconjunctival transposition, and, in specialist centres, corneal grafting. These procedures are performed under general anaesthesia by a veterinary ophthalmologist. The goal is to prevent perforation and preserve the eye, not simply to manage pain.
Related Products
Prognosis: What to Expect
Mild Superficial Ulcers
Simple superficial ulcers in dogs without complicating factors typically heal within five to seven days with appropriate antibiotic treatment and pain management. With good compliance and prompt re-examination to confirm healing, most dogs recover fully with no lasting impact on vision.
Complicated Ulcers
Ulcers that are deep, infected, slow to heal, or associated with an underlying condition require more intensive and prolonged management. Healing may take several weeks, and repeated fluorescein testing is essential to confirm progress. An ulcer that appears to be healing but then deteriorates suggests either inadequate treatment, a resistant infection, or a persistent underlying cause that has not been addressed.
Severe Cases
Deep stromal ulcers and descemetoceles carry a real risk of perforation even with treatment. Perforating ulcers may result in the loss of the eye if surgical intervention is not available or is not performed quickly enough. Even with successful surgical management, significant corneal scarring can impair vision permanently. Untreated corneal ulcers do not heal on their own. They worsen. Blindness and loss of the eye are realistic outcomes of delayed care.
Prevention of Eye Ulcers in Dogs
Protecting the Eyes from Injury
Awareness of the environments that carry high risk for eye injury, dense vegetation, encounters with cats, dusty or sandy conditions, reduces exposure to the most common traumatic causes. Dogs that frequently run through long grass or bushes are at higher risk and benefit from regular eye checks after outdoor activity.
Grooming Around the Eyes
In long-haired breeds, fur that falls across the eye surface is a persistent source of corneal microtrauma. Regular trimming of the hair around the eyes, done carefully with blunt-nosed scissors or by a professional groomer, removes this ongoing irritation before it accumulates into an ulcer.
Treating Eye Irritation Early
Any dog showing signs of eye discomfort, including mild redness, squinting, or increased tearing, should be assessed by a veterinarian promptly. What appears to be a minor irritation can be the beginning of an ulcer. Catching and treating it at the superficial stage is dramatically easier, faster, and less costly than managing a deep or infected ulcer that has been allowed to progress.
Regular Veterinary Eye Examinations
Dogs with known risk factors, including dry eye, entropion, distichiasis, or a history of corneal ulcers, benefit from periodic veterinary eye examinations. These catch recurrent or new ulcers before they reach a severity that requires more intensive intervention.
