If Your Dog Keeps Squinting — Causes and the Golden Window for Treating Corneal Ulcers and Erosions

Corneal ulcers in dogs are painful conditions caused by damage to the surface of the eye, often resulting from trauma, infection, or insufficient tear production. Early diagnosis and appropriate treatment are essential to prevent vision loss.

Corneal Ulcers in Dogs Are Painful Conditions Caused by Damage to the Eye Surface

Corneal ulcers in dogs are a painful condition caused by damage to the epithelium, the outermost layer of the cornea. They can arise from various causes, including trauma, infection, dry eye (keratoconjunctivitis sicca), and entropion, where the eyelid rolls inward. If not detected and treated early, ulcers can deepen or become secondarily infected with bacteria, leading to rapid progression. In severe cases, the cornea may melt and perforate, resulting in blindness. Be alert if your dog squints frequently, has persistent discharge such as tears or crusts, shows discomfort when the eye is touched, or if you notice a grayish-white spot on the center of the cornea. Early diagnosis and appropriate treatment are essential to preserving vision.

The Main Causes of Corneal Ulcers Are Trauma, Infection, and Insufficient Tear Production

The most common cause of corneal ulcers in dogs is trauma. The corneal epithelium can be damaged when hair or eyelashes rub against the cornea, or when it is scratched by foreign objects, cat claws, or similar irritants. Other causes include tear film abnormalities such as dry eye (keratoconjunctivitis sicca, KCS), herpesvirus infections, entropion (inward-rolling eyelids), eyelash abnormalities (distichiasis or ectopic cilia), and nerve disorders like facial nerve paralysis. Corneal ulcers are particularly common in brachycephalic breeds (such as Shih Tzus, Pugs, Lhasa Apsos, and Boston Terriers), whose protruding eyes leave the central cornea exposed. Because these ulcers tend to recur frequently, regular eye examinations and early intervention are essential.

Key Symptoms of Corneal Ulcers Include Squinting, Excessive Tearing, and White Spots

A classic sign of corneal ulcers in dogs is squinting and frequent blinking due to pain (blepharospasm). Persistent discharge, such as tears or crusty eye boogers, is also common. You may notice redness in the whites of the eyes, along with grayish spots or cloudy areas on the surface of the cornea. Because of the discomfort, your dog might resist having their eyes touched or try to rub them with their paws. If the ulcer is deep or becomes infected, the discomfort worsens and discharge increases. If you observe these symptoms, seek veterinary care immediately, as early detection is key to successful treatment.

Corneal Ulcers Are Accurately Diagnosed Using a Probe and Fluorescein Staining

The veterinarian checks for corneal damage by applying fluorescein dye to the eye. This dye adheres to damaged or eroded areas and appears green when diluted with saline, allowing for precise identification of the ulcer's location and extent. The vet also examines for underlying causes such as eyelid abnormalities, eyelash disorders, trauma, or dry eye (keratoconjunctivitis sicca). If necessary, a Schirmer tear test is performed to measure tear production, and if infection is suspected, cytology, bacterial culture, and sensitivity testing are conducted to identify the causative organism. This comprehensive approach ensures an accurate diagnosis and enables the development of a tailored treatment plan.

Corneal Ulcer Treatment Proceeds in Stages with Medication, Protection, and Surgery

Mild superficial corneal ulcers are treated with antibiotic eye drops to prevent infection and nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce pain. They typically heal well within 7 to 10 days. To prevent self-trauma from rubbing or scratching the eye, an Elizabethan collar (E-collar) should be worn. If reflex uveitis is present, mydriatic agents such as atropine may also be used. Deep ulcers or those that fail to heal may require surgery, such as a conjunctival flap procedure or corneal transplantation, to reinforce the cornea. It is important to develop a stepwise treatment plan based on the depth of the ulcer and its underlying cause.

Home Care Centers on Eye Drop Administration and Environmental Management

Eye drops must be administered exactly at the scheduled times. Missing a dose can delay healing and increase the risk of infection, so if you miss one, apply it as soon as possible. To prevent your dog from rubbing or scratching its eyes, keep the fur around the eyes trimmed short and have your dog wear an Elizabethan collar (neck cone) to avoid self-injury. Keep your dog away from irritants such as dust, cigarette smoke, and chemicals, and provide a quiet, comfortable environment for rest. Regular follow-up visits and consistent care are essential to prevent recurrence.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

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