Corneal Ulcers in Dogs

Overview

Corneal ulcers may also be called scratches or abrasions and are a very common eye problem diagnosed in pets. Ulcers are essentially open wounds within the cornea. The cornea is the clear, shiny membrane, which makes up the surface of the eyeball. It is much like a clear window. The cornea is comprised of three layers. The most superficial layer is the epithelium. Actually, this layer is comprised of many, very thin layers of cells. Below the epithelium is the stroma, and the deepest layer is Descemet’s membrane. Because all of these layers are clear, it is not possible to see them without special stains and a microscope.

An erosion through a few layers of the epithelium is called a corneal erosion or a corneal abrasion. A corneal ulcer is an erosion through the entire epithelium and into the stroma. If the erosion goes through the epithelium and stroma to the level of Descemet’s membrane, a descemetocele exists. If Descemet’s membrane ruptures, the liquid inside the eyeball leaks out and the eye collapses.

If an animals cornea becomes ulcerated it can be very painful. Most ulcers heal within a week; however, certain types of ulcers may require specialized procedures to heal. If an ulcer becomes infected it can rapidly develop into a deep wound or perforation. There are many different reasons that an animal may have a corneal ulcer. Most commonly, an animal develops an ulcer due to trauma they may be scratched while exploring outside, playing with another animal or aggressively rubbing their eye. A pet is at higher risk for corneal ulceration if they have an underlying condition such as a tear deficiency or an abnormally placed eyelash that may be rubbing on the cornea. Brachycephalic, or short-headed, animals such as the pug dog or Persian cat, are at higher risk for corneal ulcers due to increased exposure of the eye and poor blink coverage over the cornea.

Diagnosing corneal ulcers in dogs

Corneal ulcers in dogs appears with a red or painful eye or ocular discharge, the cornea should be stained to look for an ulcer. If an ulcer is found and appears to have stromal loss or a cellular infiltrate (i.e., it appears yellow or white), a sample should be collected for cytology and aerobic culture. Proparacaine may be applied before sample collection. A recent article found no significant difference in bacterial isolates before or after application of proparacaine. If the ulcer appears to be a descemetocele, great caution should be taken in sample collection. If the case is going to be referred to an ophthalmologist, it is not wrong to wait and let the specialist collect the samples.
Ophthalmologists recommend starting patients with corneal ulcers on broad-spectrum prophylactic antibiotics. For an ulcer that is already infected, treatment should be based on cytologic findings until culture results are available. Culture swabs should be refrigerated until plated. Plating should take place as soon as feasible.

Causes of Corneal Ulcers in Dogs

The superficial layer of the cornea can be damaged as a result of the following:
Chemical burns: From shampoo, skin medicine, ear cleaner, etc.
Scratches: From accidental self-trauma, roughhousing or a fight
Blunt trauma: From a car accident or running into an object, for example
Penetrating injuries: From sticks, sharp toys, claws or teeth
Rubbing: From foreign bodies under the eyelid, dry eye, lid problems or an itchy eye

Corneal ulcers in dogs can also develop when the corneal epithelium becomes diseased or infected. Minor injuries can lead to complications if they get infected. Primary infections of an otherwise healthy eye can also happen with some aggressive viruses and fungi.
Dogs can also develop a corneal ulcer for an unknown reason. In these cases, the condition is called indolent ulceration or spontaneous chronic corneal epithelial defects. This mostly occurs in dogs older than 6 years old.

Symptoms of corneal ulcers

Corneal ulcers symptoms are painful and you may notice that your dog is squinting, pawing, or rubbing at the eye. Other symptoms can include redness and excessive discharge or tearing. Superficial ulcers arent typically visible to the naked eye, and your veterinarian will look for the presence of an ulcer with a special stain called fluorescein. When the stain is placed on the eye, the dye will adhere to the ulcer and produce a green fluorescence that identifies the presence of the ulcer.
The most common signs of corneal ulcers in dogs include:
* Blinking excessively or shutting the affected eye
* Significant tearing or discharge from the eye
* Redness and/or swelling of the tissues surrounding the eye
* Poor appetite
* Hiding
* Pawing or rubbing the eye, among other abnormal behaviors

Treatment of corneal ulcers in dogs

Identify and treat the underlying cause or complicating factors before treating the ulcer. For example, a 1-year-old dog may develop a persistent corneal ulcer as a result of entropion and eyelid hair contact with the cornea. Placement of temporary eyelid tacking sutures to pull the eyelid into a more normal position is important to facilitate healing. Once the ulcer is healed, the tacking sutures can be removed and the patient reevaluated to determine if more permanent eyelid surgery is warranted. Young dogs can also develop ectopic cilia, or abnormal hairs that protrude from the conjunctiva lining the eyelid. When the animal blinks, these cilia contact the cornea and create ulceration.

Surgery, typically under an operating microscope, is required to remove the ectopic cilia and allow the ulcer to heal. Patients with dry eye disease often require topical cyclosporine or tacrolimus in addition to topical ophthalmic gel or ointment lubrication to allow ulcer resolution.

E-collar

Corneal ulcer patients should wear an appropriately fitted, hard plastic e-collar at all times to reduce the likelihood of self-trauma as well as the chance of secondary infection. Explaining the purpose of the e-collar is paramount for client compliance, as is making sure the fit is appropriate to allow eating and drinking while protecting the eye(s).

What is an indolent corneal ulcer?

Indolent corneal ulcers are ulcers which do not heal in a normal way and within the normal time frame. In dogs, this type of ulcer may also be called a Boxer ulcer or spontaneous chronic corneal epithelial defect (SCCED). Indolent ulcers in dogs often occur due to an underlying defect in the cornea that prevents the outer epithelial cells from attaching to the deeper stromal cell. Indolent ulcers are often due to a viral infection.
In order to allow healing of an indolent ulcer, a minimally invasive procedure may need to be performed by the veterinary ophthalmologist. This procedure is done using topical anesthesia