Often referred to as the eye’s “window,” the cornea is a transparent, dome-shaped surface that serves two purposes. Along with eyelids, eyebrows, and eyelashes, the cornea aims to keep the eye free of bacteria and debris, effectively serving as a buffer between the inner eye and the environment. Due to its super sensitive nerve endings, even the gentlest touch causes an involuntary closing of the eyelid. This reflex offers protection to dogs that spend a significant amount of time outdoors or around other animals, particularly cats. The cornea also plays a key role in vision, refracting light as it enters the eye and enabling focus. Given its profound effect on vision, as well as overall quality of life, the integrity of the cornea must be preserved. If your dog’s eye sustains any kind of damage, or appears to be swollen, red or irritated, immediate veterinary treatment will give your dog the best chance to retain full vision.

Since the cornea is the outer-most portion of the eye, it is prone to wounds, scratches and punctures caused by other pets, as well as damage caused by small foreign bodies/debris. The cornea is composed of three layers of tissue, including the epithelium (a very thin outer layer), the stroma (a thick middle layer) and the endothelium, a very thin inner layer. Upon injury, the potential for vision damage increases by the number of layers breached. The cornea may simply be brushed against, or it may be pierced, penetrated or perforated. Trauma, such as being hit by car, may cause a complicated injury including a perforated cornea and structural damage to other parts of the eye. A wound to the epithelium is called a corneal abrasion. An abrasion is typically caused by a scratch from a cat or a branch, and does not penetrate the eye. While the damage may be superficial, dirty cat claws may cause infection secondary to the wound. The next stage of injury, corneal laceration, results from bites, self-inflicted trauma, and other accidents. As with abrasions, prognosis depends upon seriousness of injury and how deeply the cornea was perforated. Only a veterinarian can determine depth of the injury.

Untreated corneal abrasions, lacerations or blunt-force trauma may lead to a serious condition called corneal ulcers. A corneal ulcer is a deeper erosion through the entire epithelium and into the stroma. If the erosion continues past the stroma, the eyeball may collapse or rupture, leading to loss of the eye. Certain dogs (brachycephalic breeds) are prone to corneal ulcers. These breeds include the Boxer, Boston terrier, Bulldog, Pug, Shih Tzu, and any others with flat faces and prominent, “bulgy” eyes. Ulcers may also develop secondary to diseases such as epithelial dystrophy (weakness inherited in the Boxer), keratoconjunctivitis sicca (KCS or "dye eye"), diabetes mellitus, Cushing’s disease and hypothyroidism.

A dog’s cornea is a three-layered powerhouse of cells that not only offers the eye a strong layer of protection, but also contributes almost two-thirds of its focusing power. Injury to the cornea must be evaluated by a veterinarian.

Corneal ulcers must be diagnosed by a veterinarian. Superficial abrasions are only detectable with the use of a special stain, such as fluorescein. A drop of stain is applied to the cornea and the dye will outline the abrasion. Larger ulcers are clearly visible through physical examination, and no other test is needed. In deeper wounds, samples of tissue may be taken to look for bacteria or fungi. Blood tests may check for presence of viral infection.

Treatment depends on depth and extent of abrasions and lacerations and whether ulcers are present. Additional or auxiliary treatment may occur in case of infection, or if secondary to a disease.  

Corneal lacerations and abrasions typically heal within three to five days. Medication, typically ophthalmic antibiotic drops or ointment, is prescribed to prevent bacterial infection. Additional medication, also in the form of ophthalmic atropine drops or ointment, will treat the pet’s pain, pressure, and inflammation. Oral antibiotics are not effective when treating or preventing corneal infection. 

Meant to keep dogs from pawing at their wounds, collars and patches are not tolerated by all pets. In this case, more invasive treatments such as surgery may need to be explored. 

Persistent, deep corneal ulcers may not respond to outpatient treatment, and may require a more intensive approach. To save the eye, surgery may remove dead or poorly healing layers of corneal tissue. In some cases of trauma or advanced disease, the eye may be surgically removed. For such specialty care, your veterinarian will likely refer you to a veterinary ophthalmologist (eye specialist).

The complexity of recovery depends on the extent of corneal injury. All dogs will need a follow-up veterinary appointment to examine the health of the eye and determine if further treatment is required.