A non-healing corneal ulcer (indolent or Boxer ulcer) is a superficial break in the corneal epithelial surface that refuses to heal. Indolent corneal ulcers have a characteristic non-adherent area of epithelium around the edge of the ulcer. This non-adherent epithelium cannot stick to the surface of the eye and peels off, much like a sunburn. These ulcers typically fail to heal with medical management alone and affects middle-aged to older dogs. Boxers develop this condition more often and may be affected at a younger age than other breeds.
The cornea is the clear surface of the front of the eye. It is covered with epithelium similar to the skin that covers the rest of the body. An ulcer is a break in the epithelium, similar to a scrape or abrasion of the skin. Fibronectin is a scab-like substance that forms across a corneal ulcer immediately after wounding and serves as a base for epithelial cells to migrate over and heal the wound. As these cells migrate, the fibronectin is removed by a series of enzymes. If the fibronectin is removed prematurely by excessive enzyme production or fails to be removed due to lack of enzymes, the corneal ulcer fails to heal. Although the exact reason indolent ulcers occur is unknown, dogs with this condition are found to have an abnormal layer in the superficial corneal stroma. It is thought that this abnormal layer prevents normal adhesion of the epithelium to the stroma. Approximately 80% of indolent ulcers are secondary to excessive enzyme production and about 20% from too little enzyme being produced. Excessive blood vessel infiltrate and scarring of the cornea may occur when indolent ulcers are allowed to heal without treatment. Scarring may be severe enough to permanently limit vision in the affected eye.
Whenever your pet is showing signs of a health issue your first step is to contact your primary care veterinarian. If it is indicated that your pet may suffer from an indolent corneal ulcer or another serious condition, a veterinary specialist is available at an ExpertVet certified or affiliated hospital.
Indolent ulcers present with the same symptoms as other ulcers including increased tearing, squinting, frequent blinking, corneal haziness, and red eye. An indolent corneal ulcer is diagnosed by its appearance and history of failure to respond to proper medical therapy. Generally, corneal ulcers heal very rapidly and often do not require any treatment. Some ulcers do require topical treatment. Under normal conditions even large superficial ulcerations should heal completely in five to seven days with minimal scarring. When an ulcer fails to heal and demonstrates a characteristic appearance, it is diagnosed as an indolent or non-healing ulcer. Indolent ulcers may take up to six months to a year to heal without treatment.
A veterinary ophthalmologist can frequently diagnose a non-healing ulcer based solely upon your pet’s history and the appearance of the eye. When a cotton swab is gently wiped across the surface of the anesthetized eye, the abnormal epithelium will easily peel away. It is important to rule out an underlying cause for the ulcer such as trauma, a foreign body under the third eyelid or abnormal eyelashes. Simply blinking the eyelids may cause the epithelium to pull away from the abnormal stroma resulting in an ulcer.