Superficial corneal ulcers in dogs are expected to heal quickly. Within hours of wounding, epithelial cells at the edges of a corneal ulcer start to slide across the wound to cover the defect. Over the next couple of days those cells then proliferate and, finally, form adhesions — cell to cell, and cell to the underlying stroma. These adhesions are integral to making that repair permanent. A superficial corneal ulcer that follows this process can heal within just a few days. A corneal ulcer that persists longer than a week's time is usually a sign that there's a complicating factor(s) leading to impaired healing.
Many of the possible complicating factors can be identified during the course of an exam. If a superficial corneal ulcer is not healing as expected, the patient should be re-evaluated for possible perpetuating factors including eyelid conformation abnormalities (e.g. entropion), aberrant hairs (e.g. ectopic cilia, distichia, etc.), a foreign body in the conjunctival fornix or behind the nictitans, keratoconjunctivitis sicca (KCS), and abnormal or impaired blinking. If identified and treated, non-healing corneal ulcers caused by any of the aformentioned typically go on to heal very quickly.
There are instances in which the non-healing ulcer is due to an inherent problem within the cornea itself, and one of those can be localized to the basement membrane or adhesion zone between the corneal epithelium and the underlying stroma. Patients with basement membrane abnormalities are at risk of developing spontaneous, chronic corneal epithelial defects or SCCEDs. These are superficial corneal ulcerations and are very slow to heal. The Boxer is one breed that is known to develop these types of corneal ulcers (often termed Boxer ulcers), but these non-healing ulcers can develop in any breed.
There is one clinical feature that differentiates SCCEDs from other types of corneal ulcers — a loose rim of epithelium along the wound edge that debrides away with ease, often resulting in a much larger defect. To heal, these types of corneal ulcers require more than just medical management — they require an intervention that facilitates the adhesion of epithelium to the underlying stroma. Several techniques have been described to achieve that including the grid or punctate keratotomy, diamond burr debridement, and surgical keratectomy. The keratotomy and surgical keratectomy is best managed by a veterinary ophthalmologist. The cornea is roughly 0.5mm thick and there is little room for error when addressing the eye with a needle (for keratotomy) or surgical blade (for keratectomy). Conversely, the diamond burr debridement — which has comparable success rates to the other procedures — is well-suited to be performed in the primary care setting. The procedure is technically safer (especially if one lacks experience in performing a keratotomy), does not usually require sedation (topical anesthesia is sufficient), and the equipment required involves minimal investment.
Veterinary ophthalmologists frequently see patients with non-healing corneal ulcers on a referral basis, and there is one approach that primary care veterinarians often take — before referring patients — that is nearly guaranteed NOT to work. Dr. Georgina Newbold explains:
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