By: Robert L. Peiffer, DVM, PhD and Martha Low, DVM
Indolent ulcers—also known as Boxer ulcers, recurrent epithelial erosions, or SCCED—are common in middle to older aged dogs of all breeds but most commonly, as one might suspect, Boxers. Pathogenesis is thought to involve a defect in stromal-epithelial adhesion; sliding with blinking and eye movement causes the epithelium to break down with resultant superficial ulceration and the inability of the epithelium to adhere to the underlying stroma results in abortive and prolonged healing. More often than not a history of precipitating trauma cannot be elicited and the majority occur spontaneously.
Diagnosis of an indolent ulcer is made by the following characteristics
- History of a similar prior problem, frequently with evidence of mild corneal scarring, as well as chronicity of the current problem (an uncomplicated superficial ulcer will heal in a week or less)
- The great majority are unilateral, with bilateral cases uncommon
- Variable but usually notable discomfort, as manifested by blepharospasm
- Conjunctival injection, with serous to seromucoid discharge, and frequently with protrusion of the third eyelid
- Corneal epithelial defect with a marginal lip of non-adherent epithelium that easily is removed with a cotton applicator (healthy epithelium will remain upon gentle rubbing). Fluorescein dye will facilitate visualization of the non-adherent epithelium and magnification (ideally with a biomicroscope) assists diagnosis. Edema of the adjacent stroma is variably present; while the center of the cornea is most commonly involved, peripheral and/or multiple lesions may be encountered (Fig. 1).
- Absence of infection, as evidenced by lack of stromal infiltrate
- Limbal neovascularization may or may not be present; if seen it is a favorable prognosticator of imminent healing. Exuberant vascularization and granulation are a common component of the healing process.
Fig. 1. Large central indolent ulcer; note shallow depth, non-adherent margins, absence of infiltrate, and associated stromal edema
It is critical to accurately assess the cornea for any evidence of infiltrate or infection and to determine depth of the corneal defect to make the diagnosis of an indolent ulcer. Anything other than a purely epithelial defect, or an infected ulcer, requires more aggressive medical management and/or surgical management. Keratotomy and debridement are contraindicated in deep or infected ulcers, and in cats where the procedure may precipitate sequestration.
The mechanism(s) by which keratotomy aids epithelial re-attachment is not well-understood; it may be as simple as providing an irregular scaffold for the sliding epithelial cells to latch onto. Trauma to the stroma may release cytokines that stimulate healing or allow keratocyte migration into the subepithelial space to produce binding fibrosis (Fig. 2).
Fig 2. Keratotomy following punctate keratotomy with an epithelial facet at the keratotomy site with adhering subepithelial fibrosis and stromal vascularization.
In cases of indolent ulceration, the cornea is unlikely to heal without intervention. Debridement of the non-adherent corneal edges can be performed after instillation of topical anesthesia with proparacaine. A cotton tipped swab is used to gently remove all of the loose epithelium surrounding the corneal ulcer, which will usually greatly increase the size of the defect. After debridement, shallow wounds can be made in the underlying superficial stroma in a grid or punctate fashion using a 22-25 g hypodermic needle. Alternatively a diamond burr debridement can be performed. We prefer the punctate keratotomy because it is the easiest and safest to perform, can be carried into adjacent adherent epithelium, and produces the least scarring. A soft contact bandage lens is applied after debridement and keratotomy to improve comfort and aid in healing.
We prefer Bausch and Lomb plano (no refractive power) bandage lenses, which fit most of our patients reasonably well; lenses specifically made for animals are available but in general more expensive. The lenses stabilize and protect the healing epithelium and provide comfort to the patient. In about 50% of cases the lens is retained until recheck where they are readily removed with a drop of topical anesthesia and a cotton applicator. Alternatively they may be blinked out almost as the patient leaves the office, or anytime between placement and recheck. The pet owner may not know if the contact has been retained or not. It seems that they are required for only a few days for salutary effect and we will replace them only if marked discomfort returns.
Medical management includes prophylactic antibiotic treatment with a first line topical solution (Neopolygram, tobramycin, gentamicin); once or twice daily is effective in preventing secondary infection . Stronger fluoroquinolones should be reserved for cases of corneal infection. Atropine is usually not necessary in cases of indolent ulceration if the pupil is not miotic. Our philosophy is one of minimalism in treatment, the objective being to create an optimal environment where the cornea can heal itself. Atropine decreases tear production and thus may be a detriment to healing. Discomfort is almost always ameliorated with the contact lens. Serum and other purported facilitators of healing are neither required nor beneficial. Ointments retard healing more than solutions and are less compatible with the soft contact lens.
85% of indolent ulcers treated as above will heal within 7-10 days; resolution of blepharospasm is a reliable indicator of progressive healing. Once the defect has epithelialized and is fluorescein negative a short course of topical steroids will minimize vascularization with a resultant slight superficial corneal scar that does not compromise vision. If resolution has not occurred at recheck the process is repeated. After 3 attempts with less than satisfactory results a lamellar keratectomy is performed and is almost always curative (Fig. 3).
Fig. 3. Keratectomy specimen from a dog. Refractory to multiple debridement/keratotomy/soft contact procedures. The non-adherent marginal epithelium is characteristic.
Cats may present with ulcers that mimic indolent ulcers clinically; underlying FHV-1 infection or early sequestrum should be considered in the differential diagnosis. Management of suspected indolent ulcers includes debridement with a cotton applicator soaked in dilute povidone iodine solution, a contact bandage lens, and prophylactic topical antibiotic solutions.
In our experience future recurrence in the same or fellow eye occurs approximately 50% of the time and client education in this regard should be a component of the management strategy.