Diamond Burr Debridement for Treating Indolent Corneal Ulcers
By: Shelby Reinstein, DVM, MS, DACVO
Veterinary Specialty & Emergency Center
Corneal ulceration is a very common ophthalmic disorder in both dogs and cats. There are multiple ways to classify and describe an ulcer, including its depth (superficial, deep, descemetocele), etiology (traumatic, toxic, infectious, spontaneous), and ease of healing (uncomplicated, progressive, refractory). A refractory corneal ulcer fails to heal within 5-7 days, and is referred to as an indolent ulcer.
The boxer is the most common breed to develop indolent corneal ulcers, comprising approximately 25% of cases. Other breeds that have been reported to have an increased incidence include poodle and poodle crosses, Welsh Corgis, Labrador retrievers, and German Shepherds and their crosses. The average age of dogs affected with indolent corneal ulcers is 7-9 years, with no dramatic sex predilection.
Diagnosis of an indolent corneal ulcer is achieved with a thorough eye exam. Indolent ulcers can be recognized by their typical clinical appearance: a superficial ulcer with a non-adherent epithelial border (Figures 1, 2).
Fluorescein stain can be seen diffusing under this loose lip of epithelial cells and appears as a less intense ring of stain uptake. Indolent ulcers are most often located in the axial or paraxial cornea, and are vascularized approximately 60% of the time. Without proper treatment, indolent ulcers may persistent for months, with an average time to referral of 7.5 weeks.
Normal corneal wound healing occurs when the corneal epithelial cells multiply and grow across the defect. As they do, they form strong bonds to the underlying corneal stroma. Indolent ulcers develop when there is a failure of the epithelial cells to develop normal attachments to the underlying cells. On a microscopic level, the cell attachments are being blocked by a thin abnormal membrane, which leads to the non-healing nature of the ulcer.
Disruption of this membrane is crucial in achieving ulcer healing.
Treatment of non-healing corneal ulcers requires both medical therapies along with some form of corneal debridement. The foundation and crucial first step in all successful treatment modalities is epithelial debridement. Using a sterile cotton-tipped applicator to remove the loose epithelium can be safely performed after application of topical anesthetic. Normal epithelium is well attached and will not be removed with gentle debridement. Be sure to use dry cotton-tipped applicators for the best grip – you may use 5-6 swabs per eye. It is not uncommon for a much larger area of ulceration to be present after epithelial debridement (Figure 3).
Epithelial debridement on its own has a reported success rate of about 50%. Techniques that aim to remove or disrupt the abnormal membrane have improved published success rates over epithelial debridement alone.
- Grid keratotomy is a technique that creates numerous linear channels through the abnormal membrane using a small needle, allowing epithelial cell attachments to form to the underlying stroma.
- Average success rate: 80% across multiple studies.
- Disadvantages: Risk of corneal puncture, need for sedation or general anesthesia.
- Thermal cautery has been described as a treatment for indolent ulcers in one study. After epithelial debridement, a handheld thermal cautery unit is used to make small, superficial burns throughout the affected cornea. This technique is suspected to alter the abnormal membrane to allow epithelial adherence to the exposed stroma.
- Average success rate: 100% in a study of 9 dog eyes
- Disadvantages: More significant scarring, need for sedation or general anesthesia.
- Superficial keratectomy involves removal of the abnormal corneal ulcer and associated membrane with the aid of an operating microscope.
- Average success rate: 100% across multiple studies
- Disadvantages: Requires referral, increased cost, increased scarring, most invasive.
- Diamond burr debridement (DBD) is the most recently described technique. DBD is performed using a handheld, battery powered polishing burr which removes the abnormal membrane and non-adherent epithelial cells, but does not penetrate into normal stroma (Figure 4).
- DBD has been described in human ophthalmology for the treatment of superficial, refractory ulcerations, and has been shown to be safe and effective in dogs. Recently, the DBD technique in conjunction with bandage contact lens (BCL) placement was evaluated in a clinical setting in dogs. The BCL is thought to improve healing by protecting the migrating epithelial cells, as well as improve patient comfort by covering the exposed corneal nerves. Overall, DBD is considered advantageous due to the minimal cost, lack of specialized equipment needed, ease of the procedure, and little adverse effects.
- Average success rate: 92.5%
- Disadvantages: Maintenance and care of burrs, requires patient cooperation to perform without sedation
Medical treatment of indolent corneal ulcers should include prophylactic topical antibiotics (every 8-12 hours), and oral non-steroidal anti-inflammatories or additional pain medications such as Tramadol. Tetracyclines are known to modulate the expression of certain growth factors involved in corneal wound healing.
Studies have shown that dogs treated with either topical oxytetracycline ophthalmic ointment or oral doxycycline (10 mg/kg PO q24h x 10 days) healed faster than the control group. A hard, plastic E-collar is necessary to prevent self-trauma.
Dr. Shelby Reinstein a Board-Certified Ophthalmologist at the Veterinary Specialty & Emergency Center. The Veterinary Specialty & Emergency Center operates state-of-the-art emergency and specialty veterinary hospitals that are open 24/7/365 in both Levittown PA and Philadelphia PA. For more information about our world-class emergency and specialty care, please visit VSEC on the web at www.VSECVET.com.