A dog's eye ulcer won't heal at times as one would hope it would. It can be very disappointing when dog owners treat their dog's eye ulcer religiously applying eye drops as frequently as directed and yet the eye ulcer doesn't give any signs of healing. Eyes at times can be tricky to heal, and to better understand the healing process of dog corneal ulcers, it helps to learn more about the anatomy of a dog's eye. Following is some information on when a dog's eye ulcer won't heal as expected.
Understanding Dog Corneal Ulcers
An eye ulcer is a scratch in the shiny membrane located in front of the dog's eyeball, an area known as 'cornea.' A dog's cornea is formed by three clear layers, namely, the epithelium, the stroma and the Descemet's membrane.
Sometimes, dogs may sustain some form of trauma to their cornea. This can happen for instance, when a cat scratches the dog's eye or when a branch scrapes against it. Sometimes, injury may be sustained through contact with an irritating substance or the trauma to the eye may occur secondary to other eye conditions (dry eye, congenital disorders of the eyes, eyelid abnormalities etc).
These forms of trauma may result in eating away of the surface of the epitelium, a condition known as a corneal erosion or corneal abrasion, or in more severe cases, when more than the surface is affected reaching the stroma layer, a deeper erosion known as a corneal ulcer in dogs may occur. When the trauma reaches close to the deepest layer, the Descemet's membrane, a serious condition known as a descemetocele takes place.
If your dog developed an eye ulcer, most likely your vet stained the cornea with a special green stain known as fluorescein. This stain glows under a black light. Because the layers of the cornea are transparent, fluorescein therefore helps the vet visualize any erosions or presence of ulcers on the surface of the eye.
Normally, superficial corneal abrasions will heal in under one week, while uncomplicated corneal ulcers affecting the stroma may heal in one to two weeks, explains veterinary opthamologist Dr. James V. Schoster with the University of Wisconsin.
"With an ulcer, I recommend a recheck, no matter what, in 7-10 days to ensure its healing appropriately. If there is more squinting, more inflammation, or worsening eye discharge that is bloody, green or brown, go sooner."~Dr. Andy, veterinarian
My Dog's Eye Ulcer Won't Heal
Damage to the cornea makes infections more likely to happen because microorganisms are more likely to adhere to damaged areas. When a corneal ulcer forms, the eye will engage in several protective mechanisms to prevent this from happening.
Blinking and squinting is reflex meant to protect the eye and the production of tears help keep bacteria away. A Schirmer tear test can evaluate whether the eye is producing tears. Often a dog's eye ulcer won't heal as it should when the eye's protective mechanisms fail to work properly. This makes the eye more prone to infection.
Consider as well that eyes are particularly vulnerable to developing infections considering that they have poor circulation compared to other body parts. Just imagine how loads of blood vessels running over the surface of the eye would make it challenging for the dog to see!
This poor circulation makes the body less effective in supplying enough blood cells to the area to allow the infection to heal properly. The presence of an ulcer as mentioned particularly predisposes the eye to infections.
Infected (septic) corneal ulcers may sometimes have cocci or rod bacteria, or both. Normally used antibiotics such as neomycin, bacitracin and polymyxin b are not effective against these serious infections. Left untreated, a severely infected cornea can turn into a melting corneal ulcer and the eye can rupture from perforation.
Sometimes a dog's eye ulcer won't heal as it should if the dog's immune system is not working efficiently as it may happen with senior dogs or dogs suffering from diabetes, Cushing's disease, hypothyroidism or other conditions known to impair the dog's immune system. Sometimes certain medications like steroids may play a role in compromising the healing process.
In a study, it was found that a dog's eye ulcer won't heal properly because the epithelium failed to properly attach to the underlying stroma, and that there was presence of an abnormal epithelial structure.
"Ruptures can happen, but if you can keep him from rubbing his eye (I would use an elizabethan collar), control secondary infections and keep his eye hydrated they are much less likely to occur."~Dr. Kara, veterinarian
Helping a Dog's Ulcer Heal
Most dogs with non-complicated ulcers are treated with topical broad-spectrum topical antibiotics under the form of eye drops along with atropine 1% ophthalmic solution or ointment to reduce spasms and pain. Sometimes, the addition of systemic administration (orally) of a nonsteroidal anti-inflammatory medication (NSAID) for pain and inflammation is needed. Artificial tears may be also used to keep the eye hydrated. An Elizabethan collar is helpful to prevent the dog from rubbing the eye.
If the dog's eye ulcer doesn't appear to improve within 14 days, a further evaluation, preferably by a veterinary opthamologist is important. Ulcers that do not heal within this timeframe may be considered spontaneous chronic corneal epithelial defects (SCCED) or indolent ulcers, refractory corneal ulcers, boxer ulcers (due to particular predisposition of this breed) or recurrent ulcers. Complicated cases of corneal ulcers not healing may require the intervention of a veterinary opthamologist.
Options When a Dog's Eye Ulcer Won't Heal
Sometimes to boost healing, vets may decide to spun a dog's blood and use the serum as a form of eye drops. This serum is referred to as "autogenous serum." The serum promotes healing because it contains immunoglobulins and fibronectin which play an important role in corneal defense, explains Dr. Schoster.
Other treatments may involve anticollagenase therapy (acetylcysteine) for melting stromal ulcers and antibiotics such oxytetracycline/polymyxin-B (Terramycin) or fluoroquinolone antibiotic. Changes in use of antibiotics may be needed if there is lack of improvement. Culture and susceptibility tests may help pinpoint potentially resistant strains of bacteria.
In some cases, application of Adequan, an arthritis medication has helped with some situations. A product by Virbac known as REMEND Corneal Repair Drops made with hyaluron cross-linking technology can be used under a vet's guidance.
The eye may be also scraped to encourage healing. The technical term for this is débridement. In this procedure, a sterile cotton-tipped applicator soaked in diluted povidone-iodine is used to remove all the loose epithelium that has started to heal over the ulcer. This is removed because the ulcer needs to heal from inside out.
Keratotomy, which involves cutting into the cornea of the eye may follow. While this may sound drastic, its goal is to encourage newly forming epithelium to better adhere to the stroma thus promoting the dog's cornea ability to heal ability.
Because the act of blinking can be irritating, and to protect the newly forming epithelium while ensuring it is well lubricated, some vets may opt to stitch the eye shut so to promote healing. This procedure is known as "tarsorrhaphy."A temporary third eyelid flap or a soft contact lens can be used. In severe cases, a more aggressive surgery known as a conjunctival flap may be needed to preserve vision.
"Topical tetracycline ophthalmic ointment was a safe, inexpensive, and effective adjunctive treatment for refractory corneal ulcers in dogs."~Chandler HL et al
- Complicated Corneal Ulcers Microbial Keratitis, by James V. Schoster,
University of Wisconsin USA
- DVM360: A challenging case: A dog with nonhealing corneal ulcers
- Bentley E, Abrams GA, Covitz D, et al. Morphology and immunohistochemistry of spontaneous chronic corneal defect (SCCED) in dogs. Invest Ophthalmol Vis Sci 2001;42(10):2262-2269.
- Bentley E, et al. Diseases and surgery of the canine cornea and sclera. In: Gelatt KN, ed. Veterinary ophthalmology. 4th ed. Ames, Iowa:Blackwell Publishing, 2007;690-752.
- Chandler HL, Gemensky-Metzler AJ, Bras ID, et al. In vivo effects of adjunctive tetracycline treatment on refractory corneal ulcers in dogs. J Am Vet Med Assoc 2010;237(4):378-386.