The location of the ulcer depends somewhat on the cause. Central ulcers are typically caused by trauma, dry eye, or exposure from facial nerve paralysis or exophthalmos. Ulcers in the inferior nasal cornea may be caused by foreign material trapped under the third eyelid. Entropion or distichiae may cause ulceration of the peripheral cornea. Immune-mediated eye disease can cause ulcers at the border of the cornea and sclera. Symptoms
Corneal ulcers are painful due to nerve exposure, and can cause tearing, squinting, and pawing at the eye. There may also be signs of anterior uveitis, such as miosis (small pupil), aqueous flare (protein in the aqueous humour), and redness of the eye. An axon reflex may be responsible for uveitis formation — stimulation of pain receptors in the cornea results in release inflammatory mediators such as prostaglandins, histamine, and acetylcholine. Diagnosis
Diagnosis is through direct observation of the ulcer with the use of fluorescein stain, which is taken up by exposed corneal stroma and appears green (see photos above and below). With descemetoceles, Descemets membrane will bulge forward and after staining will appear as a dark circle with a green boundary, because it does not absorb the stain. Other tests that may be necessary include a Schirmers test for keratoconjunctivitis sicca and an analysis of facial nerve function for facial nerve paralysis. Treatment
Treatment of corneal ulcers includes topical antibiotic therapy to prevent infection, and pain medications, including topical atropine to stop spasms of the ciliary muscle. Atropine may decrease tear production and interfere with corneal healing.
Superficial ulcers usually heal in less than a week. Deep ulcers and descemetoceles may require corneal suturing, conjunctival grafts or conjunctival flaps, soft contact lenses, or corneal transplant. Topical corticosteroids and anesthetics should not be used on any type of corneal ulcer because they prevent healing and will often make them worse. Bioscaffold
A new bioscaffold developed by TR BioSurgical is being evaluated for refractory corneal ulcers in dogs. The study is being conducted by board certified veterinary ophthalmologists and has shown promise in healing refractory ulcers that have failed conventional treatment . Refractory corneal ulcers
Refractory corneal ulcers are superficial ulcers that heal poorly and tend to recur. They are also known as indolent ulcers or Boxer ulcers. They are believed to be caused by a defect in the basement membrane and a lack of hemidesmosomal attachments. They are recognized by undermined epithelium that surrounds the ulcer and easily peels back. Refractory corneal ulcers are most commonly seen in middle aged or older dogs and often occur in the other eye later. They are similar to Cogans cystic dystrophy in humans. Commonly affected breeds
Alaskan Malamute
American Cocker Spaniel
Boston Terrier
Boxer
Brussels Griffon
Cairn Terrier
Chesapeake Bay Retriever
Chihuahua
Chinese Shar Pei
Dachshund
Bulldog
English Springer Spaniel
German Shepherd Dog
Golden Retriever
Irish Setter
Japanese Chin
Lhasa Apso
Maltese
Pekingese
Poodle
Pug
Rottweiler
Samoyed
Shih Tzu
Silky Terrier
Weimaraner
Welsh Corgi
Welsh Springer Spaniel
West Highland White Terrier
Wirehaired Fox Terrier

Treatment
Refractory corneal ulcers can take a long time to heal, sometimes months. Topical antibiotics are used continually to prevent infection. Pain medications are given as needed. Loose epithelium is removed with a dry cotton swab under topical anesthesia.