Keratitis is inflammation of the cornea, which is the tissue covering the pupil and the iris. The disease is most often caused by bacterial, fungal, or viral infections. If left untreated, keratitis may result in corneal ulcers that develop as a result of progressive erosion and necrosis. When deep ulcers occur, they can create a full-thickness hole in the cornea. Possible complications include scarring of the cornea, permanent loss of vision, and extension of infection to other ocular structures.
Causes of corneal ulcers are many, most typical being:
- Mechanical trauma caused by clippers, whips, eyelash abnormalities, foreign bodies, exposure, or eyelid disease (entropion).
- Bacteria: Pseudomonas are especially serious. Many ocular and eyelid lesions are caused to P. aeruginosa infection, including blepharitis, , keratitis, scleritis, chorioretinitis (inflammation of the cornea and retina), endophthalmitis (inflammation of the inner eye fluids and tissues), and orbital cellulitis (infection of the soft tissues of the orbit and adjacent structures). Ulcerative keratitis associated with P. aeruginosa infection is characterized by extensive dissolution of the corneal tissue and rapid progression of clinical signs.3
- Viruses: Canine distemper, herpesvirus (Nasisse), infectious bovine rhinotracheitis
- Fungi: Numerous species
- Chlamydophila (Gram-negative, coccoid microorganisms)
Corneal ulcers are very painful and often accompanied by blepharospasm (spasm of the eyelids producing uncontrolled winking) and photophobia. There may be clear or pus-filled discharge from the eye(s), superficial erosions, and swelling. Treatment of corneal ulcers is aimed at minimizing chances for infection. Drops may be better than ointment because of less interference with healing. If the ulcers become infected, antibiotics are usually prescribed. In case of deep or is slowly healing ulcers, it may be prudent to "bandage" the eye.
Boxer ulcers (recurrent corneal erosion) are different from classic ulcerative keratitis in that they tend to be less painful. The cornea remains clear, and there may be excessive tear production (epiphora). These ulcers are seen mainly in Boxer dogs over 5 years of age, but also in the Boston Terrier, Chihuahua, and Poodle. Treatment consists of removing loose epithelium (mechanically or by cauterization) and then treating as a mild, superficial ulcer. Hormone therapy sometimes is recommended for spayed female and old male dogs.
- The Merck/Merial Manual for Pet Health
- Comparative Ophthalmology Notes (vetmed.ucdavis.edu)
- Eric C. Ledbetter, James J. Mun,, David Kowbel, and Suzanne M. J. Fleiszig. Pathogenic Phenotype and Genotype of Pseudomonas aeruginosa Isolates from Spontaneous Canine Ocular Infections