The cornea is a clear organ that makes up the front portion of the eyeball. A thin layer of cells called theepithelium covers the cornea. The epithelium is responsible for protecting the cornea from damage. When the epithelium is disrupted, the underlying cornea may become damaged, infected or both. When the epithelium is damaged in the underlying cornea is exposed we refer to the situation as a corneal ulcer.
The cornea is very sensitive organ and when it is damaged he can be quite painful. Whenever there is a corneal ulcer, the muscles of the iris, which formed the pupil, contract in spasm. This spasming contributes to the pain associated with corneal ulcers. If you look at the eye of the pet with ulcer, you’ll notice that the pupil on the affected side is smaller in general then the non-affected side. In addition, the eyelid tends to spasm as well in the pet appears to be squinting.
Under normal circumstances, damaged corneal epithelium will slide across the cornea to seal itself in a matter of days. However, in order for this to occur the cornea must be free of foreign material or infectious agents and the corneal tissue needs to be healthy.
How do our veterinary clinic diagnose a corneal ulcer?
The normal cornea when it is covered with epithelium will not be able toabsorb a special diet called flourescein. Therefore in order to detect a scratch in the corneal epithelium, the veterinarian will apply flourescein dye to the eye. If there is an ulcer, the eye will turn green and will actually fluorescent or glow under an ultraviolet light.
How our veterinarytreats corneal ulcers?
First and foremost in the treatment of any corneal ulcer, is to be sure that there is no foreign material in the eye socket causing the ulcer. This could include the presence of plant materials such as Fox tales, sand or grit, or inverted eyelashes. The doctor and will examine the eye usually with the aid of a topical anesthetic and remove any foreign material is visible. If eyelashes are found to be inverted, a surgical procedure may be necessary to correct the anomaly.
The amount of damage to the cornea is graded from superficial, to moderate, to deep. Superficial ulcers involve the very surface portion of the cornea and frequently will heal within a few days after therapy is instituted.
Generally the deeper the ulcer the more involved the treatment becomes. Most superficial ulcers may be cured by using antibiotic ointment or drops along with the drug to help dilate the pupil called atropine. In addition, in Elizabethan collar is placed around the head to protect the eye from further damage.
Deeper ulcers may require additional drugs such as Adequan drops, or Muro 128 ointment. In addition, we frequently check the eye for bacterial infection by sending a culture and sensitivity test off to the laboratory to make sure we have selected the appropriate antibiotic ointment.
If the corneal epithelium is unhealthy, and is not sticking properly to the cornea itself than we will have to do a procedure known as corneal debridement. In this procedure, the pet is placed under anesthesia and the abnormal corneal epithelium is removed. With the bad epithelium gone, new epithelium should be able to migrate across the cornea and seal the ulcer. In some cases, the cornea itself is diseased or abnormal and will not accept the epithelium. In these cases more aggressive debridement is necessary. Sometimes we will rough up the cornea with a scalpel or laser to make it easier for the epithelium to stick to it. In some cases, we actually have to remove a small amount of the cornea to expose fresh cornea for the epithelium to stick to. Some breeds such as the box or, Boston terrier or Shih-tzu have a propensity to develop corneal ulcers. In fact, when these breeds develop ulcers they frequently develop ulcers in the other eye within a year of the initial injury.
If a treatment is successful, and the corneal epithelium seals itself, the body will try to heal the wound by bringing new blood vessels in towards the injury. These blood vessels obscure the clarity of the cornea and can impair the sight. Once the ulcer is closed and no longer stains positive with flourescein, then we will add a new drug containing a cortisone compound, which will help eliminate the blood vessels and prevent scarring of the cornea. In the end, are desired result is to have a clear scar free cornea.