One of the classical eye problems veterinarians must address is the presentation of the red eye. The red eye may or may not be obviously painful but when it is the pet can be observed squinting or even rubbing at his/her face. The conjunctiva, pink moist tissue lining the inner surfaces of the eyelids, becomes an angry red and can even swell or puff up around the eye (a condition called “‘chemosis”). In short, it is clear when the eye suddenly hurts and that veterinary attention is needed.
There are several causes of acutely red and painful eyes and one of the most common causes is a wound or scrape to the surface of the eye. The clear surface of the eye is called “the cornea” and because it is the outermost layer of the eye, it is prone to scrapes and tears. Common causes of corneal erosions include:
– Rough contact with plants, thorns, or bushes
– Scratches from another animal (note: the cat scratch wound can be especially serious as the wound quickly heals over, sealing infection within the eye)
– Self trauma (rubbing or scratching at a painful ear or even at the eye due to some other eye can lead to a scratch to the eye).
– Chemical irritaion (getting shampoo in the eye during a bath)
– Foreign body injury (plant material can get stuck under an eyelid and can scrape the cornea)
A special fluorescent stain is used to confirm the presence of the ulcer or erosion. Normally, water will run smoothly off the surface of the cornea, like rain washing off a windshield. If the cornea is damaged, the stain will stick to the damaged area and show bright green under a fluorescent lamp.
A routine corneal ulcer or erosion should heal easily.
Since the damaged cornea is at risk to become infected (or may even already be infected, as demonstrated by a purulent discharge), a topical antibiotic is needed and ideally should be used four times a day. Since it is a rare pet owner that can accommodate any medication administration four times a day, we usually have to
make do with three times a day but to properly sterilize the eye surface, the antibiotic should be used four times a day. Either drops or ointment can be used depending on the veterinarian’s preference.
The second part of treatment is a pain reliever. Some veterinarians will use Atropine 1% drops or ointment because it acts by temporarily paralyzing the pupil’s ability to contstrict (the pupil’s spasm with the ulcer is a signficant source of pain), but my own experience with Atropine is that it seems to cause more irritation than good. Instead, I will supplement antibiotic topical therapy with Genteal Drops, a topical corneal lubricant that both relieves the pain of the ulcer, while acting as a protective barrier against the elements to facilitate healing.
A special collar, called an Elizabethan Collar, is advisable to prevent self trauma of the eye. If you think your pet will rub the eye, it is important to have the pet wear this special collar until the erosion is healed. Be sure to request one if you think your pet needs it and if you are given one be sure the pet wears it for the entire course of treatment.
It is important that the eye be re-checked and stained again after one week of therapy. Most ulcers will have healed in this time, but some will require an additional treatment period until the eye is comfortable again and free of irritation. If the ulcer has not healed after two weeks, it is no longer considered routine and some special procedures may be needed and/or a veterinary ophthalmologist may be required. If the inflammation associated with the ulcer goes deeper into the eye, the situation can become more serious; so it is very important that the one week re-check not be skipped. If there is any question about the eye’s healing progress, the eye should be re-checked sooner.
Below are some special corneal ulcer considerations:
Some ulcers form with a small “lip” on the periphery of the ulcer. Since the ulcer is trying to heal from the bottom up, the lip interferes never adhering to underlying corneal tissue and creating an ulcer that seems to never get any smaller. There are several techniques used to remedy this situation: the lip can be rubbed away, serum can be harvested from a blood draw and used as eye drops to stimulate healing, or even surgery can be performed. Shih tzus, boxers, and pugs are notorious for these ulcers, but they can occur in any breed.
(pronounced “Dez-meto-seal”) Descemet’s membrane is the thin attachment of the cornea to the fluid within the eye. A Descemetocole is an ulcer that has penetrated through the cornea completely except for the last thin membrane. An eye with a descemetocoele is high risk for rupture and special measures must be taken to protect the eye. Often surgery is needed. The brachycephalic breeds (Pekingese, pug, boston terriers, etc.) are predisposed to this problem due to their prominent eyes.
Roger L. Welton, DVM
Founder and Chief Editor, Web-DVM.net
President, Maybeck Animal Hospital
Article updated 9/19/2012