Corneal ulcers in dogs and cats are known to be very painful. We veterinarians can tell by the way pets squint when they have them. Some dogs’ eyelids can be nearly impossible to open because of the pain.
In addition, we know from people that corneal ulcers are reported to be the second-most-painful physical abnormality people can experience. Kidney stones in ureters are known to be more painful.
A corneal ulcer is any defect causing a disruption of the outermost layer of the cornea. The cornea is the clear part of the eye we see through. Its structure is layered, like an onion.
Corneal ulcers may sometimes be seen with the naked eye or a small amount of magnification. If we are in doubt about the presence of an ulcer, we apply a fluorescein stain to the cornea for confirmation. If the outermost layer of the cornea is intact all of the fluorescein stain will rinse away. If there is a defect in the outer protective layer, stain will remain in the damaged area. If the ulcer is large we can easily see the outline of it. Small ulcers may be illuminated with ultraviolet or “black” light.
Ulcers most commonly occur as a result of infection which erodes that outer protective layer and possibly deeper layers, as well.
Defects in the cornea may also occur with trauma, such as a cat or stick scratching the eye. Trauma may also occur when hair on the eyelids rubs on the cornea or low tear production causes the cornea to dry out.
Treatment of damage to the cornea is driven by the cause of the damage. Secondary problems, such as glaucoma may be present and may affect treatment. For example, if a foreign object has entered the cornea any remaining particles must be removed and the eye protected from infection. If the defect is deep enough it may require surgical repair including suturing and/or conjunctival flap.
As mentioned, infection is the most common cause of corneal ulcer, and most simple, superficial ulcers will heal with appropriate antibiotic and/or antifungal medication.
Often we use autologous serum as treatment for corneal ulcers. To obtain autologous serum we take a blood sample from the patient or another dog or cat known to be healthy. That blood sample is centrifuged or spun to separate the blood cells from the liquid components of the blood. The resulting serum is then applied via medicine dropper two or more times each day until the lesion is healed. Heterologous serum is obtained from a different patient from the one in which it’s being used. One works as well as the other.
NSAIDs or Non-Steroidal Antiinflammatory Drugs may be used orally to effect a reduction in irritation in an inflamed eye. As my ophthalmology mentor, Dr. Laurence Galle says, “Eyes love Rimadyl.”
See you tomorrow, Dr. Randolph.