Ulceration is the most common corneal problem and frequently poses a substantial threat to vision because subsequent infection can rapidly lead to devastating and painful ocular disease.
A corneal ulcer is a full thickness break in the epithelium (outer surface), exposing the stroma beneath. Erosion is the loss of some of the 10 to 15 layers of the stroma.
The majority of epithelial defects in horses are a result of trauma, but primary infection with equine herpes virus does occur less commonly. Eye injuries can occur due to rubbing, foreign bodies, grass seeds, navigating doorways, branches etc. Damage to the eyelids preventing functional blinking can also cause trauma to the cornea. Laceration injuries to the eyelids should usually be stitched as a matter of urgency to prevent defects in the eyelid margin. Newborn foals should be checked for entropion (inward-turned eyelids) because the eyelashes will rub on the cornea. Older foals may also develop entropion if they become sick and dehydrated.
Signs of corneal ulceration:
- Discharge from the eye – may be clear to purulent
- Painful eye – horse doesn’t open eyelid fully
- Swelling of the eyelid
- Cloudiness or obvious defects in the surface of the eye
In order to fully examine the eye, the vet will often sedate the horse and use local nerve blocks to temporarily paralyse the eyelid. Local anaesthetic will also be applied to the eye to allow a thorough check for foreign bodies around the eye and behind the third eyelid. A fluorescent stain will be used to highlight any damage to the cornea and assess the severity of any damage.
Eye examination is much more successful in a dark place such as a stable or float.
Serial examinations may be necessary to ensure that the eye is healing as expected.
Corneal ulcers are usually not infected initially, but like wounds anywhere on the body, may worsen rapidly if infection occurs. Treatment will, therefore, involve antibiotic ointments or drops.
Eye conditions can be challenging to manage because treatment needs to be given very frequently. Some horses won’t tolerate this well and an indwelling treatment delivery system can be fitted to allow effective treatment.
Remember with eyes, early aggressive treatment is key, so if you suspect a problem, call us as soon as possible.