Why do horses injure their eyes so much? The horse’s large globe and prominent placement on the sides of their head makes the eyeball very susceptible to trauma. Injury or discomfort to the eye can be subtle. Clinical signs include squinting, tearing, increased discharge, swelling around the eye, red conjunctiva, and/or the eyelashes pointing down towards the ground.
If you notice any of these signs in your horse, see your veterinarian as soon as possible. They will need to perform an eye exam to assess and treat the issue.
Horse eye exams
When you call your veterinarian to examine your horse’s eye, they will usually start with a visual exam. This exam indicates your horse’s ability to move around his or her environment, providing a way to assess their vision. Assessed next are your horse’s cranial nerves, which are the major nerve supplies to the eye, eyelids, tear glands, and surrounding ocular muscles. Damage to these nerves can occur with trauma or chronic ocular disease. Abnormalities to specific structures help your veterinarian localize which cranial nerves are affected.
After this, your horse is sedated and a nerve block to the facial nerve is performed. This is the cranial nerve that supplies the upper eyelid. For those who have administered eye ointment to your horse, you’re well aware of how strong your horse’s eyelids are! The nerve block is performed to anesthetize the upper eyelid and allow your veterinarian to perform a better, more comprehensive ocular exam. This nerve block will usually wear off after one to two hours.
Then, a thorough ocular exam is performed, looking at all structures and layers within the eye. Tonometry may be utilized to assess your horse’s intraocular pressures. Low pressures are usually indicative of uveitis, whereas high pressure can be indicative of glaucoma. Another test is the Schirmer tear test. For this, a strip is placed in each eye under the lower lid and held in place for one minute. Horses are exceptional tear producers, so they should completely saturate the strip within one minute. For horses that have “dry eye,” they can be more prone to developing corneal ulcers due to the lack of lubrication to the surface of the eye. Lastly, fluorescein stain is applied to the eye to check for defects in the corneal surface. Any green stain uptake on the surface of the eye would indicate the presence of an ulcer.
If your veterinarian has concerns regarding the back of the eye or the retina, they might perform an ultrasound on the eye. This is commonly done for cases of uveitis to monitor the health of the retina or to identify the presence of masses or subluxation of the lens.
What to do while waiting for the vet
Are eye issues an emergency? Yes. A simple scratch, infection or inflammation left untreated can quickly lead to loss of vision. From corneal ulcers to uveitis and glaucoma to abscesses or cancerous masses, these problems are treated differently and can all negatively impact your horse’s long-term vision.
If you can’t get to your veterinarian quickly, there are some home care options for equine eye problems you can try until you can get your horse seen.
For horses with eye pain or discomfort, rinsing the eye with a generic sterile saline can be performed to irrigate and clean the eye. If you have an antibiotic eye ointment like Neo-Poly-Bac or Neo-Poly-Dex, this can also be applied, as it is a triple antibiotic ointment. However, the ointment should never be applied to an eye before your veterinarian stains it, as this ointment contains a steroid and can make a corneal ulcer worse if applied.
If there is a penetrating foreign body in the eye, please do your best to leave it in place. While this can be difficult to resist, it will help your veterinarian determine what structures are involved or injured and allow them to make a better treatment plan.
If your horse has a laceration to their eyelids, we recommend not cutting off any hanging strips of tissue. The borders of the eyelids contain numerous glands that secrete substances that form the tear film and lubricate the eye. Removing these glands increases the risk of your horse developing dry eye and corneal ulcers. Your veterinarian will need all the tissue possible to reconstruct the eyelid to maintain that protective barrier to the underlying globe.
Common equine eye problems
Some of the most common diseases our Equine Field Service sees in horses are corneal ulcers, uveitis, and ocular neoplasia.
- Corneal ulcers are usually treated with a topical triple antibiotic, a systemic anti-inflammatory such as Banamine, a mydriatic ointment to help dilate the pupil to relieve pain, and a serum or EDTA solution to prevent bacteria and white blood cell enzymatic activity from melting the corneal surface.
- Uveitis, which is inflammation of the inner eye, is typically treated with a topical antibiotic and steroid combination ointment, as well as a systemic anti-inflammatory.
- For horses that develop cancerous lesions or masses around or within the eye, there are a myriad of treatment options ranging from intra-lesional injections to surgical excision of the mass or even surgical removal of the eye, all depending on the extent of the lesion.
If your horse is experiencing an eye emergency, CSU’s Equine Field Service is available 24/7.