Near Sighted Horse

Can a horse be near sighted?

I am not sure if anybody can really answer that question- I know that none of my horses ever complained that they were having trouble reading the newspaper. The only way we can make assumptions about how well a horse sees is by performing an ophthalmic examination. This will reveal any lens cataracts, which can prevent light and images from hitting the retina, corneal scars from old injuries, retinal damage from uveitis, pupillary abnormalities, congential malformations, and reflexes to standard vision assessment tests. This will allow us to estimate how much light, motion, and detail a particular horse can perceive but there is no documented evidence of “near sightedness” as such. Horses have evolved to have very sensitive distance vision so they can spot threats in enough time to flee, but the arrangement of their eyes also leads to a small blind zone around the body. Scarily, when a horse is lifting its forehand off the ground in front of a fence, it is actually jumping from memory because he can’t see it anymore. Something I preferred not to think about at that moment.

Melissa McKee DVM

Blue Eyes and Uveitis

I’ve been told that blue eyes are more likely to develop uveitis than regular coloured eyes. I have a rising ten year old cremello with lovely sapphire blue eyes. Is there an increased likelihood of him developing this disease?

Unfortunately, horses who lack pigmentation of the iris and the skin around the eyes are more prone to problems in this area. The most commonly related condition is squamous cell carcinoma of the eyelids and skin areas around the eye, because there is not enough pigmentation in the skin to shield it from uv radiation (and horses do not develop protective tans). Horses with blue eyes also seem more likely to develop uveitis for the same reasons. This problem is also breed-related, in that certain breeds such as appaloosas have a much higher risk of developing uveitis and other eye problems. Their coat colour pattern, which often results in pink or patchy skin around the eye as well as incompletely pigmented irises, contributes to this tendency. This does not mean that every horse with light skin and eyes will develop a problem, just that you should be on the lookout more carefully than with regular colour patterns. You can do a lot to help prevent the onset of eye problems by putting a UV blocking fly mask on your horse for turnout, particularly in the summer months when flies and dust will further contribute to the irritation. If you notice and discharge from the eye or crusty sores around the lids, call your vet right away because these are much easier to deal with if caught and handled early.

Melissa McKee DVM

Sarcoid Around Eye

My horse has either a wart or sarcoid on his eye lid. It has been there since late April and in May my vet felt it was a wart and would eventually go away on its own. It is now Oct and it has grown some and developed a bit of a cauliflower look. Vet looked at it again approx 1 1/2 months ago and is not convinced it is a sarcoid. I am becoming more convinced that it is and that it is going to require treatment. It has an unfortunate placement for the use of the ointment used to treat skin cancers. I am afraid it will get into the eye ball as the growth is near the edge of the lid by his eye lashes. What would be other treatment options for this if it is a sarcoid?

The only way to truly determine what is growing on your horse’s eyelid is to perform a biopsy and submit it to a pathologist for examination under a microscope. Unfortunately, there is some evidence that irritating a sacroid in this way can occasionally stimulate, so you should only biopsy if you are prepared to move ahead with treatment. While sarcoids are common around the eye, grey horses can also suffer from melanoma in this location, and the eyelids and conjunctiva are frequently affected by squamous cell carcinoma in horses with minimal pigmentation such as paints and appaloosas. There are many ways to treat a periocular sarcoid depending on the size, aggressiveness, and proximity to the conjunctiva and cornea. Small lesions may be treated with surgical excision and cryotherapy with liquid nitrogen. There are some drugs available that can be injected directly into the tumor, including the immune stimulant called BCG, and an anti-cancer drug called cisplatin. Certain topical creams such as fluorouracil and imiquimod can be applied that will fight the sarcoid but are actually non-damaging to the conjuctiva and corneal epithelium. Severe cases are occasionally treated with radiation therapy.

You may wish to discuss these options with your vet if this tumour is indeed growing rapidly. Some of the drugs require careful handling and the horse must be referred to a specialist for application.

Melissa McKee DVM


Third Eyelid Tumor

Just wondering how long the recovery time would be and some of the risks involved if the horse has an eye tumor. Also, how often are they malignant ? Would he be on medication for life an what are the side affects of the medication if it is cancerous ? He has had this “lump” in the front corner of his eye, that is dark in color (black) and looks like one of two “globs”. Sometimes is seems to suck back under the lid/into the eye cavity, and other times he can pop it out and it is pretty visible. He has had this for about 3 years and it does not itch, weep, get irritated or anything like that. It looks very smooth, and seems well lubricated with the rest of is eye. This year it seems to be growing a little more then usual. It is currently about the size of a kidney bean. If it is surgically removed, what is generally the prognosis and what are the chances of him loosing the whole eye ?

It sounds like your horse has a mass on his third eyelid (nictitating membrane). If he is grey, it is almost certainly a melanoma, and in horses with white around the eye, the tumour is usually a type of squamous cell carcinoma. A biopsy would be required to confirm the diagnosis and level of malignancy. In general, horses can tolerate the surgical removal of the third eyelid and the procedure is fairly uncomplicated and low-risk. In some cases this can be performed in a standing horse with sedation and local anesthesia. The whole thing can then be sent to the lab for identification of the mass, which can help determine the long-term prognosis. There is little chance that he would lose the eye unless the tumor has spread onto the cornea. Usually there are obvious signs of discomfort around the eye if this has occurred, including squinting, tearing, and rubbing the face. Occasionally, the third eyelid enlarges from simple irritation during the summer from flies and dust. In any event, it is a good idea to keep a fly mask on during the day to minimize this problem. I would ask your vet to take a look at this lump if it seems to be enlarging more rapidly than before, because it is much easier to deal with a mass if it is small and has not spread to other local structures.

Melissa Mckee DVM

Runny Eye

My horse has discharge in one eye and its very pink. I have been told that I can use polysporin drops. Is there something else that I should be using or doing instead?

There are several reasons why your horse may have discharge from his eye, and the most common causes include conjunctivitis, allergy, corneal ulcer, blocked tear ducts, and uveitis (moon blindness). While mild irritation from dust and allergy is the most likely cause of the discharge, some of these problems are potentially quite serious and all will have a slightly different treatment approaches. Polysporin ophthalmic ointment is a reasonable choice for an irritated eye, but horses with conjunctivitis, allergies, and uveitis will benefit from an ointment that contains some type of steroid to reduce the pain and inflammation. The problem is that a steroid ointment will seriously impair the healing of any corneal ulcers and could result in severe consequences such as fungal ulceration and corneal perforation. Because of this, I think it is a good idea to get a veterinarian to examine the eye and stain the cornea for ulcers on any painful runny eye. Treating with the wrong medication will at best prolong the course of the problem and at worst could damage his eye and vision. In the meantime, gentle application of cloths soaked in black tea will loosen the debris and the tannic acid in the tea will soothe the inflammation.

Melissa McKee DVM

Scar on Eye

I have bought a horse with an eye injury. He is 3 and they tell me he has had this since he was a weanling. He can see but he does have a white spot about the size of the end of a pen. Is there anything that can be done at this point to clear the spot away? Is there such a thing as laser treatments?? He is a handsome fellow and it would be worth it to spend the money if the options where there.

A healthy cornea is composed of collagen fibrils that are all aligned in a very particular way so light can pass through them and into the eye. When the cornea is scratched or has an ulcer, it unfortunately fills in the defect with “cheap stuff”-still collagen but the fibrils are now scrambled up- creating a white dot of scar tissue. Lasers are used for “phacoemulsification” of cataracts but those occur in the lens, which is a completely different structure and opacity there truly does impair vision quite seriously. Although unsightly, small corneal scars do not seriously impair a horse’s vision. Until we can convince the cornea to realign the collagen in those spots, there is little that can be done to reduce the blemish. The good news is that these often will diminish in size and opacity over time, so as your guy ages the spot may become less noticeable.

Melissa McKee DVM

Trouble Adjusting to Dark

I am acquainted with a horse that has difficulty leaving a lit barn and going out into the dark.

His daytime vision seems OK and once he becomes adjusted to the dark, he seems fine–it it just the transition.

Could this be a pre-cursor so something more severe or could it just be his physiology.

Horses are naturally suspicious of entering dark and uncertain areas so this individual may just be exhibiting more caution behaviours than an average domesticated equine. In order to acclimatize to the darkness, the pupil needs to dilate to allow more light to strike the retina and this can occur more slowly in some individuals. Horses with unusually large corpora nigrans (the little dark fringes/clouds that appear to float out of the pupil) also can have trouble with the light to dark adjustment. Horses that are developing recurrent uveitis (moon blindness) typically have the opposite problem, that is, they have trouble adjusting to bright lights and will appear to be squinty and painful. Still, you may want your vet to perform a more thorough ophthalmic exam next time they are out in order to determine if there are any retinal or pupillary abnormalities.

Melissa McKee DVM


Sore Eyes form Spray

I do not think that the roundup spray is related to the eye problem your horse is experiencing, and I am sure the prognosis for his vision is good with your extremely diligent treatment. I suspect that the initial problem several weeks ago was either conjunctivitis, which inflammation of the soft tissue lining the eye socket from dust and allergens (ragweed season was in full swing at that point), or a flare up of recurrent uveitis (moon blindness). Either condition makes the eyes sore and crusty, causing the horse to rub them for relief. It is only a matter of time before they manage to scratch the cornea, causing the resulting ulcer. At this point, the cloudiness you see is because water gets into the cornea through the damaged epithelium, interfering with the normal passage of light. Once the ulcer is resolved your vet may choose to dilate the pupil in order to carefully examine the retina for signs of recurrent uveitis, because there are many treatment strategies available to prevent future flare-ups. In the case of allergic/irritant conjunctivitis, application of an antibiotic/steroid ointment and flushing the tear ducts can give tremendous relief during an episode. For now, hang in there. The successful outcome of an eye problem depends on the commitment of the person performing the treatments, so you are doing great in that department. For the future, you may want to talk to your vet about finding the underlying cause of the initial irritation so you can prevent the problem from reoccurring.

Melissa McKee DVM