Runny Eye

My horse has a red runny eye. Can I use sterile 0.9% normal saline,or what do u suggest?

It sounds like your horse may have conjunctivitis (inflammation of the tissue that lines the eyelid and eye socket), which is a common occurrence in the summer due to dust, allergies, and flies. Sterile saline is very benign and there is no harm in flushing the eye with this, it will help to rinse out any foreign material that could be causing the problem. There are medicated drops available from your veterinarian that contain lubricants and medication that are even more effective for treating conjunctivitis, however, an inflamed and watering eye can be a sign of more serious issues such as uveitis (moon blindness) or a corneal ulcer, and in some cases a steroid eye drop can make the condition far worse. Your horse may also have a blocked tear duct that requires flushing with a special catheter so the eye can drain normally again, otherwise you could have persistent tearing and irritation. If this eye problem persists for more than a day in spite of saline rinses, you should have your vet examine the horse to determine if there is a more serious underlying problem and prescribe the correct treatments to alleviate the situation.

Melissa McKee DVM


I have a horse (2005 Appaloosa/Thoroughbred mare) who has become “suddenly” blind. She was diagnosed with cataracts (at 10 years old – no signs of uveitis) that she may have been born with, but have progressively gotten worse over time. Over the last 9 years of ownership, there have been no obvious signs of vision trouble until summer this year.
At this time, I know that surgery is the only option for restoring sight, however I’ve just read a news article that scientists have developed an eye drop (lanosterol) that can dissolve cataracts. These are still in trials, so  it is unknown when they may be widely available.
Having said that, someone has told me that there is apparently already available a drop that claims to dissolve cataracts in humans and dogs. It is an N-acetylcarnosine drop. What are your thoughts on this and would it be worth asking my local vet to investigate this further?

Cataracts occur when there is scarring in the lens of the eye. The lens serves to transmit and focus light that enters the eye onto the retina, and if there is an opaque region in this structure it interferes with normal vision. Cataracts can be congenital, or they can form later in life due to injury or inflammation of the eye.

Your mare is half Appaloosa, and this breed has a very high rate of uveitis when compared to the average horse population. Even if there were no immediate clinical signs of uveitis, it can be difficult to evaluate the retina and optic nerve if a cataract is obscuring the lens without specialized examination equipment and techniques, so I would not yet rule out episodes of uveitis as the inciting factor for the worsening of her cataracts.

Since bilateral vision loss is a severe issue in horses, I suggest you consult a board certified veterinary ophthalmologist for a full evaluation of her eyes in order to develop a plan to address the cataracts and prevent further loss of sight. I would certainly obtain a leptospirosis titer to determine if this infection is present, which is a high risk factor for uveitis and the associated complications. Identifying and treating any predisposing factors in her case will help to prevent or at least slow the onset of further lens scarring.

Surgery is still the most effective treatment for mature cataracts. There has been some investigation in the use of N-Acetylcarnitine drops for reduction of mild immature cataracts, but the evidence for their effectiveness even in these cases is weak. They would not have a useful effect on a mature established cataract.

Melissa McKee DVM

Large Corpora Nigrans

My horse has a very large “bubble” of the corpora nigra in the centre of his right eye. When I first got him I was not aware of it He has always been more worried about action going on to his right side and has been seemingly irrationally spooky and nervous at times.

We have seen this problem in other horses who have become spooky and started refusing fences totally out of character.  Opthalmic examination revealed a large “floaty” corpora nigrans cyst. These structures are not painful or degenerative but can interfere with vision. There is a laser ablation procedure available that can be performed at OVC where the cyst is burned away, leaving vision and pupil function intact. If his behaviour is truly a problem you may want to consider this option.

Melissa McKee DVM

Swollen Runny Eye

About a week ago I noticed my horse’s left eye just looked a bit glossier than the right. Now it is really weepy and a  whitish goop builds up in the corner. The rim around the eye is not really pink. Is there anything I  can do to help it?

Your horse may have conjunctivitis, which is why you are starting to see a pink rim where it used to be black. The salmon-coloured flesh that lines the eye socket is inflamed and protruding visibly around the eye. The most common causes of this include irritation from dust and allergies, uveitis, infection, blocked tear duct, corneal ulcer, or foreign material in the eye. The treatment of this condition really depends on what is causing the problem, and it is important to know what the actual diagnosis is because using the wrong medication can have serious consequences. The most important thing is to determine whether there is an ulcer or scratch on the cornea because certain eye ointments that are great for simple allergic irritation will slow the healing of an ulcer and promote bacterial infection. There could also be grass awns or other particles trapped under the lids, which causes chronic irritation and need to be flushed out. As well, blocked tear ducts prevent the eye from draining normally so normal secretions accumulate in an ugly yellow crud in the corner of it. If this is a persistent problem, you may want to have your vet take a look. A few simple observations and diagnostic tests can tell you what is causing the swelling and the cure is usually very straighforward. Hopefully it is just minor irritation, but some of the problems I mentioned can have serious consequences if left too long so I would have it checked out.

Melissa McKee DVM


My 11yrs old TB gelding’s left eye turned milky white and he does not react on direct light (into the eye). He does not seem to be stressed or in pain. The vet suspects a glaucoma since he did not find any injuries in the eye. To check that out, the vet put a greenish fluorescent liquid into his eye.

The vet recommended to send him to a clinic for further checking and possibly treatment.

Here’s my problem> the clinic offered to call them on Monday for an appointment with the eye specialist. They have no idea, how long i’d have to wait for that appointment. But I also could bring my horse on the weekend – as an emergency case, although the eye specialist may not be there. But is a possible glaucoma an emergency? What are the risks if I wait?

If possible, I want to avoid total blindness in his eye, because that could make it quite dangerous (maybe even impossible) for him to return to the herd.

Any suggestions?

Glaucoma is the term used for increased fluid pressure in the eye. The cornea becomes stretched and cloudy, resulting in a barrier to the passage of light to the back of the eye. The only way to truly determine intraocular pressure (IOP) is with a device called a tonometer, which is usually only available through a specialist. Although the appearance of cloudiness can be quite sudden, most glaucoma is the result of slowly increasing pressure rather than and acute traumatic event. A dramatic increase in IOP in a short period of time is usually very painful and it does not sound like your horse is uncomfortable. Fluid accumulates in the eye for a number of reasons but it can be simply broken down into two categories: reduction in the normal drainage rate of eye fluid (aqueous humour), or abnormal overproduction of this fluid. Sometimes inflammatory debris or scar tissue can block the drainage- I wonder if your guy’s accident a few years back created some scarring that has gradually impaired normal drainage. Chronic inflammation from uveitis (moon blindness) can also cause this blockage. Glaucoma can be managed in several ways depending on the severity of the condition, with medications that control the production and drainage of fluid, by surgically destroying the tissue that produces fluid, or by enucleation (eye removal) in chronically painful and hard to manage cases. Chances are, your horse already has minimal to no vision in this eye as chronic pressure will cause the optic nerve to atrophy, but this can only be determined once the cornea clears up. Don’t worry too much about the vision loss though; partially impaired horses do incredibly well and I know several almost totally blind individuals who still raced and performed under saddle without so much as a stumble (we discovered the near-blindness during unrelated physical exams). I think you need to ask your vet what is the appropriate action in this particular situation- they may feel that this is truly an emergency and he is better off in a clinic where they can start him on meds to reduce the pressure in his eye, rather than waiting until next week. Since this is the person who actually examined the eye, I would rely on their advice. Good luck,

Melissa McKee DVM

Leptospirosis and Blindness

I am just discovering one of my broodmares is virtually blind. No spook etc when I make sudden movements etc. She seems to be 100% blind on the left and at least 75% on the right (or FREAKISHLY unspooky!!!). I was told she was quite ill for a number of weeks several years ago. No definite diagnosis was ever given, but another horse on that property DID contract lepto and did go blind.

My mare has no squinting, no lacrimation (that is not normal for a healthy eye) and it really doesn’t seem to bother her pain wise.

Will this get worse (if in fact it’s lepto induced blindness) or would it likely settle to what it is now?

Leptospirosis is a bacteria that can indirectly cause blindness if it gets into the fluids inside the eyeball and triggers repeated bouts of immune-mediated uveitis (moon blindness). We routinely check lepto titres on horses with repeated uveitis episodes, and will treat those with signs of active infection. Leptospirosis comes in many strains (called serovars) and can cause a variety of health problems including kidney disease and abortion. It is spread in the urine of infected wildlife, so it is easy to pick up from contaminated wetlands and water troughs. In endemic areas, especially in breeding operations, the small animal vaccine can be used off-label to provide some immunity to the horses.

Your mare’s history of illness could indicate she had contracted this bacteria, but I would check a titre before assuming she has an active case at this moment. The blindness that she has now would be from secondary effects of inflammation in the eye- cataracts, detached retina, corneal opacities, etc. rather than from active infection. Your vet can determine how much vision she retains by examining the eye and testing the pupil reflexes, and discuss whether vaccination might be advisable considering she is a broodmare and this bacteria can cause abortion. Quickly controlling any future episodes of inflammation is the most important thing you can do to preserve her vision going forward. Horses can adapt amazingly well to blindness, especially if it is slow to develop, and a solid old broodmare is probably not surprised by much anymore either way. You can certainly bell the foal, but be careful of course to use a quick release collar in case the little monkey gets caught J

Melissa McKee DVM

Weepy Eye

I have a mare that was thought to have scratched her eye on something outside. I had the vet come and look at it. He said it was a little infected and gave genta spray and chloramphenicol ointment. This cleared up the infection but the mare was still holding the eye mostly shut and it kept weeping clear fluid. I had the vet come back out and do a tear duct flush and more genta ointment was applied for 1 week. She was sensitive to light shining in the eye. Other then holding the eye half shut and it weeping a little less I am seeing no improvement. Any advise on what to do next?

It sounds like there may still be either a persistent scratch on the eye or she is suffering from a bout of uveitis (non-infectious inflammation that is called moon blindness when chronic). I am not sure if your vet has stained to eye to check for ulcers but it may be worth repeating this test. Sometimes a small foreign body can be trapped under the lid that continues to rub the cornea despite medication. This has been going on a little longer than normal for a routine corneal abrasion so a more thorough ophthalmic exam may be required. I suggest you give your vet a call to discuss her ongoing situation, as different medications may be in order.

Melissa McKee DVM

Preventing Uveitis Flare Ups

We are adopting a standardbred who has had uveitis. He is 5 years old. Is there anything we should do to help prevent flare-ups? Is there any reason he couldn’t show schooling shows? Are their any meds or supplements to help to prevent/during a flare up? You can’t even tell he has it right now.

It is unusual for a young Standardbred to have recurrent uveitis, and I wonder if he originally had some kind of eye injury that predisposed him to it. There is no evidence of a hereditary component to this condition in the Standardbred breed. There are a few strategies you can employ to protect the eye from future episodes, which in many cases is thought to result from an inappropriate immune response within the eye that damages tissue and causes pain and inflammation. I recommend that uveitis-prone horses wear a fly mask whenever they are on turnout, to prevent exposure to UV radiation, dust, and flies. This will reduce mechanical irritation and damage from the UV rays. In addition, we try to avoid stimulating the immune system, which can happen when the horse is dewormed and vaccinated. Alternatively, you can routinely check fecal samples for parasite eggs and only deworm when some are observed on the fecal float. We also try to keep the vaccination program as conservative as possible, only give 1-2 vaccines at a time, and pre treat the horse with banamine to keep any resulting ocular inflammation under control. Leptospirosis has been implicated as a cause of uveitis, so you can check his lepto titre, and if it is high, treat with an appropriate antibiotic. If he does have an episode, your vet will prescribe medications to reduce inflammation and dilate the pupil to ensure it doesn’t scar closed. There are many more aggressive treatment options for horses with severe chronic disease. Overall, I think you are absolutely fine to show this guy and with a little care and luck you may never have an issue.


Melissa McKee DVM

Burr in Eye

My horse came in on Sunday with tons and tons of burrs and one of his eyes was a bit puffy and runny and he was closing it a lot. We thought that maybe a little piece of a burr got into his eye and was bugging him so we put some polysporin on and drops etc. Last night I came up and his eye wasn’t as puffy and much more open (still runny though) but it looked like there was a small gray circle on his eye – almost like a blister? It looked like a spot of gray discolouration. Has anybody had anything similar to this happen?

It sounds like your horse has a corneal ulcer from the burrs scratching his eye. I would touch base with your vet since these problems can get out of hand and result in a permanent scar. The polysporin is fine to use in the meantime but be sure that there is no cortisone in the ointment as that will slow healing and enable a bacterial infection to establish. Burr fragments tend to get lodged under the eyelid and continue to scrape the cornea so I will often apply topical anesthetic and explore the underside of the lid with my finger to be sure there are no foreign bodies remaining

Melissa McKee DVM

Laser Eye Surgery

I’ve searched and read your answers on other posts about corpora negra. I suspect I’m going to have to deal with this on my pony, our vet today told us that he had extremely large ones in both eyes which more than likely are impairing his vision.

Can you tell me what the laser surgery involves in terms of preparation beforehand, I’m guessing it’s day surgery?, and what the after care instructions might be. Would I be expecting a stay of one day or more? How long is the recovery time before they can get back into work? And, if you don’t mind sharing, the general costs?

The horses that we have sent in were treated on an out-patient basis, and were home snug and sound by dinner time. There is really no preparation but they will be on some anti-inflammatory medications after the procedure since there will be some irritation in the eye for a few days. Most were back to work fairly quickly- you will not miss a big chunk of the show season if you have this done in the spring. The cost varies per case but I think that out last referral was between $1200 and $1500.

Melissa McKee DVM