September 2019 - Lameness
Join us this month during AAEP's "Ask the Vet" forum as our expert, Dr. Michael St. Blanc, answers your questions concerning equine lameness.
Click here to read this month's questions and answers.
My horse’s eyes always run and I have been told it is due to allergies since it occurs less in the winter. I assume this might be true? Any ideas for relief?(View Answer)
Tearing in horses can be due to a number of reasons. It could be due to excessive debris/allergens, an obstructed tear duct, or potentially an injury or disease of the eye causing discomfort. While there are other reasons, those are the three most likely. If the horse has been examined by a veterinarian and no infection, trauma, or inflammatory disease is identified, it is likely that the tear duct is obstructed and needs to be flushed. During spring and summer months with pollen and other environmental allergens (in addition to flies) at a higher concentration, horses are more likely to experience blocked tear ducts (nasolacrimal ducts). This duct goes from the corner of the eye to the nose and runs inside the skull. Your veterinarian might flush this duct with saline to gently clear the duct and allow the tears to once again drain from the eye. You might also try a fly mask and keeping pastures cut short. Chelsey Miller, DVM, Iron Will Mobile Veterinary Services, Burlington, NC.
How successful is cataract surgery on horses? And older horses?(View Answer)
A cataract is an opacity or white/hazy area in the lens. When this develops it blurs vision either modestly or completely depending on the size of the cataract. Cataract surgery in horses is a surgery that is done under general anesthesia and involves specialized equipment, and is typically completed by a board-certified veterinary ophthalmologist. The outcome or success of the surgery is somewhat dependent on the reason why the cataracts are present.
The most common reason for cataracts in a young horse - often diagnosed when the horse is a foal - is congenital, meaning the cataracts are present at birth. These cataracts can be successfully addressed with surgery. It is important to understand both the specifics of the surgery and the post-operative care, as the foal requires frequent topical eye medication for an extended period of time following the surgery. It is important that the owner is on-board with the post-operative regimen as it requires a good deal of dedication and multiple recheck appointments.
Cataracts develop over time in older horses. The most common reasons for older horses to have cataracts is that they have chronic inflammation in their eye(s). This is typically caused by equine recurrent uveitis (ERU). Typically, cataract surgery in these horses brings with it an additional set of potential complications because the chronic inflammation in the eye cause by ERU is still present at the time an owner might be considering cataract surgery. The decision of whether to perform cataract surgery on a horse with a cataract due to ERU would be best made following a complete assessment of the individual horse’s eyes; however, in general the success of the surgery is less in these horses. Chelsey Miller, DVM, Iron Will Mobile Veterinary Services, Burlington, NC.
My 17-year-old Quarter horse has a constantly tearing left eye. When I purchased him nine years ago, my veterinarian said he has a narrow tear duct and cleared it a couple of times. However, it just recently started tearing again. It doesn't bother him but tears enough to leave "salt" on his face after a few hours. I have stopped having it cleared since it doesn't seem to make a difference. He wears a mask during fly season. Should I be doing more?(View Answer)
Narrowed nasolacrimal ducts (tear ducts) are a common issue in horses that can lead to frequent “blocked” ducts and subsequent tearing because the tears cannot exit through the “normal” route. This issue could be related to abnormal anatomy or trauma to the skull, resulting in a structurally narrowed duct; another possibility is scarring following infection of the duct at a previous time. Often, if your veterinarian has determined that the tearing is definitely an outflow problem - narrowed tear duct - you can help reduce how often it is blocked by using a fly mask to decrease the amount of dust, pollen, and debris that the eye is exposed. By doing this, you will decrease the amount of tearing and debris that goes into the tear duct - this can be especially useful during the spring months when the allergen exposure is quite high. If appropriate, some horses sustain improvement after topical ophthalmic corticosteroids are administered for a short time to reduce swelling and inflammation in the tear duct - this may or may not be appropriate in your particular horse and discussing options with your veterinarian would be advisable. Finally, keeping the face below the eye free of dried tears is important as this build up can cause horses to rub their face/eyes and lead to cornea ulcers. Additionally, if not gently cleaned daily, they can developed dermatitis or inflammation of the skin. Chelsey Miller, DVM, Iron Will Mobile Veterinary Services, Burlington, NC.
My gelding is always swollen above and below his eye. I am referring to the skin/lower lid and upper lid into the hollow above the eye. His dam has primary glaucoma. His numbers are high normal without a daily supplement of MSM. With it, his numbers are in the mid normal range, but still shows swelling.(View Answer)
Swollen or edematous eyelids can be caused by a number of problems, and it might be useful to investigate other reasons for the swollen eyelids. A few questions that might be useful to answer would include:
What are the exact pressure measurements and how are they taken? How many times have the pressure been repeated and at what times of day?
We know that the intraocular pressure (IOP) in horses can be altered based on the time of day the pressures are taken, different operator and equipment used, whether sedation was used, and how high the head is in relation to the horse’s heart. Keeping all of those constant would be critical to determine whether the pressure are troubling or truly normal.
What is the age and breed of your gelding? Are there any other abnormalities in the affected eye/eyelids? The age and breed might lead one to suggest certain diagnostic tests, and consider different causes depending on whether the horse is old versus young, or a certain breed (squamous cell carcinoma in horses with depigmented skin, common in Appaloosas and some Quarter Horses). A sedated exam of the eyelids, including palpation of the eyelids and potentially biopsy of any abnormal conjunctiva (pink tissue lining the eyelid) might be useful.
At a basic level, getting a definitive diagnosis or explanation of what is causing the eyelid swelling is critical to the next step. Chelsey Miller, DVM, Iron Will Mobile Veterinary Services, Burlington, NC.
Does congenital glaucoma always lead to blindness if the pressure can be control with medication?(View Answer)
Glaucoma encompasses groups of vision-impairing problems in the horse that have in common the fact that horses with glaucoma have an abnormally high pressure inside the eye or globe - the intraocular pressure or IOP. When the pressure in the eye is chronically elevated, vision is compromised. Congenital glaucoma is an abnormally elevated pressure inside the eye caused by developmental abnormalities in the eye. Whether a horse with congenital glaucoma caused by one of several structural problems ultimately loses some or all vision depends on the type and severity of the abnormality, whether multiple abnormalities are present, and how well the pressure can be controlled with medication. Prognosis is determined based on ophthalmic examination, response to treatment, period of time prior to initiating treatment, and other diagnostic tests (electroretinogram to test the function of the retina and ultrasound of the globe to evaluate structural abnormalities). Chelsey Miller, DVM, Iron Will Mobile Veterinary Services, Burlington, NC.