Last Updated on February 19, 2022 by Allison Price
The Internet is an amazing resource. It allows horse owners all over the world to quickly and easily exchange ideas about horsemanship and management. Unfortunately, there is a lot of incorrect information. It seems that equine eye health information is often inaccurate. Let me address some common myths about horses’ eyes.
Myth 1: Blue eyes are more likely to have eye problems. The iris of a horse with “blue” eyes actually has blue pigments. The colored area of the inside of an eye that surrounds the pupil is called the iris. Horses typically have either a blue or brown iris, whereas humans can have a wide range of colors from blue to green to brown and violet to violet. Some horses have irises that are both brown and blue; the medical term for a two-colored iris is “heterochromiairidis.” These are more common in horses with patterned coats such as Paints and Appaloosas. Horses with light-colored coats, such as cremellos, are more likely to have blue iris. However, a horse with a blue iris does not increase the likelihood of having intraocular problems such as equine persistent uveitis.
However, eye problems can also be linked to coat color. Leopard Appaloosas, for example, are more susceptible to having trouble seeing in the dark due to a condition called stationary Congenital Night Blindness. Rocky Mountain Horses, which are chocolate-colored, are more likely have multiple intraocular abnormalities including retinal detachment. These cases show that genetics play a major role in the relationships between coat color and eye diseases.
Although a horse with a blue iris may not be more likely to develop an eye disease than a horse without it, horses with blue irises are more likely to have pink skin. Pink skin is one of the main risk factors for developing squamous cells carcinoma (SCC), a type of skin cancer. SCC is more common in horses with pink eyes. Blue irises have not been shown to be associated with SCC. SCC and pink iris have not been linked.
Myth 2: Horses’ “moonblindness” is worse when there is a full moon. ERU, also known as “moonblindness” in horses, is the most common cause for blindness in horses. The immune system attacking the horse’s inner eye causes this autoimmune disease. Many researchers are trying to understand the cause of ERU in horses.
Some horse owners believed that the phase of the moon affected their horses’ ERU flare ups before the advent of science. We now know that these episodes of active inflammation are caused by the immune system, not celestial bodies.
Myth #3: Feeding your horse a nutritional supplement can prevent eye disease. Horses don’t usually develop age-related macular degeneration or cataracts like humans. This is because horses lack a central area called the macula. These conditions can be delayed by taking vitamin supplements. There is no evidence that vitamin supplements can keep horses’ eyes healthy. To ensure a balanced diet for your horse, you should consult your veterinarian
Myth #4: My horse has lost 87.6% vision. Horse owners, veterinarians, and veterinarian ophthalmologists find it difficult to assess what a horse sees. We are left with indirect measures for vision because horses cannot tell us what they see. Many visually impaired horses can adapt well to their vision impairment and navigate well in familiar surroundings. A “menace test” is the most basic visual assessment. This involves a threat gesture (typically your open-palmed hand moving rapidly towards the eye’s surface) that will cause a horse with good vision to blink or avoid the gesture. Horses can pass a positive menace test without being visually impaired. The maze test is another method of visual assessment. A horse is asked to navigate a course of unfamiliar obstacles.
There is a lot of information available on equine eyes disease. However, your veterinarian or veterinary eye doctor will be the best source of information.
