THE HORSES EYE
AMAZING VISION
Horses use two forms of vison: monocular and binocular. The left and right eye work independently of each other and each produce a different vision due to monocular vision. This allows the horse to see both sides of its body. Maybe that is why a horse spooks and jumps sideways away from the perceived scary object. Binocular vision allows the horse to see directly ahead of it using both eyes together, creating a single more detailed image. However, directly under its head neck and chest, and in front of the forehead are areas where the horse cannot see. Keep in mind that also the horse cannot see directly behind its hindquarters and back legs.
THE LARGEST OF ALL MAMMALS
The horse’s eye is 8 times larger than the human eye. It provides it with 350-degree superior vision, protects it from predators, and is ideal for both day and night activities. The position of the horse’s eye does make it more vulnerable to trauma, and several eye conditions.
COMMON EYE CONDITIONS
Conjunctivitis is the inflammation of the conjunctiva, the tissue that lines the inside of the upper and lower eyelids. Symptoms such as eye discharge, swelling of the lids, eye closed, rubbing or redness of the eye may be seen. This may be caused by rubbing the eye, allergies, insects, disease, infection and foreign bodies. Conjunctivitis may also be seen as a result of a secondary problem such as an ulcer on the cornea. In these cases, conjunctivitis is a clinic sign, not the cause. Your veterinarian will examine the eye and diagnose the problem, such as conjunctivitis, corneal ulcers, uveitis, or glaucoma.
CORNEAL ULCERS
The cornea is a thin clear membrane that covers and protects the eye. It has a vital role of allowing light to reach the retina, and plays a critical role for improved vision and protection. Abrasions (from a piece of weed or hay in the eye) or injury to the cornea are common and can lead to a corneal ulcer. This can be very painful and permanently affect the horse’s vision. Signs of corneal ulcers are conjunctivitis, white discoloration of the cornea, excessive tearing and painful eye with the lids half open or closed.
To diagnose a corneal ulcer the veterinarian will place a fluorescein dye in the eye that will adhere and stain green the damaged area of the cornea. Treatment of the ulcer depends on the severity, using antibiotic and antifungal eye medications.
UVEITIS IN HORSES
The uvea is a layer of the eye that contains three structures, the iris (the colored part of the eye), the ciliary, and the choroid. Uveitis is the inflammation of the uvea. When Uveitis becomes chronic and recurs at regular intervals it is known as Equine Recurrent Uveitis (ERU) aka moon blindness. ERU is an auto-immune disease where the body’s immune system attacks its own eye tissues. It is one of the leading causes of blindness in horses, especially if left untreated. Appaloosas, paints, and warmbloods are all at a higher risk of developing ERU.
Common signs of uveitis are painful eye, squinting, excessive tearing, redness, clouding of the cornea, and constriction of the pupil.
GLAUCOMA
Glaucoma is where the optic nerve within the eye (that connects the brain) becomes damaged, causing increased pressure within the eyeball. This results in the loss of ability to send images to the brain causing blindness. Glaucoma has three forms. Primary (considered genetic), congenital (at birth, due to developmental abnormalities), and secondary (caused by eye trauma).
BE OBSERVENT
Any injury or abnormality of the horse’s eye should be considered as an emergency. Your horse should be examined promptly by a veterinarian to avoid vision impairment or loss.
FALL FECALS
To avoid resistance to dewormers, a fall fecal exam is recommended and not deworm unless the result is positive. If negative, deworm on April 15, using ivermectin, when all the worms are active.
BOT EGGS
Using a bot knife, pocket knife, or pumice stone, remove the eggs especially from the horse’s legs. The horse ingests the eggs when it reaches down to scratch where the fly has just laid them. Applying baby oil to the legs will decrease the eggs from sticking to the hair.
CASTRATION SIGNS
October 7-14
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