I believe horses may have the most sensitive eyes of all the domestic animals.  Many animals may have a little discharge from the eye or may be squinting, and although the eye should be examined by a vet, it is not as critical in as many cases as in a horse.  If a horse is squinting or an eye is exhibiting excessive tearing, you don’t want to wait and see what happens because horses can get such severe infections that they can go blind in just a few hours.  Some horses may just have conjunctivitis, which is inflammation of the tissues around the eyeball.  This is generally an easily treatable condition as long as there is no foreign body in the eye causing the problem, such as a piece of grass.  Because of this possibility, it is important for your vet to numb your horse’s eye and check for foreign material under the eyelids.  

The most common and potentially serious condition of the horse’s eye is a corneal ulcer due to a scratch from a piece of foreign material.  Many ulcers are superficial and will heal with just antibiotic eyedrops used for about a week.  However, some ulcers can be serious and deep, and can cause the eye to rupture in just a few hours, usually leading to blindness. 

At this point, it is important to say that you should never place ointment in your horse’s eye without having your vet examine it.  Many ointments for both human and animal eyes have cortisone, and using cortisone in a horse’s eye with an ulcer can lead to a severe fungal infection and rupture of the eyeball.  There are many other diseases of the horse’s eye, including glaucoma, and other types of inflammation.  So if you feel your horse have an eye problem, never place any ointment in the eye until your vet has examined the eye