b'DEALING WITH DETERIORATING VISIONcalled multiple congenital ocular anomaly that has been linked to the silver dapple coat color, says Dwyer. Like many genetic linked diseases in horses, it presents with a spectrum of severity, ranging from minor variants to blinding sequelae. I have seen this syndrome in horses of this coat color, as well as Miniature Horses and some other breeds that are both silver dapple and other coat colors.Dwyer also describes having seen West Nile virus cause acute blindness in a few horses within 48 hours of onset of clinical signs. What Impaired Vision Looks LikeBased on the available data, it seems horses are masters of disguise, frequently hiding deteriorating eyesight behind their lovely lashes. Owners shouldnt When assessing a horses vision,feel bad about not recognizing their veterinarians might perform a dazzlehorses diminished vision; veterinarians reex test to see how the animal reacts to illumination of his eye. attest that even the most experienced horseperson can be fooled about what a horse can or cannot see. Ridden horses with major ophthalmic abnormalities, including extensive SHELLEY PAULSONand bilateral lens opacification (a fogginess to the lenses) commonly show no behavioral evidence of visual compromise, said Andrew G. Matthews, uveitis (ERU), also referred to as moonhorses and was not identified in anyBVM&S, PhD., Dipl. ECEIM, honorable blindness, a condition most owners havehorses in Malalana-Martinezs study.Member ACVO, FRCVS, an equine at least heard of, particularly in the Appa- When it does occur, glaucoma fre- ophthalmologist from Scotland, during loosa world. Uveitis itself is defined sim- quently occurs secondary to uveitis anda presentation at a recent AAEP Focus ply as inflammation of the uvea, whichrequires aggressive multimodal therapyon Ophthalmology session. On the comprises several tissues inside the eye,to address the underlying changes in thecontrary, however, horses with minor including the iris. Classic signs suggestiveeye, Dwyer says.abnormalities such as central focal of uveitis include a red, painful, cloudyOtherLess common causes of visionlens opacities or vitreal floaters can eye accompanied by miosis, a profoundimpairment and loss stem from a wideexhibit behavior suggestive of visual constriction of the pupil. Unfortunately,variety of injuries/diseases, including: dysfunction.even with aggressive treatment, about Cranial trauma, especially trainingThis can include headshaking, shying, half of all horses with uveitis eventuallyaccidents in which a horse flips over,and/or exaggerated startle responses.suffer severe vision loss. causing skull trauma that affects theOther horses with gradually declining Reasons for loss of vision associatedvisual pathways.vision, which occurs more commonly with ERU vary, says Dwyer. Some Neoplasia (abnormal growths)than a sudden loss of vision, can begin to horses suffer detached retinas, others goinvolving the globe, retrobulbar regionshow signs of hesitation or uncertainty blind from maturing cataracts, othersof the orbit behind the eye, or brainin certain situations, herd behavior may lose vision when the eye is so damagedregion near the optic nerves. Neoplasticchange, and they can actually be observed that it just scars in on itself and becomesconditions can either arise primarily inbumping into objects or obstacles, adds what we call phthisical. the orbit or can start in the paranasalDwyer. GlaucomaDefined as a multifactorialsinuses and spread or expand into theIn his presentation Matthews described neurodegenerative ocular disease,orbit.the following abnormalities and how they glaucoma typically appears as eyes that Congenital defects in which foals arecan potentially cause visual dysfunction:are big and blue, either over the wholeborn with rudimentary, nonfunctional Retinal issues presumably impact corneal surface or a portion of it. Thiseyes.visual acuity (this is the 20/20 type of condition is relatively uncommon inThere is actually a genetic conditionvision reported in humans, indicative 26November 2018The Horse | TheHorse.com'