Equine Recurrent Uveitis
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
Emergency presentation is possibleEvery painful eye is an emergency because owner observation cannot distinguish ERU from corneal disease safely.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Equine recurrent uveitis, or ERU, is immune-mediated inflammation inside the eye that recurs in episodes or persists at a low level. It is the leading cause of blindness in horses. An initial infection or injury may trigger loss of immune tolerance; Leptospira infection is an important association in some regions, and Appaloosas have increased genetic risk.
An active episode causes squinting, tearing, light sensitivity, a small pupil, redness around the cornea, corneal cloudiness and protein or fibrin within the anterior chamber. Pain comes from iris and ciliary-body spasm. Between obvious attacks, insidious inflammation can continue without dramatic squinting, especially in Appaloosas, while retinal damage accumulates.
Repeated bouts cause iris adhesions to the lens, cataract, lens displacement, glaucoma, retinal degeneration or detachment and shrinkage of a blind eye. One or both eyes can be affected at different times. Corneal ulceration produces similar pain and reflex uveitis but requires different medication; applying corticosteroid to an ulcerated or infected cornea can accelerate melting and perforation.
There is no universal cure. Early aggressive control of each episode preserves vision, while surgical strategies can reduce recurrence in selected eyes. Prognosis depends on existing retinal and lens damage, frequency and Leptospira association. A horse can adapt well to one-eyed vision, but bilateral impairment creates major handling and environmental safety needs. Every painful eye is an emergency because owner observation cannot distinguish ERU from corneal disease safely.
Quiet intervals do not mean the eye is normal. Repeated inflammation progressively leaves posterior synechiae, corpora nigra change, cataract, vitreous haze, retinal degeneration and secondary glaucoma. Some Appaloosas develop insidious low-grade disease with little obvious pain, so loss of confidence or vision may be the first sign recognised by an owner.
Screening & Early Detection
Both eyes receive a complete ophthalmic examination even when only one appears painful. The veterinarian assesses menace and pupillary responses, cornea, anterior chamber, iris, lens, vitreous, retina and optic nerve. Fluorescein staining excludes epithelial ulceration before topical corticosteroid. Tonometry identifies the low pressure typical of active uveitis or secondary glaucoma.
History of prior episodes, photographs and previous treatment support recurrent diagnosis, but a first bout is investigated for trauma and systemic infection. Blood count and chemistry may be indicated. Leptospira serum antibody shows exposure rather than ocular causation; paired ocular-fluid testing can be more informative but sampling is invasive and reserved for specialist-selected cases.
During quiet periods, dilated fundoscopy detects retinal degeneration that is invisible from outside. Regular examinations are essential in Appaloosas and any horse with prior uveitis. Owners monitor subtle tearing, pupil asymmetry, altered confidence and night behaviour. A cloudy, closed or light-sensitive eye is examined the same day rather than treated from an old bottle.
A dilated retinal examination during remission records cumulative damage and retained visual potential.
Treatment & Management
Active ERU is treated promptly with potent topical anti-inflammatory medication when the cornea is fluorescein-negative, systemic NSAIDs and atropine to dilate the pupil, relieve ciliary spasm and prevent adhesions. Frequency is high initially and tapered only as objective inflammation resolves, often continuing beyond visible comfort. Atropine can slow intestinal motility, while systemic NSAIDs can injure kidney and gastrointestinal tissue, so appetite, manure, hydration and blood values are monitored.
Topical steroid is contraindicated with a corneal ulcer or active infection. Antimicrobials are used only for a documented infectious cause and do not replace inflammation control. Recurrent eyes may benefit from a suprachoroidal cyclosporine implant, which releases drug for years, or core vitrectomy, particularly in selected Leptospira-associated cases. Choice depends on retained vision, disease pattern and specialist expertise.
A blind painful eye is treated by enucleation or another pain-eliminating procedure rather than indefinite medication. Fly masks and UV protection improve comfort but do not cure intraocular autoimmunity. Long-term records of each flare guide prevention and surgical timing. Prognosis for vision is best before cataract, glaucoma or retinal detachment develops.
Medication is never shared between eyes without checking the bottle tip for contamination.
Breeds or species affected
Akhal-Teke
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Anglo-Arabian
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Arabian
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Barb
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Caspian
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Kathiawari
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Marwari
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Shagya Arabian
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Thoroughbred
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American Quarter Horse
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American Paint Horse
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Appaloosa
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Australian Stock Horse
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Brumby
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Waler
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Morgan
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Standardbred
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American Saddlebred
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Tennessee Walking Horse
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Missouri Fox Trotter
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Rocky Mountain Horse
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Peruvian Paso
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Criollo
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Mustang
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Canadian Horse
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Andalusian
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Lusitano
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Lipizzaner
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Friesian
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Dutch Warmblood
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Hanoverian
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Holsteiner
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Oldenburg
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Westphalian
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Trakehner
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Selle Français
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Belgian Warmblood
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Danish Warmblood
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Swedish Warmblood
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Swiss Warmblood
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Australian Warmblood
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Irish Sport Horse
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Cleveland Bay
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Württemberger
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Zangersheide
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Knabstrupper
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Orlov Trotter
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Camargue
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Icelandic Horse
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Pony of the Americas
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Quarter Pony
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Miniature Horse
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Clydesdale
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Shire
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Percheron
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Belgian Draft
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Suffolk Punch
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American Cream Draft
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Ardennes
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Breton
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Boulonnais
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Comtois
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Dutch Draft
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North Swedish Horse
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Norwegian Fjord
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Haflinger
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Gypsy Cob
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Irish Draught
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Welsh Pony and Cob
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Connemara Pony
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New Forest Pony
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Dartmoor Pony
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Exmoor Pony
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Shetland Pony
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Highland Pony
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Fell Pony
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Dales Pony
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Australian Pony
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Finnhorse
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Black Forest Horse
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