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 Featured Case of the Month - "Uvetitis in the Equine" Definition: Uveitis is by definition inflammation of the iris, ciliary body and choroid. All these structures contain most of the blood supply of the eye so think of uveitis as inflammation of the vascular components of the eye.  There is a barrier between the uveal tract and the peripheral circulation. However, there is some penetration or it can be disrupted allowing for systemic infections or inflammatory components to enter the eye. Causes: Adult - Trauma, infectious agents and equine recurrent uveitis (moon blindness) account for the vast majority of the cases in the adult horse. - Corneal ulcer---āuveitis - Uveitis and treatment----ācorneal ulceration Steroids and direct trauma Neonate - Usually associated with septicemia secondary to failure of passive transfer of maternal antibodies in colostrum, thru the umbilicus and secondary to Streptococcus and Rhodococcus infection -Gram negative organisms are the most likely cause -Trauma Signs: - Blepharospasm-squinting or tight closure of the eye from pain - Epiphora-serous drainage or runny eyes  - Miosis-pupil constriction - Corneal edema from infiltration of the inflammatory cells and damage to the dehydration function of the cornea.  - Conjunctivitis with chemosis (edema) or reddening - Hypopyon-white blood cells in the anterior chamber. They settle to the bottom and can remain for up to 2 weeks. 
- Hazy appearance to the anterior chamber (Aqueous flare) from an accumulation of inflammatory cells and complexes. - Fibrin-Appears as a thin, grey cottony material. Will then attach to the cornea as a grayish white plaque.  Signs can range from mild to severe. Why Is Treatment So Important? - Uveitis should be treated aggressively from the beginning to prevent damage to the structures of the eye that can lead to eventual blindness. Unfortunately, even with very aggressive treatment, some eyes cannot be saved, but in other cases the disease can be halted or at least slowed down. Treatment: Aimed at controlling inflammation and dilation of the pupil to prevent synechia. (iris adhesion to the lens or cornea) 1. Anti-inflammatory drugs - Can be used topically - BNP-DEX Has ant inflammatory action but will compromise ocular surface immunity Subconjunctival: - Triamcinolone. But predisposes to fungal or bacterial keratits and cannot stop therapy Systemically: - Administration of banamine or Bute orally for anti-inflammatory and pain relief action *****Never administer steroids to an eye with a corneal ulcer***** If ulceration is present then just an antibiotic with no steroid is administered - Advise owners to call immediately if any tearing or blepharspasm occurs while administering the steroid They are at an increased risk of developing corneal ulceration while administering steroids. 2. Mydriatic agent (dilates pupil) - The iris is a muscle and will have difficulty dilating when inflamed - Atropine is administered to allow to pupil to dilate and prevent Posterior synechia. - Posterior synechia can cause cataract formation  Can keep eye dilated for 7-14 days after last treatment Can be absorbed into the systemic circulation and cause GI stasis. Need to be protected from light while eye is dilated Can also relieve ciliary spasm which will help alleviate the pain Equine recurrent Uveitis (Moon Blindness) - It was so named during the 1600's because people thought recurring attacks were related to phases of the moon - Characterized by recurring episodes of active uveitis at unknown intervals. Weekly, monthly, every other year - Episodes may be bilateral or unilateral and if there are reoccurrences it may be in one or both eyes. Sometimes can start in one eye and the other eye will become inflamed later. - Not considered to have ERU until two or more episodes have occurred - If it is ERU a trigger such as irritation to the eye, sickness for any reason, stress or from stopping the anti-inflammatory medication prematurely - The appaloosa breed is at increased risk for both uveitis and blindness. They are eight times more then likely to develop uveitis and more then four times to develop blindness compared to other breeds - Repeated episodes can lead to damage to other structures in the eye such as the lens and cornea leading to blindness - There are a couple of different possible causes for the condition. It is commonly believed that parasites, viruses and bacteria are the major culprits. One bacteria in particular, leptospira, is a common cause.  |
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