3 CE Credits Equine Recurrent Uveitis: Treatment Amanda Curling, DVM Abstract: Equine recurrent uveitis has traditionally been treated with medical management to reduce ocular inflammation and control pain during a single episode. Newer management methods include surgical options such as cyclosporine implantation and vitrectomy. These methods were developed not only to control inflammation but also to eliminate the underlying cause of uveitis in order to prevent recurrence. For more information, please see companion article, cal signs have resolved. Adverse effects of topical steroids include “Equine Recurrent Uveitis: Classification, Etiology, and Pathogenesis.” potentiation of infectious agents and collagenase enzymes. Appli- cation of topical steroids when corneal ulceration is present may Medical Management result in corneal melting and perforation or delayed epithelialization reatment of equine recurrent uveitis is aimed at reducing and healing of ulcers. Subconjunctival injection can provide a ocular inflammation to control pain, minimizing production therapeutic intraocular level of corticosteroid, especially if applica- Tand release of inflammatory mediators, blocking immuno- tion frequency is not conducive to owner compliance. Topical logic mechanisms to reestablish the blood–ocular barrier, and NSAIDs such as flurbiprofen and diclofenac can be used with fewer limiting recurrence to prevent further intraocular damage. Be- adverse effects and less concern when an ulcer is present; however, cause vision loss is a common long-term manifestation of equine they can also delay epithelialization and are not as effective as recurrent uveitis, initial therapy must be aggressive.1 Therapy corticosteroids in reducing intraocular inflammation.2 should be directed at the etiologic cause, whether a primary oph- Systemic therapy is the most effective method of managing thalmic disease or secondary to a systemic problem. Nonspecific equine recurrent uveitis.2 Intravenous flunixin meglumine is therapy (TABLE 1) should include mydriatic cycloplegics, such as reportedly the most effective NSAID.2 Phenylbutazone, aspirin, topical 1% atropine, which dilates the pupil, decreases the pain of and ketoprofen may also be used according to the situation.2 ciliary muscle spasms, and reduces inflammation, decreasing Systemic dexamethasone or prednisolone is highly effective for synechiae formation. As the iris is repositioned, vascular fenestra- reducing inflammation; however, the adverse effects of steroids in tions are narrowed, decreasing the leakage of protein and inflam- horses may outweigh the benefits. Systemic steroids are reserved matory cells into the anterior chamber.1 The dosage frequency for severe cases that are depends on the response of the iris to mydriasis; once the pupil is unresponsive to NSAIDs or dilated, 1% atropine should be used only as needed to maintain for cases involving corneal Table 1. dilation of the pupil (once-daily topical dosing is usually sufficient ulceration. Common Topical Medications until inflammation has subsided). If 1% atropine is not effective, Topical, intravitreal, or Medication Dosage 3% atropine can be used; however, patients should be monitored systemic antimicrobials are for signs of colic because administration of high doses of atropine indicated when uveitis is due Mydriatics can cause decreased intestinal motility, potentially leading to to bacterial infection. When Atropine HCl 1% q6–48h Phenylephrine HCl 10% q6–12h ileus, gas distention, or cecal or large colon impaction. If dilation possible, the antimicrobial cannot be achieved with atropine alone, 10% phenylephrine should be chosen accord- Steroids hydrochloride can be used in combination with atropine. ing to sensitivity patterns Prednisolone acetate q1–6h Topical corticosteroids are most commonly used to suppress of bacteria. Tetracycline or Dexamethasone HCl q1–6h inflammation. Prednisolone acetate has the best corneal penetra- doxycycline is generally not tion; dexamethasone HCl is the next best option.2 Application fre- indicated to treat horses NSAIDs Flurbiprofen q1–6h quency (ranging from twice daily to eight times daily) depends on with leptospirosis because Diclofenac q1–6h the severity of the uveitis and should be tapered slowly once clini- systemic administration of Vetlearn.com | June 2011 | Compendium: Continuing Education for Veterinarians® E1 ©Copyright 2011 MediMedia Animal Health. This document is for internal purposes only. Reprinting or posting on an external website without written permission from MMAH is a violation of copyright laws. Equine Recurrent Uveitis: Treatment these drugs does not result in therapeutic levels in the eyes. Systemi- was manufactured for place- cally administered enrofloxacin (7.5 mg/kg IV q24h) has achieved ment in the deep scleral Key Facts intraocular therapeutic levels against Leptospira interrogans serovar lamella of horses with • Systemic antimicrobials can be pomona; therefore, this drug should be considered if uveitis has been uveitis. The deep sclera la- administered for leptospiral-induced documented to be associated with leptospiral infection.3 Medical mella is situated under the uveitis. The distribution of management of uveitis should be continued for several weeks or sclera but above the chor- tetracyclines to the eye has been even months after remission of clinical signs because rapid tapering oid and allows cyclosporine shown to be below the therapeutic of topical or systemic antiinflammatories frequently leads to flare- A to be delivered to the level; however, enrofloxacin can ups of uveitis. choroid without surgical achieve a therapeutic level against Vaccination against leptospirosis (multivalent inactivated entry into the vitreous Leptospira interrogans serovar strands of L. interrogans serovars bratislava, canicola, hardjo, cavity. This technique pro- pomona within the eye. icterohaemorrhagiae, and pomona as well as Leptospira kirschneri vided sustained delivery serovar grippotyphosa, all of which are labeled for use in swine of cyclosporine A to the • No vaccine exists for leptospiral- and cattle only) in horses with nontraumatic uveitis was shown deep sclera-suprachoroidal induced uveitis in horses. Vaccination to significantly increase the time to first recurrence after the space and achieved a high of horses using swine- or bovine- second vaccination; however, there was no effect on future recur- intraocular level of drug, labeled vaccine is not recommended. rences after the second vaccination.4 Vaccination also failed to resulting in significant re- • Implantation of a cyclosporine- slow the progression of uveitis and seemed to speed progression duction of postoperative releasing device has been shown to in the vaccinated group versus the control group. Comparison of uveitis flare-ups and rates decrease the recurrence of uveitis, antibody titers in vaccinated horses versus unvaccinated horses of vision loss.10 No toxico- decrease the severity and length of demonstrated no difference. Therefore, the use of vaccination as ses or severe complications episodes, and increase the response an adjunct therapy for equine recurrent uveitis is not supported were associated with the to topical medications in patients at this time.4 implant itself. However, with recurrent episodes by the selection of appropri- suppressing immunity and blocking Surgical Management ate candidates to receive inflammatory cytokines. Newer therapies aimed at preventing recurrence of equine recur- cyclosporine A implants is rent uveitis and providing long-term control of the disease include important for long-term • Vitrectomy can clear inflammatory implantation of a cyclosporine A–releasing device and pars plana success. For example, irre- debris from within the vitreous to vitrectomy. Cyclosporine A is an immunosuppressant that focuses versible changes due to improve vision and decrease on cell-mediated immune responses and has some effect on hu- chronic uveitis eventually inflammatory mediators that may moral immunity. Cyclosporine’s exact mechanism of action is not result in vision loss and perpetuate episodes of equine fully known, but the drug is known to inhibit T-cell responsiveness decreased success of the recurrent uveitis. and block the release of interleukin (IL)-2 and T-cell growth implantation device.11 Can- factor.5 Because high numbers of T cells and IL-2 have been found didates should be in the in eyes with equine recurrent uveitis, cyclosporine A may be ideal quiescent phase of the disease to help prevent severe inflammation in preventing T-cell activation and uveitis recurrences.6 after surgery.10 Cyclosporine A may be applied topically; however, it is hydro- Vitrectomy has been evaluated for removing immune media- phobic and does not penetrate the cornea well. Therefore, it does tors, antigens, and inflammatory debris within the vitreous, not obtain a therapeutic concentration within the eye. A device possibly reducing the recurrence of equine recurrent uveitis.12 containing cyclosporine A was evaluated for intravitreal implanta- Vitrectomy does not completely remove all the vitreous; there- tion in horses after it demonstrated a sustained drug level in the fore, interaction between the uvea and vitreous is not completely ocular tissue of rabbits with experimentally induced uveitis.7,8 eliminated. However, reduced interaction between the uvea In experimentally and naturally affected horses, intravitreal and vitreous seems to be sufficient in halting the recurrence of cyclosporine