Uveitis and Equine Recurrent Uveitis (ERU)

This set of flashcards covers key concepts regarding uveitis and Equine Recurrent Uveitis (ERU), including definitions, causes, symptoms, treatments, and genetic factors.

What is uveitis?

Inflammation of the uveal tract of the eye, a leading cause of blindness in horses.

What are the components of the uvea?

Iris (controls light), ciliary body (produces aqueous humor), and choroid (provides nutrition and oxygen to the retina).

What causes uveitis in horses?

It can be primary (ocular diseases) or secondary to systemic diseases such as infectious or inflammatory conditions.

What is the difference between blunt and sharp trauma in relation to uveitis?

Blunt trauma usually results in worse outcomes due to collateral damage, while sharp trauma may be more focused and specific.

What is Equine Recurrent Uveitis (ERU)?

A chronic, immune-mediated disease characterized by repeated bouts of intraocular inflammation and is the most common cause of blindness in horses.

What breeds are most affected by Equine Recurrent Uveitis?

Appaloosa, Quarter Horse, Thoroughbred, Warmbloods, and Hanoverian.

What are possible infectious causes of acute uveitis?

Bacterial (Leptospira, Brucella), viral (Equine influenza, EHV), and parasitic (Onchocerca, Strongylus).

What are common clinical signs of active uveitis?

Blepharospasm, photophobia, aqueous flare, miosis, corneal edema, retinal detachment.

What is the typical treatment protocol for uveitis?

Involves pupil dilation, control of pain and inflammation, potentially systemic NSAIDs and corticosteroids.

What is meant by 'insidious uveitis'?

A form of ERU characterized by persistent, low-grade inflammation without overt painful episodes, common in Appaloosas and Draft horses.

What is the prognosis for horses with Equine Recurrent Uveitis?

Guarded; many horses ultimately experience vision loss or require euthanasia due to the complications of the disease.

What is heterochromic iridocyclitis?

A condition characterized by anterior uveitis and corneal inflammation, typically seen in adult animals.

What is the implication of leptospirosis in uveitis?

Leptospirosis is a significant worldwide cause of uveitis, particularly in horses with exposure to cattle and ponds.

How can genetic factors influence ERU in horses?

Certain genetic markers in breeds like Appaloosas increase susceptibility to ERU, indicating potential hereditary links.

What role do corticosteroids play in the treatment of uveitis?

They are used to control inflammation, but prolonged use can lead to complications like delayed wound healing and corneal damage.

What characterizes Classical ERU?

The most common form, featuring repeated episodes of acute intraocular inflammation followed by periods of quiescence.

How is Posterior ERU defined?

Inflammation localized primarily to the vitreous, retina, and choroid, frequently observed in European Warmbloods.

What is the diagnostic finding for Intraocular Pressure (IOP) in acute uveitis?

Horses typically exhibit hypotony, with IOP < 15 mmHg, due to decreased aqueous production by the inflamed ciliary body.

How is the Microscopic Agglutination Test (MAT) used in diagnostics?

It compares antibody titers between serum and aqueous humor (C-ratio) to confirm intraocular Leptospira antibody production.

What is the primary function of topical Atropine in uveitis therapy?

To induce mydriasis (preventing posterior synechiae) and cycloplegia (relieving pain from ciliary muscle spasms).

What defines the surgical management of ERU with a CsA implant?

Placement of a sustained-release suprachoroidal cyclosporine device that provides local immunosuppression for 3-5 years.

What are the indications for a Pars Plana Vitrectomy?

Surgical removal of the vitreous to eliminate inflammatory debris, mediators, and potentially infectious agents like Leptospira.

Why is Leptospira vaccination controversial in equine medicine?

There is a theoretical concern that vaccination may trigger or exacerbate immune-mediated uveitis in susceptible or previously affected horses.

What are common clinical sequelae of chronic ERU?

Secondary complications include cataracts, glaucoma, phthisis bulbi (shrunken eye), and posterior synechiae.

How is Heterochromic Iridocyclitis with Keratitis (HIK) treated?

Requires aggressive, long-term topical and systemic anti-inflammatory therapy to manage both corneal edema and chronic internal inflammation.