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is equivalent to the interstitial space. In particular look for hypopyon (white blood cells), hyphema
(red blood cells), and fibrin, aqueous flare (albumin and other small proteins) and keratic precipitates (white blood cells and inflammatory proteins clumped against the corneal endothelial surface).
Chronic uveitis and its sequelae are associated with scarring (fusion of one tissue to another and cicatrization), chronic dysfunction, and neovascularization evident as glaucoma (due to scarring or clogging of the iridocorneal angle), anterior or posterior synechia (adhesions between the iris and corneal endothelium or lens, respectively), phthisis (globe contracture) or retinal detachment (due to contraction of vitreous fibrin). Altered aqueous humor composition and circulation also causes a relative malnutrition of the lens (evident as cataract) and inner cornea (evident as corneal edema, vascularization, fibrosis etc.). Lens luxation may occur due to enzymatic lysis or phagocytosis of the lens zonules, secondary to cataract development, or as a sequela to buphthalmos due to secondary glaucoma. Neovascularization of the face of the iris (rubeosis iridis) is a pathognomonic sign
of subacute or chronic active uveitis. It is one of the signs that is seen more easily in cats than in dogs due to the typically lighter iris color of cats.
Diagnosis
Box 1 highlights the important tests to diagnose whether uveitis is present. Confirming or eliminating all suspected etiological diagnoses is the essential next step. By conducting an excellent general physical and ophthalmic exam as well as gathering a focused history, the initial goal is to establish whether further diagnostic testing is strongly supported. I do this by categorizing the uveitis as present in a well or systemically ill patient, unilateral or bilateral; exogenous or endogenous; acute or chronic; and as involving the anterior uvea, choroid, or both.
An etiologic diagnosis should then be pursued through
a diagnostic workup identical to that employed for a cat with lymphadenopathy. Consider CBC, Biochemistry, urinalysis, serology, chest and abdominal imaging, etc. as appropriate for the following agents.
Etiology
The known causes of endogenous anterior uveitis in cats are expanding but still too few to explain the majority
(~ 70%) of cases.
Infectious agents as a cause of uveitis
*Via immunosuppression or oncogenesis
† Chorioretinitis predominates
¥ Seroprevalence data only; no clinical evidence Neoplasia as a cause of uveitis
The most common primary intraocular neoplasm is melanoma; however this typically causes little or no uveitis. By sharp contrast, the most common metastatic ocular neoplasm – lymphoma – tends to be associated with marked breakdown of the BAB with hypopyon formation, fibrin exudation into the anterior chamber,
and hyphema. One of the curious observations with this disease is that the degree of apparent pain often seems less than might be expected from the severity of other signs of intraocular inflammation. The exception to this is when secondary glaucoma occurs, which can be quite frequent due to the highly cellular and fibrinous nature of the anterior chamber exudate
Treatment
Treatment of anterior uveitis must be tailored to the individual case based on proven or suspected cause, severity, anatomical location, chronicity, and presence of systemic or other intraocular disease. Regardless, some general therapeutic guidelines are possible.
Your Singapore, the Tropical Garden City
 Tonometry (IOP assessment)
· Decreased or low-normal in uncomplicated uveitis
· Elevated or high-normal when complicated by glaucoma
   Pupil dilation
· Resistance to dilation
· Snow banking
   Assessment of aqueous flare
   · Serum proteins in the AC due to BAB breakdown
   Fundic examination
· Signs of posterior uveitis (Retinal detachment or degeneration, chorioretinal granulomas, hemorrhage, edema)
· Vitreous debris/infiltrates
· Snow banking (cats)
  Application of fluorescein stain
 · Corneal ulceration suggests exogenous (axonal) uveitis
· Corneal ulcers preclude use of topical corticosteroids
    Viral
  Bacterial
  Fungal/Algal
 · FIP
· FeLV* · FIV
· FHV · CDV · CAV
Parasitic Cuterebra Larval migrans
   · Bartonella spp.
· Mycobacterium spp.
· Ehrlichia spp.¥
· Borrelia burgdorferi¥
· Brucella
· Leptospira
Protozoal
· Toxoplasma gondii
· Leishmania spp.
 · Cryptococcus neoformans†
· Histoplasma
capsulatum†
· Blastomyces
  dermatitidis†
· Candida albicans
· Coccidioides immitis†
· Aspergillus spp.
 Box 1. Essential diagnostic tests to detect evidence of uveitis (Tests should be conducted in this order) IOP = intraocular pressure; KPs = Keratic precipitates; AC = Anterior chamber; BAB = Blood-ocular barrier.
 Ophthalmic test
   Look for:
   Retroillumination
 · Anisocoria (especially due to miosis)
· Dyscoria
· Corectopia
· Iridal atrophy
· Opacities in the clear ocular media (KPs, hypopyon, hyphema, vitreous debris, posterior synechia, secondary cataract)
    Oblique illumination of eye
 · Corneal edema
· Iridal swelling/nodules
· Iridal thinning/atrophy
· Rubeosis iridis
· Posterior synechia
· Iris bombé
· Hypopyon
· Hyphema
· AC fibrin
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