The uvea—made up of the iris, ciliary body, and choroid—is a pigmented, vascular structure of the eye. These anatomic components can be used to divide the uveal tract into anterior (iris and ciliary body), intermediate (ciliary body and pars plana), and posterior (choroid) locations. Inflammation of the uveal tract, or uveitis, may also involve the retina and the retinal vasculature.
CLASSIFICATION
In 2004, the First International Workshop on Standardization of Uveitis Nomenclature (SUN) endorsed an anatomic classification of uveitis based on the International Uveitis Study Group (IUSG) criteria.
Prior to these working groups, there were several grading systems in use. Standardization of classification criteria, inflammation grading schema, and outcomes allows comparisons of clinical research from different centers. Use of these criteria confers several advantages, including better definition of the clinical course of disease and more efficient evaluation of new therapies.
The SUN Classification contains several important features.
The type of uveitis is determined by the predominant site(s) of uveal inflammation.
The anatomic localizations are anterior, intermediate, posterior, and panuveitis (Table 2-1).
Identifying the predominant site of inflammation also helps to narrow the differential diagnosis (Table 2-2). Significant inflammation of the anterior chamber and vitreous is not panuveitis. (These should be classified as anterior and intermediate uveitis, respectively.)
Anatomic classification is not influenced by the presence of structural complications.
For example, the presence of macular edema or optic disk edema alone is not enough to classify an eye as “posterior uveitis.” Macular edema due to anterior chamber inflammation would be correctly categorized as anterior uveitis.
Vitritis plus peripheral vascular sheathing or macular edema is defined as intermediate uveitis, as this is the predominant site of inflammation.
Table 2-1. SUN Working Group Anatomic Classification of Uveitis
| Type | Primary Site of Inflammation | Includes |
| Anterior uveitis | Anterior chamber | Iritis, iridocyclitis, anterior cyclitis |
| Intermediate uveitis | Vitreous | Pars planitis, posterior cyclitis, hyalitis |
| Posterior uveitis | Retina or choroid | Focal, multifocal, or diffuse choroiditis; chorioretinitis, retinochoroiditis, retinitis, neuroretinitis |
| Panuveitis | Involves all compartments of the eye without one predominating |
Adapted from Jabs DA, Nussenblatt RB, Rosenbaum JT. Standardization of Uveitis Nomenclature (SUN) Working Group. Standardization of uveitis nomenclature for reporting clinical data. Results of the First International Workshop. Am J Ophthalmol. 2005;140(3):509–516.
Table 2-2. Differential Diagnosis of the Major Causes of Uveitis
| ANTERIOR UVEITIS* | |
| Granulomatous | Nongranulomatous |
| Sarcoidosis Syphilis Tuberculosis Herpes simplex Leptospirosis Brucellosis Phacoanaphylactic Idiopathic | Human leukocyte antigen-B27–associated (including ankylosing spondylitis, Reiter’s syndrome, inflammatory bowel disease, psoriatic arthritis) Juvenile rheumatoid arthritis Fuchs’ heterochromic iridocyclitis Posner-Schlossman (glaucomatocyclitic crisis) Masquerade syndromes Uveitis-glaucoma-hyphema syndrome Trauma Kawasaki’s disease Drug-induced (rifabutin, cidofovir) |
| INTERMEDIATE UVEITIS | |
| Sarcoid, syphilis Inflammatory bowel disease Multiple sclerosis Pars planitis (idiopathic) Lymphoma, Lyme Other (tuberculosis, Behçet’s, Vogt-Koyanagi-Harada, Whipple’s disease, toxoplasmosis, endophthalmitis) |
| POSTERIOR UVEITIS | |
| Focal Retinitis | Multifocal Retinitis |
| Toxoplasmosis Onchocerciasis Cysticercosis Masquerade syndromes | Syphilis Herpes simplex virus (acute retinal necrosis) Cytomegalovirus Sarcoidosis Masquerade syndromes Candidiasis Progressive outer retinal necrosis Eales’ disease Diffuse unilateral subacute neuroretinitis |
| PANUVEITIS | |
| Sympathetic ophthalmia Vogt-Koyanagi-Harada Behçet’s disease Endophthalmitis Sarcoidosis Phacoanaphylaxis Lyme disease Masquerade syndromes Toxoplasmosis Syphilis Tuberculosis | |
| CHOROIDITIS | |
| Focal Choroiditis | Multifocal Choroiditis |
| Tuberculosis Toxocariasis Nocardia Candidiasis Masquerade syndromes | Histoplasmosis Pneumocystis choroiditis Serpiginous choroiditis Birdshot Lymphoma Acute multifocal placoid pigment epitheliopathy Multifocal choroiditis/punctate inner choroiditis Masquerade syndromes Cryptococcus Mycobacterium |
*This category is usually divided up into granulomatous (mutton fat KP) and nongranulomatous uveitis. All of the granulomatous ones can look nongranulomatous, but the nongranulomatous ones do not look granulomatous.
Pearl: Sarcoid, syphilis, tuberculosis, Lyme, and lymphoma can look like anything.
Pars planitis is a specific, idiopathic disease entity defined by the presence of snowball or snowbank formation in the absence of an associated infection or systemic disease; otherwise, the correct term is intermediate uveitis.
The SUN working group criteria currently has a few limitations:
It does not provide criteria for diagnosis of specific uveitic entities.
It does not address the classification of neuroretinitis.
It is still undergoing validation.
The SUN working group also standardized the descriptors of uveitis in order to facilitate clinical descriptions of diseases both for clinical care as well as for research purposes.
Onset
Sudden
Insidious
Duration
Limited (≤3 months)
Persistent (>3 months)
Course of disease
Acute (sudden onset and limited duration)
Chronic (persistent uveitis with relapse <>3 months after discontinuing therapy)
Recurrent (repeat episodes of uveitis separated by at least 3 months without treatment)
Grading
Anterior chamber cell and flare (Tables 2-3 and 2-4)
Presence of hypopyon should be noted separately
Vitreous haze
The SUN working group adopted the National Eye Institute System (Fig. 2-1 and Table 2-5).
A more recent grading system using calibrated Bangerter diffusion filters and color photographs for assessing vitreous haze is a promising technique that requires further validation (Davis et al.).
Table 2-3. SUN Working Group Grading Scheme for Anterior Chamber Cells
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