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.
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 criteria.
Before 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. The 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 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 disc 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 because this is the predominant site of inflammation.
• 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 have a few limitations:
TABLE 2-1. SUN Working Group Anatomic Classification of Uveitis
Primary Site of Inflammation
Iritis, iridocyclitis, anterior cyclitis
Pars planitis, posterior cyclitis, hyalitis
Retina or choroid
Focal, multifocal, or diffuse choroiditis; chorioretinitis, retinochoroiditis, retinitis, neuroretinitis
Involves all compartments of the eye without one location predominating
SUN, Standardization of Uveitis Nomenclature.
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
* This category is usually divided into granulomatous (mutton fat keratic precipitates) and nongranulomatous uveitis. All of the granulomatous entities can look nongranulomatous (especially with chronicity), but the nongranulomatous ones do not look granulomatous.
Pearl: Sarcoidosis, syphilis, tuberculosis, lyme, and lymphoma can look like anything.