In 2005, the world’s major uveitis societies instituted a standard of nomenclature process, termed the Standardization of Uveitis Nomenclature (SUN) system. Uveitis specialists have widely accepted the SUN system of classification as a universal method of describing uveitis entities based on anatomic location of inflammation and specific descriptors of onset, duration, and course.
This text uses an etiologic division of uveitic entities into noninfectious (autoimmune) and infectious conditions and further describes them using the SUN system’s basic anatomical classification of uveitis into 4 subcategories: (1) anterior uveitis, (2) intermediate uveitis, (3) posterior uveitis, and (4) panuveitis. When both anterior chamber and vitreous inflammatory cells are present, but the vitritis is more than expected in an isolated anterior uveitis, the classification should be “anterior and intermediate uveitis” and not “panuveitis.”
Table 5-1 reviews these 4 groups. The SUN system further refines this anatomical classification of uveitis by defining descriptors based on clinical onset, duration, and course (Table 5-2). In addition, specific terminology for grading and monitoring uveitic activity is described in Table 5-3.
Anterior uveitis produces inflammatory signs predominantly in the anterior chamber, as a result of inflammation of the iris and ciliary body. Inflammation confined to the anterior chamber can be called iritis; if there are cells in the retrolental (anterior vitreous) space, it can be called iridocyclitis. Inflammatory processes that originate in the cornea with secondary involvement of the anterior chamber are called keratouveitis. An inflammatory reaction that involves the sclera and uveal tract is called sclerouveitis.
When more than one ocular structure is involved, the convention is that the primary site of inflammation is named first. Severe or chronic anterior uveitis may produce secondary structural complications such as uveitic macular edema, optic disc swelling, cataract, corneal edema, band keratopathy, or iris abnormalities. These complications are not part of the formal classification system but may contribute to disease recognition and therapy. Table 5-4 includes a simplified scheme for patient evaluation in uveitis. (Chapter 8 discusses anterior uveitis in greater detail.)
In intermediate uveitis, inflammation is most prominent in the vitreous cavity. Inflammation occurs in the ciliary body, pars plana and/or peripheral retina. Clinical signs include vitreous haze and cellular debris that is often associated with peripheral retinal vasculitis. Macular edema is the most common structural complication; severe or chronic disease may cause peripheral exudative or tractional detachments, retinal neovascularization, cataract, or retrolental membrane formation. The diagnostic term, pars planitis, refers to the subset of intermediate uveitis in which there are peripheral preretinal collections of exudative and inflammatory debris in the absence of an associated infection or systemic disease (see Table 5-4). (Chapter 8 discusses intermediate uveitis in greater detail.)
Posterior uveitis is defined as intraocular inflammation primarily involving the retina and/or choroid. Inflammatory cells may be observed diffusely throughout the vitreous cavity, overlying foci of active inflammation, or on the posterior vitreous face. Fundoscopy reveals focal, multifocal, or diffuse areas of retinitis and/or choroiditis, often with retinal vasculitis. Entities may have a similar clinical appearance, though some clinical patterns of disease are nearly pathognomonic for diagnosis. Structural complications such as macular edema, epiretinal membrane, and retinal or choroidal neovascularization are not sufficient for the anatomical classification of posterior uveitis (see Table 5-4). (Chapters 9–11 discuss noninfectious and infectious posterior uveitis in greater detail.)
Table 5-4 Simplified Scheme for Patient Evaluation in Uveitis
In panuveitis, inflammation is present diffusely throughout the eye without a predominantly affected site. Inflammation may be associated with an infectious or noninfectious systemic disease (see Table 5-4). (Chapters 9–11 discuss noninfectious and infectious panuveitis in greater depth, and Chapter 12 covers endophthalmitis.)
Retinal vasculitis is defined by the presence of retinal vascular changes in association with ocular inflammation. The term retinal vasculitis is used in distinction to vasculopathy, in which there are vessel changes but no visible evidence of inflammation. Retinal vasculitis encompasses perivascular sheathing, vascular leakage, or occlusion shown on fluorescein angiography studies. Peripheral vascular sheathing can be observed in intermediate uveitis but is not sufficient for the anatomical classification of posterior/panuveitis. Retinal vasculitis is not considered to be a defining feature for the anatomical classification of uveitis. Table 5-5 summarizes diseases associated with retinal vasculitis.
Excerpted from BCSC 2020-2021 series: Section 9 - Uveitis and Ocular Inflammation. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.