Intermediate uveitis refers to inflammation localized to the vitreous and peripheral retina. Intermediate uveitis was first described in the literature as chronic cyclitis by Fuchs in 1908. According to the Standardization of Uveitis Nomenclature Working Group, the primary site of inflammation is the vitreous and such entities as pars planitis, posterior cyclitis, and hyalitis are encompassed. Intermediate uveitis may be initially associated with the development of a systemic disease, such as multiple sclerosis (MS) or sarcoidosis. As such, intermediate uveitis may be the first expression of autoimmunity in these patients.
Pars planitis is considered a subset of intermediate uveitis and is characterized by the presence of white exudates (snowbanks) over the pars plana and ora serrata or by aggregates of inflammatory cells in the vitreous (snowballs) in the absence of an infectious etiology (eg, Lyme disease) or a systemic disease (eg, sarcoidosis). Some authorities believe that patients with pars planitis have worse vitritis, more severe macular edema, and a guarded prognosis compared to other patients with intermediate uveitis. This primary form accounts for over 50% of patients with intermediate uveitis.
There may be an immunogenetic predisposition for the disorder in some cases (see Causes), accounting for family clustering that is seen on occasion, indicating environmental or hereditary associations. The available evidence would suggest an autoimmune mechanism; however, the antigenic stimulus remains elusive.
Traditionally, the proportion of patients with intermediate uveitis is estimated to be 4-8% of uveitis cases in referral centers. The National Institutes of Health (NIH) reports a higher percentage (15%), which may indicate improved awareness or the nature of the uveitis referral clinic. In the pediatric population, intermediate uveitis can account for up to 25% of uveitis cases.
Permanent loss of vision is most commonly seen in patients with chronic cystoid macular edema (CME). Every effort must be made to eradicate CME when present. Other less common causes of visual loss include rhegmatogenous retinal detachment, glaucoma, band keratopathy, cataracts, vitreous hemorrhage, epiretinal membrane, and choroidal neovascularization.
No racial predilection exists for this disease.
The incidence of intermediate uveitis is equal in men and women.
Although intermediate uveitis can develop at any age, it primarily afflicts children and young adults. There is a bimodal distribution with one peak in the second decade and another peak in the third or fourth decade.
In the pediatric age group, intermediate uveitis is associated with a worse presenting visual acuity. Poorer outcomes may be related to delayed presentation/diagnosis, the inherent difficulties of immunosuppression in children, or a more aggressive disease.
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