Features
Intermediate uveitis is the general terminology for inflammation localized predominantly in the vitreous, ciliary body, and peripheral retina that may or may not be associated with an infectious agent or systemic disease. Pars planitis is a subset of intermediate uveitis where the cause is idiopathic, and clinical findings include snowbank or snowball formation. Such nomenclature is an important distinction, as pars planitis is a diagnosis of exclusion that is made only after a thorough investigation into potential infectious or autoimmune causes has been conducted. Pars planitis is a nongranulomatous bilateral uveitis occurring in young individuals (e.g., 15–35 years old). As the majority of pediatric patients with uveitis have an indeterminate cause, pars planitis is most often diagnosed in this patient population. Due to the wide spectrum of clinical findings, the reported incidence and prevalence of this disease is highly variable with an incidence of between 1.5 and 2.0 per 100,000 people. Studies have suggested a genetic predisposition, and various haplotypes such as HLA-DR2, -DR15, -B51, and -DRB1*0802 have been associated with the disease. There is a strong association with the development of multiple sclerosis in patients with pars planitis, and individuals with either the HLA-DR2 or -DR15 haplotype showed the highest association.
71.1.1 Common Symptoms
Blurred vision (74%) and floaters (61%) may be present in the majority of patients at the time of diagnosis. Other less common symptoms include pain (6.5%), photophobia (6.5%), and red eye (4.3%).
71.1.2 Exam Findings
This disease usually occurs bilaterally; however, there can be asymmetric involvements. Often, the inflammation may be limited to only a few anterior vitreous cells with or without cystoid macular edema (CME). Common clinical findings include vitritis, snowballs, snow-banking (i.e., confluent deposits of snowballs inferiorly that appears as a whitish thickened area), peripheral retinal vasculitis, and CME. The peripheral retinal vasculitis may be present for 360 degrees. In addition, there may also be associated papillitis. Anterior segment inflammation, band keratopathy, peripheral corneal opacification, and posterior synechiae are observed more often in children as compared to adults.
Vitreous snowball and snowbank formation in pars planitis is common with over 65 and 95%, respectively (▶ Fig. 71.1, ▶ Fig. 71.2). Vitreous snowballs are yellow-white inflammatory aggregates that are usually found in the mid- and inferior peripheral vitreous. The frequency of retinal vasculitis is variable. Optic disc edema is also a common finding in more than 50% of cases. The presence of retinochoroidal lesions rules out the diagnosis of pars planitis.
Fig. 71.1 (a,b) Bilateral pars planitis. Ultra-widefield fundus photographs demonstrate bilateral inferior snowballs.
Fig. 71.2 Fundus photograph demonstrating an inferior snowbank (arrowhead).
71.2 Key Diagnostic Tests and Findings
71.2.1 Optical Coherence Tomography
Optical coherence tomography (OCT) is valuable in detecting CME and other sequelae such as epiretinal membrane (ERM), macular hole, and atrophy (▶ Fig. 71.3). It is useful in tracking therapeutic response and may provide prognostic information based on foveal thickness as well as other factors such as outer retinal and photoreceptor abnormalities. Eyes with abnormal ellipsoid zones on OCT may show poor prognosis and irreversible vision loss.
Fig. 71.3 Optical coherence tomography and corresponding fundus images of the (a,b) right and (c,d) left eyes of the same patient show presence of multiple cystoid spaces in both eyes along with subfoveal serous detachment in the right eye indicating cystoid macular edema.
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