Intermediate Uveitis & Pars Planitis

The pars plana is the flattened posterior portion of the ciliary body, forming the anatomic transition between the peripheral retina/choroid and the anterior uveal tract. Intermediate uveitis is inflammation centered on the vitreous and this pars plana region. Pars planitis refers specifically to the idiopathic subtype, characterized by snowballs (vitreous inflammatory aggregates) and snowbanks (organized exudate over the pars plana/ora serrata).²

Intermediate uveitis reflects immune-mediated inflammation of the peripheral retinal vasculature, vitreous base, and pars plana, causing vitreous cellular infiltration, vascular leakage on fluorescein angiography, and, in pars planitis, characteristic snowbanking along the inferior ora serrata. Etiology can be infectious, associated with systemic disease (multiple sclerosis, sarcoidosis), neoplastic (intraocular lymphoma), or idiopathic.²

Patients present with floaters and blurred vision, typically without the pain, redness, or photophobia of anterior uveitis. A dilated fundus exam in any patient with new floaters is essential, since the diagnosis is easily missed on anterior segment exam alone.²

Key differentials/masquerades: infectious vitritis (syphilis, tuberculosis, Lyme disease), sarcoidosis- or multiple sclerosis-associated intermediate uveitis, intraocular lymphoma (particularly in older patients with atypical or resistant vitritis), and posterior uveitis/panuveitis with vitreous spillover.

Workup includes a structured review of systems, focused imaging, and laboratory/PCR testing of intraocular fluid to exclude infectious and neoplastic masquerades, since PCR has enhanced detection of these conditions.² Fluorescein angiography quantifies vascular and disc leakage and helps guide treatment decisions, since leakage scores differ significantly between eyes that ultimately require treatment and those managed with observation.¹

Not all pars planitis requires treatment. A comparison of pediatric patients treated versus observed found observed eyes had significantly less anterior chamber/vitreous cell, less haze, less disc edema, and lower FA leakage scores; final visual acuity was similar, and no untreated eyes needed surgery, supporting selective observation in carefully identified mild cases.¹ Treated eyes had substantially higher rates of ocular hypertension (52%) and glaucoma (18.9%) than untreated eyes (0%), highlighting that treatment carries meaningful side-effect burden.¹ When indicated, treatment includes periocular/intravitreal or systemic corticosteroids, and steroid-sparing immunomodulatory therapy for chronic bilateral sight-threatening disease.

• Not all pars planitis requires treatment — carefully selected mild cases can be safely observed¹
• Treatment carries substantial ocular hypertension/glaucoma risk that must be weighed against undertreated inflammation¹
• Dilated fundus exam is essential in any patient with new floaters²
• Use PCR and targeted testing liberally to exclude masquerades before labeling disease idiopathic²
• Common pitfall: treating all pars planitis uniformly rather than individualizing based on severity
• Common pitfall: missing an infectious or neoplastic masquerade