Intermediate Uveitis
Definition
Inflammation primarily involving the vitreous, pars plana, and peripheral retina, characterized by vitritis, snowball opacities, and snowbanking, with relative sparing of the anterior segment.
Clinical Snapshot
Intermediate uveitis (IU) is defined by inflammation primarily involving the vitreous, pars plana, and peripheral retina, with relative sparing of the anterior segment and no primary posterior pole involvement. It accounts for approximately 15–20% of uveitis cases. The majority are idiopathic (pars planitis). Multiple sclerosis and sarcoidosis are the most important systemic associations. Cystoid macular edema (CME) is the primary cause of vision loss. Management is guided by the degree of vitritis and the presence of CME.
Epidemiology
IU has a bimodal age distribution — peaks in children/young adults and in middle age. It accounts for approximately 15–20% of uveitis cases. Pars planitis (idiopathic IU with snowbanking) is the most common subtype. MS is associated with IU in approximately 15–25% of cases.
Pathophysiology
The pathophysiology of idiopathic IU (pars planitis) is incompletely understood — T-cell–mediated autoimmunity directed against retinal antigens is hypothesized. Snowball opacities are aggregates of inflammatory cells in the inferior vitreous. Snowbanking (exudate on the pars plana and peripheral retina) is the hallmark of pars planitis and represents fibrovascular proliferation. CME results from breakdown of the inner blood-retinal barrier by inflammatory mediators.
Risk Factors
- Multiple sclerosis (15–25% of IU cases)
- Sarcoidosis
- Lyme disease (in endemic areas)
- Tuberculosis
- Idiopathic (pars planitis — the majority)
Clinical Presentation
Floaters and blurred vision are the typical presenting symptoms — pain and photophobia are less prominent than in anterior uveitis. Slit lamp: mild anterior chamber reaction, vitritis (cells in the vitreous), snowball opacities (inferior vitreous), and snowbanking (pars plana exudate). Fundoscopy: peripheral retinal vasculitis, CME (the primary cause of vision loss), and occasionally neovascularization of the disc or periphery.
Diagnostic Pearls
- Snowbanking (pars plana exudate) is the hallmark of pars planitis — it is best visualized with indirect ophthalmoscopy and scleral depression.
- OCT is essential for detecting CME — it is the primary cause of vision loss and may be present without obvious symptoms.
- MRI of the brain and orbits is indicated in all patients with IU to evaluate for MS — periventricular white matter lesions may be present before clinical MS symptoms.
- Sarcoidosis workup (chest X-ray, ACE, lysozyme) is appropriate for all IU patients.
Differential Diagnosis
- Posterior uveitis (primary posterior pole involvement)
- Ocular lymphoma (masquerade — particularly in older patients with vitritis)
- Retinitis pigmentosa (peripheral retinal changes, no active inflammation)
Evidence-Based Management
Mild IU without CME: observation. IU with CME or significant vitritis: periocular corticosteroids (sub-Tenon's triamcinolone acetonide) are first-line — they avoid systemic side effects while delivering high local drug concentrations. Systemic corticosteroids for bilateral or severe disease. Steroid-sparing immunosuppression (methotrexate, mycophenolate) for chronic or steroid-dependent disease. Intravitreal corticosteroid implants (fluocinolone acetonide — Retisert®, Iluvien®) for refractory cases. Peripheral retinal cryotherapy or laser for neovascularization.
Monitoring & Follow-Up
OCT at every visit to monitor CME. Vitreous cell grade at every visit. Monitor for neovascularization with peripheral retinal examination.
Clinical Pearls
- CME is the primary cause of vision loss in IU — OCT monitoring is essential even in patients who feel their vision is stable.
- MRI of the brain is indicated in all IU patients — MS may be present before clinical neurological symptoms.
- Sub-Tenon's triamcinolone is highly effective for CME — it is the preferred first-line treatment for unilateral disease.
- Pars planitis in children carries a risk of amblyopia — aggressive management of CME is warranted.
Related Therapeutics — Clinician's Companion
- Anti-inflammatory Rescue — Triamcinolone (sub-Tenon's), Durezol® (Clinician's Companion)
- Oral Therapeutics — Oral Prednisone, Methotrexate (Clinician's Companion)
Key References
- 1.Babu BM, Rathinam SR. Intermediate uveitis. Indian J Ophthalmol. 2010.
- 2.Jabs DA, et al. Standardization of uveitis nomenclature for reporting clinical data. Am J Ophthalmol. 2005.
This entry is an educational reference designed to support clinical reasoning and awareness. It does not constitute medical advice, establish a standard of care, or replace individualized patient assessment. Clinicians should consult current guidelines and applicable clinical resources when making patient care decisions.