Intermediate uveitis refers to a group of inflammatory and proliferative diseases that involve the pars plana of the ciliary body, vitreous base, peripheral retina, and choroid. Historically, this condition has been known by various names such as posterior cyclitis, chronic posterior cyclitis, pars planitis, and peripheral uveitis. The International Uveitis Study Group (IUSG) standardized the terminology for these disorders, naming them collectively as intermediate uveitis. This condition predominantly affects individuals under the age of 40, occurs equally in males and females, and often involves both eyes either simultaneously or sequentially. It usually presents as a chronic inflammatory process.
Clinical Manifestations
Symptoms
The onset is insidious, and the exact timing of onset is often uncertain. Mild cases may be asymptomatic or present only with floaters, while severe cases can involve blurred vision or temporary myopia. Significant visual deterioration may occur with macular involvement or the development of cataracts. A small number of patients may also experience redness and pain in the eyes.
Signs
The most common findings include vitreous "snowball" opacities, "snowbank" changes at the pars plana, periphlebitis of peripheral retinal veins, and inflammatory lesions. Additionally, anterior segment and posterior pole retinal changes may also be observed.
Anterior Segment Changes
These may include mutton-fat or small granular keratic precipitates (KP), mild flare in the anterior chamber, as well as a small to moderate number of anterior chamber cells. Posterior synechiae, anterior synechiae, or tented peripheral anterior synechiae may occur. In pediatric patients, signs of acute anterior uveitis, such as ciliary hyperemia and a large number of inflammatory cells in the aqueous humor, may be present.
Vitreous and Pars Plana Changes
Vitreous "snowball" opacities are the most common finding, typically located in the inferior vitreous base, appearing as uniformly sized, grayish-white, dot-like opacities. Snowbank changes are characteristic and refer to tongue-shaped lesions at the pars plana extending into the central vitreous. These lesions are usually located inferiorly, but in severe cases, they may involve nasal and temporal quadrants or even all quadrants.
Retinal and Choroidal Involvement
Peripheral retinal inflammation, retinal vasculitis, and peripheral retinochoroiditis may occur, predominantly in the inferior retina.
Complications
Macular Changes
Cystoid macular edema is the most common complication, followed by epiretinal membrane formation and macular holes.
Complicated Cataracts
Complicated cataracts are frequently observed, mainly presenting as posterior subcapsular opacities.
Other Complications
Retinal neovascularization, vitreous hemorrhage, proliferative vitreoretinopathy, optic disc edema, and optic atrophy may also occur.
Diagnosis
The diagnosis can be established based on typical features such as vitreous "snowball" opacities, snowbank changes, and peripheral retinal vasculitis, particularly in the inferior retina. However, this condition is prone to misdiagnosis or missed diagnosis in clinical practice, warranting detailed examination. Tri-mirror lens examination, indirect binocular ophthalmoscopy, and peripheral fundus evaluation may be indicated in the following scenarios:
- Worsening floaters
- Posterior subcapsular opacities of unexplained origin
- Cystoid macular edema without an identifiable cause
Fluorescein fundus angiography (FFA) can reveal signs such as retinal vasculitis, cystoid macular edema, and optic disc edema, which are helpful for diagnosis.
Treatment
Active inflammation requires prompt treatment.
For unilateral involvement, a posterior sub-Tenon injection of corticosteroids is recommended. Triamcinolone acetonide (20–40 mg/ml) or prednisolone acetate (40 mg/ml) is commonly used, with an injection volume of approximately 0.5 ml.
For bilateral involvement, oral prednisone is preferred, with an initial dose of 0.6–1 mg/(kg·day), which is gradually tapered as the condition improves. The medication is typically continued for more than six months. In cases where inflammation is difficult to control, other immunosuppressants such as chlorambucil, cyclophosphamide, or cyclosporine may be administered. Side effects and systemic toxicity should be monitored when using these agents.
In unresponsive cases, cryotherapy of the pars plana may be performed. Retinal neovascularization may require laser photocoagulation or intravitreal injection of anti-vascular endothelial growth factor (VEGF) agents. Vitrectomy can be considered to remove inflammatory mediators, toxic substances, and antigens, aiding in the resolution of refractory inflammation.
For anterior segment involvement, corticosteroid eye drops and cycloplegics are commonly used.