Fluorescein angiography is the most useful test, both diagnostically and as a guide to therapy, in pars planitis. It can confirm the presence of CME, and evaluate for optic nerve involvement, peripheral retinal vasculitis, and neovascularization. OCT has replaced fluorescein angiography as the imaging modality of choice in establishing a diagnosis of CME, and macular thickness can be used to monitor the therapeutic response to treatment.

Treatment

After the diagnosis of pars planitis is made, treatment follows a 4-step approach [73]. The goal of treatment is complete elimination of the inflammatory process, but this rarely is achievable. There is little role for topical steroids unless there is clinically significant anterior segment inflammation, as they do little to decrease posterior segment inflammation.

Step 1

Periocular corticosteroids are the first line of treatment. A series of four injections, once every 4 weeks, can disclose if a patient will have a therapeutic response. The clinician must carefully monitor for a rise in intraocular pressure. Systemic corticosteroids are considered for those patients with significant bilateral disease, those who do not respond to periocular treatment, or those who cannot tolerate the injections. Oral steroids are usually given initially in a dose of 1 mg/kg/ day for 2–3 weeks, and then slowly tapered if there is a response. In refractory cases, intravitreal triamcinolone can be considered, with care taken to avoid areas of snowbanking and other areas with peripheral retinal pathology.

Step 2

If corticosteroid therapy fails, the next line of treatment is peripheral ablation of the pars plana snowbank with cryotherapy or indirect laser photocoagulation to the peripheral retina. Cryotherapy is applied in a double row of transconjunctival cryopexy to an area one clock-hour beyond all evidence of disease activity using a freeze-thaw technique. Alternatively, photocoagulation burns are placed confluently in three or four rows just posterior to the snowbank, and may be

extended to the equator. Care must be taken to avoid direct treatment of the snowbank, which can cause contraction of the vitreous base and lead to secondary retinal tears. Treatment can be repeated after a delay of 3–4 months. The mechanism by which inflammation is decreased by these treatments is not known.

Step 3

Immunosuppressive therapy with cyclosporin, azathioprine, methotrexate, or cyclophosphamide is next considered. Their use necessitates careful monitoring of efficacy and potential side effects by an experienced clinician. In children, methotrexate and cyclosporine are the preferred drugs.

Step 4

Pars plana vitrectomy, with induction of posterior hyaloidal separation and peripheral laser photocoagulation to the pars plana snowbank, is more commonly being used as a diagnostic and therapeutic modality in pars planitis. In appropriate cases it may be considered before immunosuppressive therapy. Therapeutic PPV may clear the vitreous of debris and cellular infiltration and possibly reduce the “antigenic load.” Any traction on the macula is also relieved, which may improve or stabilize CME. PPV is indicated in the management of complications such as retinal detachment, vitreous hemorrhage, cataract formation (pars plana lensectomy/vitrectomy) and in cases refractory to medical therapy.

Complications

Neovascularization along the inferior pars plana snowbank can develop from chronic ischemia from retinal phlebitis and angiogenic stimulation from inflammation in 5–10% of cases. The neovascularization can subsequently bleed and lead to vitreous hemorrhage,peripheralretinaltractionandrhegmatogenous retinal detachment. With chronicity of inflammation, vitreous opacification and an epiretinal membrane can develop. Anterior segment findings can include posterior synechiae, posterior subcapsular cataracts, and band keratopathy. Elevated intraocular pressure from both open angle and angle-closure glaucoma can arise [64].