Pars planitis

An additional clinical use of acetazolamide is unrelated to its ocular hypotensive properties.The 500-mg acetazolamide capsule administered daily for 2 weeks may produce either a partial or a complete resolution of macular edema in patients with cystoid macular edema (CME), retinitis pigmentosa, and chronic intermediate uveitis (pars planitis). Macular edema produced by primary retinal vascular diseases (branch and central retinal vein occlusion and macular telangiectasia) did not respond to acetazolamide therapy. It is believed that acetazolamide may improve visual function if the macular edema stems from retinal pigment epithelial dysfunction. Improved macular edema in these conditions may be associated with fluid movement from the retina to the choroid. However, acetazolamide does not appear to alter macular blood flow. 

Intermediate uveitis Describes inflammation confined to the posterior aspect of the ciliary body (pars plana) and/or the peripheral choroid. Secondary involvement of the retina and vitreous may also be seen. The most common form of intermediate uveitis in the United States is pars planitis. 

Visual acuity is often compromised on presentation in intermediate uveitis. A study in 2001 found a mean entering visual acuity of 6/12 (20/40) in patients with pars planitis on average, children with this disease were foimd to have worse visual acuity than adults at the time of initial presentation. CME is the most common cause of reduced acuity in intermediate uveitis. Other complications, including chronic vitreitis, cataract, and band keratopathy, may ensue in cases of untreated or undertreated intermediate uveitis, resulting in potentially significant visual compromise. 

Guest S, Funkhouser E, Lightman S. Pars planitis a comparison of childhood onset and adult onset disease. Clin Exp Ophthalmol 2001 29 81-84. 

CME results from many ocular conditions but is not an independent disease entity. Retinal cell processes in Henle s layer run parallel to the surface of the internal limiting membrane, and the laxity of this layer fc>rms a potential reservoir for extravascular fluid resulting from breakdown of the blood-retinal barrier, which forms extracellular cystoid spaces in the perifoveal area. CME accompanies several retinal vascular diseases, including diabetic maculopathy central retinal venous occlusion, and branch venous occlusion. It may follow surgical procedures, most often cataract extraction and retinal detachment repair, or posterior inflammatory conditions, including pars planitis, chronic uveitis, and miscellaneous conditions such as retinitis pigmentosa. 

CME occurs in other somewhat imcommon posterior segment disease states. Pars planitis is associated with CME at a frequency of 28% of cases, and CME is the primary cause of vision loss in chronic severe uveitis. 

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