Pars planitis is a true posterior/intermediate uveitis that chronically affects younger, healthy patients with no significant medical history. It is idiopathic and unassociated with systemic disease. Patients are frequently asymptomatic, but may present with moderately diminished vision that is slowly progressive, as well as complaints of floaters. There have been some implications of an associate of autoimmune disease (juvenile rheumatoid arthritis) and demyelinating disease. Inflammatory mediators will increase vasopermeability of retinal capillaries resulting in posterior segment inflammatory cells as well as cystoid macular edema.
The first observable sign of pars planitis is the presence of vitreal cells in an active vitritis. The vitritis may cause vitreous degeneration with a resultant posterior vitreous detachment. The vitritis frequently will result in an accumulation of inflammatory exudate. The accumulation may be the fundus but is typically regulated to the inferior fundus by gravity. There may also be the presence of cataracts, especially posterior subcapsular, and cystoid macular edema. In extreme cases, there may be a retinal neovascularization.
Pars planitis is generally benign. Vision loss tends to be mild, if it occurs at all. Only in extreme cases is vision loss profound. In these cases, the cause of vision loss is retinal neovascularization with its attendant complications of vitreous hemorrhage or traction retinal detachment. As pars planitis is typically a relatively benign disease, treatment should be conservative and often involves only periodic monitoring.
If treatment is undertaken due to mild vision loss from cystoid macular edema or vitreous clouding, then steroids are the modality of choice. Topical steroids are employed only if there is a concomitant anterior uveitis. Oral prednisone is more commonly used. However, once a commitment to use oral steroids is made, typically they must be used for months. In severe cases, subtenon injections of steroids may be used, as well as vitrectomy to clear the inflammatory agents have been used to treat attendant cystoid macular edema with some success.
In most cases, pars planitis is unassociated with systemic disease. However, in order to avoid a possible misdiagnosis, patients can be tested for multiple sclerosis and sarcoidosis as these diseases may present a similar clinical picture.