Pars Planitis

Signs and Symptoms
The patient with par planitis is typically a younger patient with no significant medical history. Patients are frequently asymptomatic, but may present with modestly diminished vision that is slowly progressive, as well as complaints of floaters. A history of similar occurrences of symptoms may be disclosed.

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 small (snowballs) or extensive (snowbanks) and may occur anywhere in the fundus but is typically regulated to the inferior fundus by gravity. There also may be the presence of cataracts, especially posterior subcapsular, and cystoid macular edema. In extreme cases, there may be retinal neovascularization.

Pathophysiology
Pars planitis is a true posterior/intermediate uveitis that chronically affects younger, healthy patients. Pars planitis is idiopathic and unassociated with systemic disease. However, there have been some implications of an association of autoimmune disease (juvenile rheumatoid arthritis) and demyelinating disease. There are exacerbations and remissions and typically this disorder runs a very long course. Inflammatory mediators will increase vasopermeability of retinal capillaries resulting in posterior segment inflammatory cells as well as cystoid macular edema (CME). Vision loss occurs due to cataracts and CME.

Management
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 and tractional 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 form the cornerstone. Topical steroids are employed only if there is a concomitant anterior uveitis. However, in these cases, the anterior chamber reaction is not a true anterior uveitis, but a spill-over from the posterior uveitis. Thus, topical steroids are rarely indicated. Oral prednisone is more commonly used. However, once a commitment to use oral steroids is made, typically they must be used for months. With this treatment comes the possible attendant complications of steroid induced cataracts and glaucoma. In severe cases, sub-tenon’s injections of steroids may be used, as well as vitrectomy to clear the vitreous and cyclocryotherapy to destroy the inflamed areas and infiltrates. Topical and oral non-steroidal anti-inflammatory agents have been used to treat attendant CME with some success.

In most cases, pars planitis is unassociated with systemic disease. However, in order to avoid a possible mis-diagnosis, have the patient tested for both syphilis and sarcoidosis as these diseases may present a similar clinical picture.

Clinical Pearls

Posterior vitreous detachment is rare in younger patients; however, PVD is quite common in pars planitis. Consider pars planitis when encountering PVD in younger patients.

Always consider pars planitis in cases of asymptomatic vitreous cells in healthy, younger patients.

When suspecting pars planitis, carefully examine the inferior retina and vitreous for snowballs and snowbanking.

Pars planitis can be safely monitored without treatment. If the decision to treat is made, however, expect to treat with oral steroids for several months.

If pars planitis is definitively diagnosed, medical testing is unnecessary. However, if the diagnosis is in question, remember that the differential includes sarcoidosis, syphilis, multiple sclerosis with vascular sheathing and intermediate uveitis, toxoplasmosis, and toxocariasis.