You are here: Home / Rare Disease Information / Rare Disease Database

Search Rare Diseases

Enter a disease name or synonym to search NORD's database of reports.

0-9 - A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

Pars Planitis

NORD is very grateful to Dr. Patricio A. Pacheco, Bsc, MD, MRCOphth, Senior Clinical Fellow /Uveitis Service, Moorfields Eye Hospital, London, UK for assistance in the preparation of this report.

Synonyms of Pars Planitis

  • Intermediate Uveitis (UI)
  • Peripheral Retinal Inflammation
  • PP
  • Vitritis

Disorder Subdivisions

  • No subdivisions found.

General Discussion

Although pars planitis is generally benign, there can be significant vision loss in extreme cases. It is an immunological disorder of the eye characterized by inflammation of a part of the uvea, the layer of tissue between the sclera and the retina, the membranes protecting the eyeball. The uvea, in turn, is made up of three portions: the iris, the ciliary body, and the choroid. In addition, the uvea contains many of the blood vessels that supply the eye.

The pars plana is a narrow section of the ciliary body, inflammation of which is known as pars planitis. In association with the inflammation or immunological response, fluid and cells infiltrate the clear gelatin-like substance (vitreous humor) of the eyeball, near the retina and/or pars plana. As a result, swelling of the eye or eyes can also occur, but more importantly blurred vision and progressive increase in the vision of floaters is reported as main symptoms by patients suffering this condition as a result of the infiltration of the vitreous humor.

The inflammation occurs in the intermediate zone of the eye; that is, between the anterior part(s) of the eye (iris) and the posterior part(s), the retina and/or choroid. It has therefore been designated as one of the diseases of a family of intermediate uveitis.

In some cases, the disturbance of vision may be slightly progressive.


The symptoms of pars planitis include blurred vision and dark floating spots that intrude upon clarity of eyesight. Swelling can occur inside the eye, particularly on the peripheral retina or macula that may lead to decreased vision. Glaucoma may occur as well.

The clinical picture may be complicated by cataracts, retinal detachment, or fluid within the retina (macular edema)

More often the examining ophthalmologist (specialist in diseases of the eye) will see clusters of white blood cells trapped within the eyeball that are called snowballs. The term physicians may use for these is inflammatory exudate. These are clusters of white blood cells trapped within the eyeball. If these clusters are located on the pars plana, they are known as snowbanks.


Pars planitis is thought to be an autoimmune disorder. An autoimmune reaction causes the inflammation that is thought to cause symptoms of this disorder.

Autoimmune disorders are caused when the body's natural defenses against foreign or invading organisms (e.g., antibodies) begin to attack healthy tissue for unknown reasons. In rare cases, pars planitis has occurred within families; however, as yet, no genetic inheritance pattern has been identified.

Some clinicians have put forward the idea that the immunological response may be the result of one of two possible causes: (1) an isolated set of events internal to the patient (endogenous), or (2) an association with some other disorder (exogenous). Among the disorders with which pars planitis has been associated are: multiple sclerosis, Lyme disease, Behcet disease, sarcoidosis, and tuberculosis, among others.

Affected Populations

Pars planitis is an uncommon ocular disorder of children and young adults that affects males slightly more frequently than females.

Related Disorders

The following disorders may be associated with pars planitis as secondary characteristics. They are not necessary for a differential diagnosis:

Cystoid macular edema is characterized by swelling (edema) of the central part of the retina as a result of abnormal leakage of fluid from capillaries. In pars planitis, swelling or leakage of fluid due to inflammation can affect the peripheral retina. Cystoid macular edema can often be a complication of pars planitis.

Ocular hypotension is a condition defined as lowered intraocular pressure as a result of decreased production of aqueous humor secondary to decreased blood pressure in the veins or capillaries inside the eye tissue. When this happens, vision disturbances similar to those of pars planitis may occur. This condition may in some cases be a complication of pars planitis.

Autoimmune endotheliopathy (endothelitis/ vasculitis) is an attack by the immune system on the layer of flat cells lining blood vessels (endothelium). This condition can occur in the blood vessels of the eyes as a complication of pars planitis, but can also occur alone in any part of the body. A more common name for this is: autoimmune vasculitis

Standard Therapies

Pars planitis is usually diagnosed by means of a thorough physical evaluation, detailed patient history, and specialized eye examination.

If no external causes of Pars planitis are found, treatment typically consists of corticosteroid drugs to control inflammation. If steroids are used, the patient must be carefully monitored.

If an external association of pars planitis is identified, then treatment of the associated disorder may take care of the inflammation.

Pars planitis may be accompanied by blood leaking from ruptured small blood vessels in the eye. These are generally not serious and, if necessary, can be treated by laser or cryotherapy (freezing of tissue) to seal blood vessels and arrest leakage.

Other treatments are symptomatic and supportive, as well as treatment of the complications (cataracts, glaucoma, cystoid macular edema, etc).

Investigational Therapies

Information on current clinical trials is posted on the Internet at All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

Also website: has information regarding this condition and current trials available.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010

For information about clinical trials sponsored by private sources, contact:

Pars Planitis Resources

NORD Member Organizations:

(To become a member of NORD, an organization must meet established criteria and be approved by the NORD Board of Directors. If you're interested in becoming a member, please contact Susan Olivo, Membership Manager, at

Other Organizations:


Guest S. Pars Planitis. In: NORD Guide to Rare Disorders. Lippincott Williams & Wilkins. Philadelphia, PA. 2003:656-57.

Beers MH, Berkow R, eds. The Merck Manual, 17th ed. Whitehouse Station, NJ: Merck Research Laboratories; 1999:726.

Kanski JJ, ed. Clinical Ophthalmology. 4th ed. Butterworth-Heinemann. Oxford, UK; 1999:309-11.

Newell FW, ed. Ophthalmology: Principles and Concepts. 7th ed. Mosby Year Book, St. Louis, MO; 1991:333-34.

Abu El-Asrar A, Geboes K. An immunohistochemical study of the 'snowbank' in a case of pars planitis. Ocul Immunol Inflamm. 2002;10:117-23.

Greiner KH, Kilmartin DJ, Forrester JV, et al. Grading of pars planitis by ultrasound biomicroscopy/echographic and clinical study. Eur J Ultrasound.2002;15:139-44.

Miserocchi E, Baltatzis S, Ekong A, et al. Efficacy and safety of chlorambucil in intractable noninfectious uveitis: the Massachusetts Eye and Ear Infirmary experience. Ophthalmology. 2002;109:137-42.

Lauer AK, Smith JR, Robertson JE, et al. Vitreous hemorrhage is a common complication of pediatric pars planitis. Ophthalmology. 2002;109:95-98.

Prieto JF, Dios E, Gutierrez JM, et al. Pars planitis: epidemiology, treatment, and association with multiple sclerosis. Ocul Immunol Inflamm. 2001;9:93-102.

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

Biousse V, Trichet C, Bloch-Michel E, et al. Multiple sclerosis associated with uveitis in two large clinic-based series. Neurology. 1999;52:179-81.

McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Pars Planitis. Entry Number; 606177: Last Edit Date; 8/8/2001.

Douglas RS. Uveitis. Medical Encylopedia. MEDLINEplus. Update: 12/22/2002. 3pp.

Pars Planitis: A Syndrome of Unknown Etiology or a Clinical Picture of Multiple Etiologies.
Massachusetts Eye and Ear Infirmary, Immunology Service, 1999. 1p.

Ocular Immunology. MEEI. Last Update: 04/08/2003. 3pp.

pars planitis. General Practice Notebook. © 2003. 1p.

Pars Planitis. Handbook of Ocular Disease management. nd. 2pp.

The information in NORD’s Rare Disease Database is for educational purposes only. It should never be used for diagnostic or treatment purposes. If you have questions regarding a medical condition, always seek the advice of your physician or other qualified health professional. NORD’s reports provide a brief overview of rare diseases. For more specific information, we encourage you to contact your personal physician or the agencies listed as “Resources” on this report.

Report last updated: 2008/10/27 00:00:00 GMT+0

0-9 - A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

NORD's Rare Disease Information Database is copyrighted and may not be published without the written consent of NORD.

Copyright ©2015 NORD - National Organization for Rare Disorders, Inc. All rights reserved.
The following trademarks/registered service marks are owned by NORD: NORD, National Organization for Rare Disorders, the NORD logo, RareConnect. .