الفهرس 
• Anatomy of the uveal tractOnly 14 pages are availabe for public view
 |  | from | 170 |  |  |
| | | from | 170 | | |
Abstract
Uveitis is an inflammation of the uveal tract, which lines the inside of the eye behind the cornea. Much of the uvea lies between the retina and tough, outer sclera. The uveal tract has three parts: the iris, the ciliary body, and the choroid. Uveitis is categorized according to the part of the uveal tract that is affected. Anterior uveitis is an inflammation of the front part of the uveal tract; it includes inflammation of the iris (iritis) and inflammation of the iris and the ciliary body (iridocyclitis). Posterior uveitis is an inflammation of the part of the uveal tract behind the lens of the eye. It includes inflammation of the choroid (choroiditis) and inflammation of the choroid and retina (chorioretinitis). Uveitis that affects the entire uveal tract is called panuveitis or diffuse uveitis.
Many cases will resolve rapidly, but a significant number of patients develop persistent disease with inflammatory damage to ocular structures resulting in severe visual impairment. The main causes of sight loss are cystoid macular edema, cataract, and glaucoma.
Approximately 5-20% of legal blindness in developed countries is due to uveitis, and it has been estimated that uveitis accounts for 10-15% of all cases of total blindness in the USA. Acute anterior uveitis is the commonest subtype and carries the best visual outcome, with a worse visual prognosis seen in patients with posterior uveitis and panuveitis.
The causes of uveitis are not fully understood, but they can be a result of trauma, allergy, or a response to a systemic or ocular disease. Uveitis may be a type of immune-response mechanism. In people with impaired immune systems, uveitis may be due to an infection (bacteria, virus, parasite, or fungus).
For many years, uveitis was considered a single disease entity; therefore, the approach to treatment varied very little. As knowledge of the disease process grew and the sophistication of immunologic and microbiologic testing increased, the fact that uveitis entails a multitude of diseases became clear. Although some diseases are local ocular immune phenomena, many of them are systemic diseases with ocular manifestations. Because the spectrum of disease pathogenesis ranges from autoimmunity to neoplasia to viruses, the practitioner of uveitis requires an understanding of internal medicine, infectious diseases, rheumatology, and immunology.
Patients with uveitis can present with some of the most challenging diagnostic dilemmas in all of ophthalmology. Because the treatment and prognosis of various uveitic entities varies greatly, accurate diagnosis is imperative. Many diseases, including Fuchs heterochromic iridocyclitis, Behçet disease, toxoplasmosis, cytomegalovirus (CMV) retinitis, ocular histoplasmosis, and Vogt-Koyanagi-Harada (VKH) disease, are clinical diagnoses that require little, if any, laboratory analysis. Likewise, the patient presenting with an initial episode of acute nongranulomatous anterior uveitis and an unremarkable review of systems and physical examination does not require a laboratory evaluation.
The part of the eye affected by inflammation may determine the duration of the condition. With proper treatment, anterior uveitis can clear up in a matter of days to weeks. Posterior uveitis, on the other hand, may last several months or years and could permanently alter your vision.
In non-infectious causes, therapy is usually aimed at dampening down the immune response with corticosteroids being the first line treatment. In sight threatening disease immunosuppressive agents as methotrexate, cyclosporine and cyclophosphamide may need to be added to improve or preserve sight.
Another new treatment modality is the use of intraocular pharmacotherapy via intravitreal injection and surgically placed implants as (Retisert).
Autoimmune uveitis is a treatable condition that may require the use of systemic immunomodulatory medication to halt it’s progression. Although corticosteroids remain the primary initial treatment for patients with uveitis, use of non-corticosteroid immunomodulatory agents in selected patients with uveitis allows for improved control and decreased risk of corticosteroid-induced side effects.
Based on the increasing knowledge of the immune mechanisms that underlie autoimmune diseases, a new group of “biologicals” has been generated. These are immunologically active proteins focussing on specific cells, receptors or ligands. They target those immune responses that are involved in uveitis, either by blocking inflammatory cytokines (anti-TNF therapies such as etanercept, infliximab or adalimumab), by affecting T-helper cells (anti-IL2 receptor such as daclizumab) or suppressing the autoantigen-specific immune response by induction of mucosal tolerance (oral tolerance).
Vitrectomy may sometimes be necessary for diagnosis and treatment of uveitis.