|
Idiopathic Juxtafoveal Macular Telangiectasia (MacTel) is a condition of the retina about which little is known. It may result in blindness. It is a form of pathologically dilated blood vessels (telangiectasia) at the region of highest visual acuity, the yellow spot in the human eye (macula). The tissue deteriorates and the retinal structure becomes scarred due to the development of liquid-filled cysts, which impairs nutrition of the photoreceptor cells and destroys vision permanently. MacTel seems to be distinguishable from AMD (age-related macular degeneration by the involvement of different vasculature. In the latter case the choroidal (basal) vessel system is often altered, while in MacTel the retinal capillaries change shape before irreversible changes are taking place and destroy the photoreceptors. the origin of the disease is unknown and no treatment has been found to be effective to prevent further progress. Because the lost photoreceptors cannot be recovered, early diagnosis and treatment appear to be essential to prevent blindness. Several centers are currently trying to find new diagnostics and treatments to understand the causes and biochemical reactions in order to halt or counteract the adverse effects. MacTel (Macular Telangiectasia) is a disorder of the blood vessels which supply the macula, the central part of the retina that lines the back of the eye and picks up the light like the film in a camera. The “fovea,” in the center of the macula, has no blood vessels at all because they would interfere with central vision. MacTel refers to a curious, very poorly understood condition of the blood vessels around the fovea (juxtafoveal) which become dilated and incompetent, like varicose veins but on a much smaller scale. While MacTel does not usually cause total blindness, it commonly causes loss of the central vision, which is required for reading and driving vision, over a period of 10–20 years. Although MacTel has been previously regarded as a rare disease, it is in fact probably much more common than previously thought. The very subtle nature of the early findings in MacTel mean the diagnoses are often missed by optometrists and general ophthalmologists. No new information has emerged about the condition since its clinical features were first well described by Dr. J. Donald Gass in 1982. There is much work to be done to understand the disease better, to raise its profile and to search for treatments. ==Possible treatments== Treatment options for IJFT I include laser photocoagulation, intra-vitreal injections of steroids, or anti-vascular endothelial growth factor (anti-VEGF) agents. Photocoagulation was recommended by Gass and remains to date the mainstay of treatment. It seems to be successful in causing resolution of exudation and VA improvement or stabilization in selected patients. 1,2 Photocoagulation should be used sparingly to reduce the chance of producing a symptomatic paracentral scotoma and metamorphopsia. Small burns (100–200 μm) of moderate intensity in a grid-pattern and on multiple occasions, if necessary, are recommended. It is unnecessary to destroy every dilated capillary, and, particularly during the initial session of photocoagulation, those on the edge of the capillary-free zone should be avoided. Intravitreal injections of triamcinolone acetonide (IVTA) which have proved to be beneficial in the treatment of macular edema by their anti-inflammatory effect, their downregulation of VEGF production, and stabilization of the blood retinal barrier,12,13 were reported anecdotally in the management of IJFT I. In two case reports, IVTA of 4 mg allowed a transitory reduction of retinal edema, with variable or no increase in VA. As expected with all IVTA injections, the edema recurred within 3–6 months, and no permanent improvement could be shown.14,15 In general, the effect of IVTA is short-lived and complications, mainly increased intraocular pressure and cataract, limit its use. Indocyanine green angiography-guided laser photocoagulation directed at the leaky microaneurysms and vessels combined with sub-Tenon’s capsule injection of triamcinolone acetonide has also been reported in a limited number of patients with IJFT I with improvement or stabilization of vision after a mean follow-up of 10 months.16 Further studies are needed to assess the efficacy of this treatment modality. Recently, intravitreal injections of anti-VEGF agents, namely bevacizumab, a humanized monoclonal antibody targeted against pro-angiogenic, circulatory VEGF, and ranibizumab, a FDA-approved monoclonal antibody fragment that targets all VEGF-A isoforms, have shown improved visual outcome and reduced leakage in macular edema form diabetes and retinal venous occlusions. In one reported patient with IJFT I, a single intravitreal bevacizumab injection resulted in a marked increase in VA from 20/50 to 20/20, with significant and sustained decrease in both leakage on FA and cystoid macular edema on OCT up to 12 months.17 It is likely that patients with IJFT I with pronounced macular edema from leaky telangiectasis may benefit functionally and morphologically from intravitreal anti-VEGF injections, but this warrants further studies. Today, laser photocoagulation remains mostly effective, but the optimal treatment of IJFT I is questioned, and larger series comparing different treatment modalities seem warranted. The rarity of the disease however, makes it difficult to assess in a controlled randomized manner. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Macular telangiectasia」の詳細全文を読む スポンサード リンク
|