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Ferenc B. Sallo, Tunde Peto, Emily Y. Chew, Alan C. Bird, Traci E. Clemons, MacTel Study Group; Function And Phenotype In The Natural History Of Type 2 Idiopathic Macular Telangiectasia. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4523.
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The clinical features of type 2 Idiopathic Macular Telangiectasia (MacTel) include neurodegenerative changes such as inner and outer retinal cavities or a break in the photoreceptor inner-outer segment (IS/OS) junction line and vascular abnormalities including late-stage fluorescein leakage. Our aim was to compare progression in the phenotype of the disease with change in central visual function.
Patients were selected from the MacTel study, an international multi-centre prospective study of type 2 MacTel. Fluorescein angiographic (FA) images of eyes with leakage in a maximum of one subfield of the grading grid at baseline were graded for extent and level of leakage. An increase by at least two subfields was considered significant. Stratus OCT scans were graded for the presence and location of retinal cavities and/or an IS/OS break. Grading was performed according to the MacTel Study protocol and correlated with best-corrected visual acuities (BCVA).
Mean loss in VA associated with a significant progression in fluorescein leakage (34 of 147 eyes), was 4.7±1.8 letters (95% CI: 1.2 - 8.2) after one year, and in 18 eyes a further 3.0±2.4 letters (95% CI: -1.7 - 7.8) after 2 years. The development of inner cavities involving the foveal centre (23 of 119 eyes) was associated with a mean VA loss of 4.7±1.9 letters (95% CI: 1.0 - 8.3) after one year and in 9 eyes (39%) a further 3.1±1.9 letters (95% CI: -0.5 - 6.8) after 2 years. At 2 years 10% of these eyes lost 13+ letters. The progression of an IS/OS break to involve the fovea (276 eyes) was associated in 37 eyes (13%) with a mean VA loss of 6.3±1.7 letters (95% CI: 3.0 - 9.6) after one year, 29 eyes (78%) progressed by 2 years with a further loss of 8.2±5.8 letters (95% CI: -3.2 - 19.7) letters.
The retinal abnormalities examined were variable but in combination useful predictors of BCVA loss. Further analyses are necessary to determine risk factors for developing vision loss of 10+ letters. Establishing the sequence, time course and functional significance of retinal changes in MacTel is essential for developing a new classification system for describing the natural history and predicting the progression of the disease.
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