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F. B. Sallo, I. Leung, U. E. Wolf-Schnurrbusch, A. C. Bird, T. Peto, MacTel Study Group; Retinal Crystals in Type 2 Idiopathic Macular Telangiectasia. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3549.
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Background: Idiopathic Macular Telangiectasia (IMT) is a progressive retinal disease characterized by a slow deterioration of visual acuity and metamorphopsia starting in the fifth to seventh decades. The etiology and pathogenesis of the disease are poorly understood. Clinical features of the disease include ectatic capillaries, blunted and right-angle veins, a late-stage diffuse leakage mainly temporal to the fovea as well as a loss of retinal transparency, pigment plaques and retinal crystals.
To characterize intraretinal crystalline deposits in a large cohort of type 2 IMT.
Patients with retinal crystals were selected from the MacTel study, an international multi-centre prospective study of IMT. Grading of stereoscopic 30° colour fundus (CF), blue light reflectance (BL), red-free (RF) and infrared (IR) images was performed according to the MacTel protocol and staged using Gass and Blodi classification. Associations with potential risk factors and best-corrected visual acuities (BCVA) were analysed.
Out of 308 patients enrolled in the MacTel study, 133 patients (43%) showed crystalline deposits; 71% were bilateral. Mean age of those with crystals was 61 years (SD=8 years), 61% were female, 76% caucasian; 33% had a history of diabetes. None of these factors were significantly different from the full MacTel cohort. Crystals were present at all stages of the disease, most freqently in stages 3 (38%) and 4 (48%). The mean follow up period was 2 years (range 0-3 years). In 96% of the eyes studied, crystals seen at one visit were detectable also at subsequent visits. Mean BCVA was 20/32 in the better eye and 20/50 in the worse eye; again, this was not significantly different from the full cohort. In 12 cases crystals were detectable in IR images as well as in other modalities.
Intraretinal crystals are a frequent phenomenon associated with IMT and they appear in all stages of the disease, without direct association with worse vision or different vascular risk factors. These crystals appear in all imaging modalities, which raises questions about their biochemical properties and composition.
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