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R. P. Finger, P. Charbel Issa, H. M. Helb, F. G. Holz, H. P. N. Scholl; Fixation Stability in Type 2 Idiopathic Macular Telangiectasia and Its Relation to Foveal Sensitivity, Visual Acuity and Reading Speed. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4144.
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© ARVO (1962-2015); The Authors (2016-present)
To assess fixation stability and its relation to foveal sensitivity, distance visual acuity, reading acuity and speed in type 2 idiopathic macular telangiectasis (type2-IMT). We have previously shown that type2-IMT exhibits parafoveal scotomas (ARVO 2006 #5210/B625). We hypothesize that reading acuity and speed may therefore be impaired despite stable central fixation.
54 eyes of 27 patients (median age: 63 years; range 49 - 79 years) exhibiting type2-IMT were included. Patients were examined by means of ophthalmoscopy, OCT- and cSLO-imaging and best-corrected visual acuity (distance with ETDRS charts and reading acuity with Radner charts). Fundus controlled static threshold perimetry was performed with the MP1 (Nidek), using Goldmann III stimuli and a white background illumination. The range of luminance was 0-20 dB. Fixation stability was assessed over a period of 30 seconds and calculated as Bivariate Contour Ellipse Area (BCEA), within which the centre of the target was imaged 68% of the time. Several eyes (n=4) were excluded as BCEA could not be calculated due to two preferred retinal loci or a distribution of fixation points other than normal. The BCEAs were analysed using t-tests and correlation analysis.
BCEAs in most eyes were within normal ranges (mean 665.17 minArc2, range 161.53 - 2726.62; reported normal mean for similar fixation target 1286.9 minArc2). Distance VA was reduced in most eyes (mean20/40; range: 20/200-20/20), as was mean reading acuity (mean 20/50; range: 10/125-20/20) and maximum reading speed (mean 153 words/min). Reading acuity and speed correlated well with distance VA (p=0.01). Foveal sensitivity (mean 14.25 dB; range: 0 - 20) was higher in patients with better fixation stability. BCEA was inversely correlated to maximum reading speed.
These findings indicate that type2-IMT is associated with functional impairment of reading in late stage disease despite stable central fixation, suggesting that parafoveal scotomas affect this visual function. Reading acuity and speed are good predictors of vision related quality of life, which appears to be threatened in type2-IMT.
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