Reading with macular telangiectasia type 2 – a case of binocular confusion.

Abstract

Purpose : To assess binocular gain in patients with macular telangiectasia type 2 (MacTel) and its correlation to the characteristic paracentral scotomas.

Methods : Sixty eight patients with macular telangiectasia type 2 were consecutively recruited for a cross-sectional analysis. Best corrected visual acuity (BCVA), reading acuity and reading speed were tested monocularly and binocularly with ETDRS letter charts and Radner reading charts. Macular retinal sensitivity was examined with fundus-controlled perimetry (microperimetry). Scotomas were quantified by depth, size and proximity to the fovea.

Results : Mean reading speed was higher in the right than in the left eyes (155 vs. 137 words per minute [wpm], p-value < 0.0001). Binocular reading acuity and speed were lower than reading acuity and speed in the functionally better eye (142 vs. 159 wpm and 0.43 vs. 0.28 logRAD, p-value < 0.0001). The difference between the right eye and the left eye was correlated to the height of binocular inhibition of reading speed (R²= 0.61), but not of reading acuity or of BCVA (R²<0.03). Scotoma depth, size and proximity to the fovea were strongly correlated to binocular reading speed (adjusted R² = 0.65), but there was only a weak correlation to binocular reading acuity or BCVA (adjusted R² = 0.39). The effect of scotoma characteristics on binocular reading speed was significant for scotomas of the left eye, but not for scotomas of the right eyes.

Conclusions : The results indicate a significant impact of the worse eye on reading ability. Patients with binocular inhibition of reading performance might benefit from occlusion of one eye for reading. The worse performance of left eyes may be explained by the typical localisation of the scotoma nasally to fixation, resulting in projection of the scotoma into reading direction.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.