The effect of dioptric blur on reading performance

Abstract

Little is known about the systematic impact of blur on reading performance. The purpose of this study was to quantify the effect of dioptric blur on reading performance in a group of normally sighted young adults. We measured monocular reading performance and visual acuity for 19 observers with normal vision, for five levels of optical blur (no-blur, 0.5, 1, 2, and 3D). Dioptric blur was induced using convex trial lenses placed in front of the testing eye, with the pupil dilated and in the presence of a 3mm artificial pupil. Reading performance was assessed using eight versions of the MNREAD Acuity Chart. For each level of dioptric blur, observers read aloud sentences on one of these charts, from large to small print. Reading time for each sentence and the number of errors made were recorded and converted to reading speed in words per minute. Visual acuity was measured using 4-orientation Landolt C stimuli. For all levels of dioptric blur, reading speed increased with print size up to a certain print size and then remained constant at the maximum reading speed. By fitting nonlinear mixed-effects models, we found that the maximum reading speed was minimally affected by blur up to 2D, but was approximately 23% slower for 3D of blur. When the amount of blur increased from 0 (no-blur) to 3D, the threshold print size (print size corresponded to 80% of the maximum reading speed) increased from 0.01 to 0.88 logMAR, reading acuity worsened from -0.16 to 0.58 logMAR, and visual acuity worsened from -0.19 to 0.64 logMAR. The similar rates of change with blur for threshold print size, reading acuity and visual acuity implicates that visual acuity is a good predictor of threshold print size and reading acuity. Like visual acuity, reading performance is susceptible to the degrading effect of optical blur. For increasing amount of blur, larger print sizes are required to attain the maximum reading speed.

Uncorrected Hyperopia and Preschool Early Literacy

“…32 Some have speculated that this level of blur may result in distortions and confusions in letters. 32 Others have reported that the print size of the reading material should be double the reading acuity to allow comfortable reading. 33 Furthermore, any asthenopia associated with moderate hyperopia may cause young children to read less.…”

Uncorrected hyperopia and preschool early literacy: results of the Vision in Preschoolers-Hyperopia In Preschoolers (VIP-HIP) Study

“…32 Some have speculated that this level of blur may result in distortions and confusions in letters. 32 Others have reported that the print size of the reading material should be double the reading acuity to allow comfortable reading. 33 Furthermore, any asthenopia associated with moderate hyperopia may cause young children to read less.…”

“…Therefore, the association between reading and binocular near VA may be attributed to the effect of blur on reading; 3D or more of dioptric blur has been shown to affect reading. 32 Some have speculated that this level of blur may result in distortions and confusions in letters. 32 Others have reported that the print size of the reading material should be double the reading acuity to allow comfortable reading.…”

The Visual Word Form Area remains in the dominant hemisphere for language in late-onset left occipital lobe epilepsies: A postsurgery analysis of two cases

“…Reading speed was assessed by measuring the time taken to read each one of the 36 phrases of reading tests of PALPA-P. Reading times for each sentence were recorded and converted to reading speed in words per minute using the methodology suggested by Chung [34]. The reading speeds of the two patients were compared with the recommended goal for 9th grade students according to the Portuguese Education Ministry [35].…”