Abstract
Purpose: We are modelling noise pattern masking as a means to simulate the decrease of S/N in aged or diseased retinas. We previously observed that text oscillation improves reading speed and error rate.
Methods: Subjects (5 females and 5 males) with spherical error 3.5 to −7.5, normal contrast sensitivity (Pelli-Robson), and no macular scotoma were divided into groups younger (31.4 + 5.0 yr) and older (62.8 + 5.8 yr). Using a digital light ophthalmoscope (DLO), we presented sentences via Maxwellian view in a 25 × 18 deg field and determined retinal locus by simultaneously capturing coplanar retinal images at 860 nm. Subjects read IU Read sentences separately, at a 1920 × 1080 pixel resolution and 20/60 Helvetica font. The text contrast (delta I/I) was 50%. The added noise had a center spatial frequency of 5.8 c/deg, and Michelson contrast 0 - 40% with, 10 sentences per condition. Each 10 - 14 word sentence was stationary or oscillating sinusoidally and horizontally, amplitude 0 - 2 deg.
Results: Errors increased with a nonlinear function of noise contrast, and the improvement of reading with text motion depended on noise contrast. With no text motion, younger subjects read faster than older ones (p=.039), but errors did not significantly differ (p=.199). Younger vs. older errors were 52.2 vs. 57.7 and 9.8 vs. 7.3 for no motion vs. motion at noise contrast 0.4.
Conclusions: Slower reading speeds but not more errors in older subjects are consistent a speed-accuracy trade-off, with motion improving reading in most subjects.