Implementing silent reading speed and oculomotor behaviour as a clinical measure of functional reading performance

Visual acuity offers limited value as a clinical endpoint for evaluating functional vision deficits. Alternative measures, such as the assessment of reading efficiency, address how vision-related challenges affect quality of life.

Although oral reading speed is typically employed as the principal measure of reading performance, it fails to simulate everyday reading activities, for which silent reading is preferred. In this study, eye movements were analysed additionally to reading speed, as potentially useful clinical indicators of silent reading performance.

Silent reading performance was evaluated binocularly in 53 presbyopes (52 ± 4 years old) using the Greek IReST reading passages, displayed at 40 cm distance. Near correction was achieved with reading spectacles worn over single vision contact lenses. A subgroup of 26 participants were tested on a second visit under two conditions: (i) without best-correction for near ('blur') and (ii) following instructions for 'comprehension'. Eye movements were recorded during passage reading using video oculography. Data analysis included computation of reading speed, fixation duration, forward fixations and regressions. Frequency distributions of fixation durations were analysed with ex-Gaussian fittings.

The strongest correlate of silent reading speed was the number of forward fixations (r = -0.86), accounting for 74% of its variance, while modest correlations were found with the percentage of regressions (r = -0.57) and the ex-Gaussian parameter τ (r = -0.59). Reading speed was significantly slower in both 'blur' and 'comprehension' conditions (p < 0.001). Comprehensive reading showed an increased number of forward fixations and regressions. Blur had a significant impact on fixation duration, ex-Gaussian parameter μ, and the number of forward fixations.

Oculomotor behaviour during silent passage reading could complement reading speed measures to address the influence of visual (pre-cortical) vs. cognitive factors in the assessment of functional reading performance.