Correlation between reading time and characteristics of eye fixations and progressive lens design

OBJECTIVE: The purpose of this study is to evaluate reading time and characteristics of fixations at different distances when looking through different areas of progressive power lenses (PPL) with different power distributions by means of eye-tracking technology. METHOD: A wearable eye tracker system (Tobii-Pro Glasses 3) was used to record the pupil position of 28 PPL subjects when reading at near and distance vision while using 3 different PPL designs: a PPL optimized for distance vision (PPL-Distance), a PPL optimized for near vision (PPL-Near) and one of them balanced for a general use (PPL-Balance). Subjects were asked to read out loud a text displayed on a digital screen located at 5.25m and 0.37m when they were looking through the central and peripheral regions of each PPL. Reading time, total duration of fixations, and the number of fixations were analyzed for each reading condition and PPL. Statistical analysis was carried out using Statgraphics Centurion XVII.II Software. RESULTS: The analysis of eye movements at distance-reading vision showed a statistically significant lower reading time (p = 0.004) and lower total duration of fixations (p = 0.01) for PPL-Distance. At near-reading vision, PPL-Near provided statistically significant lower reading time (p<0.001), lower total duration of fixations (p = 0.02), and less fixation count(p<0.001) in comparison with PPL-Balance and PPL-Distance. CONCLUSIONS: Reading time and fixations characteristics are affected by the power distribution of a PPL. A PPL design with a wider distance region provides better distance-reading performance while a PPL with a wider near area performs better at a near-reading task. The power distribution of PPLs influences the user performance at vision-based tasks. Thus, to provide the user with the best visual experience, PPL selection must consider user needs.