Experimental Method for Identifying Regions of Use of a Progressive Power Lens Using an Eye-Tracker: Validation Study.

Power distribution of progressive power lenses provides usable regions based on power distribution analysis. However, recent studies demonstrated that these regions are not always used for certain tasks as predicted. This work determines the concordance between the actual region of lens use and compares it with the theoretically located regions. The pupil position of 26 subjects was recorded using an eye-tracking system (Tobii-Pro-Glasses 3) at distance and near-reading tasks while wearing a general use progressive power lens. Subjects were asked to read aloud a text showed on a screen placed at 5.25 m and 37 cm while looking though the central and lateral regions of the lens. The pupil position was projected onto the back surface of the lens to obtain the actual region of use for each fixation. Results showed that the actual region of use matched with the theoretically located. On average, the concordance between the actual and theoretical regions of use was 85% for a distance-reading task and 73% for a near-reading task. In conclusion, the proposed method effectively located the actual regions of the lens used, revealing how users' posture affects lens usage. This insight enables the design of more customized progressive lenses based on the areas used during vision-based tasks.