Age-Related Changes in Mesopic Reading Vision Across Adulthood.

Abstract

Purpose: Reading is indispensable for daily activities such as reading books, menus, and food labels, occurring under a wide range of luminance conditions from mesopic (dim light) to photopic (daylight). Despite its significance, there has been limited attention on age-related changes in mesopic reading vision. The current study aims to investigate how mesopic reading vision changes across adulthood.

Methods: Using the MNREAD iPad app, we assessed both mesopic (2 cd/m2) and photopic (220 cd/m2) reading vision in 157 normally-sighted individuals aged from 18 to 84, grouped into seven age groups. Reading vision was evaluated using four MNREAD parameters: maximum reading speed (MRS), critical print size (CPS), reading acuity (RA), and reading accessibility index (ACC).

Results: There was a significant age-related decline in reading vision under both mesopic and photopic conditions, with a more pronounced decline observed in mesopic conditions. The decline was linear from age 20 to 80: MRS decreased by 30 words-per-minute in mesopic conditions and 29 words-per-minute in photopic conditions; ACC declined by 0.18 (mesopic) and 0.12 (photopic); CPS declined by 0.3 logMAR (mesopic) and 0.16 logMAR (photopic); RA declined by 0.24 logMAR (mesopic) and 0.18 logMAR (photopic).

Conclusions: Our results show a monotonic decline in reading vision from ages 20 to 80 under both mesopic and photopic conditions, with a more pronounced decline in mesopic light. Given the significance of reading vision as a clinical measure, assessing reading vision under mesopic conditions may offer a more comprehensive evaluation of functional vision in everyday life.