Age-Related Changes in Mesopic Reading Vision Across Adulthood

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.