The Age-Related Dynamic Accommodative Characteristics Associated With Light Intensity and Chromaticity

Abstract

Visual accommodation plays a critical role in one's visual perception and activities of daily living. The age-related accommodation loss poses a greater risk to older adults' safety and independence. Although extensive effort has been made to study the effects of aging on accommodation, the relationship between aging and the dynamic aspects of accommodation is still unknown. Furthermore, since light is the carrier of external stimuli for accommodation, it is of value to assess the influences of light on the age-related accommodation loss. Therefore, a study was conducted to investigate the age-related dynamic accommodative characteristics under various conditions of the intensity and chromaticity of light. To ascertain the effects of aging, ten individuals from each of three age groups (i.e., younger group: 20 to 29 years old, middle-aged group: 40 to 49 years old, and older group: 60 to 69 years old) were recruited, and their dynamic accommodation responses were examined. Laboratory experiments were designed to measure accommodation in a simulated condition where a person must alternate from viewing outside to reading the dashboard while driving. It was hypothesized that the advancing of age will lead to the deterioration of one's dynamic accommodative performance, and light of different intensities and chromaticities will interact with the effects of aging on accommodation. The results of the study supported the above hypotheses. It was found that the advancing of age, the decrease of light intensity, and the change of light chromaticity all led to the alteration of one's dynamic accommodative performance. The present study concluded with a biomechanical and neural model elaborating the mechanism of an accommodation process within the scope of the study.