The Effects of Age and Ametropia on the Dark Focus of Visual Accommodation

Abstract

The effects of age and ametropia on the dark focus of visual accommodation have gone largely unmeasured. Subject populations of young people are generally screened and their vision “standardized” by testing them while they wear corrective lenses. In this study, 301 participants of both sexes, aged 17 to 67, both nearsighted and farsighted were measured for their near points, far points, and dark focuses. It was found that the more nearsighted the eye the larger the dark focus shift. This increase in shifts, however, is relatively small over the commonly found range of ametropia. Age was also found to have a small effect on the dark focus. Older individuals tended to have a smaller dark focus shift, and the dark focus was found to recede with age at roughly the same rate as the far point.