The human visual system undergoes myriad anatomical and physiological changes with age. For example, senescence of the optical components of the eye results in less light reaching the retina chiefly due to reduced pupil size (Kadlecová, Peleska, & Vasko,
1958) and lens brunescence (van de Krats & van Norren,
2007; Weale,
1988). There is an age-related reduction in photoreceptor numbers (Curcio, Millican, Allen, & Kalina,
1993; Panda-Jonas, Jonas, & Jakobczyk-Zmija,
1995) and a loss of retinal ganglion cells (Curcio & Drucker,
1993; Harman, Abrahams, Moore, & Hoskins,
2000). These changes are accompanied by substantial losses in sensitivity of all three cone pathways (Werner, Bieber, & Schefrin,
2000). Nevertheless, color perception is remarkably stable with age (Hardy, Frederick, Kay, & Werner,
2005) unless the stimuli are below a critical size (Knau & Werner,
2002). Stability of color perception across the life span has been taken to reflect a continuous renormalization of color mechanisms to compensate for early stage losses (Delahunt, Webster, Ma, & Werner,
2004). Similar processes may support stability of spatial vision with losses in contrast sensitivity (Owsley, Sekuler, & Siemsen,
1983) across the life span (Elliott, Hardy, Webster, & Werner,
2007), but this has been studied less extensively.