Investigating the origin of visual loss during the normal aging process using an adapted Landolt-C technique.

Abstract

Purpose. The objective of the present study was to investigate the change of visual functioning with age at both ocular and neural levels. This was done using an adapted Landolt-C technique where the “C”s were either defined by luminance-contrast or texture-contrast, the latter necessitating increased neural processing to be perceived. Methods. Performance was measured psychophysically by asking each participant to indicate the orientation of the “C” gap-opening, presented in either of 4 orientations (up, down, left or right) at different levels of luminance-contrast (first-order condition) or texture-contrast (second-order condition). A 4AFC constant stimuli procedure was used to measure gap-opening orientation-identification thresholds for 4 age groups; 18–35 years, 35–50 years, 50–65 years and 65+ years. Only participants presenting a Snellen acuity of 6/7.5 or better were tested. Older participants presenting nuclear cataracts of grade 3 (or worse) or other ocular pathologies were excluded. Inclusion criteria were confirmed by a thorough optometric examination. Results. Gap-opening orientation-identification thresholds for the texture-defined “C”s increased with age at a faster rate compared to the thresholds for the luminance-defined “C”s. Conclusions. The results suggest that neurally-based complex visual information processing becomes progressively compromised with age, possibly reflecting less efficient neuro-integrative functioning within early visual areas of the aging brain. Furthermore, the results demonstrate that this novel technique is sensitive enough to measure subtle neural dysfunction during the aging process and can be used to dissociate peripheral (ocular) from centrally (neural) mediated visual loss.

Footnotes

 Support: CIHR # MOP- 5353291 (JF) & CIHR graduate fellowship (AB).