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Rod sensitivity recovery in the older eye
Laura Patryas, Neil R.A. Parry, Dave Carden, Tariq Aslam, Ian J. Murray
In: European Conference on Visual Perception; 28 Aug 2011-01 Sep 2011; Toulouse, France. 2011.
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Abstract
It is well known that dark adaptation (DA) becomes slower with age. The underlying cause of this impairment is not well understood but may be related to structural changes in the Bruch’s membrane-Retinal Pigment Epithelium (RPE) complex. We examined the characteristics of abnormal rod kinetics in normal older observers (mean age 57.6, n = 15) and compared this with younger observers (mean age 24.92, n = 15). Thresholds were measured following a minimum of 30% bleach, using a white 1 deg stimulus (1 Hz), presented 11 degrees below fixation on a CRT monitor, expanding its luminance range with ND filters. The effects of stimulus size and repeated bleaching were also examined. The ‘S2’ region of rod recovery was 0.04 log10 units min-1 (p < 0.001) slower in the older group (0.19 ±0.03 log10 units min-1) compared with the younger group (0.23 ±0.02 log10 units min-1). Neither repeated bleach, nor stimulus size had any effect on the time constant of ‘S2’ in healthy observers of both ages. The characteristics of slowed time constant in older eyes are compared with systemic causes of delayed DA and the extent to which older observers’ night vision may be improved by modifying diet are considered.