Purchase this article with an account.
D.W. Kline, R.W. Gagnon; Aging Effects on Binocular Summation for Sequential versus Simultaneous Spatial Interval Hyperacuity . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4596.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose:To measure aging effects on cortically mediated visual functioning, age differences on binocular summation were compared for spatial contrast threshold, simultaneous spatial interval (SI) acuity, and sequential SI acuity. Methods: Two groups, each of 12 healthy observers (6 men, 6 women) refracted to best acuity (mean < 1.0 arcmin) at the test distance, participated in the study: a young group (M age = 21.2 years, SD = 2.2) and an old group (M age = 74.1 years, SD = 3.3). Monocular and binocular contrast thresholds were determined for sinusoidal gratings of 1, 2, 4, 8, and 18 c/deg. Monocular and binocular SI discrimination thresholds were determined for intervals defined by two pairs of light–on–dark (Michelson contrast = .128, line strength = 25.64%min) vertical lines (12.0 by 2.0 minarc) presented either simultaneously, or sequentially with a 500ms ISI. Results:Age deficits (p < .05) were seen on monocular (best eye) and binocular contrast threshold at 18.0 c/deg, on both monocular and binocular sequential SI, and on monocular simultaneous SI, but not binocular simultaneous SI. No age effects were seen on binocular summation ratio (BSR = best–eye monocular/binocular threshold) for contrast threshold (p < .05), simultaneous SI acuity (p < .05), or sequential SI acuity (p < .05). Although binocular SI thresholds were lower than monocular thresholds for both young (36.8 vs. 45.2 arcsec, p < .05) and old observers (49.0 vs. 66.0 arcsec, p < .05), single–sample t–tests showed that BSRs did not exceed probability summation for either age group on any of the three tasks. Simple main effects showed little difference for the young on simultaneous versus sequential SI acuity; for old observers, however, thresholds were markedly elevated (p < .05) on the sequential version of the task. Conclusions: Binocular summation of contrast information did not appear to be affected by aging among observers in good visual health, and there was little evidence for binocular summation on SI acuity beyond the gain due to simple probability. Differential age deficits on sequential versus simultaneous SI acuity suggest an age–related decline in the cortical mechanisms that mediate the temporal SI comparison; they are also consistent with prior research showing that, at least, cortical engagement for orientation comparisons, is task– rather than attribute–specific (e.g., Orban & Vogels, 1998).
This PDF is available to Subscribers Only