Page:Latency of Pupillary Reflex to Light Stimulation and Its Relationship to Aging.djvu/12

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 * Figure 8. Composite curves of average response of pupil vs. light intensity.
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with the highest setting is approximately one million peak candles measured on the axis of the parabola at a distance of 10 inches from the glass face plate. The latency values used at each intensity setting were means of 10 digital readings, a plot of which is shown in Figure 9. The standard deviation of the readings about each mean was approximately five milliseconds, and their standard deviations did not vary significantly from one intensity level to another.

A scattergram (Fig. 7) of the average latency period by age shows a positive relationship (r=.54) between pupillary latency period and aging. As one grows older, his pupillary latency period increases. A chi-square of 11.87 (each variable split at the median) with one degree of freedom, a p<.001 shows that this is highly significant. The slope of this increase is shown by the regression equation y=.77x+222.3.