C D Chan

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The defocus levels required for normal observers to notice the first perceptible blur of a clear test target (blur threshold) and the least perceptible change in the degree of blurriness of an already blurry target (threshold of perceived change in blur) were measured using both the source and observer methods. In the source method observers viewed(More)
The relation between refractive error and visual acuity has been measured by two very different methods. In one called "source methods," emmetropes or corrected ametropes view defocused stimuli presented on projection screens or photographs. In the type called "observer methods," focused stimuli are presented to the observers who are either uncorrected(More)
PURPOSE To compare the baseline blink rates (BBR) measured under different (baseline) conditions, and to compare the blink rates measured when performing two visual tasks of different levels of difficulty at two positions of gaze. METHODS In the first single masked experiment, BBR were measured under three different conditions - (i) conversation with the(More)
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