Neural Science 2014

The spatial contrast sensitivity function (CSF) is one of the most important single measures to determine the limits of the human visual system’s performance. The measure is the minimum contrast (contrast threshold) of a sinusoidal grating stimulus that can be detected by an observer on a background of the same space averaged mean luminance. To construct a complete contrast sensitivity function the contrast threshold is measured for a range of spatial frequencies. Acuity and spatial resolution are terms that are commonly used to describe the highest spatial frequency that the human observer can resolve. Acuity can be obtained by extrapolating the high frequency limb of the contrast sensitivity function to a contrast of 1. For normal observers under optimal conditions and with bright illumination this value is about 60 cycles/degree of visual angle. There are a number of ways 1 in which acuity is measured in the clinical setting. One of the most common is to use the Snellen letter chart which is described in the first part of this laboratory exercise. When conducting an experiment that involves sensory performance it is important to determine your subject has normal capacities. In the visual domain this often involves measuring the subject’s spatial, color and stereoscopic performance. The next sections provide an introduction to the initial screening that might be undertaken to determine normal vision