Method to estimate the human pupil size from the bandwidth of coherent retinal images

A new technique for extracting information on the size of the pupil of the human eye is presented. It is based on the recording of coherent short-exposure retinal images of a point source after double pass through the ocular media. The eye's pupil size is then estimated by computing the cutoff frequency in the power spectrum of these coherent images, which is related with the average width of the speckle. First the validity of the technique is established by use of an artificial eye, and then results are obtained in the living human eye. This method has the potential of determining the eye's pupil diameter with a standard error of the order of 0.1 mm and can be used in different visual optics experiments, although with its present components it is especially appropriate for experiments based on the recording of coherent retinal images.