A binocular perimeter.

A newly designed visual field testing instrument may be used either binocularly, as a quick screening test, or uniocularly, for plotting field defects. During binocular testing, the patient views a single target light at various points in the binocular central field. The eyepieces through which the patient looks and which contain weak prisms induce an artificial diplopia, and the patient sees two target lights. If the patient responds that he sees only one, then a field defect is present in one eye. Further analysis of the fields is then tested uniocularly. The instrument is simply constructed, yet should provide the means for assessing visual fields quickly and accurately.