Improved viewing of half-tone display of Octopus perimeter

The half-tone display of the Octopus perimeter utilizes circles and squares of various sizes as symbols for static threshold levels of light sensitivity in localized areas of the visual field. Under normal lighting conditions at a normal reading distance the symbols do not blur into shades of gray, thus limiting the clinician's ability to screen quickly for contour abnormalities. Four methods that enhance contour discrimination of the half-tone display are (1) viewing at a distance, (2) viewing in dim light, and using either a (3) -14 diopter or (4) +20 diopter lens. In a survey conducted to determine ophthalmologists's preferences, all methods were ranked superior to viewing under normal conditions of lighting and reading distance.