Volume Perimetry

In 1988, we published the first geometrically accurate analyses of the relationship between visual scotomas (blind spots) and the three-dimensionality of the functional visual field  which formed the basis of volume perimetry and the notion of volume scotomas (terms we coined). These led to 1) an appreciation of the shortcomings of assessing the functional impact of the perimetrically measured visual fields with any two-dimensional perimetric procedure, including the popular binocular Esterman method incorporated in the Humphrey Field Analyzer firmware, 2) a novel theory about why the human optic disk evolved to its location some 13-18 deg in the nasal retina, and 3) methods for visualizing functional visual field effects in computer-aided design of visual environments such as cockpits (1,2,3,4,).

The main window in the picture above depicts two eyes (suspended in mid-air!) viewing a tabletop scene of tinker toys and other simple objects.  Each eye has a central scotoma of 5 degrees diameter, displayed on the superimposed left and right eyes' visual fields in the inset in the upper right of the picture, along with the two eyes' natural blind spots -- the so-called "physiological scotomas."  (In the inset, a green patch represents the left eye's blind spot, a red patch represents the right eye's blind spot, and the large central patch is the central scotoma that both eyes share.)  Contrary to intuition, there are three distinct volumes of space rendered blind to this observer, represented as elongated yellow shapes.  Each volume scotoma is a region of space in which imagery from real objects falls into blind regions in both eyes; objects in the double-coned volume scotoma fall into the central scotomas of both eyes, while those in the other volume scotomas farther away from the eyes fall into the central scotoma of one and the natural blind spot of the other eye!