A New Laboratory and Clinic Perimeter.

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Abstract
Describes the means by which factors in perimetric determinations like the intensity of the stimulus, the brightness of the pre-exposure and surrounding fields, the intensity of the general illumination, and the accuracy and steadiness of fixation are controlled.The device for controlling intensity of the stimulus consists of an 180° and 90° arc joined together at the center of rotation at right angles to each other. At the end of the 90° arc is placed a type C Mazda lamp housed by a box with an aperture so that the light radiates freely without shadows and with equal intensity to every point on the arm of the perimeter. The brightness of the surrounding field is controlled by pasting Hering pigment papers onto grey cards, with tints equated to the brightness of the colors. The control of the pre-exposure field is provided by the use of grey cards of various brightnesses which cover the stimulus card until the S has taken a fixation. Two devices aid in securing accuracy and steadiness of fixation. One consists of a small circular mirror as a fixation object in which the S sees the image of his own eye. From the position of the image of his pupil and iris as seen in the mirror the S can determine the fixation. The second device is similar in principle to a peep-sight. A small black disc at the center of rotation of the perimeter is situated with respect to a circular aperture nearer the eye of the S. When the eye has the proper position and fixation, the edge of the opening is seen concentric to the disc with a narrow ring of the grey arm of the perimeter showing between. A head rest aids in maintaining correct fixation. Describes certain additional controls which make for finer technique in special clinical perimetric determinations. From Psych Bulletin 19:09:00548. (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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