The ability of the eye to fix a point of reference is essential to standard methods of scotometry. Though fixation theoretically may be accomplished by any portion of the retina, it is certainly necessary that the visual line remain (relatively or absolutely) stationary in order to permit the plotting of a defect.1 Fixation of a point of reference on a chart by the macula constitutes the standard by which the anomalous types of fixation are judged, but macular fixation is in itself a complicated process, and many of the elements concerned are as yet poorly understood. In the following pages an effort is made to summarize certain aspects of the problem so as to emphasize the importance of this act in scotometry.
If a defect is projected on a tangent screen placed at 2,000 mm. and again on one at 330 mm., it is found by calculation
EVANS JN. FIXATION IN SCOTOMETRY: A CRITICAL INQUIRY. Arch Ophthalmol. 1936;16(1):106–118. doi:10.1001/archopht.1936.00840190116015
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