The instrument described in this paper was devised for the especial purpose of making comparative studies of light sensitivity from the center to the periphery throughout the entire retina. A review of the recent literature on instruments and technics for measuring light sense and dark adaptation1 indicated that none of them were suitable for this particular type of investigation.
In the first paper of this series I outlined what I believed to be the requirements of an ideal clinical instrument for testing light sense. These requirements were as follows: (a) a preexposure field of constant brightness; (b) illumination of the test field with light of known composition, variable in intensity by known amounts over a wide range ; (c) standardization of the size of the pupil; (d) control of fixation, and (e) norms for distinguishing between pathologic and normal light thresholds. This instrument was devised to fulfil these five requirements
SLOAN LL. INSTRUMENTS AND TECHNICS FOR THE CLINICAL TESTING OF LIGHT SENSE: III. AN APPARATUS FOR STUDYING REGIONAL DIFFERENCES IN LIGHT SENSE. Arch Ophthalmol. 1939;22(2):233–251. doi:10.1001/archopht.1939.00860080077006
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