With a supplementary preadapting field of high intensity, measurement of the rate of dark adaptation with alternate blue and yellow test objects permits differentiation of the responses of cones and of photopic and scotopic rods. This technique is useful in the diagnosis of congenital achromatopsia. Selective impairment of rod function can be studied by measurement of a scotopic threshold gradient. Scotopic kinetic perimetry may be a useful supplementary test. In photopic perimetry the use of red test objects may assist in detection of localized areas of selective cone impairment with normal rod function. An auxiliary perifoveal fixation target is helpful in maintaining foveal fixation when there is a large dense central scotoma. The absolute light intensity provided by the calibration standard should be checked for error.
Sloan LL. The Tubinger Perimeter of Harms and Aulhorn: Recommended Procedures and Supplementary Equipment. Arch Ophthalmol. 1971;86(6):612–622. doi:10.1001/archopht.1971.01000010614002
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