Learning effect, short-term fluctuation, and long-term fluctuation in frequency doubling technique

PURPOSE: To evaluate short-term and long-term fluctuations and learning eff ects in healthy subjects tested with the frequency doubling technique, whic h is based on a low spatial frequency and a high temporal frequency stimulu s. METHODS: Twenty-three healthy adult subjects were consecutively recruited f rom volunteers, and 20 subjects finished the study. All the visual fields w ere assessed by the frequency doubling technique, program C-20, full thresh old. The frequency doubling technique presents stimuli on a black-and-white video monitor with specialized control circuitry interfaced to a microproc essor. During program C-20, full threshold, 17 points are tested, one round point centrally and 16 square ones in the periphery up to 20 degrees of ec centricity. Each stimulus consists of a 0.25-cycle/degree sinusoidal gratin g undergoing a 25-Hz counterphase flicker. One eye of each patient was chos en at random. Each subject was tested once in the first session, three time s in the second session, and once in the third and fourth sessions. Both sh ort-term and long-term fluctuation were studied either as the average fluct uation value of all the points tested or as a point-to-point fluctuation, T o study the learning effect, the results of the first session were compared with those of the second, the third, and the fourth sessions. RESULTS: The average mean sensitivity of the three examinations of the seco nd session was 30.4 +/- 1.24 dB, and the average short-term fluctuation of all the subjects was 2.16 +/- 0.5 dB, The short-term fluctuation of each po int tested ranged from 1.4 to 3.4 dB, The average mean sensitivity for all the sessions was 32.4 +/- 1.14 dB, with an 0average long-term fluctuation o f 3.23 +/- 0.5 dB, and the long-term fluctuation of each tested point range d from 2.5 to 4.4 dB, A mild learning effect was found between the first se ction and the others, CONCLUSION: Short-term and long-term fluctuations were similar to those kno wn to occur with the conventional threshold perimetry when they were compar ed with the literature data. A learning effect was also observed and should be taken into account for the clinical use of this test. (C) 2000 by Elsev ier Science Inc. All rights reserved.