The learning effect in visual field testing of healthy subjects using frequency doubling technology

Purpose: To evaluate the presence, duration and magnitude of a learning effect in serial visual field (VF) testing, using the commercially available frequency doubling technology (FDT) instrument. Patients and Methods: 21 healthy adults with no prior VF experience underwent 6 serial VF tests, using the full-threshold C-20 program of the Zeiss-Humphrey FDT analyzer, on one randomly chosen eye. Tests were spaced at least two days apart. Results: The average mean sensitivity was 32.37 +/- 2.6 dB; the average mean deviation (MD) was 1.22 +/- 1.8 dB. The MD at the first examination (0.28 +/- 2.1 dB) was significantly poorer than at any of the other testing sessions (p<0.003). Similarly, the mean sensitivity at the first examination (31.16 +/- 3.0 dB) was significantly lower than any other testing session (p<0.004). The proportion of improvement from the first to the second session was 63% and 65% of the total improvement, for mean sensitivity and MD, respectively. Mean test duration showed a modest reduction, from 4.40 +/- 0.3 minutes in the first session to 4.17 +/- 0.4 minutes in the last session (p = 0.023). A sub-analysis comparison of the different VF segments showed a more prominent learning effect in the peripheral and nasal visual segments (p<0.0001). Conclusion: Baseline measurements should best rely on the second testing session, since MD and mean sensitivity are somewhat poorer when subjects with no prior VF experience are first tested on the FDT instrument. This may be especially true for the purpose of following patients over time.