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Carrie K. Doyle, Gideon J. Zamba, Chris A. Johnson, Michael Wall; The Repeatability of Mean Deviation with Size III and Size V Standard Automated Perimetry. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5523.
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© ARVO (1962-2015); The Authors (2016-present)
The mean deviation (MD) of the visual field is a statistical index used to determine the average difference in visual field sensitivity compared to the mean sensitivity of a normal observer of the same age. MD has also been used to monitor overall visual field change over time. Our goal was to investigate the relationship of MD and its standard deviation (SD) for two clinically used strategies (SITA standard size III and full threshold size V) in glaucoma patients who were tested 5 times.
We tested 46 subjects glaucoma with Humphrey program 24-2 SITA Standard for size III and full threshold for size V each 5 times over a 5 week period. Mean Deviation (our age-adjusted MD was calculated from our set of 60 normals tested twice) for size III was -10.19 ± 6.9; for size V -7.85 ± 6.0. The standard deviation of MD was regressed against the MD for the five repeated tests (Fig). A paired t-test was used to compare the standard deviations of the two testing methods.
The graph shows the well known relationship of increasing variability with increasing visual field damage. The R2 of SITA III was 0.19 and size V was 0.29. The SD of size V was less than size III (p = 0.024).
The repeatability of size V full threshold MD appears slightly better than size III SITA testing. When using MD to determine visual field progression, a change of 1.5 to 4 dB is needed to be 2 SDs, varying with the size of the stimulus and the amount of visual field damage.
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