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Sarah Muscat, Stuart Parks, Ewan Kemp, David Keating; Repeatability and Reproducibility of Macular Thickness Measurements with the Humphrey OCT System. Invest. Ophthalmol. Vis. Sci. 2002;43(2):490-495.
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purpose. To assess the accuracy, precision, repeatability, and reproducibility
of measurements made by the Humphrey optical coherence tomography (OCT)
system (Humphrey-Zeiss Medical Systems, San Leandro, CA).
methods. The performance of the system was first investigated by scanning a test
object containing an air gap of known size. Measurements were repeated
with water or glycerin in the gap. In the clinical setting, macular
thickness measurements were obtained from a control group of 20 normal
subjects. For analysis, these scans were divided into eight sections,
each containing 10 A-scans.
results. The average gap thickness was found to be close to the true value in
all cases. The overall coefficients of intersession reproducibility
were less than 1% for the test object and 1.51% for the control
group. There was no significant difference between scans acquired
during different sessions. The overall coefficients of repeatability
for the test object were between 0.2% and 1.1% and between 1% and
2% for the control group. The range of normal retinal thickness in
terms of the 5th and 95th percentiles was 222 to 248 μm in women and
234 to 257 μm in men.
conclusions. Measurements made from OCT scans were found to be accurate and precise.
Introducing water or glycerin into the test object resulted in
considerable degradation of the signal, but measurements of gap
thickness were still shown to be accurate, precise, reproducible, and
repeatable. Retinal thickness measurements in the macular area were
repeatable and reproducible. This demonstrates that OCT is a useful
tool in the monitoring of patients with conditions that affect macular
thickness, even when there is considerable degradation of the OCT
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