  PURPOSE: Establishing and obtaining consistent quantitative indices of
retinal thickness from a variety of clinically used Spectral-Domain Optical
Coherence Tomography scanners. DESIGN: Retinal images from five Spectral-Domain
Optical Coherence Tomography scanners were used to determine total retinal
thickness with scanner-specific correction factors establishing consistency of
thickness measurement across devices. PARTICIPANTS: 55 Fovea-centered
Spectral-Domain Optical Coherence Tomography volumes from eleven subjects were
analyzed, obtained from Cirrus HD-OCT, RS-3000, Heidelberg Spectralis, RTVue
and Topcon2000, seven subjects with retinal diseases and four normal controls.
METHOD: The Iowa Reference Algorithm measured total retinal thickness.
Nonlinear model of total retinal thickness measurement comparisons was derived
and used for device-specific comparisons. Bland-Altman plots and pairwise
predictive equations yielded pairwise scanner-specific differences. Mendel test
determined whether measurement biases were constant for each scanner pair.
RESULTS: Mendel test revealed that all pairwise scanner differences of total
retinal thickness were constant across the cohort (p=0.992). Individual
measurements can thus be bias-corrected and the Iowa Reference Algorithm serve
as a scanner-agnostic independent standard of total retinal thickness across
the five tested SD-OCT scanners. CONCLUSIONS: Combination of the Iowa Reference
Algorithm with scanner-specific bias correction yields cross-scanner
consistency of total retinal thickness measurements, facilitating
scanning-device independent quantitative assessment of total retinal thickness,
longitudinal follow-up quantification without requiring patients to be imaged
on the same scanner model, and allowing for multi-center studies with
heterogeneous device utilization when using the Iowa Reference Algorithm.
