Zeiss CIRRUS HD-OCT 500, User Manual

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Appendix
2660021169012 Rev. A 2017-12 CIRRUS HD-OCT User Manual
A-4
Note that CIRRUS RNFL and Macula normative databases are adjusted only by age, not by
ethnicity or any other parameter. The normative limits provided for comparisons of
individual data to the normative database do not take into account differences that may be
present due to ethnicity, axial length, refraction, optic disc area, or signal strength.
Data Analysis
From these scans the normative databases for the Macular Cube 512x128, the Macular
Cube 200x200 and the Optic Disc Cube 200x200 scans were created. The age range for all
databases was from 18 to 84 years. Mean age of the subjects was 46.5 years for the RNFL
normative database and 46.6 years for the macula normative database.
The regression model analyses were used to estimate the normative limit of each of the
CIRRUS HD-OCT RNFL and macular thickness parameters adjusted by age. Subject's age is
considered as a clinically important factor for the RNFL and macular thickness
measurements.
For each fitted regression model, the residuals were derived for each eye by subtracting
estimated expected mean reading, ET(age0), from the measured or observed reading,
Obs(age0). In other words, residual = Obs(age0) – ET(age0). The goal was to predict the
100x

th
percentiles (NL, normative limit) of the residuals, so that the 100x

% limit of the
CIRRUS HD-OCT parameter readings could be estimated as follows:
ET(age0) + NL(100x

%) < Obs(age0) (A)
The 1st, 5th, 95th, and 99th percentiles of the residuals were estimated by the empirical
distribution of residual. Then the estimated 1%, 5%, 95% and 99% normal limits of
CIRRUS HD-OCT parameters for a normal subject with an age of age0 were established by
Equation (A). It should be noted that the study site effect was not considered in the
normative limits calculation since the objective was to establish the normative limits for the
general population.