Download FORUM Glaucoma Workplace Software Version 2.0.4

Appendix N: CIRRUS: Asian Normative Databases
FORUM Glaucoma Workplace
increase with disc size, including Rim Area (slope = +0.24 mm2 of rim per
mm2 of disc, R2 = 0.13, p = 0.042), Cup Volume (slope = +0.25 mm3 of cup
per mm2 of disc, R2 = 0.39, p = 0.011), and Cup to Disc Ratios (slope = +0.35
per mm2 of disc, R2 = 0.35, p < 0.001 for average CDR, slope = +0.29 per
mm2 of disc, R2 = 0.34, p < 0.001 for vertical CDR).
Ethnicity
Ethnicity breakdown of the CIRRUS RNFL normative database is as follows:
44% Chinese, 44% Japanese, and 12% Indian. Only 13 subjects (less than
5%) had discs larger than 2.5 mm2 in the study eye. Ten subjects (less than
5 %) had discs smaller than 1.3 mm2. There was no statistically significant difference among different ethnicities with respect to the Rim Area (p = 0.16) or
the Cup Area (p = 0.38).
The Cup to Disc Ratio (Average and Vertical) as well as the Cup Volume,
showed differences among ethnicity groups (mean difference for both ACDR
and VCDR was 0.06, p = 0.012, mean difference in Cup Volume was
0.04 mm3, p = 0.03).
Results revealed that the mean difference in the average GCL + IPL thickness
between any two race groups is within 2.5 mm. Indians have thinner
GCL + IPL thickness on average, while Chinese have thicker (p = 0.02).
Calculation of Normal Limits
As with the post-hoc analysis of the original normative databases, analysis
of the ONH parameters for the Asian Normative Data found that these parameters depend on both optic disc area of the subject eye and subject age.
A linear fit is used to model the age effects. The variability of parameters such
as Rim Area and Cup to Disc Ratio on Disc Area was found to depend on the
size of the disc. For this reason, quantile regression was used rather than
linear regression to set the limits on the ONH parameters with respect to Disc
Area. This is a method whereby the slope and offset are independently fit for
each limit. See Artes and Crabb1 for a description of quantile regression.
Page 306
Version 2.4
G-30-1911-us