CIRRUS HD-OCT User Manual 2660021169012 Rev. A 2017-12Appendix A-33The Cup to Disc Ratio (Average and Vertical) as well as the Cup Volume, showeddifferences 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 anytwo 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 LimitsAs with the post–hoc analysis of the original normative databases, analysis of the ONHparameters for the Asian normative data found that these parameters depend on bothoptic disc area of the subject eye and subject age. A linear fit is used to model the ageeffects. The variability of parameters such as Rim Area and Cup to Disc Ratio on Disc Areawas found to depend on the size of the disc. For this reason, quantile regression was usedrather than linear regression to set the limits on the ONH parameters with respect to DiscArea. This is a method whereby the slope and offset are independently fit for each limit.SeeArtes and Crabb3 for a description of quantile regression.ConclusionThe CIRRUS HD-OCT Asian RNFL, macular thickness, ONH, and Ganglion Cell AnalysisNormative Databases were created using data from subjects that were deemedrepresentative of a normal population. The CIRRUS HD-OCT Asian Normative Database forRNFL thickness established reference values for the Optic Disc Cube 200x200 scan. TheMacula Asian Normative Database established reference values for the Macular Cube512x128 and Macular Cube 200x200 scans. Post–hoc analysis was used to developreference values for Ganglion Cell Analysis and ONH as well. The doctor can use thesenormative databases to compare individual patient measurements to those acquired in anormal population.
