- Disc Area remains largely stable throughout life but there are ethnic variations
- Normal mean disc area is 2.27 mm² (st. dev ±0.412)
Distribution of Disc Area from Marsh et al. 2010 
Variation in Disc Area by Ethnicity from Girkin et al. 2011
| Area of Descent | African | European | Hispanic | Indian | Japanese |
|---|---|---|---|---|---|
| Mean Disc Area in mm² (SD) | 2.09 (0.41) | 1.81 (0.38) | 2.06 (0.37) | 2.03 (0.31) | 1.93 (0.37) |