Table 1
Subject demographics by iris color.
| Blue Eyes | Brown Eyes | |
| N | 7 | 6 |
| Male/Female | 5/2 | 3/3 |
| Age (mean ± SD) | 25.2 ± 6.0 | 25.8 ± 5.4 |
| Self-reported | 4 Caucasian | |
| Race or Ethnicity | 7 Caucasian | 1 Hispanic 1 Asian |
| Owl-Lark Score | 52.7 ± 6.1 | 52.3 ± 10.5 |
Figure 1
Protocol diagram. This protocol is for a subject sleeping from 23:00–7:00 at baseline (days 1–7). Shaded rectangle with L inside shows time of bright light exposure (2 h, ~4000 lux).
Figure 2
Circadian rhythm phase delays with a single bright light pulse and delayed sleep/dark episode. The horizontal lines represent the median phase delays.
Table 2
Color dimensions (mean ± SD) for subjects with blue and brown irises.
| Iris Color | Blue Irises | Brown Irises | Correlation with |
| Dimension | n = 7 | n = 6 | phase shift (n = 13)b |
| Bluea | 125.5 ± 9.6** | 42.7 ± 9.3 | r = .40, p = 0.17 |
| Greena | 143.0 ± 5.2** | 93.3 ± 18.0 | r = .31, p = 0.31 |
| Reda | 130.1 ± 2.2 | 123.0 ± 17.3 | r = .14, p = 0.64 |
| Lightness | 57.9 ± 1.4* | 43.0 ± 7.2 | r = .29, p = 0.33 |
* p < 0.01; ** p < 0.001, t-test comparing subjects with blue vs brown irises
a Measured from 3 dimensions of the RGB color system.
b Positive correlations indicate that subjects with darker irises had larger phase delays.