Figure 3.

Line plot showing linear regression analysis of mean pupil size and age for five different illumination levels. The colour-coded caption indicates the different illumination levels of 0, 0.5, 4, 32, and 250 lux. The ordinate shows pupil size in mm, the abscissa shows eight different subgroups for age decades in years. The black line indicates the linear regression line for each illumination level; R² and p values are described in the caption. Note that R² and p values indicate a linear correlation at all illumination levels, except 250 lux. The mean pupil size decreases with increasing age and illumination intensity. The results of the linear regression analysis indicate a linear correlation between pupil size and age. Number of cases per age group: ages 6–19, n = 5; 20–29, n = 27; 30–39, n = 41; 40–49, n = 40; 50–59, n = 41; 60–69, n = 36; 70–79, n = 42; and 80–87, n = 12.