That is the remarkable part of the portrait. After rotating (lining up background vetically) and a crop of unnecessary stuff, base layer is copied and used as foundation.
- First layer over base is in Overlay mode, 20% Opacity.
- Eyes are erased to show base layer.
- Eyes of base are copied/pasted on Lighten layer, 30% Opacity
- Two front teeth are copied/pasted on Lighten layer, 60% Opacity
- Gradient Lighten vignette added, adjusted to draw attention to face
