"You can look closely at the iris (colored part of the eyes) in the mirror and tell how well your skin is eliminating. If you can see a darker ring around the very most outer edge of the iris then you have what is called a scurf ring.
Seeing a scurf ring always means that your skin is not eliminating toxins well, and it is being reflected on the iris of the eye. It is not a disease of the eye, but simply a reflex sign of an overload of toxins at the level of the skin. You can observe your eye and watch it improve as you progress with your detox protocol."
This is from his link called Inexpensive Treatments:
I would only stay in the sauna for 10 to 15 minutes and build up to it or maybe do lots of detox baths before even trying the sauna. Is it an infrared sauna?
Hope this helps! Denise