Appendix A

Ocular Changes During Sleep

Five major 'environment' changes when the eyes are closed.

1. There is no lid actions (blinking) to aid tear exchange and to eliminate debris.

2. There is a reduction in the oxygen supply to the cornea.

3. The tears become more acidic.

4. There is an increase in corneal temperature which can lead to increased corneal metabolic activity.

5. There is change in tear osmolarity due to no tear evaporation.

All these changes can affect contact lens wear.