Diurnal variation in corneal endothelial morphology

Transient changes in the corneal endothelium were the earliest detectable response to low atmospheric oxygen in experimental animals. Similar changes have been reported after hard and soft contact lens wear. We describe widespread transient cell changes by wide-field specular microscopy in the normal corneal endothelium after 12 hours of a light eye patch. The relative anoxia of lid closure during normal sleep appears to be the cause of observable changes. This observation questions the safety of extended wear contact lens over a prolonged period of time, and its significance to age-related endothelial cell density reduction and cornea guttata remains to be seen.