Corneal edema with hydrogel lenses and eye closure: effects of lens thickness

Subjects wore hydrogel lenses of two different thicknesses (0.07 mm and 0.18 mm) on one eye and no lens on the other eye during 3-hour periods of eye closure. They developed more corneal edema (12.7%) with the thicker lenses than with the thinner lenses (7.9%) and more corneal edema with the thinner lenses than with no lens (0.9%). The results suggest that hydrogel lens thickness would have to be less than 20 nm to reduce corneal edema to levels that develop when the eyes are closed without a contact lens.