Dehydrated contact lenses (drying) can occur especially at higher temperatures and when the air is dry, incomplete or irregular blinking, age or contact lenses.
During dehydration varies the geometrical parameters of the material – a thinner contact lens, smaller radius of curvature and diameter. Thinning tear film:/glossary/tear-film.html, originally flat application becomes steeper and the edges of the lenses can irritate the eye surface. It also reduces elasticity of the lens as it becomes harder and more brittle. Reduced water content reduces oxygen permeability, reduces wettability of the surface and increases refractive index of the contact lenses.