The effect of time, patching, and lens flexibility on RGP lens adherence

The effects of time, eye patching, and lens flexibility on rigid lens adherence was evaluated in five overnight, in-laboratory test sessions. Patching was investigated with a group of 11 subjects in two overnight test sessions. Sleep time and lens flexibility were investigated in three separate overnight test sessions with two groups of subjects wearing two lens types of fluorosilicone materials (Dk 92 and 60). Adherence occurred in a significant portion of eyes within a 2-hour time period, and the incidence increased throughout the night. There was no significant difference between the incidence of adherence for lenses of a flexible material compared to lenses of a more rigid material (p greater than 0.6, X2 test), nor did patching have a significant influence on the incidence of adherence. The mechanism of lens adherence may be related to several factors including arbitrary lens movement to a peripheral corneal position, the creation of a geometric spacing between the lens and the eye, lid forces producing a negative pressure, and an increase in tear viscosity throughout the night.