Effect of lens movement on vision with RGP contact lenses

Vision is reduced on lid closure as a result of blink suppression and, in contact lens wearers, by an additional sensitivity loss due to a prismatic shift of the retinal image resulting from lens movement. This study measures this sensitivity loss in two rigid gas permeable (RGP) lens wearers. The stimulus, a sine-wave grating, was presented for 16msec at various times after the blink. The loss in contrast sensitivity at onset times of less than 100msec after the blink was found to be greater than that with hydrogel lenses, and was related to the amount and duration of RGP lens movement.