Movement and rotation of soft contact lenses. Effect of fit and lens design.

Control of the movement of a contact lens on the eye is of particular importance in the case of a toric lens fitted on a toroidal cornea. Lens rotation was measured on 13 eyes fitted with each of three types of spherical contact lenses, regular, prism ballasted-truncated, and truncated only. Edge lift was varied in three steps, and lenses fitted flat and steep were tested for the amount of blink-associated rotation. Rotation can be reduced by decreasing the radius of the base curve or providing truncation and/or prism ballast.