Comparison by contact lens cytology and clinical tests of three contact lens types

To determine if hydrogel lens materials from different FDA groups have different effects on the human ocular surface.

Contact lenses from Groups I and II, and Group IV were tested on 10 healthy adapted hydrogel contact lens wearers. For each comparison, the subject wore 2 new contact lenses for approximately 45 min. Lens movement was measured, and comfort evaluated using a subjective scale. After removal of the lenses, fluorescein staining and tear break-up time were measured. Cells were collected by contact lens cytology (CLC), and the size and number of cells harvested from each lens were determined.

There were differences between lens groups in lens movement and comfort, but no differences in fluorescein staining or tear break-up time. CLC showed no differences in cell counts or cell size. There was no correlation between the results of CLC and the clinical tests for lens movement, lens comfort, tear break-up time, and fluorescein staining.

With short durations of lens wear, differences in ionicity and water content have no effect upon the size and number of cells collected from a contact lens. This suggests that, in the short-term, the shedding of cells beneath a hydrogel lens is not affected by the choices of lens material.