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

PURPOSE: To determine if hydrogel lens materials from different FDA groups have different effects on the human ocular surface. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Fitting characteristics of Dailies daily disposable hydrogel contact lenses.

PURPOSE: We evaluated the fitting characteristics of nelfilcon A contact lenses to determine the optimal time for judging lens performance during trial fitting. METHODS: Twenty subjects wore a pair of DAILIES (daily disposable soft lenses) for 8 hours. A slit lamp camera was used to videotape lens fit every 5 minutes during the first 30 minutes and at 8 hours. Lens movement and centration were measured in 0.1 mm increments by a single observer. RESULTS: Lens movement decreased significantly during the first 30 minutes of wearing time (P < 0.001). Mean lens movement measured 0.31 mm initially, decreased to 0.17 mm at 25 minutes of wear, and then increased to 0.33 mm at 8 hours (P < 0.001). At 5 minutes, 93% of eyes showed lens movement within 0.2 mm of the value at 8 hours. Lens centration did not change during the first 30 minutes of wear and was comparable to centration measured at 8 hours. CONCLUSIONS: During trial fitting, the optimal time for evaluating movement of nelfilcon A contact lenses is during the first 5 minutes of wear. Lens movement measured at 8 hours will likely be greater than lens movement measured 10 to 30 minutes after insertion.