Analysis of tear film breakup on Etafilcon A hydrogel lenses

There is a need to understand better the biomaterial characteristics responsible for tear film stability during hydrogel lens wear. The underlying cause of pre-lens tear film instability may be indicated by the distribution of sites of breakup. The purpose of this study was to compare the distribution of rupture sites during wear of a common biomaterial to that without lenses.

A videokeratography unit, the Topographic Modeling System, was used to capture an image of the tear film at the moment of breakup. Forty measurements were made for each of ten subjects, and the resultant rupture site distributions evaluated. The pre-lens tear film breakup locations were studied for Acuvue (Etafilcon A) disposable contact lenses using the same technique.

There was a statistically significant trend for pre-corneal tear film breaks to occur more commonly in parameniscal zones than in areas overlying the central cornea (ANOVA, p = 0.002). With the Etafilcon A lenses, a significant difference in breakup frequency between the two regions was not observed.

The pre-corneal tear film findings are consistent with the meniscus model of tear film stability; however, the biomaterial surface characteristics of Etafilcon A give other factors a more dominant role in tear film rupture.