SEATTLE, WA (October 26, 2013) – Coefficient of friction in human corneal tissue provides a measurable goal for contact lenses that strive to be close to the natural ocular environment. Until now, it had been an elusive value to determine, as many physiological constraints exist that hamper a viable measurement.
For the very first time, a coefficient of friction value on human corneal donor tissue has been measured according to new research conducted by Johnson & Johnson Vision Care, Inc. The research also shows that while coefficient of friction is dependent on the type of buffer solution, it may not be dependent on donor age or on the time of death when measuring fresh corneal tissue. These findings were presented today at The American Academy of Optometry meeting.
“Now that we’ve measured the coefficient of friction value, additional investigation into the frictional behavior of cornea tissue and its relation to contact lenses can be studied,” says Tawnya Wilson, O.D., Principal Research Optometrist at VISTAKON® Division of Johnson & Johnson Vision Care, Inc. “This knowledge will ultimately lead to the development of better contact lenses that can mimic corneal properties and that can address end-of-day comfort for our patients.”
About the Study
Coefficient of friction testing was conducted utilizing a micro-tribometer on a minimum of five fresh human donor corneas with intact epithelium for four different buffered solutions: tear-mimicking solution (TMS-PS) (420-430 mOsm/kg), tear-mimicking solution with phosphate buffer saline (TMS-PBS) (300-310 mOsm/kg), tear-mimicking solution with HEPES buffer and sodium chloride (TMS-HEPES) (300-310 mOsm/kg), and tear-like fluid with phosphate buffer saline (TLF-PBS) (300-310 mOsm/kg). Corneal tissue was supplied within eight hours after death (between 2.10 hours and 7.29 hours), and excised from the globe with coefficient of friction testing conducted within nine hours (between 3.30 hours and 8.48 hours) of death. The applied normal force varied between 0.25 and 4.0 mN with a measured stroke length of 1.0mm at normal blink speed of 0.1mm per second. A mucin-coated glass disc was used as counter surface mimicking the inner eyelid. Descriptive statistics were used to summarize the coefficient of friction values by solution.
This novel pilot study found that the coefficient of friction means (SD) were 0.0134 (0.01018) in TMS-PS, 0.0060 (0.00290) in TMS-PBS, 0.0144 (0.00484) in TMS-HEPES, and 0.0153 (0.00941) in TLF-PBS. In addition, there was no clear trend observed between the age of the donor or the time of death to measurement and the coefficient of friction value.
Source: Wilson, T, Aeschlimann, R, Tosatti, S, Toubouti, Y, Kakkassery, J, Osborn-Lorenz, K, “Coefficient of Friction of Human Cornea Tissue.” Poster presented October 26, 2013 at The American Academy of Optometry 2013 meeting.