Hendrik Walther is a graduate student at the Centre for Contact Lens Research, School of Optometry and Vision Science, University of Waterloo. Chau-Minh Phan is a former CCLR graduate student, currently working at Triclops Technology.
It can be a challenge to test contact lens performance in the early stages of development. Although the human eye would be the ideal testing environment, it is unfortunately not always practical or cost-effective, so we rely on in vitro research to understand how a lens responds to varying ocular conditions such as tear fluid composition, ocular surface temperature and blinking, extrapolating the results to predict in vivo lens performance.
Conventional in vivo methods, however, are limited by conditions that truly mimic the human eye. While simply submerging a lens in a vial of saline solution or artificial tears can provide some information to help us understand the “hows” and “whys” of lens performance, there are a number of ways that this static fluid model does not truly reflect the ocular environment:
- Submerging a contact lens requires 2-5 mL of liquid, significantly more fluid than would come into contact with a contact lens on eye (typically about 7.0 μL at any given time).
- The ocular surface is not a static environment: constant tear flow and tear replenishment over time is missing from the simple vial model.
- Any effects of the mechanical blink (e.g. the eyelid rubbing against the contact lens) are missing from the static vial model.
- On eye, a contact lens undergoes intermittent air exposure between blinks.
CCLR graduate students, Chau-Minh Phan and Hendrik Walther, were unsatisfied with these limitations. While they were certainly not the first to try to come up with a better in vitro testing system, their tenacious approach in developing various iterations of the OcuFlow® has produced a remarkable device that manages to include all the pieces missing from the conventional in vitro testing model. These include an adjustable range of motion representative of the natural blink, adjustable fluid volume and flow and intermittent air exposure. Test solutions housed in separate chambers can be released separately and collected for in vitro analysis.
Walther presented the evolution of this device at the 2016 meeting of the American Academy of Optometry. Here’s what it looks like:
