The Relationship of Residence Time and Visual Effect of Optive and Systane in Dry Eye Subjects

Study Summary

The benefits of artificial tears to relieve dry eye symptoms include, but are not limited to: stabilizing the tear film layer, fluid supplement action, improving visual acuity, and comfort. Studies have found a relationship between some of these benefits. For example, stabilization of the tear film is important not only to increase the tear break up time (TBUT), but is key in improving and maintaining visual acuity. These studies have alluded to the fact that there may or may not be a relationship between residence time and visual performance. Viscosity is one reason behind the uncertainty. Some solutions contain polymers which influence the ocular surface when contacted. This can impact residence time and ultimately visual performance. No prior research has explored the direct relationship between residence time and visual performance. Residence time refers to the duration at which the artificial tear resides on the eye. Methods have been developed to assess residence time by admixing fluorescent tracers to the solution and then measuring the amount of fluorescence over time. The caveat to methods using certain tracers has lead to uncertainty in elimination measurements due to corneal penetration or differing molecular weights (MW) from the active vehicle ingredient in the solution. For example, low-MW tracers can be eliminated at a different rate than higher-MW polymers. In addition, the low-MW tracers may be able to penetrate the corneal epithelium giving a false pre-corneal residence time. Meadows, Paugh, Joshi, and Mordaunt addressed this issue by developing a technique using a polymer which did not penetrate the cornea and had the same MW as the active ingredient in the solution FITC-dextran. Based on the assumption that similar weights are eliminated at the same rate, this technique has shown to be more economic, manageable, and amendable than previous procedures measuring residence time. Any ophthalmic drop has the potential to impact visual acuity upon in