Relationship between hydration layer thickness and friction property of contact lens with the addition of eye drop ingredients

Abstract

Contact Lens (CL) causes eye damage and discomfort by increasing friction with upper eyelids. To improve the safety and wearing comfort of CL, eye drop has an important role in reducing friction on CL. Therefore, it is essential to understand the friction mechanism between a CL and an upper eyelid in eye drop. In a previous study, we investigated the relationship between the hydration layer thickness and frictional properties of CL surfaces in a saline solution. We used a high-resolution tribometer and frequency-modulation atomic force microscopy (FM-AFM) to observe the hydration layer. The hydration layer of the CL in a saline solution was found to increase or decrease in thickness because of micro abrasion However, the effects of eye drops on friction mechanism of CL have not yet been investigated. In this study, we investigated the effects of hyaluronic acid on CL surface friction and hydration layer thickness. In friction tests, the coefficient of friction of hyaluronic acid solution was higher than that of saline solution, regardless of the amount of hyaluronic acid added. In addition, FM-AFM observations indicated that the hydration layer thickness on the CL surface increased in PBS with hyaluronic acid solution compared to that in saline solution. Therefore, the frictional properties of the CL in PBS with hyaluronic acid solution were not determined by the hydration layer thickness.