Mechanisms for the symptoms of dryness in soft contact lens wearers.

Dryness symptoms in soft contact lens (SCL) wearers are common, especially at the end of the day, and are the most common reason for discontinuing wear. With reference to mechanisms for dry eye syndromes in non-SCL wearers, this review examines mechanisms whereby dryness symptoms are generated during SCL wear, including the significance of endogenous tear dysfunctions, pre-lens tear film instability, post-lens tear film volumes and stagnation, tear hyperosmolarity, blink inefficiency, SCL material dehydration, and front surface biocompatibility and wetness. Numerous efforts have been made to reduce dryness symptoms by improving SCL materials and surfaces, but the prevalence of dryness symptoms remains stubbornly high. It is possible that symptoms might be due to neuropathy and associated increases in corneal and/or lid wiper sensitivity that develops during SCL wear. For example, over time, sensory thresholds for SCL awareness may be lowered and/or conditions that increase their perception sharpened. There are several mechanisms contributing to thinner pre-lens tear films and reduced SCL biocompatibility. Dryness symptoms may occur with bandage SCL, especially in a previous wearer of SCL. [ABSTRACT FROM AUTHOR]