Tribology and the Ocular Surface.

Introduction: Tribology is known as the science of friction, lubrication and the determination of what occurs when two surfaces slide against one another. The required partners in this science are a minimum of two surfaces and relative motion. Tribology could be a key factor in dissecting the issues that surround and confound dry eye in patients as well as contact lens discomfort and intolerance. Specifically, it is this issue that is a potential causative underlying factor that could lead to conditions like lid wiper epitheliopathy (LWE). Methods: Peer-reviewed literature was reviewed as It pertains to ocular tribology and the application to the ocular anatomy. A PubMed review was performed using the keywords: tribology, friction, lid wiper epitheliopathy, contact lens, and dry eye. All manuscripts were reviewed for mentions of tribology and friction. The exact same process was performed with The Association for Research in Vision and Ophthalmology (ARVO) abstracts. Results: In relation to the ocular surface, tribology describes the mechanical interactions between the upper and lower lid wipers and the globe. The Stribeck curve can be applied, as the sliding partners are separated by a complex, lubricating tear film. The surface brush anatomy at the eye to eyelid juncture reduces friction and alters the Stribeck curve in favor of the hydrodynamic regime, allowing for high velocity movement with minimal wear. Changes to the tear film or the introduction of a contact lens can displace the Stribeck curve, increase friction, and induce wear thus leading to patient symptomology. Conclusion: Further studies may provide new insight into contact lens discomfort and ocular surface disease, including LWE; however, adaptation of tribology work performed in vitro to in vivo patient care is challenging.