The TFOS International Workshop on Contact Lens Discomfort: Report of the Contact Lens Materials, Design, and Care Subcommittee

Abstract

Examining the role of the contact lens material, design, and the care system is fundamental to understanding contact lens discomfort (CLD). However, a systematic review that tries to determine the governing factors is fraught with difficulties. A lack of a validated “instrument” (or single validated questionnaire) for measuring discomfort makes it impossible to compare between studies because reported levels of comfort (or discomfort) are inconsistent. Subject classifications can vary widely, from studies that include only neophytes or asymptomatic contact lens (CL) wearers to studies including only those contact lens–wearing subjects who experience marked dryness or symptoms of discomfort. Also, it is difficult to measure issues of importance in isolation because changing one factor in a contact lens or care solution can invariably affect another. An illustration of this relates to a change in hydrogel water content, which also affects oxygen permeability, oxygen transmissibility, modulus, and possibly lens thickness. Finally, various confounding factors between studies also make true comparisons problematic. Typical examples would include differences between brands of lenses made from the same material (which may have differing geometric designs, edge configuration, or production methods); wearing modality (lenses may be worn on a daily wear [DW] basis, overnight occasionally, or for up to 30 nights on a continuous wear [CW] basis); duration of use prior to replacement, wearing time during the day (from just a few hours to most of the day); and care product differences or exposures (which could range from no exposure in the case of daily disposable [DD] materials to a preserved system that has extensive uptake and release from the contact lens material being examined). The purpose of this report is to summarize evidence-linking associations, mechanistic and etiological factors between contact lens materials, designs, and care solutions with CLD. The potential factors associated with this are many and varied, and graphically display the complexity of this issue.