Contact Lens Discomfort: Can Past Workshops Provide Insight?
BY WILLIAM L. MILLER, OD, PHD, FAAO
Contact lens-related discomfort, especially late in the day or after prolonged near activities, is a significant problem for many of our patients. My column usually focuses on the frank treatment of anterior segment and contact lens conditions. In this column, I will summarize what we know about contact lens-related irritation based on what we’ve learned from the DEWS Report and the MGD Workshop. The DEWS report cited contact lens discomfort and dryness as primary reasons why our patients become less tolerant of contact lens wear (DEWS Report). Some of these patients are known (complainers) and some unknown (silent tolerators) to our staff and ourselves. The former are likely to drop out of contact lens wear entirely. Between 50 and 75 percent of all patients complain of some form of ocular irritation while wearing contact lenses (DEWS Report). Dropout rates for contact lens wearers have been reported to be between 12 and 28 percent, depending on the criteria used in the particular study (Schlanger, 1993; Weed et al, 1993; Pritchard et al, 1999; Young et al, 2002; Richdale et al, 2007; Rumpakis, 2010; Dumbleton et al, 2013). More troubling is that despite advances in lens materials, wetting agents and designs, not much has changed over several decades with regard to contact lens comfort.
According to the 2007 DEWS Report, dry eye as defined by the report is broadly defined as aqueous (Sjogrens or non-Sjogrens) and evaporative (MGD). Contact lenses are seen as extrinsic factors that affect the tear film, causing evaporative effects. This may be the result of a thinning of the pre-lens tear film or an insufficient wetting of the contact lens surface, both of which affect tear film stability on the anterior surface of the contact lens. Material properties may lead to wettability issues with additional issues caused by lens deposition in the form of denatured protein and lipids. This can be addressed using adequate lens care regimen compliance, but also through the prescribing of daily disposable contact lenses. Although contact lenses cause evaporative effects, they may also disturb aqueous production through a sensory reflex block mechanism. Higher water contact lenses have been associated with dryness, however this has not been a universally accepted truth and thus remains controversial within the field (DEWS Report).
Additional information about the effects of contact lens on the tear film as they relate to the meibomian gland is described in the MGD workshop report. (Knop et al, 2011) As reported, because of its action on the meibomian gland, estrogen treatment can lead to tear film instability and reduced contact lens tolerance (Knop et al, 2011). Contact lenses may also cause epithelial keratinization as well as meibomian gland orifice obstruction that can further complicate successful wear. It has also been noted that contact lens wearers have a high meibomian gland drop out rate that may be related to the keratinization cycle, however the precise mechanism is not known. This dropout rate mimics what is found in the normal aging process. A critical reading of two well regarded published reviews on ocular dryness and meibomian gland dysfunction may help in addressing many issues that affect contact lens patients. Further management in the form of topical drops, contact lens care systems and novel contact lens technologies may further help more patients stay comfortable throughout the day, reduce intolerance and limit drop outs.
For references, please visit www.clspectrum.com/references.asp and click on document SE2013.
Dr. Miller is an associate professor and chair of the Clinical Sciences Department at the University of Houston College of Optometry. He is a member of the American Academy of Optometry and the AOA. He is a consultant or advisor to Alcon and Vistakon and has received research funding from Alcon and CooperVision and lecture or authorship honoraria from Alcon and Bausch + Lomb. You can reach him at firstname.lastname@example.org.