SILICONE HYDROGEL FINDING
Conjunctival Appearance Related to Silicone Hydrogel Lens Wear
Researchers discuss the clinical implications of a new silicone hydrogel lens finding.
By Desmond Fonn, Dip Optom, MOptom, FAAO, Kathy Dumbleton, MSc, MCOptom, FAAO, and Eric Papas, PhD, MCOptom, DipCL
Silicone hydrogels appeared on the global market in the late 1990s and are well-accepted because of their physiological advantages, long-term comfort and continuous wear capability. In this issue, Tom Løfstrøm, OD, MScOptom, and Allan Kruse, OD, report an interesting finding that appears to be related to their use. We thank Drs. Løfstrøm and Kruse for allowing us to preview their article before its publication, which gives us an opportunity to provide a clinical opinion and perspective of their findings.
The authors describe a "bunched" appearance of the conjunctival tissue, which they call Lens-Induced Flap Excess of conjunctiva (LIFE), in some silicone hydrogel patients who wear their lenses on a continuous wear basis. Since the authors' initial reports of this condition, we have monitored the bulbar conjunctiva and have noted a similar appearance in a small number of successful silicone hydrogel wearers. It's interesting that despite the numerous clinical studies conducted over the past decade and the millions of worldwide wearers, no one had previously reported this sign. There could be a number of reasons for this, but most likely are its extremely subtle clinical presentation and lack of associated signs or symptoms. It's likely that clinicians would overlook this conjunctival disturbance or categorize it as conjunctival indentation unless they instill fluorescein to examine the bulbar conjunctiva using a yellow barrier filter with sufficiently high magnification.
Indentation and even mild staining of the conjunctival tissue are generally not too concerning if no subjective discomfort or associated adverse effects occur. In the few cases we've observed, the appearance seems to suggest a mechanical etiology, perhaps related to pressure from the lens edge, resulting in a "wrinkling" or "bunching" of the loose conjunctival tissue. We found no sign of associated inflammation in the area, and the lens wearers have been asymptomatic. None of our cases have warranted discontinuation of lens wear and the condition appears to have no clinical relevance.
The prevalence levels that Drs. Løfstrøm and Kruse reported are from a pilot study, which by its very nature includes a small number of wearers and provides an imprecise measure of prevalence. A larger study of silicone hydrogel wearers will offer a better estimate. Our results suggest that the prevalence is approximately 10 percent in silicone hydrogels, and the number varies with the type of silicone hydrogel worn. We need to further explore these differences between lens types to better understand the causes. We've observed that the wrinkled appearance is no longer noticeable within several hours after lens removal, but this may depend on severity.
While the condition appears benign, we aren't suggesting that you should ignore this finding. We encourage clinicians, researchers and manufacturers to investigate these conjunctival disturbances and determine their etiology. We'll no doubt see widespread discussion of this subject initially, as was the case when mucin balls were first reported with silicone hydrogel lenses. At this stage we consider this conjunctival change to be a pressure effect from the edge of the silicone hydrogel lens and not of any significant clinical relevance. It would be prudent to avoid the term "conjunctival flap," as this might be confused with the surgical procedure of the same name.
Clinicians recognize the benefits of eliminating hypoxia. We should therefore consider any unfamiliar responses associated with silicone hydrogel wear in this context and continue to prescribe these lenses for our patients while researchers and manufacturers continue to examine their performance and refine their materials and designs.
Dr. Fonn is director of the Centre for Contact Lens Research, and professor, School of Optometry, University of Waterloo.
Dr. Dumbleton is senior researcher, Centre for Contact Lens Research, School of Optometry, University of Waterloo.
Dr. Papas is executive director of Research & Development, Vision Co-operative Research Centre, and adjunct senior lecturer, School of Optometry & Vision Science, University of New South Wales, Sydney, Australia.