SILICONE HYDROGEL FINDING
Conjunctival Appearance Related to Silicone
Hydrogel Lens Wear
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
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
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.
Contact Lens Spectrum, Issue: September 2005