Adaptation to Silicone Hydrogel Materials
N. REX GHORMLEY, OD, FAAO
Some patients immediately adapt to silicone hydrogel contact lenses when refit from low-Dk soft lenses. But, a small percentage
of such patients need several weeks to adapt. Clinicians know
that all eyes are different and that some undergo greater physiological changes
following a dramatic change in oxygen supply. In addition, silicone hydrogel lens
materials are different in many ways from low-Dk hydrogel contact lenses.
Following is a discussion I had with Kathy Dumbleton,
MSc, MCOptom, FAAO, about patient adaptation to silicone hydrogel contact lenses.
Dr. Dumbleton is a staff member of the Center for Contact Lens Research, School
of Optometry, at the University of Waterloo. She has extensive clinical experience
with silicone hydrogel contact lenses.
Dr. Ghormley (RG): Some existing patients wearing
low-Dk soft lenses require an adaptation period when refit with silicone hydrogel
contact lenses. Why?
Dr. Dumbleton (KD): There are a number of reasons
why some patients require an initial adaptation period following refitting with
silicone hydrogel lenses. Any change in lens design or material may result in transitory
changes in sensation. The difference with silicone hydrogel materials is that some
have significantly greater modulus than that of conventional hydrogel materials.
This may create initial lens awareness that's short-term for most patients. Carefully
counsel new silicone hydrogel wearers about this possibility to assist patient understanding
of this brief period of adaptation.
RG: Is it true that as the cornea stabilizes from
oxygen deprivation, it may become more sensitive? Is this similar to what we observed
years ago when we refit PMMA patients into GP lenses?
KD: When we relieve hypoxia that results from extended
or daily wear of low-Dk/t hydrogel lenses, either by ceasing lens wear or by continuing
lens wear with a significant increase in oxygen supply, certain physical and physiological
changes may occur. The literature describes a rapid, but transient, increase in
microcsytic response. The increase in lens awareness reported by some patients is
more anecdotal. It does, however, seem similar to the initial increase in sensitivity
that occurs when refitting PMMA wearers into GP materials.
RG: What patient management tools are helpful when
refitting a patient into silicone hydrogels?
KD: The key management tools for such patients are
really no different from those we use every day. Careful and comprehensive patient
counseling are crucial for contact lens success. Letting patients know what to expect
is helpful it's ineffective to discuss only the long-term benefits of these
lens materials without first explaining the transition period that may prove necessary
for their ultimate success.
Physicians often tell patients when treating them for certain
medical conditions that they may feel worse before they feel better. Refitting patients
into silicone hydrogel contact lenses is similar, and patients seem to understand
I would like to thank Dr. Dumbleton for sharing her expertise
and clinical experience.
I believe silicone hydrogel lenses are the future of contact lenses.
But, the cornea and our patients need to adapt to this new technology. Contact lens
education and quality professional care will help all our patients adapt to silicone
Dr. Ghormley is in private
practice in St. Louis, MO. He is a past president of the American Academy of Optometry
and a Diplomate of its Cornea & Contact Lens Section. He is also a consultant
for CIBA Vision.
Contact Lens Spectrum, Issue: September 2005