Article Date: 9/1/2005

contact lens materials
Patient Adaptation to Silicone Hydrogel Materials

BY 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.

Adaptation Times

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.

Corneal Sensitivity

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.

Managing Patients

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 this explanation.

Final Thoughts

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 hydrogel lenses.

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