Contact Lens Design & Materials
GP Lenses in the United States: What Do We Need to Rethink?
BY NEIL PENCE, OD, FAAO
For a number of years now, Contact Lens Spectrum’s January issue has featured national and international data on contact lens prescribing trends. These data show that GP lens use in the United States has been roughly flat (Nichols, 2010 to 2014; Morgan et al, 2010 to 2014). GPs have averaged a 5.5% share of the U.S. market while averaging 10% worldwide. The worldwide numbers show a slight increasing trend, but this is not the case in the United States (Morgan et al, 2014).
This column discusses several factors that U.S. practitioners might consider when formulating GP utilization habits.
Not Just for Irregular Corneas
GP lenses are often the only option for best vision in irregular cornea patients. Modern scleral lenses are a tremendous advancement and have been very helpful in these cases.
Many other patients, however, could benefit from the attributes of well-fit GP lenses, whether scleral or corneal. All types of refractive errors, in particular astigmatic errors, can be well corrected with GPs. There are many successful GP multifocal designs as well. Clear, stable vision from GP lenses is appreciated by many, but even more could benefit.
There are many new designs intended for “normal” corneas that can be employed for wider benefit. In particular, GP lenses can help relieve symptoms for dry eye patients; for extremely dry eyes, scleral GPs can be life altering. Practitioners must get away from the habit of thinking of GP lenses only for their irregular cornea patients.
Not Your Father’s GPs
In relatively recent years, dramatic technological advancements have occurred in GP lenses. The latest generation of CNC lathes have tremendous capabilities to create nearly limitless options in terms of surfaces, curvatures, edge profiles, thicknesses, etc. Lenses can be produced, and more importantly reproduced, to extreme accuracy. Sophisticated software allows topography to guide lathes in producing lenses that more closely mimic and align with individual corneal eccentricities.
GP materials have advanced as well, providing higher oxygen transmissibility, better stability, and often better wetting compared to what was possible before. High-Dk materials even allow extended wear with GP contact lenses, which, with an admittedly limited sample size, has been remarkably problem-free.
Finally, larger-diameter corneal lenses (10.5mm and above) can be a significant improvement over the smaller designs that several decades of practitioners learned to fit. Most labs have at least one larger-diameter GP design, featuring well-controlled alignments and edge designs that significantly lessen lid interaction, resulting in much improved comfort. Such designs offer the benefits of easy application and removal, lower cost compared to scleral lenses, and they fall well within the comfort level of most fitters.
You Don’t Have to Do It Alone
All labs have consultants available who are very helpful and underutilized. GP lenses can benefit many more patients than those currently wearing them. Labs are eager to partner with practitioners to help make that happen. In fact, that partnership helped me in writing this column. CLS
I would like to thank George Mera (TruForm Optics), Mike Johnson (Art Optical), Richard Dorer (Blanchard), and Tim Koch (Contamac) for sharing their thoughts regarding GP lenses of today.
For references, please visit www.clspectrum.com/references and click on document #227.
Dr. Pence serves as associate dean, Clinical and Patient Services, Indiana University School of Optometry in Bloomington, Ind. He is a consultant or advisor to B+L, Alcon, and Vistakon and has received research funding from AMO. You can reach him at firstname.lastname@example.org.