Contact Lens Design & Materials
The Future of Presbyopic Contact Lens Correction
BY NEIL PENCE, OD, FAAO
At the recent Borish Symposium held at Indiana University in honor of Dr. Irvin Borish, the title of a requested presentation was “The Future of Presbyopic Contact Lens Correction.” This column will summarize the general thoughts that I presented.
On the Horizon
Despite long hours staring intently and repeated attempts to clean its surface, I have to admit my crystal ball was a bit cloudy. We have already seen contact lenses that employ segmented, aspheric, annular, and diffractive designs as well as combinations of those. It is difficult to see dramatically different approaches on the horizon, aside from possibly pinhole or multiple pinhole lenses (which have likely been tried, but not on any large commercial basis).
One exception could be to irradiate a contact lens and change the index of refraction of that material. If one-half of the lens was masked from such radiation, the result would be a contact lens with two different focuses created by the two indices of refraction. The ability to do this exists, but a number of questions need to be answered. Is optical clarity affected? Can it be perfectly uniform in its application? Will the areas at the edge of the masking be affected negatively? What is the optimal pattern for the masking?
Three Possible Advancements
So if future designs are basically what we have today, how will improvements occur? We might identify three possible areas.
1. In the case of annular bifocals with two spherical zones, the assumed optimal case would be 50 percent of the incoming light focused for distance, 50 percent for near. That is probably not the case, with a 40-percent to 45-percent range for each more likely, with some lost or incorrectly focused light also occurring. The closer that lens designs and manufacturing come to achieving 50/50, the better the results.
2. There is perhaps more to learn about maximizing the increased depth of focus created by small amounts of spherical aberration combined with possibly slight shifts in the distance and/or near powers. Add a slight bit of modified monovision effect, and patient success might improve.
3. Improvements will occur to achieve a focus for distance, near, and possibly intermediate that is more consistent. This means more consistency across all refractive error corrections and through the full range of add powers. In other words, we will come closer to having what we think we are getting now, but likely are not.
Are dramatic changes in presbyopic contact lens correction on the horizon? Probably not, but we are likely to see incremental improvements coming.
We should also not forget a fourth item that could potentially improve success as much as or more than the three mentioned. Increased recommendation and utilization of contact lenses for presbyopes, and better communication and patient management skills, may still be the largest potential factors for increased success. In other words, it still falls on us to be as knowledgeable as possible about available options for the benefit of an ever graying population. CLS
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 email@example.com.