prescribing for presbyopia
Topographer Applications for Presbyopic Patient Analysis
BY CRAIG W. NORMAN, FCLSA
At the recent Global Specialty Lens Symposium (GSLS) in Las Vegas, I had the pleasure of moderating an international panel discussion on presbyopia. On this panel were Catherine Peyre, MD, from France; Ron Beerten, BOptom, from the Netherlands; and Edward Bennett, OD, MSEd, from St. Louis, Mo.
One of the more fascinating topics discussed was how important a corneal topographer could be in evaluating prospective presbyopic lens wearers. For sure, topography is helpful for analyzing corneal surface curvature, width of astigmatic area, and subtle irregularities; the panel also agreed it's a wonderful tool for initial lens design and post-fit corneal analysis. But following are some other uses worth considering.
Pupil Size Evaluation
I discussed pupil analysis in my September 2008 column, “The Importance of Pupil Size in Presbyopic Fitting Success,” along with the pupil's importance when fitting either soft or GP presbyopic lens designs.
Although numerous studies over the last 20 years have documented that pupil size becomes smaller in a linear fashion as we age, there can be significant individual variability; thus, I believe that this evaluation remains the most critical factor in presbyopic contact lens visual success and should be evaluated closely in all prospective contact lens wearers.
Why use the topographer for pupil size evaluation? Primarily for consistency as the results are reproducible. Different office members can perform topography, yet pupil measurements will remain the same. Comparison from one patient to another is easy and can be at a level as precise as 0.1mm (Figure 1). Furthermore, for a premium lens fit it seems archaic to use a pupil diameter stick or a card with circles on it to approximate pupil size.
Figure 1. Topography-based pupil size measurement.
Most contact lens practitioners would agree that dry eye or contact lens-related dry eye are major challenges when fitting aging presbyopes. Many traditional tests are available with varying ease of use and success. The major advantage of topography is that it allows you to observe the subtle dryness that is not easily detected. For instance, we've long known that instilling artificial tears can smooth out the ocular surface to provide better topographical maps; conversely, when you see slight mire irregularity that momentarily changes when a patient blinks, be aware that this patient is apt to have less-than-adequate tear film to support some contact lens types.
It's well established that upper and lower lid position is important especially for GP multifocal and bifocal lenses. Once again, there can be great variability in how this is measured. Topography-based measurements provide consistency in head position during testing and with some instruments can even help determine the appropriate segment height.
The Experts Agree
As the GSLS panel suggested, consider using topography for all presbyopic patients to improve their clinical outcomes. CLS
Craig Norman is director of the Contact Lens Section at the South Bend Clinic in South Bend, Indiana. He is a fellow of the Contact Lens Society of America and is an advisor to the GP Lens Institute. He is also a consultant to B+L.