prescribing for presbyopia
Try Soft Toric
BY CRAIG W. NORMAN, FCLSA
A remaining challenge in presbyopic contact lens correction is the astigmatic patient. Do we consider only GP multifocal/bifocal alternatives? We've discussed the advantages of GPs for presbyopes in some detail in this column, and they're obviously an excellent choice for many patients.
The UltraVue 2000T Multifocal Toric has scribe marks at three o'clock and nine o'clock.
But what about soft lens wearers? Should we relegate them to wearing distance soft lenses with reading glasses or is monovision their best option? For low astigmats, should we ignore the astigmatism and expect the patients to live with the decreased visual results? Or is now the time for us to begin embracing soft toric multifocals for this patient group?
Spotlight on a Soft Option
Soft toric multifocals have been available for some time, but have received little industry publicity in print or from the podium. Yet the Contact Lenses & Solution Summary Web site at
www.clspectrum.com/class lists products in this category from eight manufacturers, offering virtually any cylinder and add power.
In the March issue, Kenneth Young, OD, discussed the Essential Soft Toric Multifocal design (Blanchard). Another design that we've also found useful for these presbyopic patients is the UltraVue 2000T Multifocal Toric (CooperVision).
The design features the same Balanced Progressive Technology that CooperVision uses in its other soft multifocals, consisting of a D lens (dominant eye, distance in the center with intermediate progressing to near in the periphery) and an N lens (non-dominant eye, near in the center with intermediate progressing to distance in the periphery) with a combination of spherical and aspherical optics. The back surface features the lathed toric optic, and dual thin zones stabilize the lens, with axis markers at three o'clock and nine o'clock (Figure 1). This custom-made lens is available in three base curves, cylinder powers from 0.75D to 6.00D at any axis and add powers up to +4.00D in 0.25D steps.
You can empirically fit this design by simply ordering the lenses based on spectacle prescription, keratometry measurements, dominant eye and add power. We typically increase the add power in the D lens by 0.25D, while ordering the same N-lens add power as the patient's refraction.
During progress checks, we evaluate the patients in normal lighting conditions to gauge their vision without the influence of pupil dynamics. We first test vision at both distance and near binocularly, then by individual eye, if necessary. We incorporate any necessary power adjustments to the toric component first, then address the distance and near power. As with most soft multifocal lenses, don't attempt to make major power adjustments, but instead work in 0.25D steps.
Sometimes patients who have predominant near demands prefer two N lenses, while two D lenses may work best for astigmatic early presbyopes to maximize their overall visual function.
Try Something New
Consider using soft lenses for your astigmatic presbyopic patients. You may find yourself pleasantly surprised that astigmatic presbyopes have another option for their contact lens correction.
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.
Contact Lens Spectrum, Issue: May 2005