prescribing for astigmatism
Better Designs Improve Success With Soft Toric Multifocals
BY JOHN MARK JACKSON, OD, MS, FAAO
I am a strong believer in hydrogel torics. I feel the same about hydrogel multifocals. Both of these options, once considered specialty lenses and difficult to use, have become somewhat mainstream in contact lens practice. The technology for both designs has improved dramatically in the last few years.
Until recently, however, I wasn't a believer in toric multifocals. I felt the technology previously wasn't ready to make this modality successful. Soft-lens-wearing astigmatic presbyopes were mostly left to choose monovision with soft torics or a move to multifocal GP lenses — both reasonable, but not ideal, choices for previous soft lens wearers.
When I've tried multifocal torics in the past, I was always frustrated with the results. If things weren't going well, it seemed difficult to determine the reason for poor acuity with these lenses. Was it because of instability of the lens rotation? Was the multifocal design itself not working for the patient? Were they both at fault? Fortunately, with newer lens designs the toric lens stability and aspheric optics are better than ever and worth trying.
I was also never fond of multifocal torics because of the limited replacement schedules. Most designs have an annual replacement schedule due to cost. In modern contact lens practice, there's little place for lenses replaced on a yearly basis when other options are available.
Some multifocal torics are now available in quarterly and monthly replacement. As examples, the C•Vue 55 Toric Multifocal (Unilens) is available as a quarterly replacement lens, and the Proclear Multifocal Toric (Cooper-Vision) is designed for monthly replacement. This is a welcome change for this modality.
I recently examined a perfect candidate for toric multifocals. She wore toric lenses successfully for distance but was tired of wearing reading glasses. She had tried monovision but couldn't adapt; she was very aware of every little bit of lens rotation, as often happens with monovision torics. She was very motivated to try multifocals. Her spectacle prescription was OD –2.00 –1.25 x020, OS –1.50 –1.75 x160 with a +1.75D add. K readings were 42.50/43.00 @ 090 in each eye.
We tried the Proclear Multifocal Toric. This design has the same D and N lenses as the spherical design. We fit her right (dominant) eye with an 8.8mm base curve, 14.4mm diameter, –2.00 –1.25 x020/+1.50D lens and her left eye with an 8.8mm base curve, 14.4mm diameter, –1.50 –1.75 x160/+1.50N lens. Acuities were 20/25 OD, 20/30 OS, 20/25 OU at distance and 20/60 OD, 20/50 OS, 20/50 OU at near. Each lens was rotating 15 degrees temporal (but stable) and we felt that was likely the main reason for the decreased acuity. Using LARS, we ordered trials of –2.00 –1.25 x035/+1.50D and –1.50 –1.75 x145/+1.50N.
With the new trial lenses, her acuity improved to 20/20 OD, 20/25 OS, 20/20+2 OU at distance and 20/40 OD, 20/30 OS, 20/30 OU at near. She felt her vision improved slightly at near with loose +0.25D lenses over each eye. She wore the trial lenses for a week and reported good comfort and vision at her follow-up visit. She was very happy to not need reading glasses for most tasks.
Combining the benefits of soft torics and multifocals can be challenging, but with newer designs and replacement schedules, patients can truly benefit from the advances in lens technology. CLS
Dr. Jackson is an assistant professor at Southern College of Optometry where he works in the Advanced Contact Lens Service, teaches courses in contact lenses and performs clinical research.