Article Date: 6/1/2012

Evidence for a Better Choice

Evidence for a Better Choice

A clinical roundup of multifocal contact lens research supports multifocals over monovision.

By John Schachet, OD

Despite the many excellent multifocal contact lens options available to practitioners today, many still fit presbyopes with monovision. In this roundup of studies on multifocal lenses and monovision, you'll see the clinical repercussions of this choice and the real-world difference it makes for patients.

MONOVISION CAUSES ANISOMETROPIA

Researchers at the University of Houston College of Optometry found that induced ametropia in primate subjects created by blurring one eye “may cause a difference to develop between each eye's correction (anisometropia) when none existed before wearing the correction.”1

The researchers evaluated vision before monovision contact lens correction and after at least 12 months in the lenses, and compared the results from 62 subjects to control groups wearing spectacles and binocular contact lenses. Monovision wearers had significantly more anisometropia than those in the spectacles (p = 0.043) or the group wearing like-powered contact lenses (p = 0.025). Some 29% of monovision subjects had anisometropia changes at or above 0.50 D, with some as high as 1.25 D.

PATIENTS PREFER MULTIFOCAL LENSES TO MONOVISION

Researchers at the Ohio State University College of Optometry in Columbus compared visual performance and patient satisfaction among patients with no previous presbyopia correction wearing multifocal lenses and monovision.2

Thirty-eight presbyopic patients were randomized to multifocals (Bausch + Lomb SofLens Multifocal) or monovision (SofLens 59). After 1 month, researchers measured near stereoacuity and high- and low-contrast visual acuity at distance and near. The patient satisfaction test was the National Eye Institute Refractive Error Quality of Life Instrument (NEI-RQL).

Next, researchers fit each patient with the modality that they had not worn the preceding month and had them return a month later for the same testing. Finally, they asked patients to report which lens they preferred.

Testing showed that patients with both modalites had at least 20/20 distance and near binocular vision in high-contrast conditions. Under low contrast conditions, patients with both modalities lost less than a line of best-spectacle-corrected vision at near, but multifocal wearers lost five to six letters, and monovision wearers lost two letters. In terms of lens preference, 76% of patients preferred multifocal contact lenses, while 24% preferred monovision.

In another single-masked study comparing multifocal lenses to monovision, with both made of omafilcon A, researchers at the Clinical Eye Research Facility at the University of Alabama at Birmingham, School of Optometry, randomized 46 patients to the two modalities.3 Subjects were a mixture of previous, current and new contact lens wearers. They wore one lens modality for 1 month and then switched to the other modality for the second month.

When asked which modality they preferred, 14 of the 46 patients chose monovision, while 32 chose multifocals. Just two of the six subjects who had previously been successful in monovision preferred that modality, and two of six previous multifocal wearers preferred monovision. Numbers for all of the subjective assessments followed these preferences. Interestingly, results of visual function tests did not correlate to patient preferences.

PRACTITIONERS ACHIEVE SUCCESS WITH MULTIFOCAL FITTINGS

A pre-market evaluation of Air Optix Aqua Multifocal contact lenses (Alcon) showed that practitioners were pleased with the lenses and comfortable fitting them.4 Alcon mailed complimentary trial sets to 350 doctors along with the fitting guidelines and asked the practitioners to report their experiences in fitting 10 patients. The result was a report on 2,455 patients.

Here's the percentage of practitioners who agreed to the following statements:

• 95.5% agreed the lenses are easy to fit
• 81.5% agreed they had an easier time fitting these lenses compared to other multifocal soft contact lenses
• 65.6% agreed they had an easier time fitting these lenses compared to monovision
• 79.7% agreed that the success rate for these lenses is higher than that for other multifocal soft contacts

Practitioners' overall success rate was 76%. While 70.6% said they fit most patients on the first try, fitting averaged 2.4 patient visits and fewer than four lenses.

MULTIFOCALS BEST FOR EMERGING PRESBYOPES

Researchers at the Centre for Contact Lens Research, School of Optometry, University of Waterloo in Waterloo, Ontario, Canada compared the performance of four different soft lens correction options on existing soft contact wearers who were exhibiting early signs of presbyopia.5 This prospective, double-masked, randomized dispensing trial put all patients in all four modalities for 1 week apiece. The alternatives, all made from Lotrafilcon B material, were: Air Optix Aqua Multifocal lenses, monovision, habitual correction and optimized distance visual correction.

Vision testing included both LogMAR and “real-world” vision tests. Most vision tests showed no difference. However, in low-contrast near-vision LogMAR with low lighting, acuity with monovision was better than multifocal or habitual correction. “Realworld” subjective ratings showed that participants found Air Optix Aqua Multifocal lenses performed better than mono-vision, especially for driving. Subjects preferred Air Optix Aqua Multifocal lenses for daytime and nighttime driving, and they had less glare or haloes and saw road signs better. They also liked Air Optix Aqua Multifocal lenses better than monovision for watching TV, using a computer and refocusing from distance to near. In 15 out of the 15 real-world vision tests, patients preferred Air Optix Aqua Multifocal contact lenses over monovision.

LENS MATERIALS MATTER

Alcon performed a study comparing multifocal contact lenses made of lotrafilcon B (Air Optix Aqua Multifocal Lenses) versus balafilcon A (PureVision Multi-Focal, Bausch + Lomb).6 Researchers evaluated visual acuity, as well as subjective factors such as comfort, visual satisfaction, intent to purchase the lenses and lens preference. Half of the patients were randomized to each lens material, and all were advised to use the same lens care regimen.

Subjects wore the lenses for up to 8 days. They gave Air Optix Aqua Multifocal lenses higher ratings for comfort at every stage of wear, from initial dispensing to end-of-day to their follow-up visit. Asked if they would purchase their lenses if their doctor offered the option, subjects answered quite differently for the two lens materials. Among Air Optix Aqua Multifocal wearers, 58% definitely or probably would buy the lenses, 30% might, and 2% definitely would not buy them. In contrast, 21% of PureVision Multifocal wearers definitely or probably would buy the lenses, 36% might, and 34% definitely would not purchase them.

MULTIFOCALS SURPASS MONOVISION

These studies reinforce the prevailing wisdom: Better vision, patient experience and long-term results have led multifocal contact lenses to replace monovision as the standard of care for patients with presbyopia. Patients prefer multifocals to monovision by dramatic margins, and emerging presbyopes say they see better with multifocals. From the practitioner's perspective, we can add the elimination of anisometropia into multifocals' plus column, and we enjoy the ease of fitting new multifocals. To give patients the best care, multifocals are the first line of correction for presbyopes.

REFERENCES

1. Wick B, Westin E. Change in refractive anisometropia in presbyopic adults wearing monovision contact lens correction. Optom Vis Sci. 1999;76(1):33-39.
2. Richdale K, Mitchell GL, Zadnik K. Comparison of multifocal and monovision soft contact lens corrections in patients with low-astigmatic presbyopia. Optom Vis Sci. 2006;83(5):266-273.
3. Benjamin WJ. Comparing multifocals and monovision. Contact Lens Spectrum. February 2007.
4. Dzurinko V, Quinn T, Woods J. Multifocal studies support a first-line approach. Contact Lens Spectrum. February 2012.
5. Woods J, Woods CA, Fonn D. Early symptomatic presbyopes: What correction modality works best? Eye Contact Lens 2009;35(5):221-226.
6. Long B, Giles T. Silicone hydrogel options for presbyopes. Optician. June 2, 2009. 32-37.



Contact Lens Spectrum, Volume: , Issue: June 2012, page(s): 6 - 7