Current Research on Multifocal Contact Lenses
BY S. BARRY EIDEN, OD, FAAO
The January 2014 Contact Lens Spectrum article “Contact Lenses 2013” reported that 72% of surveyed practitioners preferred fitting presbyopes with multifocal contact lenses, compared to 20% preferring monovision and only 8% preferring spectacles worn over distance-correcting contact lenses. This preference for multifocal contact lenses has increased annually since 2008, when it was only 59% (Nichols, 2014).
With their popularity increasing, what is current research telling us about multifocal lenses? And, how should that influence contact lens prescribers?
Numerous studies have demonstrated that patients prefer multifocal lenses over monovision when exposed to both modalities. For example, a crossover study of the performance of a center-near soft multifocal found that 76% of subjects preferred the multifocal lens over monovision (Richdale et al, 2006). Another crossover study evaluated the performance of a balanced progressive technology multifocal soft lens versus monovision and found that overall, almost 70% of subjects preferred the multifocal lens; also, 76% of subjects new to presbyopic contact lens correction preferred the multifocal (Benjamin, 2007).
In a study performed on successful monovision wearers who were fit into a multifocal soft lens design, 68% of subjects preferred the multifocal over their prior monovision correction six months after being refit. In addition, all measures of visual function other than near vision in low light were rated higher in the multifocal design (Situ et al, 2003).
Multifocal Lens Performance
Although some studies have suggested that visual acuity (VA) at both distance and near may be somewhat better with monovision and with single vision contact lenses worn with near spectacles (Fernandes et al, 2013; Gupta et al, 2009; Madrid-Costa et al, 2012; Ferrer-Blasco and Madrid-Costa, 2011), the differences were not clinically significant. Furthermore, binocularity measures were significantly better with multifocal contact lenses versus monovision and were equivalent between multifocal contact lenses and distance contact lenses combined with near spectacles. Other measures of visual performance, such as near range of clear vision, were superior in multifocal lenses when compared to monovision (Gupta et al, 2009). Also keep in mind that multifocals often outperform monovision in areas of “real world” visual performance.
Predicting Multifocal Success
Being able to identify optimal candidates for specific designs is valuable to clinicians. A recent study evaluated the effects of wearers’ pupil size and spherical aberration on visual performance with a center-near, aspheric multifocal design (Plainis et al, 2013). Both near VA and depth-of-focus improved with the tested lens, with the effects being more pronounced for smaller pupils. Additionally, a linear correlation was found between VA at near and the wearer’s ocular spherical aberration, with higher positive spherical aberration resulting in worse near VAs. By contrast, no correlation was found between distance VA and spherical aberration.
Adaptation to Multifocals
Adaptation to multifocal correction is important for success. A recent study looked at visual adaptation comparisons between subjects fit in a balanced progressive technology multifocal lens design and single vision monovision contact lenses (Fernandes et al, 2013). The results of this crossover study showed no visual adaptation binocularly with either the multifocal or monovision lenses after 15 days. However, both low- and high-contrast monocular distance VA improved significantly over the 15-day period in the nondominant eye with the multifocal lens, and monocular near acuity improved in the dominant eye with the multifocal lens. No such change was found with monovision contact lens wear. This suggests that patients adapted to the multifocal over time. Additionally, stereoacuity was found to be significantly better with the multifocal than with monovision (p<0.01). The study authors concluded that multifocal contact lens correction provided satisfactory levels of VA comparable with monovision without compromising stereoacuity.
Technology for Evaluating Multifocal Contact Lenses
A clear understanding of multifocal lens optics helps establish appropriate expectations for on-eye performance. A recent study utilized the Nimo TR1504 contact lens power mapper and wavefront analyzer (Lambda-X S.A.) to evaluate the power distribution of a center-near, front-aspheric multifocal contact lens design. The near refractive add power was +0.30D, +1.30D, and +1.44D for the low, median, and high add powers, respectively. This shows that the add power differential in this design is much greater between the low and median add versus between the median and high add powers. Additionally, the nominal distance power was achieved at 1.5mm from the lens center for the low add design and 1.8mm from the lens center for both the median and high add designs. Finally, the lens power profiles tended to change toward more positive power values with smaller aperture sizes. The researchers concluded that the relation between patient pupil diameter and the lens power profile has a crucial impact on the final distance correction and near addition that these lenses provide (Montes-Mico et al, 2013).
Multifocal Contact Lenses for Non-Presbyopic Use
Multifocal contact lens designs that induce peripheral myopic defocus are thought to have the ability to inhibit myopia progression and axial elongation. Using multifocals for this purpose would be considered off-label. A study utilizing a center-distance multifocal contact lens with a +2.00D add versus a single vision distance-correcting contact lens evaluated the rate of myopia progression and axial elongation in 40 children ages 8 to 11 who had myopic refractive error at study entry ranging from –1.00D to –6.00D and astigmatic errors of less than 1.00D. Subjects were age and gender matched between the test (multifocal) and control (single vision) groups. At the completion of the two-year study, the adjusted spherical equivalent progression of myopia was –1.03D ± 0.06D for the single vision lens wearers and –0.51D ± 0.06D for the soft multifocal wearers (p<0.0001). The adjusted mean axial elongation was 0.41 ± 0.03 and 0.29 ± 0.03 for the single vision and soft multifocal wearers, respectively (p<0.0016). Soft multifocal lens wear resulted in a 50% reduction in the progression of myopia and a 29% reduction in axial elongation during the treatment period (Walline et al, 2013).
Another study looked at myopia progression and axial elongation over a two-year period in 221 children ages 8 to 13 who had entry levels of myopia between –1.00D and –5.00D and astigmatism of 1.00D or less. Subjects were randomly assigned to wear either a defocus incorporated soft contact (DISC) lens multiple concentric ring design with +2.50D add that alternates with the distance correction or a single vision distance correction contact lens. Myopia progressed 25% more slowly for children in the DISC group compared with those in the control group (p=0.031). Likewise, there was less axial elongation for children in the DISC group versus the single vision group (p=0.009). Treatment effect correlated positively with DISC lens wearing time (r=0.342; p=0.005). The researchers found that myopia in children who wore the DISC lenses for five or more hours/day progressed 46% less compared to those in the single vision group (Lam et al, 2014).
Evidence-based outcomes have expanded the use of multifocal lenses in clinical practice and will continue to significantly do so. Research findings will allow clinicians to better understand how and when to fit multifocals, how to best select patients, and how to establish realistic expectations in terms of their performance. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #221.
Contact Lens Spectrum, Volume: 29 , Issue: April 2014, page(s): 14, 15