Article

RESEARCH REVIEW

MULTIFOCAL LENSES AND MYOPIA PROGRESSION

Myopia prevalence is increasing dramatically worldwide (Kempen et al, 2004; Vitale et al, 2009; Lin et al, 2004; and others. Full list available at www.clspectrum.com ). The implications of myopia are significant. Ocular health consequences include increased risk for myopic macular degeneration, retinal detachment, glaucoma, and cataract development (Saw et al, 2005). Additionally, myopia has significant lifetime economic consequences and can negatively impact perceived quality of life (Kandel et al, 2017). It is estimated that if we can reduce the rate of myopia progression by 33%, we could reduce the development of myopia more than 5.00D by 73%; reducing progression by 50% would reduce the rate of greater than 5.00D of myopia by 90% (Brennan, 2012).

Evidence-based clinical approaches are critical for eyecare practitioners to have an impact on this dramatic threat to our patients. Well-designed and performed studies conducted over the past decade have suggested three clinical approaches that can successfully impact myopia progression: corneal reshaping (orthokeratology [orthok]), the application of atropine eye drops, and the use of multifocal contact lenses. Each modality has advantages and disadvantages. The best approach for each patient is based on unique elements and determined on a case-by-case basis.

This article will review the current state of research pertaining to the use of multifocal lenses for myopia progression management.

Theoretical Mechanism of Action

It has been proposed that myopia progression via axial length elongation is stimulated by peripheral retinal hyperopic defocus; conversely, inhibition of myopia progression and axial length elongation is achieved when a peripheral myopic defocus is created on the retina (Smith et al, 2013). As such, the use of distance-center and near-peripheral-focus daytime-wear contact lenses has been suggested for myopia progression control (Walline et al, 2013). The optical array created by such lens designs would mimic the resultant optical array created by corneal reshaping (ortho-k).

Clinical Study Outcomes

A number of clinical trials evaluating the ability of multifocal contact lenses to control myopia progression and axial length elongation have been published. Walline and co-workers (2013) conducted a study that sought to determine the progression of myopia and axial elongation of children fitted with commercially available distance-center soft multifocal contact lenses for two years. Children 8 to 11 years of age who had –1.00D to –6.00D of spherical component and less than 1.00D of astigmatism were fit with soft multifocal contact lenses with a +2.00D add. They were age- and gender-matched to participants from a previous study who were fitted with single-vision contact lenses. A-scan ultrasound and cycloplegic autorefraction were performed at baseline, after one year, and after two years.

The adjusted mean ± standard error spherical equivalent progression of myopia at two years was –1.03D ± 0.06D for the single-vision contact lens wearers and –0.51D ± 0.06D for the soft multifocal contact lens wearers (p < 0.0001). The adjusted mean axial elongation was 0.41mm ± 0.03mm and 0.29mm ± 0.03mm for the single-vision and soft multifocal lens wearers, respectively (p < 0.0016). Soft multifocal contact lens wear resulted in a 50% reduction in the progression of myopia and a 29% reduction in axial elongation during the two-year treatment period compared to a historical control group. The researchers stated that results from this and other investigations indicate a need for a long-term randomized clinical trial to investigate the potential for soft multifocal lens myopia control.

A group of investigators in Asia published a study looking at the impact on myopia progression of a custom soft multifocal lens design (Lam et al, 2014). The lenses incorporated concentric rings, which provided an addition of +2.50D, alternating with the normal distance correction. A two-year, double-blind, randomized controlled trial was carried out in 221 children aged 8 to 13 years who had myopia between –1.00D and –5.00D and astigmatism of ≤ 1.00D. Subjects were randomly assigned to the multifocal (n = 111) or the single-vision (SV; n = 110) contact lens group. Refractive error (cycloplegic autorefraction) and axial length were measured at six-month intervals. Differences between groups were analyzed using unpaired t test.

Myopia progressed 25% more slowly for children in the multifocal lens group compared with those in the control group (0.30D/year; 95% confidence interval [CI]: –0.71D to –0.47D versus 0.4D/year; 95% CI: –0.93D to –0.65D, p = 0.031). Likewise, there was less axial elongation for children in the multifocal lens versus the SV group (0.13mm/year; 95% CI: 0.20mm to 0.31mm versus 0.18mm/year; 95% CI: 0.30mm to 0.43mm, p = 0.009). Treatment effect correlated positively with multifocal lens wearing time (r = 0.342; p = 0.005). Indeed, myopia in children who wore the multifocal lenses for five or more hours/day progressed 46% (mean difference = –0.382D, p = 0.001; 95% CI: –0.59D to –0.17D) less compared to the SV group. The researchers concluded that the daily wearing of the study’s custom soft multifocal lens design significantly slowed myopia progression and axial elongation in Hong Kong schoolchildren. The findings demonstrated that simultaneous clear vision with constant myopic defocus can retard myopia progression.

Two ongoing studies looking at myopia progression control and multifocal soft daytime wear contact lenses are taking place and should provide additional data as to their efficacy. One study is evaluating a distance-center soft daily disposable contact lens (clinicaltrials.gov, NCT01917110). This lens incorporates a center-distance dual-focus alternating zone design. The study is a prospective, multi-center, double-masked, randomized multi-year study that enrolled 144 myopic children aged 8 to 12 years from Singapore, Canada, England, and Portugal. According to the sponsor, the three-year data is anticipated in late 2017.

Interim two-year data was presented at the American Academy of Optometry annual meeting in 2016. Mean cycloplegic spherical equivalent was significantly lower in the test group by 0.40D (95% CI: 0.30D to 0.51D) at 12 months and by 0.54D (95% CI: 0.40D to 0.68D) at 24 months, respectively, when compared to the control group. Mean axial length growth was less in the test group by 0.15mm (95% CI: 0.19mm to 0.11mm) at 12 months and by 0.24mm (95% CI: 0.30mm to 0.19mm) at 24 months. A highly significant correlation between spherical equivalent and axial length change was found for the control and test groups.

The other ongoing study is the Bifocal Lenses In Nearsighted Kids (BLINK) study. Information pertaining to study methods and baseline data was recently published (Walline et al, 2017). The BLINK study is a National Eye Institute-sponsored, double-masked, randomized clinical trial to investigate the effects of soft multifocal contact lenses on myopia progression. Subjects were 7 to 11 years old, had –0.75D to –5.00D of spherical component and less than 1.00D of astigmatism, and had 20/25 or better logMAR distance visual acuity with manifest refraction in each eye and with +2.50D add soft bifocal lenses on both eyes. Children were randomly assigned to wear commercially available single-vision lenses, distance-center soft multifocal lenses with a +1.50D add power, or distance-center soft multifocals with a +2.50D add power. Researchers examined 443 subjects at the baseline visits, and 294 (66.4%) subjects were enrolled. The mean (± standard deviation) age was 10.3 ± 1.2 years.

The authors stated that the BLINK study subjects are similar to patients who would routinely be eligible for myopia control in practice, so the results will provide clinical information about soft multifocal lens myopia control as well as information about the mechanism of the treatment effect, if one occurs.

Concluding Remarks

The importance of myopia management cannot be over emphasized. Ever increasing evidence in the literature supports the efficacy of a number of treatment modalities that can control myopia progression. Yet, very few eyecare practices have incorporated these into their clinical armamentarium. At minimum, it is incumbent upon practitioners to educate patients about the implications of progressive and high myopia and to make them aware of the evidence-based treatment options that could potentially control myopia progression. CLS

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