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The progression of myopia has long been viewed as an inevitable future for children with early stages of myopia. Traditionally, it was managed by simply correcting the refractive error of the individual, providing them with the best corrected distance vision. As such, we didn’t influence the trajectory of myopia progression in children.
In the last 2 decades, however, researchers have developed tremendous advances in our understanding of clinical strategies to alter the trajectory of myopia progression. By randomizing children to either treatment or placebo groups, reduction in the rate of myopia progression has been demonstrated by a variety of means. Low dose atropine drops, orthokeratology and multifocal contact lenses have all demonstrated success with reducing the rate of myopia progression and in reducing the axial length of the eye.1-3 Recently, a lens with a multifocal lens design has been approved for the management of myopia progression, the first to receive FDA approval.4
Understanding how these lenses work, their optical profiles, and patient selection protocols is key to using these devices to hinder the progression of myopia early.
Why Multifocals Work for Myopia Management
Why have multifocal lenses received so much attention for managing myopia progression? Interestingly, the concept of undercorrecting myopia, once thought to reduce it, doesn’t influence its progression.5 Conversely, it may actually accelerate myopic progression.5 We now know peripheral retinal focus is a more important consideration for myopia progression.6 Animal models have demonstrated that ocular growth can occur by altering peripheral retinal defocus with hyperopic peripheral retinal defocus, stimulating axial length elongation, and myopia progression.7 Creating peripheral retinal myopic defocus with multifocal soft contact lenses has reduced myopia progression in children randomized to either a single vision soft lens or soft multifocal lens.8
Orthokeratology provides peripheral retinal defocus by flattening the central cornea, correcting the myopic refractive error. The peripheral cornea has a resultant reverse curve, which can create myopic peripheral defocus if the treatment zone encroaches onto the pupil.9 As such, it not only corrects refractive error, but also provides myopic peripheral retinal focusing, which is likely the reason orthokeratology has been shown to reduce myopia progression.10
Certain types of contact lens designs have similar optical properties to a cornea that has undergone orthokeratology. A multifocal contact lens with distance optics located centrally and near optics located peripherally, mimics the optics that are created on the cornea through the use of orthokeratology lenses. Researchers believe the central optics in the lenses correct the refractive error, while the peripheral optics provide myopic correction in the peripheral retina.10,11 This may remove the hyperopic peripheral retina focus, a likely risk factor for myopia progression.10,11
Lens Selection
Recent research has evaluated the differences between near and distance centered multifocal contact lenses to determine their focus on the central and peripheral retina out 40 degrees nasally and temporally from the fovea. Additionally, visual acuity was assessed to determine the effects on vision compared with single vision contact lenses.11
Healthy, non presbyopic adults were recruited to analyze the visual performance of the various lenses. Three distance centered designs and 1 near centered design were studied.
From a visual perspective, multifocal lenses with central distance optics provide visual acuity similar to that of single vision contact lenses under high contrast visual acuity testing. The near center design, not surprisingly, performed worse under high contrast visual acuity testing. On average, participants wearing the near-centered design were able to see 1.5 lines fewer than participants fitted with the single vision control lens. Notably, these lenses were tested monocularly for visual acuity, although they are designed to be used binocularly when correcting presbyopia.11
All multifocal designs performed worse than the single vision lens design when tested with low-contrast visual acuity. Additionally, the distance centered multifocal designs performed better with low- contrast visual acuity than with the near centered design.
Diagnostic technology was incorporated into this study to acquire autorefraction measurements along the line of sight and at multiple points nasally and temporally located to the line of sight out 40o in each direction. We would expect the distance centered multifocal lenses to have more myopic focusing in peripheral regions of the fovea, which was, in fact, confirmed. Two of the distance centered lens designs performed as anticipated by increasing their myopic defocus further from the point of fixation measured in the macula. The third distance centered lens exhibited the unique property of having myopic focus at lower points of eccentricity from the point of fixation while having hyperopic defocus in further eccentric regions.
All 3 of these distance centered multifocal designs have demonstrated a reduction in myopia progression.12-15 Even with the mixed myopic/hyperopic defocus with one of the distance centered lenses, the myopic defocus seems to be adequate to slow myopia progression in peripheral regions. Research in primates has demonstrated that any peripheral myopic defocus outweighs the presence of hyperopic defocus.16,17
The near centered multifocal lens design demonstrates peripheral hyperopic defocus. This may be the trigger for myopic progression, and the reason that near centered multifocal lenses are not actively utilized in myopia progression management.
Fine Tuning
Biophysical measurements taken on the various lens designs, along with measurable improvements in vision, support the current practice of utilizing distance centered multifocal lenses for myopia progression management. Interestingly, even with the distance centered multifocal design’s ability to provide high-contrast distance acuity similar to a standard spherical lens, low contrast vision is reduced. As discussed earlier, the lenses may perform better under low-contrast testing if measured binocularly.
Another factor to consider that may influence future lens designs is line of sight. Contact lens horizontal centration was measured using a reticle in the slit lamp ocular and ranged from 0.05 mm to 0.17 mm temporally.11 A patient’s line of sight is typically decentered nasally. Optics of multifocal contact lenses will oftentimes decenter temporally relative to the patient’s line of sight.18 There are a variety of new multifocal contact lens designs that incorporate line of sight to provide better optical alignment for patients with presbyopia. Research has shown improved visual outcomes when the multifocal optics are appropriately lined up with a patient’s line of sight.19
To the best of my knowledge, multifocal contact lens treatments that consider line of sight for myopia progression have never been studied. Future research may look at this as a variable to determine whether taking line of sight into consideration may optimize patient outcomes.
Managing myopia progression is becoming increasingly sophisticated as our knowledge base and understanding of the risk factors become more clear. Understanding optical profiles is critical in our ability to cater appropriate treatments for our patients.
Mile Brujic, OD, practices in Bowling Green, OH.
References
1. Pei-Chang W, Meng-Ni C, Choi J, et al. Update in myopia and treatment strategy of atropine use in myopia control. Eye (Lond). 2019; 33(1):3-13. doi:10.1038/s41433-018-0139-7
2. Cho P, Tan Q. Myopia and orthokeratology for myopia control. Clin Exp Optom. 2019; 102(4):364-377. doi:10.1111/cxo.12839
3. Zhu Q, Liu Y, Tighe S, et al. Retardation of myopia progression by multifocal soft contact lenses. Int J Med Sci. 2019;16(2):198-202. doi:10.7150/ijms.30118
4. Chamberlain P, Peixoto-de-Matos SC, Logan NS, et al. A 3-year randomized clinical trial of MiSight lenses for myopia control. Optom Vis Sci. 2019;96(8):556-567. doi:10.1097/OPX.0000000000001410
5. Chung K, Mohidin N, O’Leary DJ. Undercorrection of myopia enhances rather than inhibits myopia progression. Vis Res. 2002;42(22):2555-2559. doi:10.1016/s0042-6989(02)00258-4
6. Wallman J, Gottlieb MD, Rajaram V, Fugate-Wentzek LA. Local retinal regions control localeye growth and myopia. Science. 1987;237:73–7. doi:10.1126/science.3603011
7. Smith EL III, Hung LF, Huang J, Armugam B. Effects of local myopic defocus on refractive development in monkeys. Optom Vis Sci. 2013;90:1176–86 doi:10.1097/OPX.0000000000000038
8. Aller TA, Liu M, Wildsoet CF. Myopia control with bifocal contact lenses: A randomized clinical trial. Optom Vis Sci. 2016;93:344–52. doi:10.1097/OPX.0000000000000808
9. Guo B, Cheung SW, Kojima R, Cho P. One‐year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) study: a prospective randomised clinical trial. Ophthalmic Physiol Opt. 2021;41(4):702–714. doi:10.1111/opo.12834
10. He M, Du Y, Liu Q, et al. Effects of orthokeratology on the progression of low to moderate myopia in Chinese children. BMC Ophthalmol. Published online July 27, 2016. doi:10.1186/s12886-016-0302-5
11. Hair LA, Steffensen EM, Berntsen DA. The effects of center-near and center-distance multifocal contact lenses on peripheral defocus and visual acuity. Optom Vis Sci. 2021;98(8):983-994. doi:10.1097/OPX.0000000000001753
12. Walline JJ, Greiner KL, McVey ME, Jones-Jordan LA. Multifocal contact lens myopia control. Optom Vis Sci. 2013;90(11):1207-14. doi:10.1097/OPX.0000000000000036
13.Walline JJ, Walker MK, Mutti DO, et al. Effect of high add power, medium add power, or single-vision contact lenses on myopia progression in children: The BLINK randomized clinical trial. JAMA. 2020;324(6):571-580. doi:10.1001/jama.2020.10834
14. Cooper J, O’Connor B, Watanabe R, et al. Case series analysis of myopic progression control with a unique extended depth of focus multifocal contact lens. Eye Cont Lens. 2018;44(5):e16-e24. doi:10.1097/ICL.0000000000000440
15. Aller T, Achenbach P, Cooper J. Myopia management with NaturalVue (etafilcon A) multifocal 1 day contact lenses: continuing evidence from clinical practice. Cont Lens Ant Eye. 2019;42(6-S1):E24.
16. Arumugam B, Hung LF, To CH, et al. The effects of simultaneous dual focus lenses on refractive development in infant monkeys. Invest Ophthalmol Vis Sci. 2014;55:7423–32. doi:10.1167/iovs.14-14250
17. Benavente-Perez A, Nour A, Troilo D. The Effect of simultaneous negative and positive defocus on eye growth and development of refractive state in marmosets. Invest Ophthalmol Vis Sci. 2012;53:6479–87. doi:10.1167/iovs.12-9822
18. Lampa M, Kelvin S, Caroline P, Kinoshita B, Andre M, Kojima R. Assessing soft multifocal contact lens centration with the aid of corneal topography. Poster presented at: Global Specialty Lens Symposium; 2011.
19. Schulze M, Luensmann D, Ng A, Panjwani F, Srinivasan S, Jones L. The relationship between the positioning of multifocal contact lens optics and satisfaction with vision. Poster presented at: American Academy of Optometry 2015; New Orleans. Abstract 155256.
