Highly aspherical lenslet spectacles and orthokeratology: addressing myopia progression in two ways in young patients

Two optical treatment modalities have accumulated the strongest evidence base for slowing pediatric myopia progression without the need for pharmacologic intervention, ie, spectacle lenses incorporating highly aspherical lenslets (HAL)¹ and orthokeratology (ortho-k) contact lenses.²

Both treatments are based on the same underlying theory, that is, that peripheral retinal defocus is a growth signal for axial elongation‚ but the treatments focus on different structures of the visual system, one through a manufactured spectacle lens surface (HAL) and the other through temporary corneal reshaping (ortho-k). This overview summarizes the optical and physiologic mechanisms of each, which may be helpful for clinicians evaluating or counseling on optical myopia management options.

Paul E. Levine, OD, underscored the importance of addressing myopia in his pediatric patients as early as possible. “The battle against pediatric myopia continues. What an opportune time it is to slow and, in some cases, stop progression of myopia! We have more tools at our disposal than ever before, and the industry has woken up to the dangers of myopia. We now have the ability to be proactive in our approach to managing myopia instead of the historical reactive mode,” he stated. Levine is in private practice in Southborough, MA.

HAL spectacle lenses

HAL lenses have a central optical zone for standard single-vision correction, while the periphery contains about 1,000 undetectable micro-lenslets in concentric rings, each of which is less than 1 mm in diameter.³ This characteristic distinguishes HAL from the design of Defocus Incorporated Multiple Segments (DIMS), which uses roughly 400 uniform +3.50-diopter plus-powered lenslets arranged in a honeycomb pattern around a 9-mm clear central zone.⁴

Optical Mechanism

According to Singh and de Garcia, the defining feature of HAL is that the surface curvature of each lenslet varies continuously and nonlinearly across its own aperture, and both the power and asphericity vary ring-to-ring moving outward from the optical center. This differs from the uniformity of the DIMS design, which produces one discrete focal plane of myopic defocus and instead generates the so-called volume of myopic defocus, defined as a continuous, three-dimensional spread of focal points anterior to the retina spanning a measurable range of depth (reported at ~0.7 mm), rather than A flat plane.³ The central clear zone preserves unimpaired foveal visual acuity for distance vision; the surrounding lenslet field continuously imposes simultaneous myopic defocus and some higher order-aberration loading on the peripheral retina during lens wear, independent of the gaze direction or accommodative state.³

Clinical evidence

In a 2-year randomized clinical trial,⁵ Bao and colleagues established the efficacy of the HAL design compared with single-vision spectacles in Chinese children, followed by their 3-year extension data⁶ that supported the design’s sustained effect. Those investigators reported the 2-year outcomes, ie, roughly 60% and 70%, respectively, in the relative reduction in axial elongation and comparable reduction in spherical equivalent progression versus single-vision controls, with dose-dependence on wear time.⁵

In a head-to-head data comparison of the HAL lenses with DIMS in Chinese children,⁶ in 2023, Guo et al. reported that the adjusted mean axial length increased by 0.17 and 0.28 mm for children wearing HAL lenses and DIMS lenses, respectively, a difference of 0.11 mm less axial length elongation than that in DIMS users.

A recently published randomized clinical trial of US children reported that spectacle lenses with HAL reduced myopia progression and axial elongation over 24 months. While longer term data are needed to evaluate whether the treatment efficacy can be sustained, HAL was considered a safe and effective myopia control intervention and these results underlie FDA authorization of the study device, according to the authors.⁸

Ortho-K

Ortho-k technology uses a rigid gas-permeable, reverse-geometry contact lens worn overnight during sleep and removed upon waking. The lens base curve is flatter than the central cornea, with a steeper reverse (alignment) curve in the mid-periphery; the design is fit empirically or topography-guided to each individual's corneal shape, requiring specialty training and instrumentation such as corneal topography and fluorescein fitting pattern evaluation that is unnecessary when prescribing standard spectacle or soft contact lens.⁹

How this technology works

During overnight wear, Nti and Berntsen explained that trapping of the tear film between the posterior lens surface and cornea exerts hydraulic and mechanical forces that redistribute the corneal epithelium; the central epithelial cells become thin and are displaced toward the mid-periphery, while the mid-peripheral epithelium thickens. This activity results in flattening of the central cornea. This reshaping is superficial, that is, limited to the epithelium and less so the anterior stromal, and elastic. The effect is temporary and when the lenses are not worn it reverses over days, which is why ortho-k requires nightly or near-nightly wear to maintain both the refractive and the myopia-control effect.¹⁰

Because the mid-periphery steepens relative to the flattened center, the periphery produces relative peripheral myopic and achieves the same directional shift in the peripheral defocus signal as the HAL lenses do. However, this occurs physically on the optical surface of the eye in ortho-k, rather than because of a spectacle lens in front of it.^11,12

Clinical evidence

The ROMIO trial¹³ is one of the foundational 2-year randomized trials that established the ability of ortho-k to control axial elongation (approximately 43% relative reduction versus single-vision spectacle controls in that cohort), with subsequent studies and reanalyses (eg, protective association with baseline axial elongation rate) extending the evidence base. The efficacy varies depending on the baseline myopia magnitude, age at initiation, and lens fitting parameters, and has been directly compared against HAL spectacle lenses in more recent 2-year trials.⁷

Safety considerations

Unlike the HAL spectacle lenses, ortho-k carries the inherent risks associated with overnight rigid contact lens wear, most notably microbial keratitis, which, while uncommon with appropriate hygiene, lens care, and follow-up‚ represents a categorically different risk profile than a spectacle-based intervention and is a standard part of informed consent discussions and should not be ignored.¹⁴

Bullimore and colleagues¹⁵ estimated that the overall incidence of microbial keratitis is 7.7 per 10,000 years of wear (95% confidence interval [CI] = 0.9 to 27.8). For children, the estimated incidence of MK is 13.9 per 10,000 patient-years (95% CI = 1.7 to 50.4). For adults, the estimated incidence of MK is 0 per 10,000 patient-years (95% CI = 0 to 31.7), they reported.

The investigators advised that while the Cis overlap The fact that the CIs for the rates estimated overlap, this “should not be interpreted as evidence of no difference. True differences fewer than 50 cases per 10,000 patient-years were beyond the study’s power of detection.”

Acanthamoeba and gram-negative bacilli, especially Pseudomonas aeruginosa, are the most common pathogens, according to Tseng et al.¹⁴

References

1. Huang Y, Li X, Wang Y, Drobe B, Chen H, Bao J. Effect of spectacle lenses with highly aspherical lenslets on changes in peripheral eye length and asymmetry. Ophthalmic Physiol Opt. 2025;45:1040–8. doi: 10.1111/opo.13500
2. American Academy of Ophthalmology. https://www.aao.org/eye-health/glasses-contacts/what-is-orthokeratology
3. Singh NK, de Gracia P. Next-generation spectacle lenses for myopia control: optical designs, mechanisms, and clinical efficacy. J Clin Med. 2025;14:7872. doi:10.3390/jcm14217872
4. Lam CSY, Tang WC, Tse DY, et al. Defocus Incorporated Multiple Segments (DIMS) spectacle lenses slow myopia progression: a 2-year randomised clinical trial. Br J Ophthalmol. 2020;104:363-8.
5. Bao J, Huang Y, Li X, et al. Spectacle lenses with aspherical lenslets for myopia control vs single-vision spectacle lenses: a randomized clinical trial. JAMA Ophthalmol. 2022;1;140:472-8.
6. Guo H, Li X, Zhang X, Wang H, Li J. Comparing the effects of highly aspherical lenslets versus defocus incorporated multiple segment spectacle lenses on myopia control. Sci Rep. 2023;13:3048. doi:10.1038/s41598-023-30157-2
7. Liu Q, Chen Y, Feng Y, Zhang S, Mao X, Xu J. Comparison of two-year myopia control efficacy between spectacle lenses with highly aspherical lenslets and orthokeratology lenses. Contact Lens Anterior Eye. 2025;102376. doi:10.1016/j.clae.2025.102376
8. Shen J, Hunt C, Young G, et al. Spectacle lenses with highly aspherical lenslets for myopia control. a randomized clinical trial. JAMA Ophthalmol. 2026; published online August 20. doi: 10.1001/jamaophthalmol.2026.3288
9. Swarbrick HA. Orthokeratology for myopia control: an optometrist's view. Ann Eye Sci. 2018;3:17. https://aes.amegroups.org/article/view/4150/html
10. Nti AN, Berntsen DA. Optical changes and visual performance with orthokeratology. Clin Exp Optom. 2020;103:44-54. doi:10.1111/cxo.12947
11. Kang P, Swarbrick H. Can manipulation of orthokeratology lens parameters modify peripheral refraction? Optom Vis Sci. 2013;90:1237-48. doi: 10.1097/OPX.0000000000000064
12. Queirós A, Pinheiro I, Fernandes P. Peripheral defocus in orthokeratology myopia correction: systematic review and meta-analysis. J Clin Med. 2025;14:662. doi:10.3390/jcm14030662
13. Cho P, Cheung SW. Retardation of Myopia in Orthokeratology (ROMIO) Study: a 2-year randomized clinical trial. Invest Ophthalmol Vis Sci. 2012;53:7077-85. doi:10.1167/iovs.12-10565
14. Tseng C-H, Fong C-F, Chen W-L, Hou Y-C, Wang I-J, Hu F-R. Overnight orthokeratology-associated microbial keratitis. Cornea. 2005;24:778-82. doi: 10.1097/01.ico.0000153101.81657.0b.
15. Bullimore MA, Sinnott LT, Jones-Jordan LA. The risk of microbial keratitis with overnight corneal reshaping lenses. Optom Vis Sci. 2013;90:937-44
https://www.researchgate.net/publication/253334766_The_Risk_of_Microbial_Keratitis_With_Overnight_Corneal_Reshaping_Lenses