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Spectacle Lens Technologies for Myopia Control

by | Oct 1, 2023 | Manuscripts | 0 comments

Aksha Shetty, M.Optom

Ph.D. Scholar (BITS-Goa), Clinical Operation Head, Kids Eye Project, Mumbai, India

 

The most frequent refractive error worldwide is myopia. Progressive myopia if untreated can result in issues with vision, ocular alignment, and physiological blindness. The search for a treatment that will prevent the progression of myopia in recent years has produced several alternatives.

Peripheral Hyperopic Defocus and high accommodation lag are researched factors that increase the eye’s axial length, thereby resulting in myopia progression. Myopia-correcting single vision (SV) ophthalmic lenses have been demonstrated to exacerbate hyperopic defocus at the retina’s periphery. (1,2) Different kinds of peripheral defocus lenses are available in the market.

DIMS (Defocus Incorporated Multiple Segments)

It comprises a central clear zone of 9mm for clearing refractive error and an annular zone of multiple segments in a honeycomb design of 33mm having a relative power of +3.50D. Each segment of +3.5D is made of 1.033mm diameter. In a two-year study, Children who use DIMS have an efficacy of refractive myopia of about 50% and an axial length efficacy of 60%, with a change of 0.44D lower refraction and 0.34mm less axial elongation. (3) Commercially available by Hoya as MiYO SMART.

H.A.L.T. (Highly Aspherical Lenslet Target)

These lenses have spherical front surfaces with 11  contiguous aspheric concentric rings of 1.1mm diameter each. The updated Atchison eye model was modified to calculate peripheral refraction for computations of the lenslets. This aspherical lens continuously shifts light rays nonlinearly, producing a three-dimensional amount of light in front of the retina. Opposed to other lenses which have 2 distinct images.  One year’s study showed the efficacy of refractive myopia of 70% and axial myopia of 60% with an absolute effect of 0.54D refraction and 0.23mm less axial elongation. (4) Commercially available by Essilor as Stellest.

C.A.R.E. (Cylindrical Annular Refractive Elements)

These lenses have alternative clear and defocus zones in the ring-like pattern towards the periphery and a clear center zone of 7 to 9mm. These defocus zones of mean addition power +3.8D to +4.6. They purposely form an extended focus range like cylinder power rather than a single focus point. The fill factor is a ratio between the functional zone to the zones of regular power and describes the relationship between these zones. This determines the amount of defocus that the lens will create, which in turn affects the wearability. (5) Commercially available by Zeiss as MyoCare has a fill factor of 0.5.

 

References

  1. Erdinest N, London N, Lavy I, Berkow D, Landau D, Morad Y, Levinger N. Peripheral Defocus and Myopia Management: A Mini-Review. Korean J Ophthalmol. 2023 Feb;37(1):70-81. doi: 10.3341/kjo.2022.0125.
  2. Charman WN. Near vision, lags of accommodation, and myopia. Ophthalmic Physiol Opt. 1999;19:126–133.
  3. Lam CSY, Tang WC, Tse DY, et alDefocus Incorporated Multiple Segments (DIMS) spectacle lenses slow myopia progression: a 2-year randomized clinical trial, British Journal of Ophthalmology 2020;104:363-368.
  4. Bao J, Yang A, Huang Y, Li X, Pan Y, Ding C, Lim EW, Zheng J, Spiegel DP, Drobe B, Lu F, Chen H. One-year myopia control efficacy of spectacle lenses with aspherical lenslets. Br J Ophthalmol. 2022 Aug;106(8):1171-1176.
  5. ZEISS MyoCare- Technical Insight Paper. (n.d.). Zeiss.de/Vision.

Declaration of interest:

The blog is written solely for educational purposes, and it does not have any financial support or conflict of interest.

 

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