REFRACTIVE ASTIGMATISM IS present in most progressive myopes. While the degree of astigmatism is often mild and does not complicate treatment options, there are also some instances in which higher astigmatism makes it necessary to tailor the approach to optimize treatment.

Treating a child with low-dose atropine can be an effective solution (Yam et al, 2022); however, because patients treated with atropine still need refractive correction, I generally prefer to implement an optical intervention. While bifocals have shown some effect for slowing myopia progression (Cheng et al, 2014) and there are now specialized spectacle options for myopia management (Lam et al, 2020) (albeit not available in the U.S.), many patients prefer to wear contact lenses.

TORIC ORTHOKERATOLOGY

Orthokeratology (ortho-k) is a well-established intervention for slowing myopia progression in children (Guan et al, 2020). While lower amounts of corneal and refractive toricity can often be managed with traditional ortho-k designs, the introduction of toric ortho-k has opened the door for many moderately astigmatic progressive myopes to achieve clear daytime vision without corrective lenses.

Whereas spherical ortho-k lenses employ symmetric reverse and alignment curves, toric designs incorporate toricity into these peripheral lens parameters. When fit properly, toric periphery design ortho-k results in improved centration, lower corneal astigmatism, and reduced staining on toric corneas, compared with spherical designs (Zhang and Chen, 2018).

Toricity is not incorporated into the base curve of toric ortho-k lens designs. Since most refractive astigmatism is corneal, eliminating corneal toricity often minimizes or eliminates refractive astigmatism. However, since a spherical treatment zone will result in a spherical central cornea, it is important to rule out significant lenticular/internal astigmatism by comparing the manifest refraction with topography or keratometry readings.

SOFT MULTIFOCAL LENSES

Soft multifocal lenses are a safe, effective method for correcting and slowing the progression of myopia in children (Chalmers et al, 2021; Yu et al, 2022).

The first method to address astigmatism with soft multifocal lenses is to simply prescribe the spherical equivalent. I have had the best success with an extended depth of focus design, and it is often surprising how much cylinder can be masked. There is no firm threshold astigmatism limit for this method and the results tend to be patient-specific, so make sure to consider patient satisfaction and your own fit assessment.

When a child’s refractive astigmatism must be corrected, practitioners may choose to prescribe a toric multifocal soft lens. Since higher-add multifocal lenses have been shown to be more effective at slowing myopia progression, this should be a consideration when selecting lens power (Yu et al, 2022). Finally, consider prescribing a spherical multifocal lens in addition to cylinder correction glasses worn over the contact lenses—depending on the individual case, the glasses may be able to be worn on a part-time basis. CLS

References

1. Yam JC, Zhang XJ, Zhang Y, et al. Three-year clinical trial of low-concentration atropine for myopia progression (LAMP) study: Continued versus washout: Phase 3 report. Ophthalmology. 2022 Mar;129:308-321.
2. Cheng D, Woo GC, Drobe B, Schmid KL. Effect of bifocal and prismatic bifocal spectacles on myopia progression in children: Three-year results of a randomized clinical trial. JAMA Ophthalmol. 2014 Mar;132:258-264.
3. Lam CSY, Tang WC, Tse DY-Y, et al. Defocus incorporated multiple segments (DIMS) spectacle lenses slow myopia progression: A 2-year randomised clinical trial. Br J Ophthalmol. 2020 Mar;104:363-368.
4. Guan M, Zhao, Geng Y, et al. Changes in axial length after orthokeratology lens treatment for myopia: a meta-analysis. Int Ophthalmol. 2020 Jan;40:255-265.
5. Zhang Y, Chen YG. Comparison of myopia control between toric and spherical periphery design orthokeratology in myopic children with moderate-to-high corneal astigmatism. Int J Ophthalmol. 2018 Apr 18;11:650-655.
6. Chalmers RL, McNally JJ, Chamberlain P, Keay L. Adverse event rates in the retrospective cohort study of safety of paediatric soft contact lens wear: the ReCSS study. Ophthalmic Physiol Opt. 2021 Jan;41:84-92.
7. Yu Z, Zhong A, Zhao X, Li D, Duan J. Efficacy and safety of different add power soft contact lenses on myopia progression in children: A systematic review and meta-analysis. Ophthalmic Research. 2022;65:398-416.