Which is best? Myopia Management for an astigmatic myope

The benefit of optical treatments for myopia are that they both correct refractive error and control progression. Here we have a case involving an astigmatic myope presented by AA on the Myopia Profile Facebook group.

Most commenters suggested fitting orthokeratology lenses. There are two key reasons to consider orthokeratology:

1. Full correction of astigmatism is possible, if the refractive and corneal astigmatism are similar
2. Orthokeratology (OK) is the only optical intervention for which there is evidence of myopia control in higher levels of astigmatism. Toric OK for myopes with astigmatism up to 3.50DC appears to be just as effective for myopia control as spherical OK for myopes with minimal astigmatism.^1-3 The Menicon Bloom Night Toric lens was the first for which this efficacy in controlling myopia with moderate to high astigmatism was demonstrated.¹

A simple rule-of-thumb for OK fitting is that the refractive astigmatism should not exceed the corneal astigmatism by more than 0.75D. Since OK only corrects astigmatism on the cornea, any additional refractive astigmatism will be likely to be residual after treatment. This is an important rule for beginner and intermediate OK fitting eye care practitioners; experienced OK fitters using specific designs may be able to manage corneal-to-refractive astigmatism mismatch to still achieve a good visual outcome for the patient.

If OK is not a suitable choice for the patient or their family, soft contact lens options could be considered. This may be required if the patient's refractive and corneal astigmatism are not in close alignment.

The CooperVision MiSight 1 day contact lens, as mentioned in the comment, appears to show similar myopia control efficacy to OK,⁴ but only children with up to 0.75D of astigmatism were included in the clinical trial.⁵

For this patient, fitting MiSight 1 day would mean that the full astigmatism amount would need to be corrected with spectacles, worn over the contact lenses. As mentioned by KG, the child and parent would need to understand the imperative to wear the astigmatism-correcting spectacles PLUS the soft contact lenses. To not wear the spectacles whilst wearing the glasses could both impede reading and learning performance⁶ as well as lead to more myopia progression due to undercorrection.⁷

As this patient is 8 years of age and hence in the time of fastest progression (between 7 and 10 years of age),⁸ it is worthwhile considering the combination of atropine with an optical intervention. Orthokeratology again holds a special distinction here, as the only intervention for which increased efficacy when combined with low-concentration atropine has been shown.⁹

One meta-analysis of primarily 0.01% atropine combined with OK showed a mean 0.25mm axial elongation in a year, compared to 0.35mm in OK alone, giving a mean difference of 0.09mm additional efficacy provided by the combination.⁹ The longest clinical study of 0.01% atropine combined with OK, though, showed a significant effect only for 1-3D myopes and not for 3-6D myopes.¹⁰ In atropine monotherapy, stronger concentrations of 0.025% to 0.05% appear to be needed to achieve effective myopia control.11 This concentration-dependent efficacy has not been investigated or demonstrated when atropine is used in combination with OK.

Considering this patient has spherical component of myopia of R -5.50D and L -4.50D, the combination may not be effective. Monotherapy with OK alone could be considered first, and combination treatment could be discussed at the outset for parental informed choice or considered based on future outcomes.

Orthokeratology has the largest volume of evidence for myopia control - as arguably the first optical intervention to show a significant impact for slowing myopia progression, back in 2005,¹² there are simply more studies on OK which have been published since compared to other treatments. The evidence for soft contact lens options, so far, indicates that the MiSight is likely to have similar efficacy to OK while other multifocal options may have slighly lower efficacy.⁴

In addition to efficacy, though, it's important to consider what is going to best suit the patient. This case highlights the example of astigmatism, for which the best monotherapy could likely be achieved with OK. There are numerous other considerations in comparing the practicalities and wearer experience of both options, which are important to discuss with the patient and their parent(s). The table below provides a brief summary.

1. Orthokeratology has a large volume of evidence for myopia control and the only evidence for myopia control with astigmatism up to 3.50D.
2. Consider what best suits the patient and their family as well as selecting the best option for myopia control
3. Combining atropine (typically 0.01%) with orthokeratology has evidence for an additive myopia control effect, but this might be most effective in lower myopes under 3D.

• Is orthokeratology useful for myopia control in low myopia?

• Clinical case: Fitting orthokeratology successfully for a patient with astigmatism

• Clinical case: Getting parents onboard with orthokeratology

If you'd like to get started fitting orthokeratology yourself, check out our Myopia Profile Academy online course Orthokeratology Fundamentals, which is structured to step you through your first handful of fits with safety and success.