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Are you measuring the cornea in myopia management?

 Posted on September 26th 2021 by Connie Gan

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In this article:

Measuring the cornea in myopes is crucial to understanding their clinical picture and even their profile of myopia risk.

Do you measure keratometry or corneal topography routinely in your practice? Measuring the cornea in myopes is useful when it comes to contact lens fitting, but can also fill in the puzzle pieces of the clinical picture. PC shared this interesting case about child with flat corneas. Note that in the post below, 'AXL' refers to axial length measurement, and 'K readings' refer to corneal curvature measurements.

PC Be particularly wary of myopic children with flat corneas. I had a case referred to me this week where at a glance it seems to be relatively mild myopia - a 13 yo boy at R -2.50 L -1.50. Low risk? Not necessarily. I suspected he might have long axial lengths when the K readings came up in pre-testing: 8.50mm (39.75D) R&L. Measuring his AXL confirmed it: R 26.57 L 26.00mm. At 13, he still has potential for further AXL elongation for several years. While not every practice has biometry, we all have keratometers in our rooms. I suggest it’s a good idea to look at the K readings for every myopic child (whether we are fitting CLs or not) because it can often give some indication of axial length risks. Patients with very flat Ks are also more challenging to manage for myopia control - more limitations to mould the corneas with Ortho K and potentially tight fitting lenses in a MF SCL. So I would say there is a greater urgency to start myopia control treatment for kids with flat corneas, even if their Rx seems mild.

Flat corneas and axial length

During the early emmetropization process, the cornea flattens as axial length increases.1 Then, during myopia progression in school-aged children, the corneal curvature tends to be stable while axial length increases.2 Therefore, when a patient has a flat cornea with mild or moderate myopia, it may be quite likely that the flat corneas mask the excessive growth of axial length. As the risk for ocular diseases in progressive myopia is largely linked to longer axial length,3 patients with flat corneas and low-to-moderate myopia are likely to be at a higher risk than one may think.

KG Important point PC. I’ve similarly seen -2.00s with 26mm eyes and -4.00s with 24mm eyes. 😳PC Yeah it’s quite alarming to see these cases. Perhaps one day high myopia will be defined by AXL and not by dioptres ie. >-5D.YS We measure AL for all our Myopes and yes it springs up lot of surprises! Low powers are not equal to low risks. I liked your idea of defining Myopia by AL and not by DsPC ...K’s are something we can all measure and I think it’s of value for assessing myopes for myopia management if other biometric data are not available.AV Also watch out for possible Marfans syndrome. Flat Ks, and axial elongation are common I believe.

Whilst not every eye care practitioner has access to axial length measurements, it is far more likely that they would have access to K readings. Hence, paying attention to patients with flat K readings can alert us to the greater need and urgency for myopia management. One commenter also pointed out that flat K readings can mask longer axial length in Marfan Syndrome, where these patients may not always present with high myopia as expected.4

Flat corneas and orthokeratology

AP For orthok Do flat Ks matter as much as "corneal tissue volume" as amount of tissue to mold more important than curvature? Granted these can correlate however

As the mechanics of orthokeratology (OK) lenses involve flattening the central cornea, one commenter asked if OK would be ruled out due to flat corneal curvature. One case report of two children with high myopia and the flat meridian of corneal curvature being around 8.3mm (40.5D) presented successful outcomes.5 These sorts of cases, though, are likely to be easier for the more experienced OK practitioner, as steeper corneal curvature and other corneal parameters such as eccentricity are important to predict treatment capacity.6

Take home messages:

  1. Be on alert when examining a myope with flat corneal curvature. These patients are likely to be a higher risk of myopia-related ocular health issues than expected from looking at their refraction alone.
  2. If you cannot measure axial length yourself, consider working with colleague eye care professionals with this instrumentation to obtain axial length data. This helps to quantify ocular health risk and can support strategizing myopia management.

Further reading

Meet the Authors:

About Connie Gan

Connie is a clinical optometrist from Kedah, Malaysia, who provides comprehensive vision care for children and runs the myopia management service in her clinical practice.

Read Connie's work in many of the case studies published on MyopiaProfile.com. Connie also manages our Myopia Profile and My Kids Vision Instagram and My Kids Vision Facebook platforms.

About Kimberley Ngu

Kimberley is a clinical optometrist from Perth, Australia, with experience in patient education programs, having practiced in both Australia and Singapore.

Read Kimberley's work in many of the case studies published on MyopiaProfile.com. Kimberley also manages our Myopia Profile and My Kids Vision Instagram and My Kids Vision Facebook platforms.

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