STUDIES CONFIRM that orthokeratology (ortho-k) can slow myopia progression by approximately 50%, which is the goal most practitioners set for any myopia control strategy (Sun et al, 2015). Managing both the nuances of ortho-k and parents’ expectations for myopia control can be challenging. The case below demonstrates how having an objective assessment of myopia progression, such as axial length, can be a lifesaver when clinical data seems to be conflicting.

A 12-year-old Hispanic female who had been wearing ortho-k lenses successfully for four years presented for her annual eye examination. Over the years, she was compliant with wearing her lenses nightly and reported to the office for biannual visits. A cycloplegic refraction was performed annually along with axial length measurements biannually; both were consistently stable.

Minor adjustments were made to the lenses over the years as needed. Visual acuity remained stable at 20/20 OD and OS. However, at her most recent visit, visual acuity dropped to 20/30 OD and OS. Topography demonstrated excellent overnight treatment with an appropriate bull’s-eye pattern and centration in both eyes (Figure 1).

Periodic reduced vision and slight variation in vision from visit to visit can be a common occurrence for ortho-k patients. Quality of vision can be affected by several variables: the amount of wear time, consistency of overnight wear, decentration during wear, and lens warpage (most often due to the age of the lens). If none of these variables are the culprit for the reduced vision, the clinician is faced with the possibility that the child’s myopia could perhaps be worsening. For parents truly invested in myopia control, this is the worst-case scenario.

Performing a refraction on ortho-k patients often provides unreliable and inconsistent information that does not reflect the child’s true refractive error, even if there is myopic progression. This is secondary to the induced corneal irregularity and can also be coupled with unreliable responses from younger patients. In these types of scenarios, an objective measurement, such as axial length measured with an optical biometer, can easily differentiate between true myopic progression and simple outlier data. When assessing myopia control success in terms of axial length, the general goal is to achieve < 0.2mm elongation in children under 10 years old and < 0.1mm elongation in children over 10 years old per year (Mutti et al, 2007; Tideman et al, 2018).

In this case, the patient’s axial length was essentially stable when compared to the prior visit, and she ultimately admitted that she had forgotten to wear her lenses the night before our visit (Figure 2 available online). After returning to her normal wear schedule, the patient’s visual acuity improved to 20/20 OD and OS.

Axial length is an incredible asset to ortho-k when it’s being used for myopia control. The only other option to determine progression is to periodically wash the patient out of ortho-k and perform a cycloplegic refraction. Even though this provides helpful clinical data, most families are hesitant to subject their children to this, especially when the treatment is working as intended. CLS

References

1. Sun Y, Xu F, Zhang T, et al. Orthokeratology to control myopia progression: a meta-analysis. PLoS One. 2015 Apr 9;10:e0124535.
2. Mutti DO, Hayes JR, Mitchell GL, et al. Refractive Error, Axial Length, and Relative Peripheral Refractive Error before and after the Onset of Myopia. Invest Ophthalmol Vis Sci. 2007 Jun;48:2510-2519.
3. Tideman JWL, Polling JR, Vingerling JR, et al. Axial length growth and the risk of developing myopia in European children. Acta Ophthalmol. 2018 May;96:301-309.