Impact of age on measurement variability for axial length in myopic children

ABSTRACT

Clinical relevance

Axial length is a primary outcome in the management of progressive myopia. However, young children may have difficulty fixating during these measurements compared to older children, which can result in higher measurement variability. This may affect perceived axial length progression, leading to inappropriate management.

Background

This study assessed the impact of patient age on measurement variability for axial length measurements taken with the IOLMaster 700 and IOLMaster 500 in myopic children.

Methods

A retrospective review of records was undertaken at a university optometry clinic. Five axial length measurements captured at the same visit were collected with the IOLMaster 700 and IOLMaster 500 for myopic patients ≤16 years. The within-subject standard deviation and R² were calculated for each instrument to examine the effects of age on instrument variability.

Results

Data was collected for 51 patients (30 female and 21 male), and the mean age was 10.98 ± 2.77 years. Mean axial length measured with the IOLMaster 700 was longer compared to the IOLMaster 500 (difference −0.02 ± 0.02 mm; p < 0.001). There was no effect of age on within-person variability for the measurement of axial lengths with either instrument, with R² values of 0.021 (p = 0.305) and 0.13 (p = 0.420) for the IOLMaster 700 and IOLMaster 500, respectively. The within-subject variability of axial measurements with the IOLMaster 700 was significantly lower than that with the IOLMaster 500 (p < 0.001).

Conclusion

Measurement variability of axial length measurements with the IOLMaster 700 and IOLMaster 500 was not dependent on age. However, axial length measurements captured with the IOLMaster 700 were significantly longer and less variable than those with the IOLMaster 500. Eye health care practitioners should be aware of the differences between the two instruments and refrain from using them interchangeably, especially for myopia control where small changes in axial length can affect patient management.

KEYWORDS:

• Age
• axial length
• IOLMaster
• myopia
• variability

Acknowledgements

The authors thank the UNSW Optometry Clinic for its assistance and Dr Nancy Briggs for her contribution towards the statistical analysis used in this study. There are no financial disclosures.

Disclosure statement

No potential conflict of interest was reported by the author(s).