How to use axial length data in practice

Regular follow up of young patients with myopia enables us to keep track of progression. Here is a case showing a 13-year-old girl with rapid myopia progression, despite wearing a myopia control contact lens design for 2 years. Data on refractive error and axial length progression are provided below, redrawn from an original presentation by the post author.

Axial length measurements can act as an objective indicator to check if our myopia control goals are achieved. There are numerous ways to use axial length data, including comparing growth to that expected of an emmetropic eye, where reducing growth rate towards the emmetropic rate can indicate myopia control success. In this case, JW’s patient has axial elongation of more than 0.5mm over two years, which is much in excess of emmetropic eye growth in children of the same age (0.02mm a year for a child aged 11-14).¹

When looking at the data over the past year, though, a more positive picture emerges. Axial length appears to have only increased by around 0.1 to 0.2mm, indicating a slower rate of eye growth and one closer towards the expected rate for an emmetrope. ¹

These comparisons can be made simpler when utilizing built-for-purpose myopia management instruments, which measure axial length and provide software to help in analyzing data. The OCULUS Myopia Master axial length database is built on evidence-based data including 14,127 Asian eyes and 7,204 European eyes. This provides robust comparison data to support the eye care practitioner, parent and patient to visualize myopia progression rate and outcomes of treatment. For example, comparisons to percentile growth charts enables tracking of growth over time, to see if it is increasing (accelerated growth) or decreasing (slowed growth) compared to previous measures. 

JW also notes that this patient's axial length is close to 26mm which is a benchmark to very high risk for future ocular disease and visual impairment.² Excessive axial length growth increases the risk of eye diseases associated with myopia such as retinal detachment and myopic macular degeneration, and hence increases the risk of visual impairment.³ From this measurement, we can inform the parents of the importance in continuing treatment and proactively managing myopia to slow eye growth as much as possible.

The patient’s data includes two years of myopia control treatment outcomes. Looking at each year separately, it appears that there was rapid progression in the first year and slower progression in the second year. In comparison to age-matched progression and prior progression, the evidence suggests that the current intervention is providing reasonable myopia control outcomes over this past year, as axial length growth appears to be slowed. 

The first year of data shows axial eye growth to be almost 0.5mm. There was also a fast increase in refraction that year, from around -2.75D to over -4.00D in each eye. As the patient was reportedly wearing myopia control soft contact lenses, it is important to rule out the possible factors that can impact efficacy such as non-compliance or insufficient wearing time of optical treatments. Advising on good visual environment habits will also help to support the child’s best chance of success with myopia management. 

The second year of data shows around 0.1 to 0.2mm of axial length growth and around 0.25D of refractive progression in the pooled eye data. This shows an improved result in comparison to prior progression, and most accurately, an eye growth rate closer to that expected of a similarly aged emmetropic child. 

If this data was applied to axial length percentile growth charts, it would provide a way to visualize the presumed reduction in the rate of eye growth observed between the first and second years of treatment. This would provide a strong framework for explaining what success looks like for myopia control outcomes.

1. Axial length measurement is a key measure to track myopia progression as well as to educate the parent(s) and patient on the importance of myopia management.
2. There are various ways to use axial length data: as standalone information to look at changes over time, to compare to emmetropic eye growth rates, and to consider the 26mm ‘line’ for elevated ocular health risk. Utilizing data within analysis software (such as with growth charts) can provide a simple and accurate way to communicate outcomes and changes over time.