The standard of care for all aspects of health care is constantly evolving. This especially holds true for myopia management, with many products and technologies arriving to the market in recent years. Most agree that comprehensive myopia management should include routinely measuring axial length. Consequently, the technology currently available to eyecare practitioners has made acquiring this information much easier than it was in years past.

Traditionally, axial length measurements were exclusively used by practitioners when calculating intraocular lens (IOL) power to achieve a specific refractive outcome. Due to increased visual demands and the advent of premium IOLs, the technology for taking the necessary preoperative measurements has drastically improved from the original applanation biometry to what is now known as optical coherence biometry (or optical biometry for short). For reference, optical biometry refers to a non-invasive automated method for measuring the anatomical characteristics of the eye, including axial length, keratometry, and anterior chamber depth.

Myopia progression is a function of axial elongation beyond what is expected for a patient’s age. Thus, routinely measuring axial length is a crucial factor when determining myopia progression.

Accurate Measurements

Subjective refraction should always be used in conjunction with axial length but can be highly variable and quite unreliable, especially for orthokeratology (ortho-k) patients. During ortho-k, a patient’s refractive error is intentionally altered to as close to plano as possible, rendering refractive error an essentially useless data point for determining myopia progression. Change in refractive error for these patients could potentially be due to a variety of reasons that may be indistinguishable from one another: inconsistent overnight wear, poor treatment, an ill-fitting lens, a warped lens, or actual myopia progression.

For an accurate refraction to be obtained, the patient must discontinue ortho-k for several weeks, which creates an inconvenience for both the patient and the practitioner. Thankfully, axial length is a quick and reliable adjunctive method for determining myopia progression that can alleviate this issue to some degree. The altered corneal curvature and thickness after ortho-k appears to have minimal effect on axial length (Cheung and Cho, 2013).

However, for the sake of the utmost accuracy, consider performing baseline measurements prior to treatment, again once the ideal treatment has been determined, and then every six months thereafter. It may also be prudent to take several measurements and record the average.

Today’s Technology

Currently, there are several optical biometers on the market that are designed with myopia management and the busy practitioner in mind. For many offices, time and space are two commodities limiting what practitioners can offer in their practices.

Many of the optical biometers available now include several technologies in addition to axial length, including pupillometry, keratometry, corneal topography, and contact lens-fitting tools. An all-inclusive option versus multiple units is extremely attractive when trying to incorporate new technology into an office. In addition, some of these biometers offer progression analyses providing an easy and efficient method for tracking progression. Lastly, incorporating optical biometry can elevate a practice to the highest level of myopia management by offering tools that can assist from the initial designing of lenses to the long-term management of every patient. CLS

References

1. Cheung SW, Cho P. Validity of Axial Length Measurements for Monitoring Myopic Progression in Orthokeratology. Invest Ophthalmol Vis Sci. 2013;54:1613-1615.