In this special issue of Contact Lens Spectrum discussing specialty lenses, it’s pertinent to address the next frontier of contact lens myopia management: How can we optimize efficacy to achieve better results? The answer may involve how each type of lens design influences the accommodative response at near.

Soft Contact Lenses Reduce Accommodative Response

Center-distance multifocal soft contact lens (MFCL) wear in children and young adult myopes appears to reduce the accommodative response (increases accommodative lag) (Gong et al, 2017; Kang et al, 2016). This effect may vary with lens design—continuous aspheric designs appear to influence accommodation similarly independent of their labelled “add” power, while one concentric dual-focus design had minimal influence on accommodation compared to single-vision CLs (Gifford et al, 2019). The potential mechanism for this reduced accommodative response is that in young eyes, which have larger pupils, a significant percentage of the pupil area is covered by the add zone in combination with the central distance zone. Smaller central optic zone diameters (OZDs) could be associated with a reduced accommodative response, as young eyes use the add at near rather than accommodating. A reduced accommodative response could result in the distance portion of the MFCL generating hyperopic defocus, which is presumably deleterious in achieving myopia control (Faria-Ribeiro et al, 2018).

OK Increases Response

Orthokeratology (OK) appears to improve the accommodative response, reducing accommodative lag (Tarrant et al, 2009; Gifford, Gifford, et al, 2020) and increasing amplitude (Zhu et al, 2014) in kids compared to single-vision correction, although it may have minimal effects on other accommodative functions in young adults (Kang et al, 2018; Felipe-Marquez et al, 2015). Compared to MFCLs, OK generally has a larger central OZD; the treatment zone is around 5mm on average in low-to-moderate myopes (Tahhan et al, 2003). OK creates a center-distance, peripheral-add optical profile similar to MFCLs (Gifford et al, 2013; Fedtke et al, 2017).

Other research in OK includes reducing OZD, based on the assumption that bringing the zone of midperipheral steepening closer to the central pupil will increase peripheral refractive shifts and myopia control efficacy. While reducing the OZD can reduce the treatment zone diameter (Marcotte-Collard et al, 2018), this change does not translate through the eye to a significant change in peripheral refraction, and it has not yet been proven to alter myopia control efficacy (Gifford, Tran, et al, 2020).

Why It Matters

In OK wear, one study has correlated a below-average amplitude of accommodation in myopic children at baseline with a larger increase in amps when wearing OK and a better myopia control effect (Zhu et al, 2014). With MFCLs, a novel lens design employing positive spherical aberration (effectively a center-distance design) reduced accommodative response, which was correlated with a reduced myopia control effect (Cheng et al, 2019); this relationship wasn’t found in the single-vision-distance CL control group, indicating a complex interaction between MFCL optics and accommodation. There’s a lot more that we need to learn about comparative optics between MFCLs and OK to maximize myopia control efficacy.

What This Means in Practice

This research points to the value of assessing accommodation in young myopes. A normal accommodative response seems to be increasingly valuable for myopia control efficacy. We may in the future select a particular type of lens for myopes based on their accommodation—and/or seek to improve accommodative responses through specific corrections or training—to optimize myopia control efficacy. CLS

For references, please visit www.clspectrum.com/references and click on document #299.