Study: Ortho-K Lenses with Smaller Optical Zone Diameter May Provide Better Myopia Control

Some level of overcorrection is a target when using ortho-K lenses to compensate for diurnal corneal regression of the effect induced by the lens, and this may be a source of bias that emerged when evaluating the SER changes in the included studies. Click image to enlarge. Options to manage nearsightedness in children have been evolving constantly as new research elucidates and refines what strategies, concentrations and designs may work best. Conventional orthokeratology (ortho-K) lenses have an optical zone diameter (OZD) of  ≥6.0mm; these have been used effectively to treat myopia by decelerating axial length growth via peripheral defocus.More recently, a smaller OZD has been thought to potentially provide better performance. As such, researchers of a recent study compared the efficacy of small (≤5.5mm) and large (>6.0mm) OZDs in ortho-K designs, taken from seven articles for a systematic review. This included six clinical trials and one pseudo-experimental pre-post study. Their paper was published in Eye & Contact Lens.It was found across all articles that there was significantly slower axial length increase in those who were wearing ortho-K lenses with small OZDs, which was confirmed through meta-analysis. Four articles also found that small OZDs resulted in increased instances of higher-order aberrations (HOAs).Delving deeper into the results of the studies analyzed, the authors mention that one clinical trial displayed in two studies that significantly less axial length elongation occurred in kids who wore ortho-K lenses with a 5.0mm OZD during the first six months, but after this period, axial length growth pattern displayed a similar behavior in both OZD groups up to two years.Another parameter some studies looked at was change over time in spherical equivalent refraction (SER). Also demonstrating a difference in OZD groups, the one study found significant differences in the level of SER correction between both size groups at six, 12 and 18 months, with higher SER correction in the small OZD group; this did not extend to 24 months. There was also no difference seen in SER change when analyzing time effect from six months to two years of follow-up. As the authors explain in their paper, these together indicate that SER reduced in both small and large OZD groups, but with greater change observed in the 5.0mm group, which stabilized after six months.One main adverse effect reported in the studies was increased HOAs of spherical aberration and coma seen at different follow-ups. The researchers elucidate that although myopia control is confirmed to be more efficient with an OZD of 5.0mm, it should be remembered that this can also decrease optical quality due to increased HOAs, potentially affecting visual quality. They also mention that increased compression factor in ortho-K lenses has been reported to possibly increased HOAs in comparison with conventional compression factor.Considering the trade-off of these qualities, the authors argue that “these findings highlight the importance of performed geometric modifications in OKLs to achieve better myopia control outcomes but considering the potential loss of visual quality that they may cause.”Click here for the journal source. Zamora-Castro C, Piñero DP, Plaza EM. Effect of optical zone diameter in orthokeratology on myopia control: a meta-analysis and systematic review. Eye Contact Lens. June 10, 2025. [Epub ahead of print].