Findings from a recent study published in Contact Lens & Anterior Eye assessed the efficacy of orthokeratology (ortho-k) contact lens wear to slow axial elongation in the eye of myopic children.
Give me some background.
Myopia is the most common refractive error that affects approximately 30% of the world’s population,
- Of note: Estimates expect the prevalence of myopia to increase to 50% by 2050.
Now on to ortho-k …
Overnight ortho-k is one of the most effective and popular treatment options for myopia management, with a bulk of scientific evidence supporting its efficacy.
However, many of these previous studies had relatively small sample sizes—not to mention a dearth of multicenter studies with participants from different countries to evaluate the effect of age, gender, mean spherical refractive error, and ethnicity on treatment outcomes.
Now the study.
As a result, an international research team pooled data from three prospective clinical trials conducted in Madrid, Spain and Hong Kong, China.
Their target: To assess the efficacy of overnight ortho-k contact lens wear compared to distance, single-vision spectacles for slowing myopia progression over a 2-year period.
Any financial disclosures?
Menicon Co. Ltd.—a Japanese contact lens manufacturer—funded this research; one study author is an employee of the company.
Findings?
In total, data from 125 ortho-k and 118 control subjects was analyzed in the study; 101 (81%) and 88 (75%) ortho-k and control subjects respectively completed the 2-year follow-up period.
Further: The interactions of groups with age, gender, mean spherical refractive error, and ethnicity at baseline were not significant (p>0.05).
What was the treatment effect of ortho-k?
Below is the change in axial length at the 2-year visit in comparison to the baseline for the two groups:
- Ortho-k group: 0.41±0.25 mm
- Control group: 0.65±0.30 mm
Meaning: Ortho-k provided a 0.24 mm (95% confidence interval [CI] 0.15-0.34 mm) treatment effect after 2 years of lens wear.
Tell me more.
About 40% of the ortho-k subjects experienced remarkably low levels of myopia progression (8% of this group showed no axial length elongation or shrinkage), while 25% experienced comparatively high levels of myopia progression (2-year axial elongation: ≤0.30 mm and >0.59 mm, respectively).
Note: Around 33.6% of ortho-k lens wearers experienced moderate to low levels of myopia control efficacy.
Anything else?
The rate of increase in axial length over time was significantly lower in the ortho-k group versus the control group.
Also, the lower axial elongation of the ortho-k vs. the control group was statistically significant at all time points (all p<0.001)—with significant differences also present between each of the different pairs of time points (all p<0.001).
Expert opinion?
According to the study authors, “The slowing in the axial elongation of the eye in the first year was over 60% of that found in the second year.”
They noted that this indicated an apparent initial burst in efficacy during the first year of treatment, with efficacy typically decreasing over time.
Take home.
These findings suggest that ortho-k lens wear slows the axial elongation of the eye in comparison to spectacle lens wear in myopic children.