A peer-reviewed study recently published in Contact Lens and Anterior Eye assessed the efficacy of the Euclid Emerald lens designs (Euclid Vision) for orthokeratology (ortho-k) pediatric myopia management in global markets over the last 20 years.
Let’s start with some background.
Ten years after the FDA approval of the first ortho-k daily lens, the proprietary Euclid design and material (oprifocon A) was registered in 2004 as the Euclid Emerald lens.
While initially approved for the temporary reduction of myopia, its ortho-k potential for myopia control in pediatric patients was revealed in a peer-reviewed report published in 2005.
Give me more details on the lens.
The Euclid ortho-k lenses are designed as rigid, oxygen-permeable lenses capable of being worn overnight. Other features include:
- Multi-curve design
- Optimized treatment zone
- Elevation adjustments (for astigmatic patients)
Lens replacement is recommended every 12 to 14 months.
What diopters of myopia can be treated with these lenses?
According to Euclid Vision, the lenses are approved up to -5.00D.
OK … now talk about this study.
Researchers conducted a comprehensive systematic search using Medline and with the following search terms:
- Orthokeratology AND myopi* AND (axial or elong*) NOT (review or meta)
Eligible articles included retrospective and prospective studies published (in English) up to March 2023 and with at least 6 months of longitudinal axial length data on myopia children (ages 6 to 18 years).
Out of 189 articles, they reviewed 140 published papers; of those, 49 (35% of the total) reported data on Euclid’s ortho-k lens design.
How many included axial elongation?
A total of 37 papers included data—14 of which compared axial elongation in myopic children with Euclid overnight ortho-k to a spectacle-wearing group.
Give me some numbers.
The 14 studies included 1,315 overnight ortho-k patients (ages 7 to 16 years) compared to a control group (1,308).
What kind of studies were they?
Of the 14, three were of randomized clinical trials, seven were prospective studies (with no randomization), and four were retrospective record reviews.
Twelve studies were conducted in China; the remaining two in Japan.
And study duration?
Time duration ranged from 6 months (one); 12 months (eight); 24 months (four); ; and 60 months (one).
How about the studies with no control group?
The 23 papers consisted of 2,353 overnight ortho-k patients (ages 7 to 17 years); two were of randomized clinical trials; 11 of retrospective studies comparing axial elongation to multifocal soft contact lens; and 10 were retrospective studies.
All but one were conducted in China (the remaining in Taiwan); time duration ranged from 12 months (14); 24 months (five); and both 12 and 24 months (three).
How did Euclid ortho-k lenses perform?
When evaluating the 12-month efficacy between the 14 control group studies’ and the 23 studies without a control, there did not appear to be a difference in axial length distribution of the data (0.20 ± 0.06 mm and 0.20 ± 0.07 mm, respectively; t = 0.16, p = 0.88).
And for the 24-month data?
Conversely, the 24-month efficacy data on the lenses within the 5 controlled studies and 11 studies without a control was comparable when observing the mean axial length data (0.39 ± 0.05 mm and 0.47 ± 0.18 mm years, respectively; t = 0.89, p = 0.39).
Let’s get specific.
For control group studies, the mean 12- and 24-month efficacy was 0.18 and 0.28 mm, respectively—which is consistent with other overnight ortho-k data.
Further, efficacy in Year 2 of Euclid ortho-k lens wear decreased from Year 1 (0.110 ± 0.03 mm vs. 0.195 ± 0.09 mm), while four studies showed a mean efficacy that was 56% of that in Year 1—findings that are also consistent with most myopia control interventions.
Did age play a factor?
According to the study authors, age was unrelated to the efficacy of the lenses for myopia control—a conclusion also consistent with previous studies.
What about race?
Good question … all but one of the 37 studies on the Euclid lenses were conducted in East Asian pediatric patients.
While there’s both differences and similarities in myopia between East Asian and European patients (myopia increases 30% faster in East Asians), regardless of race, myopia progression slows 15% per year, according to the investigators.
And in relation to axial elongation?
Per the study, “Myopia progression is strongly related to axial elongation in all races and the ratio of progression to elongation appears to be independent of race.”
Any data on refractive error?
For the most part, no.
The majority of the 14 studies didn’t report any refractive error outcomes; only one reported a myopic shift of −0.37 ± 0.42 D in patients who wore ortho-k lenses for 12 months and discontinued wear for one month (compared to −0.70 ± 0.42 D in the spectacle group).
Limitations?
The study authors noted the potential for multiple sources of bias among the journals as well as loss to follow-up (which could introduce bias) due to an average of 91% of patients completing the studies.