The recently published outcome from this multi-site USA based study is in agreement with previous studies comparing effect of orthokeratology in slowing progression of myopia in children compared to disposable soft contact lenses.
- Multi-site study across USA with patients followed for 3 years
- Children aged 11-14
- Emerald lens design vs PureVision
- OK group progressed by -0.13D over 3 years, and soft lens wearers by -1.03D
- Empirical fitting of Emerald successful in 80% improving to 95% with one lens change
- 32% drop out for OK = discomfort. 34% drop out for soft lens control = loss of interest
- No loss of best correct visual acuity – important safety measure
Over three years’ myopia progressed by -0.13D in the OK group compared to -1.03D in the soft lens wearers, however these results should be viewed in context of the inherent weaknesses of the study design, the biggest of these being that axial length measurement was deemed by the authors to be unreliable due to measurement errors between the various investigation sites. The authors present no values for axial length and only report lack of significant difference between the groups, though made the point that their findings should not distract from previous studies which show effect of OK in slowing axial elongation.
On the flip side, the study has a large subject cohort and the key measurement metric of refraction was well controlled. At the main yearly measurement intervals, the OK wearers had to cease wear until full regression was achieved before their measurements were included for analysis. The study also provided additional interesting outcomes.
Empirical lens fitting of the Emerald OK lenses was shown to be 80% successful with the first dispensed lens, reaching 95% with one lens replacement. Drop out from OK was also found to be no different compared to soft lenses, though for different reasons. Children wearing OK dropped out of the study due to lens discomfort, while the soft lens wearers instead lost interest in contact lens wear. Also, neither group suffered any loss in best corrected visual acuity which the authors claimed as a critically important safety measure of OK and soft contact lens wear in children.
The paper is published in Advances in Ophthalmology and Visual System as an open access article, so it's free to download and well worth a read, even if you just read the introduction which gives a thorough and concise review of the current literature on studies comparing different contact lens designs for myopia control. A summary of a meta-analysis paper investigating influence of OK on slowing progression of myopia can also be found in my earlier blog.