As another illustration of the dual status of OK ('mainstream or specialty'), Contact Lens Update, which usually covers mainstream contact lens topics, published an entire issue on OK recently. The special is hosted by Paul Gifford and covers a couple of things. From a fitting perspective, the editor discusses in his column things such as 'central toricity' versus 'limbus-to-limbus toricity.' But safety issues and myopia management options are discussed as well. 'At what age should I start OK?' The answer is that there really isn't an age limit, according to Gifford. It is well known, though, that due to the fact that myopia progresses faster at younger ages, the impact of the treatment is better/higher for younger kids. A study by Hiraoka et al (open access) showed that the increase in axial length during the 5- year study period was 0.99±0.47 and 1.41± 0.68 mm for the OK and control groups, but one of the most interesting findings of the study is that a significant difference in the annual increase in axial length between the OK and control groups was observed until the third year, but not in the fourth and fifth years. The ' getting started with OK' fitting guide offers very clear tips on making the procedure more insightful. The spherical and cylindrical values should not exceed 6D combined (rather less than that preferably), and flat corneas (42D/8.05mm) and corneas with low eccentricities (under a value of 0.5) are more likely to under-correct. The guide also points attention to the quality of the topography measurement - which indeed is absolutely crucial. If there is more than 40 microns of difference between the steep and the flat meridian, it is advised to use toric-back-surface designs. If a residual astigmatism of 0.75D or higher is present, toric front optics are probably desired.

Orthokeratology Special - Contact Lens Update, Nov 2019