The effect of overnight corneal refractive therapy (CRT) lenses on vision and corneal curvature in Chinese myopes: A prospective, multi-Centre study.

Purpose

To evaluate the effects of orthokeratology lenses (Paragon CRT® 100 [CRT 100] and CRT Dual Axis® [CRT-E], Paragon Vision Sciences, a CooperVision company) on vision and corneal curvature in myopic Chinese children and adults.

Methods

This was a 12-month, multi-centre, bilateral-dispensing, single-arm clinical trial. Subjects were eligible for enrolment if both eyes had -0.50 to -4.00 DS, up to -1.50 DC, and no corneal abnormality. Uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), and corneal curvature were assessed at baseline and at follow-up visits after lens-wear periods of 1 day, 1 week, 2 weeks, and 1, 3, 6, 9, and 12 months.

Results

Four sites in China enrolled 254 subjects aged 8 to 43 years (median: 11 years). Data were collected from both eyes of all subjects. Mean UDVA and MRSE were significantly improved compared to baseline values at all follow-up visits (P < 0.05). Mean UDVA improved by 0.44 ± 0.25 logMAR at Day 1 and 0.68 ± 0.20 logMAR at 1 month compared to baseline (0.65 ± 0.27 logMAR). Mean MRSE improved by 1.66 ± 0.92 D at Day 1 and 2.64 ± 0.69 D at 1 month compared to baseline (-2.66 ± 0.94 D). At 1 month, 94% of eyes had UDVA of ≤0.1 logMAR and - 0.50 D < MRSE < +0.50 D (472/502 eyes, 95%CI: 92-96%). Compared to baseline values, mean corneal curvatures (both steep and flat meridians) were significantly flatter at all follow-up visits (P < 0.001), and mean corneal astigmatism was slightly but significantly lower from the 1-week visit onward (P ≤ 0.007). There were no significant ocular adverse events.

Conclusions

The CRT® orthokeratology lenses are able to temporarily flatten the cornea during overnight wear, temporarily correct myopia, and effectively improve UDVA after lens removal in a large proportion of predominantly paediatric Chinese eyes.