The prescription range
Ortho-K is most effective for myopia up to approximately -5.00 to -6.00 dioptres, with astigmatism up to about -1.50 dioptres. Within this range, most wearers achieve unaided vision of 6/6 or close to it. Higher prescriptions are possible to treat with Ortho-K, but the correction is less complete, vision is improved but may not reach 6/6 without additional daytime lenses. The best results are at lower prescriptions, which is another reason to start myopia control early.
Corneal topography, the key assessment
The most important part of the candidacy assessment is corneal topography: a detailed scan of the cornea's curvature. Ortho-K lenses are custom-designed based on these measurements. We look at the corneal eccentricity (how curved it is from centre to periphery), the corneal diameter, and any existing irregularities. A cornea with good eccentricity values and adequate diameter is well-suited to Ortho-K. Some corneal shapes are not ideal, and it's better to know this before fitting than after.
The child's age and maturity
There is no absolute minimum age, but practically speaking, most children below 7–8 lack the manual dexterity and hygiene awareness to handle rigid lenses safely. The key requirements are: the child can insert and remove the lenses themselves (with parental supervision), they understand the hygiene protocol, and they are motivated, not just the parent. We assess this during the consultation. A 9-year-old who is engaged and eager is a better candidate than a 12-year-old who would rather not bother.
How quickly does it work?
Most children notice a significant improvement after the first night. Full correction typically develops over the first week of consistent wear. We ask families to expect a gradual clearing rather than immediate perfection, the cornea responds cumulatively. After the first 2 weeks, most wearers are at their final level of correction. We schedule a topography review after the first night and again at one week to confirm the response and make any needed adjustments.
What happens at school, sports, swimming?
Since the lenses are only worn at night, they have no impact on daytime activities. Children can play sports, go swimming, and participate in all activities without any lens-related restrictions during the day. This is one of the practical advantages over daytime soft lens options, there is nothing to manage, lose, or worry about once the lenses are out in the morning. For swimming, standard guidance applies: lenses should not be worn in water, which is not an issue here since they're removed before the school day.
What is the ongoing commitment?
Ortho-K requires consistent nightly wear for the correction to remain stable. If a night is missed, vision the following day may be slightly blurred. Lenses are typically replaced every 12–18 months depending on wear and parameter changes as the myopia is monitored. We review corneal topography and axial length at 6-monthly intervals to track the myopia control effect and update lens parameters if the prescription changes.
Ortho-K candidacy assessment at Second Sight
We offer a thorough Ortho-K candidacy assessment that includes corneal topography, refraction, axial length measurement, and a detailed discussion of your child's routine and motivations. We'll give you an honest view of whether your child is a strong candidate, the expected correction outcome, and what the myopia control benefit is likely to be. No pressure, no rush.
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