Overnight Orthokeratology: How Sleeping in Specially Fitted Contact Lenses Can Slow Nearsightedness in Children

Table of Contents

• Key Points
• What Is Overnight Orthokeratology?
• The History: From Flat-Fitting Lenses to Modern Designs
• Three Technologies That Transformed Orthokeratology
• Regulatory Timeline: How Approvals Changed Worldwide
• How Common Is Orthokeratology?
• How Does Orthokeratology Change the Cornea?
• Does It Slow Myopia in Children? The Key Studies
• What the Combined Analyses Show
• Long-Term Results: Five and Seven Years of Data
• How Long Do Results Last After Stopping?
• Why It May Work: Peripheral Defocus
• Safety of Overnight Lens Wear
• What This Means for Patients
• Limitations of the Evidence
• Actionable Recommendations
• Frequently Asked Questions
• Source Information

Key Points

• Ortho-K uses custom rigid gas permeable lenses worn overnight to temporarily reshape the cornea and reduce short-sightedness.
• In children, a review of 11 studies found ortho-K slowed eye growth by about 0.20 to 0.36 mm over two years compared with spectacles.
• The vision correction is temporary: about half is lost within 24 hours of stopping lens wear and 90% within 72 hours.
• The main safety concern with overnight wear is microbial keratitis; modern high-oxygen materials and careful fitting help reduce risks.
• Most change occurs in the first seven nights and levels off by about day 30; regular follow-up with corneal mapping is important.

What Is Overnight Orthokeratology?

Orthokeratology — almost always shortened to "ortho-K" — is a treatment that uses specially designed rigid gas permeable (RGP) contact lenses to reshape the front surface of the eye. RGP means the lens is made of a hard, rigid plastic that still allows oxygen to pass through to the eye. The lenses are worn overnight while you sleep and removed the moment you wake up.

The formal definition used in the medical literature is this: orthokeratology is the planned, temporary reduction in myopia (short-sightedness) produced by wearing flat-fitting rigid contact lenses. In plain terms, the lens is deliberately made slightly flatter than your cornea so that it gently moulds the eye's surface overnight.

Two large companies market specific versions of the treatment under their own brand names. Bausch + Lomb calls it Vision Shaping Treatment (VST). Paragon Vision Sciences calls it Corneal Refractive Therapy (CRT). Both describe the same underlying approach.

The main attraction is lifestyle. The lenses go in before bed, the cornea reshapes while the patient sleeps, and the lenses come out in the morning. Good vision then lasts most or all of the day without glasses or daytime contacts. This is appealing for swimmers, athletes and anyone with an active routine. There is one catch that patients must understand from the start: the effect is temporary. Lenses must be worn nearly every night to hold the result.

Orthokeratology is now prescribed predominantly for children. The goal in children is not only clear daytime vision but myopia control — slowing the progression of short-sightedness and limiting axial elongation (the eye growing longer front-to-back, which is the underlying driver of worsening myopia).

The History: From Flat-Fitting Lenses to Modern Designs

Researchers have known since the earliest days of contact lenses that wearing rigid gas permeable lenses can change the shape of the cornea. The first deliberate attempt to exploit this was reported in the early 1960s, using a technique called "orthofocus".

The first formal evaluation came in the 1970s. Kerns compared a group wearing flat-fitting rigid lenses during the day against both spectacle wearers and people wearing conventionally fitted rigid lenses. Kerns fitted the ortho-K lenses 0.25 to 0.50 D flatter than the flattest meridian of the cornea. (A "D" or dioptre is the unit used to measure lens power; the "flattest meridian" is the least curved direction of the cornea.)

After 300 days of lens wear, the average reduction in myopia was +0.77 ± 0.91 D. That average hid enormous variation, however. Individual results ranged from a 2.62 D decrease in myopia to a 1.00 D increase, and some patients developed astigmatism (blur from an irregularly shaped cornea) because the lens sat off-centre. Kerns concluded the procedure was unpredictable and uncontrollable.

Binder and colleagues then compared people wearing flat-fitting PMMA lenses (polymethyl methacrylate, an older oxygen-impermeable hard plastic) daily against people wearing conventionally fitted PMMA lenses. Their ortho-K lenses were fitted between 0.50 D and 2.75 D flatter than the flattest corneal meridian. Like Kerns, they found the reductions in myopia inconsistent and unpredictable.

In the early 1980s, Polse and colleagues ran The Berkeley Orthokeratology Study — a randomized clinical trial, the strongest type of study design, comparing a group wearing flat-fitting lenses daily with a control group wearing conventionally fitted lenses. The mean reduction in myopia was +1.01 ± 0.87 D in the orthokeratology group versus +0.54 ± 0.58 D in the control group. Polse again judged these reductions to be variable and unpredictable, pointing to the relatively large standard deviations (the statistical spread of results around the average).

Then came a decade with essentially no peer-reviewed research on orthokeratology. That changed in the 1990s, when three separate technologies converged at once — and that convergence is what made modern ortho-K possible.

Three Technologies That Transformed Orthokeratology

The old flat-fitting approach using conventional rigid lenses caused problems with lens centration (keeping the lens centred on the cornea). Poor centration produced poor and variable results. Three advances fixed this.

1. Reverse geometry contact lenses. Wlodyga and Stoyan collaborated to develop a new lens family. In these lenses, the base curve radius (the central back surface of the lens) is deliberately designed to be flatter than the central corneal curvature, while the secondary curve is steeper than the base curve radius. At the junction between these curves, the lens and cornea form a tear reservoir — a band where tears pool in the mid-peripheral cornea, visible with fluorescein dye. This design dramatically improved centration and stability, and produced much more predictable and consistent reductions in myopia.
2. Higher oxygen transmissibility. The earlier research used PMMA lenses, which block oxygen. Newer rigid materials were developed that, in theory, should limit corneal oedema (corneal swelling) to levels normally seen during sleep — about 3% to 4% swelling — while minimising other changes to the eye. The authors caution that much of these data come from soft contact lens wear, whereas rigid lenses including ortho-K lenses are smaller in diameter but also thicker. Still, the new materials gave oxygen transmissibility values that minimise, and perhaps eliminate, hypoxic stress (oxygen starvation) and corneal oedema during overnight wear. This is what made overnight corneal reshaping feasible. Importantly, overnight corneal swelling still exceeds the lens-free level, particularly in the peripheral cornea, though the magnitude may shrink over weeks of overnight wear.
3. Corneal topography instruments. These devices, developed largely in response to the boom in refractive surgery, map the shape of the cornea in detail. They let the practitioner monitor exactly how much the cornea has changed, which zone has flattened, and whether the lens is properly centred — reflecting the centration of the lens itself. Before topography, clinicians had to rely on the far less quantitative interpretation of fluorescein patterns and keratometry (manual measurement of corneal curvature). Today some manufacturers design a custom ortho-K lens directly from the topography map plus a few other measurements.

In 1997, Mountford published the first report of orthokeratology in patients wearing reverse geometry contact lenses on an overnight basis. Unlike the earlier evaluations, Mountford reported more predictable and sustained reductions in myopia. Pre-treatment mean refraction was –2.19 ± 0.79 D; post-treatment mean was 0.00 ± 0.68 D; mean change was +2.19 ± 0.57 D.

Mountford then studied how well the effect held up after lens removal. Most of the refractive change occurred within the first month of lens wear. He found the amount of regression (loss of effect) during the day to be between 0.50 and 0.75 D. He also predicted that greater regression would occur in higher corrections, which is why modern designs build in a "compression factor" — an additional flattening of the base curve — to compensate.

Nichols and colleagues extended these findings and quantified the time course in more detail. Ten myopic adults were fitted with reverse geometry rigid contact lenses and examined repeatedly over the 60 days after starting wear; eight completed the study. All visual, refractive and topographical outcomes were sustained across an 8-hour day. Mean uncorrected visual acuity improved from +0.52 ± 0.23 logMAR (about 6/20) to –0.04 ± 0.12 logMAR (about 6/5.5) by day 14. Mean manifest refraction was significantly reduced from baseline at day 60 (mean change +1.83 ± 1.23 D), accompanied by significant central corneal flattening (mean change in apical radius +0.20 ± 0.09 mm) and corneal thinning (mean change –12 ± 11 μm, where μm means micrometres). Beyond 7 nights of wear, visual acuity stayed constant for 8 hours after lens removal.

Together, these studies established that overnight orthokeratology with rigid gas permeable lenses effectively reduces myopia temporarily and provides good vision through the day in people with myopia up to –4 D. Later studies demonstrated partial or complete effectiveness in patients with myopia up to –10 D. Most of the change in visual and refractive outcomes occurs in the first seven nights and levels off around day 30.

Regulatory Timeline: How Approvals Changed Worldwide

Regulatory approval for orthokeratology has expanded steadily over three decades, but the approved purposes differ by country.

• 1994: The United States Food and Drug Administration (FDA) granted the first daily wear approval for a lens indicated for orthokeratology — the Contex OK-Lens.
• 2002: Paragon Corneal Refractive Therapy (CRT) lenses, made by Paragon Vision Sciences, received FDA approval for overnight wear. Other lens designs and materials were covered by the original approval.
• 2003: Paragon received CE marking (the European Union's regulatory approval) for its family of CRT lenses.
• 2004: Bausch + Lomb received approval for overnight wear of the Boston Vision Shaping Treatment (VST) lens. A range of branded designs is marketed under the VST approval, including the Contex OK E-system, Euclid Emerald, DreamLens and the BE Retainer lens.
• January 2017: The China Food and Drug Administration granted approval and commercial availability for Paragon CRT lenses in China. As in the United States, this Chinese approval covers only temporary myopia reduction — not myopia control.
• May 2019: Menicon received the first and only CE-marked orthokeratology lens approved for myopia control — the Menicon Bloom.

The distinction matters. Most approvals worldwide cover a temporary reduction in myopia, which is a vision correction claim. Only one lens had, at the time of this review, a regulatory approval specifically for myopia control — the claim that the treatment slows the progression of short-sightedness.

How Common Is Orthokeratology?

Several large surveys have measured how widely ortho-K is used, and the numbers show steady but modest growth.

Cope and colleagues conducted a population-based survey in the United States. They estimated there are 40.9 million contact lens wearers aged 18 or older, of whom approximately 6.5% wear RGP lenses (2.7 million people). That survey did not include children and did not ask specifically about orthokeratology.

Efron and colleagues asked practitioners in 38 countries to document their first 10 contact lens fits (new fits or refits) over five years. Patients under 18 years old accounted for 13.2% of fits, but this varied widely by country — from 25% in Iceland to 1% in China. Orthokeratology accounted for 28% of all rigid contact lenses prescribed to minors, including 47% among 6- to 12-year-olds. The authors attributed this to the popularity of myopia control. Two cautions: these data represent proportions of lens fits, not wearers, so they may overestimate the proportion of children among all wearers; and the response rate was only 13%, leaving potential for respondent bias. The mean age for new fits did rise from 28 years in 2002 to 32 years in 2014.

Morgan and colleagues reported 14 years of data from contact lens fitters in 45 countries, each reporting at least 500 fits, creating a database of 295,044 contact lens fits. Orthokeratology represented 1.2% of all contact lens fittings, ranging from 0% in some countries to 6% in the Netherlands. Ortho-K fitting rose slowly but steadily across the 14-year survey period, from 0.5% in 2004 to 1.3% in 2017. Ortho-K lenses were also fitted to a younger population than other lenses (25 ± 13 years versus 40 ± 15 years), which likely reflects its growing use for myopia control.

Wolffsohn and colleagues surveyed 971 respondents worldwide using a self-administered internet questionnaire. Respondents rated orthokeratology as the most effective method of myopia control, ahead of increased time outdoors and pharmaceutical approaches. Among effective myopia therapies, ortho-K was the most frequently prescribed option for progressing young myopes in every region, at around 20% in Australasia and Europe but only 10% in Asia and the Americas. The authors noted the survey was completed by people both cynical and enthusiastic about the topic, so how well the findings generalise to all practitioners is uncertain. The results have since been updated.

How Does Orthokeratology Change the Cornea?

The original belief was that orthokeratology flattened the cornea by bowing it. Limitations in measuring instruments made it impossible to test this or competing explanations. Modern imaging finally settled the question.

Swarbrick and colleagues provided the first real insight into the anatomical changes. They found significant thinning of the central corneal epithelium (the outermost layer of the cornea) accompanied by thickening of the total mid-peripheral corneal thickness. Nichols and colleagues confirmed the central thinning but could not demonstrate significant changes in mid-peripheral thickness.

Context matters here: overnight, without any contact lens wear, the cornea naturally swells by 3% to 4%. Wearing most lenses overnight increases that swelling.

Haque and colleagues evaluated corneal and epithelial thickness after 4 weeks of overnight CRT wear in 23 people, using optical coherence tomography (OCT, a light-based scanning technique that images layers of tissue). After the first night of wear:

• The central cornea swelled significantly by 4.9%;
• The paracentral cornea (just next to the centre) swelled by 6.2%;
• The central epithelium thinned by 7.3%;
• The mid-peripheral epithelium thickened by 13%.

Corneal swelling recovered within the first 3 hours after lens removal. Maximal overnight central epithelial thinning was 13.5%, reached after four nights of wear. Three days after lens wear was discontinued, both corneal and epithelial thickness had returned to baseline values.

Reinstein and colleagues reported a single case in which the patient's epithelial, stromal and corneal thickness was measured with high-frequency digital ultrasound before and during orthokeratology. The central epithelium thinned by 18 μm and the mid-peripheral epithelium thickened by up to 16 μm. They concluded that refractive changes are mainly caused by alterations in epithelial thickness; while stromal changes (deeper in the cornea) may occur, their contribution is limited.

Qian and colleagues used Fourier-domain OCT to map epithelial thickness in 60 children fitted with myopic ortho-K lenses and 44 control children. Epithelial thickness in the central 2 mm was significantly thinner in the ortho-K group. The superior and inferior mid-peripheral corneal epithelium was thickest in patients with more than 14 days of ortho-K wear.

Lau and colleagues fitted ortho-K lenses with different compression factors (0.75 D versus 1.75 D) in 28 children aged 7 to 11 and measured ocular components weekly for one month of lens wear and for three weeks after stopping. Central corneal thickness decreased by 9 μm at week 1 and then stabilised. Interestingly, anterior chamber depth (the space between the cornea and the iris) decreased by 41 μm after one week of wear and stayed stable thereafter, then rebounded in the first week after wear stopped. The authors attribute this to accommodative changes (changes in focusing effort) rather than to corneal bowing, though bowing or other posterior surface changes could contribute.

Evidence on the posterior cornea (the back surface of the cornea) is mixed. Owens and colleagues fitted 19 young myopes with ortho-K lenses worn nightly for a month. Owens and colleagues evaluated corneal thickness, topography and posterior corneal radii within two hours of waking on four occasions. They found significant anterior corneal flattening after one night and beyond, plus significant posterior corneal flattening after one week. In contrast, Yoon and Swarbrick found no change in posterior corneal radius. Yoon and Swarbrick did observe a more oblate (flatter-edged) shape, while acknowledging that their posterior geometry was calculated rather than directly measured.

Chen and colleagues reported changes in, and recovery of, posterior corneal curvature after 6 months of overnight orthokeratology in 28 young adults, using rotating Scheimpflug imaging (a rotating camera that builds a 3-D map of the front of the eye). The posterior cornea significantly steepened after the first overnight wear, but these changes were not seen at later visits. The posterior cornea was steepest immediately after lens removal and significantly flatter two hours later.

Finally, Gonzalez-Mesa and colleagues evaluated anterior chamber depth and posterior corneal curvature over one year of overnight ortho-K. They found a significant reduction in anterior chamber depth and a flattening of posterior corneal curvature across the year.

In summary: the refractive changes that accompany orthokeratology come from local changes in corneal epithelial thickness — the centre thins, the mid-periphery thickens — which flattens the central cornea.

Does It Slow Myopia in Children? The Key Studies

Practitioners began discussing orthokeratology for myopia control around the start of the millennium, and the first peer-reviewed report of its effectiveness was published in 2005.

Cho and colleagues enrolled 43 children fitted by eight private practitioners, of whom 35 completed two years of follow-up. A historical control group of 35 children wearing single-vision spectacles from an earlier study was used for comparison. The increase in axial length was 0.29 ± 0.27 mm in the orthokeratology group and 0.54 ± 0.27 mm in the control group.

A key methodological point: because ortho-K deliberately changes corneal curvature and refractive error, nearly all studies measure effectiveness in terms of axial elongation rather than glasses prescription. Axial elongation — the eye growing longer — is the underlying cause of myopia progression, and the two are highly correlated. For reference, a 0.1 mm difference in axial length is equivalent to around 0.25 D.

Walline and colleagues confirmed the results using a historical comparison group of 28 soft lens-wearing children. Forty subjects aged 8 to 11 were fitted with overnight ortho-K lenses and followed for two years, with 28 completing the study. Despite being conducted in an ethnically different population, the results were remarkably consistent with Cho's: axial length increased by 0.25 ± 0.22 mm in the ortho-K group and 0.57 ± 0.51 mm in the control group.

The first randomized clinical trial randomized 102 children aged 6 to 10 to either orthokeratology or spectacles. Among the 78 patients who completed the two-year study, mean axial elongation was 0.36 ± 0.24 mm in the ortho-K group and 0.63 ± 0.26 mm in the control group.

The review tabulates 11 peer-reviewed studies with a control group and axial length data. Here are the two-year (or longer) axial growth figures:

The range of treatment effects varied. The largest effect came from a study of partial myopia reduction in high myopia, and the smallest from a case report of a pair of twins. Drop-out rates (the percentage of participants who left the study before finishing) ranged widely too. Drop-out rates were 6% to 54% in the ortho-K groups and 17% to 49% in the control groups, which is worth noting when interpreting any single study.

A few additional studies are worth mentioning even though they lacked a robust control group. Downie and Lowe reported a retrospective study of 26 myopic children wearing orthokeratology lenses. A range of lens designs has been used across the research. These designs include Menicon Z Night (used in three studies), Euclid Emerald (two or three studies) and Paragon CRT HDS-100, among others.

What the Combined Analyses Show

Between 2015 and 2016, four separate meta-analyses (statistical analyses that pool results from multiple studies) summarised the effects of orthokeratology on myopia progression. Their findings were strikingly consistent.

The studies included in each meta-analysis overlap heavily. Six studies are common to all four analyses, and the maximum number included in any one analysis is nine. Not surprisingly, the treatment effects are nearly identical:

• Si et al. (2015): –0.26 mm (95% CI: –0.31 to –0.21 mm)
• Sun et al. (2015): –0.27 mm (95% CI: –0.32 to –0.22 mm)
• Wen (2015): –0.25 mm (95% CI: –0.30 to –0.21 mm)
• Li (2016): –0.27 mm (95% CI: –0.32 to –0.23 mm)

The 95% confidence interval (CI) is a range that is 95% likely to contain the true effect. In plain language, the estimates cluster tightly around a quarter of a millimetre of slowed eye growth across roughly two years of treatment.

Li and colleagues also showed that the treatment effect was the same whether studies were randomized clinical trials (–0.28 mm, 95% CI: –0.35 to –0.20 mm) or cohort studies (–0.27 mm, 95% CI: –0.32 to –0.22 mm). That consistency strengthens confidence in the finding.

Long-Term Results: Five and Seven Years of Data

Most studies report two-year outcomes, but two groups have followed patients much longer.

Hiraoka and colleagues reported five-year data. Of the original 59 enrolled subjects, 43 (22 ortho-K and 21 control) completed the five-year study. The increase in axial length was 0.99 ± 0.47 mm in the orthokeratology group and 1.41 ± 0.68 mm in the control group. The gap between groups therefore widened over time — a difference of about 0.42 mm over five years.

Santodomingo and colleagues reported seven-year follow-up data. Fourteen of the 29 ortho-K subjects who had completed the original two-year trial were re-examined five years later, along with 16 of the 24 control subjects. By that point, four controls still wore spectacles and 12 had switched to soft contact lenses after the initial two-year trial.

After seven years of lens wear, axial elongation in the orthokeratology group was 0.44 mm lower than in the control group. A striking finding was that the rate of eye growth over the first two years was similar to the rate over the subsequent five years, in both groups:

• Ortho-K group: 0.42 ± 0.05 mm over the first two years, then 0.39 ± 0.04 mm over the next five;
• Control group: 0.71 ± 0.10 mm over the first two years, then 0.65 ± 0.11 mm over the next five.

One important caveat: at seven years the subjects were all between 17 and 19 years old, and the majority of their myopia would have stabilised regardless of treatment.

How Long Do Results Last After Stopping?

This is one of the most important practical facts for anyone considering ortho-K: the vision correction is temporary. If lens wear is discontinued, refractive error regresses back towards the original baseline.

• Around half of the myopia reduction is lost after 24 hours;
• 90% is lost within 72 hours.

Within a treatment course, the visual and refractive changes are well sustained across an eight-hour day. Regression during the daytime (the slow drift back toward the original prescription between lens removal in the morning and bedtime) was measured by Mountford at 0.50 to 0.75 D. Because higher corrections tend to regress more, modern lens designs build in an extra compression factor to compensate.

The research also showed that the structural changes reverse. Haque and colleagues found that three days after lens wear stopped, both corneal and epithelial thickness had returned to baseline. Lau and colleagues found that anterior chamber depth rebounded in the first week after wear ceased.

Why It May Work: Peripheral Defocus

One leading explanation for why orthokeratology slows myopia progression is that it changes how light focuses in the peripheral retina. The peripheral retina is the outer part of the light-sensing tissue at the back of the eye.

Researchers found that ortho-K produced:

• Elimination of uncorrected myopia within the central 20 degrees of retinal eccentricity (the central field of vision);
• No change in spherical equivalent (overall prescription) at 25 degrees eccentricity;
• A myopic shift (light focusing in front of the retina) beyond 25 degrees eccentricity.

They also found an association between greater amounts of treated myopia and larger myopic shifts in peripheral refractive error beyond 20 degrees eccentricity. Several subsequent studies have confirmed that reshaping the cornea with orthokeratology converts relative peripheral hyperopic defocus before treatment into relative peripheral myopic defocus after orthokeratology. This shift in the peripheral focus is believed to signal the eye to slow its growth.

Safety of Overnight Lens Wear

Because ortho-K lenses are worn while sleeping, safety is a central concern — and one the review addresses directly. The primary risk of any overnight contact lens wear is microbial keratitis, an infection of the cornea caused by bacteria, fungi or other organisms.

Several physiological effects of overnight wear are relevant:

• Corneal swelling. Overnight, even without any lens, the cornea swells by 3% to 4%. Wearing most lenses overnight increases this swelling further.
• Peripheral swelling. Overnight corneal swelling above lens-free levels still occurs with ortho-K, particularly in the peripheral cornea, although the magnitude may diminish over weeks of overnight wear.
• Hypoxic stress. Modern rigid gas permeable materials have oxygen transmissibility values designed to minimise — and perhaps eliminate — hypoxic stress (oxygen deprivation) and corneal oedema during overnight wear. Earlier PMMA lenses could not do this.

These physiological findings explain why careful fitting, high-oxygen materials and regular professional monitoring matter so much for anyone wearing lenses overnight.

What This Means for Patients

Orthokeratology offers two distinct benefits, and patients should understand the difference.

1. Temporary vision correction. Lenses worn overnight reshape the cornea so that daytime vision is clear without glasses or daytime contacts. This benefit works in myopia up to about –4 D reliably, with partial or complete effectiveness reported up to –10 D. It reverses in days if lens wear stops.
2. Myopia control. In children, nightly ortho-K slows axial elongation by roughly 0.20 to 0.36 mm over two years compared with spectacle-wearing controls, and by about 0.25 to 0.27 mm in pooled analyses. Over five to seven years, the accumulated difference reaches 0.42 to 0.44 mm. Since 0.1 mm of axial length corresponds to about 0.25 D, that translates into a meaningful difference in eventual prescription.

For context, the typical change in visual and refractive outcomes happens fast — most change in the first seven nights and levelling off by about day 30. Ortho-K is also rated by practitioners as the most effective myopia control method available, ahead of increased outdoor time and pharmaceutical approaches.

Limitations of the Evidence

The review is candid about the weaknesses in the literature.

• Few randomized trials. Many studies used historical controls — a comparison group from an earlier study — rather than truly randomized comparison groups. The first randomized clinical trial in this field enrolled 102 children.
• High drop-out. Drop-out rates ranged from 6% to 54% in ortho-K groups. Participants who leave a study may differ from those who stay.
• Survey bias. The Efron survey had a 13% response rate. The Wolffsohn survey was completed by respondents both cynical and enthusiastic about the topic, so generalisability is uncertain.
• Wide variability in individual results. Even in the best modern studies, standard deviations around the mean changes are substantial. Individual outcomes vary.
• Age confounds long-term data. At the seven-year follow-up, subjects were 17 to 19 years old, an age at which myopia typically stabilises regardless of treatment.
• Older oxygen data come from soft lenses. Some of the oedema data used to justify overnight wear were derived largely from soft contact lens wear, whereas rigid lenses are smaller in diameter but thicker.
• Mixed evidence on the posterior cornea. Some studies found posterior corneal changes, others did not, and at least one used calculated rather than measured values.

Actionable Recommendations

1. Understand the commitment. Ortho-K requires nightly lens wear. Roughly half the correction disappears within 24 hours of stopping and 90% within 72 hours.
2. Set realistic expectations for vision. Excellent results are typical for myopia up to about –4 D. Patients with higher prescriptions up to –10 D may get partial correction.
3. For children, measure eye growth, not just prescription. Because ortho-K changes corneal shape on purpose, the glasses prescription is not a reliable measure of whether the treatment is working. Ask your practitioner to track axial length.
4. Expect fast initial change and a plateau. Most change happens in the first seven nights, stabilising around day 30.
5. Ask about the lens material's oxygen transmissibility. Higher oxygen transmission is what makes overnight wear safer by minimising hypoxic stress and corneal swelling.
6. Ask about infection risk and hygiene. The main safety concern with overnight wear is microbial keratitis. Follow cleaning and storage instructions exactly, and report eye pain, redness, light sensitivity or discharge immediately.
7. Keep every scheduled follow-up. Corneal topography monitoring is how your practitioner confirms the lens is centred and the cornea is responding as expected.
8. Review the long-term plan. If ortho-K continues for five to seven years in a child, the cumulative effect on axial length may reach roughly 0.42 to 0.44 mm. This must be weighed against the demands and risks of nightly lens wear.

Frequently Asked Questions

What is overnight orthokeratology and how does it work?

Overnight orthokeratology, or ortho-K, uses custom-made rigid gas permeable contact lenses worn only while sleeping. The lenses are deliberately made slightly flatter than your cornea, gently reshaping the eye's front surface overnight. When you remove them in the morning, you can see clearly without glasses or daytime contacts. The effect is temporary, so the lenses must be worn nearly every night to maintain clear vision.

Can ortho-K slow my child's short-sightedness?

Yes, research shows it can. A review of 11 studies found that children wearing ortho-K lenses had about 0.20 to 0.36 mm less eye growth over two years than children wearing single-vision spectacles. Four combined analyses each reported a slowing of about 0.25 to 0.27 mm. This slowing of eye growth is the underlying driver of myopia progression, so it may reduce how short-sighted your child eventually becomes.

What happens if we stop wearing the lenses?

The vision correction is temporary. About half of the improvement is lost within 24 hours of stopping lens wear, and 90% is lost within 72 hours. The structural changes also reverse: corneal and epithelial thickness return to baseline within three days. If your child stops wearing the lenses, their eyes will likely return to their original prescription, and any slowing of myopia progression will cease.

What are the risks of wearing contact lenses overnight?

The main safety concern with overnight lens wear is microbial keratitis, an infection of the cornea. Overnight wear also causes corneal swelling, which is higher than without lenses, especially in the peripheral cornea. Modern high-oxygen materials are designed to minimise oxygen deprivation and swelling. Careful fitting, good hygiene, and regular professional monitoring are essential to reduce these risks.

How much does ortho-K cost and is it covered by insurance?

The article does not provide information on the cost of orthokeratology or whether it is covered by insurance. It focuses on the clinical effectiveness, safety, and regulatory approvals of the treatment. For cost and insurance coverage, you would need to consult with your eye care practitioner or insurance provider directly.

How quickly will my child see results from ortho-K?

Most of the change in vision and eye shape happens in the first seven nights of wearing the lenses, and the effect levels off around day 30. In one study, mean uncorrected visual acuity improved from about 6/20 to about 6/5.5 by day 14. After the first week, vision typically stays stable for at least eight hours after lens removal.

Is ortho-K safe for my child's eyes long-term?

The review indicates that modern reverse-geometry lens designs, high-oxygen materials, and corneal mapping have made ortho-K far more predictable than its 1960s origins. However, overnight wear carries a risk of microbial keratitis. Long-term safety depends on careful fitting, strict hygiene, and regular follow-up. The article notes that some data on corneal swelling come from soft lens wear, not rigid lenses, so uncertainties remain.

My child has high myopia (around -8.00) and was recommended overnight orthokeratology for myopia control — when should I get a second opinion?

Ortho-K reliably corrects myopia up to about -4 D, with only partial or complete effectiveness reported up to -10 D. A -8.00 prescription sits in the range where results vary and a second opinion is reasonable. Because ortho-K deliberately changes corneal shape, the glasses prescription is not a reliable measure of myopia control; axial length must be tracked instead. A second opinion can review whether the lens design, oxygen transmissibility and monitoring plan fit your child's case. Diagnostic Detectives Network provides independent expert second opinions.

Source Information

Original article title: Overnight orthokeratology

Authors: Mark A. Bullimore (University of Houston, College of Optometry, Houston, TX, United States) and Leah A. Johnson (University of Houston, College of Optometry, and Paragon Vision Sciences, Gilbert, AZ, United States)

Publication: Contact Lens and Anterior Eye, Volume 43 (2020), pages 322–332

DOI: https://doi.org/10.1016/j.clae.2020.03.018

Publication history: Received 29 September 2019; received in revised form 19 March 2020; accepted 27 March 2020

License: Published by Elsevier Ltd on behalf of the British Contact Lens Association. This is an open access article under the CC BY-NC-ND license.

Note: This patient-friendly article is based on peer-reviewed research. It is intended for educational purposes and does not replace personalised advice from an eye care professional.