$Refractive Correction$

Myopia Progression Control with Orthokeratology

Orthokeratology (OK) is a treatment in which specially designed hard contact lenses are worn overnight to reshape the cornea, maintaining uncorrected visual acuity during the day.
For myopia control, multiple meta-analyses and RCTs have reported a 30–50% inhibition rate of axial elongation over 2 years. ¹⁾
Major RCTs such as the LORIC study (Cho 2005) and ROMIO study (Cho 2012) have demonstrated efficacy. ³⁾¹³⁾
Infectious keratitis (especially Acanthamoeba keratitis) is the most important risk; lens washing with tap water is strictly prohibited.
A 2-year RCT of combination with low-concentration atropine 0.01% showed superior axial length control compared to monotherapy. ²⁾
As of April 2025, it is not approved in Japan for myopia control (self-pay treatment).

1. What is Orthokeratology?

Orthokeratology (OK) is a treatment that uses specially designed hard contact lenses worn on a planned schedule to reshape the cornea and correct refractive errors. With advances in lens materials, overnight wear (wearing lenses at bedtime and removing them upon waking) has become standard. A major feature is that patients can go without glasses or contact lenses during the day.

Originally developed for myopia correction, prescriptions for myopia control in schoolchildren have increased rapidly in recent years. Myopia prevalence is particularly high in Asian children, creating a strong demand for myopia control.

Structure and Mechanism of Action of OK Lenses

OK lenses consist of four concentric curves from the center to the periphery:

Base Curve (BC) Zone: The area that flattens the central cornea, reducing myopic refractive power.
Reverse Curve (RC) Zone: Designed steeper than the BC, creating negative pressure that traps tears and redistributes corneal epithelium to the periphery.
Alignment Curve (AC) Zone: The area that aligns with the corneal shape, providing stability and centration.
Edge Lift (EL) Zone: The outermost area, allowing tear exchange and drainage.

Wearing this lens causes thinning of the central corneal epithelium (about 5–10 μm) and thickening of the mid-peripheral cornea, resulting in reduced myopia and improved uncorrected visual acuity. The effect is noticeable the morning after the first wear and stabilizes with continued use.

Mechanism of Myopia Progression Control

In addition to central corneal flattening, mid-peripheral corneal thickening induces myopic defocus on the peripheral retina, suppressing axial elongation. This mechanism is shared with multifocal contact lenses and DIMS spectacles, based on the “peripheral retinal myopic defocus hypothesis.”

Q How does orthokeratology correct myopia?

The base curve of the OK lens flattens the central cornea, reducing the excessive refractive power that causes myopia. Simultaneously, tears accumulate in the reverse curve area, and corneal epithelial cells redistribute from the center to the periphery, causing a shape change. This corneal deformation is reversible after discontinuation of lens wear, so it is not a permanent change independent of the lens.

2. Main Symptoms and Clinical Findings

Fluorescein staining pattern (bullseye pattern) during orthokeratology lens wear

Maiz-Alonso O, et al. Clinical tool to measure fluorescein patterns in orthokeratology. PeerJ. 2022;10:e14068. Figure 1. PMCID: PMC9512001. License: CC BY 4.0.

Under cobalt blue illumination, fluorescein staining shows a concentric bullseye pattern observed during OK lens wear. Four zones are clearly identifiable: a central dark “bearing zone,” a bright green “tear reservoir” around it, a mid-peripheral “alignment zone,” and a peripheral “edge lift.” This corresponds to the fluorescein pattern evaluation discussed in section “2. Main Symptoms and Clinical Findings.”

Fluorescein Pattern of a Good Fit

Fluorescein staining reveals a concentric pattern called a bull’s eye.

Central dark zone (bearing zone): The BC contacts the central cornea, appearing as a thin, dark area of tear film.
Intermediate bright zone (tear reservoir): The tear pool under the RC appears as a bright green ring.
Mid-peripheral dark zone (alignment zone): A dark ring aligned with the cornea.
Peripheral bright zone (edge lift): The outermost bright zone where tears circulate.

In an ideal bull’s eye pattern, the central dark zone is uniformly circular, adequately covers the pupillary area, and confirms good centration.

Post-treatment corneal findings

A good treatment response yields the following findings:

Central corneal flattening (decrease in flat K value)
Mid-peripheral corneal thickening (change in e value)
Improvement in uncorrected visual acuity (usually from the morning after starting wear)
Uniform change in corneal epithelial thickness (on OCT)

Problematic fitting

Improper fitting results in the following findings:

Decentration: The bull’s eye is displaced from the pupil center, causing increased coma aberration and ghost images.
Central touch: The BC makes excessive contact with the central cornea, causing excessive flattening or epithelial damage.
Insufficient edge lift: Tear exchange is hindered, leading to staining at the 3 and 9 o’clock positions of the cornea.

3. Causes and Risk Factors

The main risk factors for myopia and its progression that are indications for orthokeratology are shown below.

Early onset (onset around ages 8–10 carries a high risk of high myopia in the future)
Both parents are myopic, especially if both are myopic
Long near-work time and little outdoor activity
Urban residence and Asian ethnicity

Infection risk factors

Because OK lenses are worn overnight continuously, the risk of infectious keratitis is higher compared to regular rigid contact lenses. A survey by Watt and Swarbrick (2007) reported an increased incidence of microbial keratitis¹¹⁾, and the LOOK study by Rah et al. (2002) emphasized the importance of safety monitoring¹²⁾. The risk increases particularly in the following situations.

Rinsing lenses or cases with tap water or pool water (highest risk for Acanthamoeba keratitis)
Insufficient cleaning and drying of lens cases
Extended wear (wearing beyond the recommended time)
Continued wear in the presence of corneal epithelial damage

4. Diagnosis and Examination Methods

Mandatory Pre-prescription Examinations

According to the OK Guidelines (2nd edition), the following examinations are performed to confirm suitability.

Examination Item	Purpose	Main Points to Check
Refraction and Visual Acuity Test	Confirm range of suitability	Spherical equivalent, corrected visual acuity
Corneal Topography	Calculate prescription parameters, rule out contraindications	Flat K value, corneal eccentricity (E value), rule out keratoconus
Corneal Thickness Measurement (Pachymetry)	Confirm contraindications	Rule out corneal thinning and dystrophy
Axial length measurement	Baseline setting	For myopia progression monitoring
Slit-lamp examination	Exclusion of anterior segment diseases	Check for active inflammation and corneal epithelial disorders
Tear film test	Assessment of contact lens suitability	Presence of dry eye

Selection of Prescription Parameters

Based on the results of refraction/visual acuity tests and corneal topography analysis, two factors are selected: the flat K (flat meridian) value and the target power (desired correction). Using the attached conversion table, the recommended base curve is determined from the intersection of the flat K value and the target power.

Indications and Contraindications

Indications (from OK Guidelines 2nd edition):

Spherical equivalent myopia approximately within -4 D (up to -6 D depending on lens type)
Relatively low corneal astigmatism (less than -1.5 D standard; for higher astigmatism, use toric OK lenses)
Good corrected visual acuity
Dry eye is not severe
No age limit (but consider management ability)

Contraindications:

Keratoconus (absolute contraindication due to risk of progression of corneal ectasia)
Active corneal or anterior segment inflammation
Severe dry eye
Corneal dystrophy or severe corneal opacity
When proper lens care is deemed impossible

Follow-up Schedule

The basic follow-up schedule after starting lens wear is as follows.

Follow-up Timing	Main Items to Check
Next morning after wear (or within 1 week)	Correction effect, corneal epithelial status, fluorescein pattern
1 month later	Confirm stability of visual acuity and refraction, check compliance
3 months later	Axial length measurement (comparison with baseline), complication screening
Every 6 months thereafter	Axial length measurement, myopia progression monitoring, safety check

At each follow-up, fluorescein pattern evaluation, corneal epithelial status check, visual acuity, refraction, and axial length measurement are performed. Regular axial length measurement is essential for monitoring the myopia control effect and serves as a criterion for continuing, intensifying, or changing treatment.

Q What tests are required for orthokeratology prescription?

Corneal topography measures flat K value and corneal eccentricity to determine prescription parameters. It is important to rule out contraindicated conditions such as keratoconus. Axial length measurement must be recorded as a baseline for myopia progression monitoring. Corneal thickness, tear film, and slit-lamp examination are also mandatory pre-prescription tests.

5. Standard Treatment

Lens Selection and Initial Fitting

The selected trial lens is placed on the patient and the fit is checked. Good centration and about 1 mm of movement with blinking are sufficient. The patient takes a nap or rests with eyes closed for 1–2 hours in the clinic, after which the effect is evaluated.

Key points for wear instruction:

The first fitting must always be performed at an ophthalmology clinic, where insertion and removal techniques are taught.
Wearing time should match sleep time, with a minimum of 6–8 hours recommended.
A follow-up examination of visual acuity and corneal condition should be scheduled the morning after the first wear.
Instruct patients to remove the lens immediately and seek medical attention if they experience discharge, redness, or pain.

Management of astigmatism: For corneal astigmatism of 1.5 D or more, toric OK lenses are recommended (Chen et al., TO-SEE study 2013)¹⁰⁾. Because the alignment curve provides parallel fitting, centration and movement are improved.

Management of high myopia: Conventional OK lenses were limited to about −4 D, but with the development of double-zone designs and high-power lenses for high myopia, lenses that can handle cases of −6 D or more have become available. However, the effect is often more limited than in moderate myopia.

Types and Characteristics of OK Lenses

Spherical OK Lens

Indications: Spherical myopia with corneal astigmatism less than 1.5 D

Characteristics: Standard 4-zone design. Easy to prescribe.

Prescription range: Up to approximately −4 D

Toric OK Lens

Indications: Cases with corneal astigmatism of 1.5 D or more

Characteristics: Aspheric alignment curve design. Improved centration and stability.

Prescription range: Myopia with astigmatism

Care and Infection Prevention (OK Guidelines 2nd Edition)

The OK Guidelines (2nd Edition)¹⁵⁾, revised in December 2017, recommend the following measures against corneal infections:

Use only dedicated multipurpose contact lens care products (rinsing with tap water or saline is contraindicated)
Replace the lens case regularly with a new one (at least once a month)
Remove lenses before prolonged water activities (swimming, bathing)
If redness, pain, discharge, or sudden vision loss occurs, immediately stop wearing lenses and see a doctor
Have the condition of the lenses checked regularly by an eye doctor

Complications and Management

Complication	Frequency/Features	Management
Corneal epithelial damage (non-infectious)	Relatively common. Confirmed by fluorescein staining	Discontinue lens wear, artificial tears, fitting adjustment
Infectious keratitis (bacterial)	Increased risk with overnight wear	Immediate discontinuation, culture, antibiotic eye drops
Acanthamoeba keratitis	Severe. Mainly caused by tap water use	PHMB eye drops, chlorhexidine eye drops, long-term treatment required
Decentration	Irregular astigmatism, ghost images	Re-evaluate fitting, change base curve
Halos and glare	Especially at night	Consider switching to a lens with larger optical zone

Myopia control effect

Multiple meta-analyses and RCTs have reported a 30–50% inhibition rate of axial elongation over 2 years¹⁾.

Key RCT evidence is shown below.

Study	Subjects	Duration	Axial length suppression rate	Notes
LORIC (Cho 2005)¹³⁾	Hong Kong children	2 years	Approximately 46%	Pilot study; first demonstration of OK myopia suppression
ROMIO (Cho 2012)³⁾	Hong Kong children aged 6–10	2 years	43%	RCT design
MCOS (Santodomingo-Rubido 2012)⁹⁾	Spanish children	2 years	Approximately 32%	Efficacy confirmed in Western children
TO-SEE (Chen 2013)¹⁰⁾	Myopia with astigmatism	2 years	Significant suppression	Efficacy of toric OK lens confirmed
Lipson 2008⁶⁾	Adults and children	Long-term	—	Long-term clinical outcomes reported
Walline 2004⁷⁾	Pediatric RCT	3 years	No difference in axial length	Confirmed limitations of RGP

The effect persists during continued wear, and after discontinuation, the corneal shape returns to baseline within a few days to 2 weeks (reversible). However, the axial length elongation suppression effect obtained during the wearing period is partially maintained after discontinuation.

A 2-year combination RCT with low-concentration atropine 0.01% (Kinoshita 2020) showed significant suppression of axial elongation compared to orthokeratology alone²⁾. This additive effect is thought to be based on complementary mechanisms: optical defocus correction (OK) and scleral remodeling suppression (atropine).

The value of “1 diopter” of myopia progression is significant; Bullimore and Brennan (2019) estimated that suppressing myopia by 1D can reduce the risk of myopic maculopathy by 40%⁴⁾.

A meta-analysis by Haarman et al. (2020) showed that the risk of myopia complications (retinal detachment, glaucoma, macular degeneration, etc.) increases exponentially with increasing myopia⁵⁾, highlighting the importance of delaying axial elongation even by one year.

Q What is the effect of combining orthokeratology and atropine eye drops?

In a 2-year RCT by Kinoshita 2020, the combination of orthokeratology + 0.01% atropine showed significant suppression of axial elongation compared to monotherapy²⁾. Orthokeratology provides optical defocus correction, while atropine provides pharmacological suppression of scleral remodeling, and they are thought to brake myopia progression through complementary mechanisms. It is an effective option when monotherapy does not provide sufficient effect.

6. Pathophysiology and Detailed Mechanisms

Mechanism of corneal changes by OK lenses

During OK lens wear, the tear film becomes thinner in the base curve area, and mechanical pressure is applied to the central corneal epithelium. Meanwhile, negative pressure occurs in the reverse curve area, causing tear accumulation. This pressure difference redistributes central corneal epithelial cells toward the periphery, thinning the central epithelium.

No significant changes occur in the corneal stroma; deformation is mainly limited to the corneal epithelium (reversible). After discontinuation, the shape almost returns to baseline within 3 to 14 days. Multiple studies have shown that even long-term wear returns to baseline corneal shape, indicating low concern for permanent corneal deformation³⁾.

Optical mechanism of myopia progression suppression

Thickening of the mid-peripheral cornea causes peripheral light rays to focus in front of the fovea (peripheral myopic defocus). This optical signal acts as a suppressive signal for axial elongation. It shares the same mechanism as multifocal contact lenses and DIMS spectacles, and is widely supported as the “peripheral retinal myopic defocus hypothesis” ³⁾.

Pathogenesis of Acanthamoeba keratitis

Acanthamoeba protozoa are widely present in tap water, pools, and rivers. Infected water adheres to the cornea via lenses or cases, and enters through minor epithelial abrasions. Overnight wear accumulates corneal microtrauma, increasing infection risk. Acanthamoeba phagocytizes corneal stromal keratocytes, causing severe stromal keratitis and ring infiltrates.

Treatment for Acanthamoeba keratitis involves long-term (usually 6 months or more) use of PHMB (polyhexamethylene biguanide) eye drops or chlorhexidine eye drops. If an accurate diagnosis is not made early, visual prognosis is poor. Therefore, if keratitis suspicious of Acanthamoeba occurs in an orthokeratology wearer, promptly refer to a specialist facility.

Watt and Swarbrick (2007) investigated the trend of orthokeratology-related microbial keratitis and reported that the risk is particularly high in Asian and younger populations ¹¹⁾. Since orthokeratology lenses are worn overnight, the infection risk is relatively higher than with regular contact lenses, and appropriate patient education is key to infection prevention.

Summary of myopia progression suppression and framework for treatment selection

In myopia management, orthokeratology is particularly suitable for the following patients:

Athletes and swimmers who want to avoid daytime contact lenses or glasses
Elementary school students who have recently started wearing contact lenses (orthokeratology under parental supervision)
Cases with moderate myopia (−1 to −4 D) and good corneal shape
Rapidly progressing cases aiming for maximum effect in combination with low-dose atropine ²⁾

In a long-term clinical outcome study by Lipson (2008), the long-term safety and efficacy of overnight corneal reshaping were confirmed in both adults and children ⁶⁾, supporting long-term use under appropriate patient selection and management. Regarding the significance of axial length in myopia management, Bullimore and Brennan (2019) estimated that suppressing 1 D of myopia can reduce the risk of myopic maculopathy by 40% ⁴⁾, indicating the importance of starting treatment one year earlier.

Q Will myopia progress again if orthokeratology is discontinued?

After discontinuation, the corneal shape returns to its pre-wear state within a few days to two weeks, so the myopia correction effect disappears. However, the effect of suppressing axial elongation (not shortening of axial length but suppression of elongation) obtained during the wearing period is irreversible and partially maintained even after discontinuation. If discontinued at an age when myopia progression continues, explain to the patient and parents that progression will continue along the normal course after discontinuation.

7. Latest Research and Future Prospects

Long-term Evidence of Myopia Progression Control

Multiple meta-analyses have confirmed the 2-year axial elongation suppression rate of orthokeratology ¹⁾, but long-term follow-up data of 5 years or more are limited. Further verification is also needed regarding the long-term stability of axial length after treatment discontinuation. In a randomized controlled trial by Walline et al. (2004), the rigid contact lens group showed less refractive progression, but there was no significant difference in axial length increase ⁷⁾. Therefore, simple RGP wear is not justified for myopia progression control.

A Cochrane Database Syst Rev (Walline 2011) ¹⁴⁾ systematic review evaluated the overall evidence for optical interventions to slow myopia progression, confirming the effectiveness of multiple interventions including OK.

Optimization with Low-concentration Atropine

Evidence for the combination of orthokeratology plus 0.01% atropine is accumulating ²⁾, but standard protocols for optimal concentration (comparison of 0.01%, 0.025%, 0.05%) and optimal start/discontinuation timing have not yet been established. From a new perspective by Kang and Swarbrick (2016), optimization of prescription parameters to maximize OK peripheral defocus is also being studied ⁸⁾.

Impact on Higher-order Aberrations and Visual Quality

After wearing OK lenses, corneal asphericity changes, and higher-order aberrations (especially coma and spherical aberrations) may increase. Research is ongoing on the trade-off between the optimal defocus profile for myopia progression control and visual quality ³⁾.

Quantification of Infection Risk and Preventive Measures

Quantifying the risk of Acanthamoeba keratitis and bacterial keratitis and optimizing prevention protocols are challenges. A survey by Watt and Swarbrick (2007) reported that OK lens-related microbial keratitis tends to occur more frequently in young Asian individuals ¹¹⁾, and individualized guidance based on understanding risk factors is important.

Domestic Regulatory and Approval Trends

As of April 2025, orthokeratology is not approved in Japan for the indication of myopia progression control. Proper use according to the OK guidelines of the Japan Contact Lens Society (2nd edition, 2017) ¹⁵⁾ is required, and future approval trends are of interest.

8. References

Si JK, Tang K, Bi HS, et al. Orthokeratology for myopia control: a meta-analysis. Optom Vis Sci. 2015;92:252-257.
Kinoshita N, Konno Y, Hamada N, et al. Efficacy of combined orthokeratology and 0.01% atropine solution for slowing axial elongation in children with myopia: a 2-year randomized trial. Sci Rep. 2020;10:12750.
Cho P, Cheung SW. Retardation of myopia in orthokeratology (ROMIO) study: a 2-year randomized clinical trial. Invest Ophthalmol Vis Sci. 2012;53:7077-7085.
Bullimore MA, Brennan NA. Myopia control: why each diopter matters. Optom Vis Sci. 2019;96:463-465.
Haarman AEG, Enthoven CA, Tideman JWL, et al. The complications of myopia: a review and meta-analysis. Invest Ophthalmol Vis Sci. 2020;61:49.
Lipson MJ. Long-term clinical outcomes for overnight corneal reshaping in children and adults. Eye Contact Lens. 2008;34:94-99.
Walline JJ, Jones LA, Mutti DO, et al. A randomized trial of the effects of rigid contact lenses on myopia progression. Arch Ophthalmol. 2004;122:1760-1766.
Kang P, Swarbrick H. New perspective on myopia control with orthokeratology. Optom Vis Sci. 2016;93:497-503.
Santodomingo-Rubido J, Villa-Collar C, Gilmartin B, et al. Myopia control with orthokeratology contact lenses in Spain (MCOS): refractive and biometric changes. Invest Ophthalmol Vis Sci. 2012;53:5060-5065. doi:10.1167/iovs.11-8005. PMID:22729437.
Chen C, Cheung SW, Cho P. Myopia control using toric orthokeratology (TO-SEE study). Invest Ophthalmol Vis Sci. 2013;54:6510-6517.
Watt K, Swarbrick HA. Trends in microbial keratitis associated with orthokeratology. Eye Contact Lens. 2007;33:373-377.
Rah MJ, Jackson JM, Jones LA, et al. Overnight orthokeratology: preliminary results of the Lenses and Overnight Orthokeratology (LOOK) study. Optom Vis Sci. 2002;79:598-605.
Cho P, Cheung SW, Edwards M. The longitudinal orthokeratology research in children (LORIC) in Hong Kong: a pilot study on refractive changes and myopic control. Curr Eye Res. 2005;30:71-80.
Walline JJ, Lindsley K, Vedula SS, et al. Interventions to slow progression of myopia in children. Cochrane Database Syst Rev. 2011;(12):CD004916.
日本コンタクトレンズ学会オルソケラトロジーガイドライン委員会. オルソケラトロジーガイドライン（第2版）. 日眼会誌. 2017;121:936-938. URL: https://www.nichigan.or.jp/member/journal/guideline/detail.html?dispmid=909&itemid=310

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