The Science

The science behind
clear vision, overnight.

Orthokeratology, commonly known as OrthoK, OK lenses, or overnight/night lenses, reshapes the cornea while you sleep. Here's a closer look at how it works, the decades of research behind it as a myopia control treatment, and how it compares to other options.

What Is OrthoK?

It really is this simple

OrthoK is a set of custom contact lenses worn overnight to gently reshape your cornea while you sleep, giving you clear vision all day, without glasses or daytime contacts. However complex the science behind it, the routine itself couldn't be easier.

Depending on where you've heard of it, you might know OrthoK by a different name: night lenses, sleep lenses, dream lenses, OK lenses, or — informally — "eye braces," since the lens reshapes your cornea overnight the same way braces gradually reshape teeth. In Chinese-speaking communities it's commonly called OK镜 or 角膜塑形镜. Whatever term brought you here, it's the same treatment: custom overnight lenses, no daytime glasses, no daytime contacts.

1. Insert Lenses Before Bed

Pop your custom OrthoK lenses in as part of your normal bedtime routine, just like regular contacts.

2. Sleep

While you sleep, gentle fluid forces reshape your cornea. No effort required. The treatment happens overnight.

3. Wake Up With Clearer Vision

Remove your lenses in the morning and enjoy clear vision all day, no glasses, no daytime contacts.

A Brief History

Decades of research, not a new idea

OrthoK has been refined for over 60 years, but it's the last two decades of rigorous clinical research that transformed it into a leading myopia control treatment.

1960s

The origins

Optometrist George Jessen introduces "Orthofocus" lenses, the earliest form of orthokeratology, observing that fitting rigid lenses flatter than the cornea could temporarily reduce myopic refractive error.

1980s

Reverse geometry is born

Advances in lens lathing technology allow the development of the first reverse geometry lens designs, generally credited to Dr Richard Wlodyga and Nick Stoyan, laying the foundation for modern OrthoK.

1990s

Overnight OrthoK arrives

Computerised corneal topography makes precise, repeatable lens designs possible for the first time, while new high-oxygen-permeability lens materials make safe overnight wear achievable, giving rise to modern "accelerated" OrthoK.

2000s–
Today

The myopia control era

Research shifts from vision correction alone to myopia control. Landmark studies, including Professor Pauline Cho's LORIC, ROMIO and TO-SEE trials at the Hong Kong Polytechnic University, provide robust clinical evidence that OrthoK meaningfully slows myopia progression in children.

The research behind myopia control

Much of today's evidence for OrthoK as a myopia control treatment comes from Professor Pauline Cho's team at Hong Kong Polytechnic University. Her ROMIO study, a two-year randomised controlled trial in Investigative Ophthalmology & Visual Science, found OrthoK-wearing children had significantly slower eye elongation than those in glasses, with the youngest showing the greatest protective effect.

Her related TO-SEE study extended this to astigmatic children using toric OrthoK lenses, while a 2017 reanalysis confirmed OrthoK meaningfully reduces rapid progression risk, particularly at ages 6–8. This remains some of the most cited evidence in myopia management. Search "Pauline Cho orthokeratology" on PubMed to explore it yourself.

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How It Works

Reverse geometry lenses & fluid forces

OrthoK lenses look nothing like standard contact lenses, and that difference is exactly what makes reshaping the cornea possible.

Unlike a standard contact lens, which simply follows the curve of your cornea, an OrthoK lens uses a specialised reverse geometry design. Its base curve is deliberately fitted flatter than your cornea centrally, with a steeper "reverse" curve in the mid-periphery, the opposite curvature relationship to a conventional lens.

This shape creates a thin layer of tears trapped between the lens and your eye, thicker in the mid-periphery, thinner centrally. As you sleep, this tear film generates gentle fluid forces, combined with light pressure from your eyelid, that redistribute the outer layer of corneal cells. The result is a precise, temporary reshaping of your central cornea's curvature, with no cutting, no permanent tissue change, and no surgery involved.

Fluorescein pattern showing a well-centred OrthoK lens fit with an ideal bullseye reverse geometry treatment zone

Assessment of an OrthoK lens on a patient's eye using fluorescein dye, captured in detail with our high-definition anterior eye camera and blue light.

Myopia vs Hyperopia

Not every OrthoK lens works the same way

Because myopia and hyperopia are optically opposite problems, the lens design needed to correct each is opposite too.

Short-Sightedness

Correcting Myopia

Corneal elevation map showing a central treatment zone after OrthoK for myopia

In myopia, light focuses in front of the retina because the cornea is too steep (or the eye too long). The OrthoK lens gently flattens the central cornea, reducing its focusing power so light lands precisely on the retina, sharpening distance vision.

Long-Sightedness

Correcting Hyperopia

Corneal elevation map showing a hyperopic OrthoK treatment pattern

In hyperopia, light focuses behind the retina because the cornea is too flat for the eye's length. Here, the lens design is essentially inverted. It steepens the central cornea instead, increasing focusing power so light converges correctly on the retina.

Astigmatism

Correcting astigmatism with OrthoK

Medmont corneal topography scan showing astigmatism
Fluorescein pattern showing a toric OrthoK lens fitted on an eye to correct moderate astigmatism

The scan above is a real corneal topography map of an eye with −2.00D of astigmatism. The red figure-of-eight shape shows just how differently the cornea curves vertically compared to horizontally, more like a rugby ball than a sphere, which scatters light into two separate focal points instead of one.

A standard, symmetrical OrthoK lens can struggle to centre well on a cornea shaped like this. That's where toric (or dual axis) OrthoK lenses come in, designed with two different curves on the back surface, precisely aligned to the orientation of your corneal astigmatism. Using sophisticated computer software, we tailor each lens design precisely to your individual corneal shape, allowing even moderate to high astigmatism to be corrected with OrthoK, and ensuring the lens aligns accurately with your corneal surface.

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OrthoK for Kids

Myopia management for children

OrthoK is one of the most popular starting points for parents searching for myopia control Melbourne and myopia management for children, and for good reason. Beyond correcting short-sightedness overnight, it's backed by strong evidence for slowing myopia progression, without the daily hassle of glasses or daytime contact lenses for active kids.

No glasses or daytime contacts to lose, break, or forget at sport and swimming

One of the most effective myopia control options currently available for children

Fully reversible, so there's no long-term commitment if it's not the right fit

Explore Myopia Management for Children →
OrthoK vs LASIK

Which is right for you?

OrthoK and laser refractive surgery are popular ways to reduce dependence on glasses. They both shape the cornea but they work very differently, and suit different people.

Non-Surgical

OrthoK

No surgery, no downtime, and non-permanent. You simply stop wearing the lenses and your cornea returns to its original shape. A good fit for anyone not ready for surgery, still growing or progressing, or worried about potential risks of a surgical procedure. It's also the only option of the two that can actively slow myopia progression in children. Keeping myopia low gives more options for surgical treatments later, with better outcomes.

Surgical

LASIK

A permanent surgical procedure that reshapes the cornea using a laser, typically only for adults with a stable prescription within a suitable refractive power range. Recovery involves some downtime, and the changes made can't be undone. Surgery involves some risks, and some patients may suffer long-term dry eye symptoms. It doesn't offer any myopia control benefit for children or teens whose eyes are still changing.

See OrthoK Cost & Treatment Plans →
The Process

Your OrthoK journey

From your first assessment to ongoing care, here's exactly what to expect at every step of starting OrthoK with us.

Step 1

Assessment

A comprehensive eye test with our optometrist, including corneal topography mapping to assess your eye shape and suitability, plus a full eye health evaluation.

Step 2

Treatment Discussion

We talk through OrthoK for your individual case, your prescription, eye shape and treatment goals, with an honest discussion of the benefits and risks involved.

Step 3

Custom Lens Design

If you decide to proceed, your optometrist personally designs and customises your OrthoK lenses, drawing on experience designing thousands of lenses for our patients. Lenses typically arrive within around 2 weeks.

Step 4

Fitting & Delivery

We check how your custom lenses fit your eyes, then a member of our team patiently guides you through insertion, removal and lens care, with plenty of hands-on practice.

Step 5

Your First Night

You start wearing your OrthoK lenses that very evening.

Step 6

Early Review

Your first review happens within just a few days of starting treatment, to check how things are settling in.

Step 7

Follow-Up Reviews

Further reviews follow at 2 weeks, then 1, 3, 6 and 9 months. More complex cases may need more frequent visits along the way.

Step 8

Ongoing Care

Once established, reviews continue roughly every 6 months, to keep your eye health and treatment results on track.

Ready to Learn More?

Curious if OrthoK is right for you?

Book a comprehensive assessment and we'll map out exactly what treatment would look like for your eyes.

Book an Appointment Call (03) 9819 7695
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