ortho-k | OK lens faqs

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Frequently Asked Questions

Our Orthokeratology practitioner answers our patients' commonly asked questions about the process of Ortho-K overnight vision correction and OK lenses.

I've heard different names for orthokeratology lenses, are they all the same?

Dream lenses, sleep lenses, night lenses, eye braces, Ortho-K, OK lenses, Paragon CRT (corneal refractive therapy), VST (vision shaping treatment) — you may have come across different terms and marketing names for orthokeratology lenses. While there are different orthokeratology lens fitting systems and designs, the principles behind them in reshaping the cornea are similar.

All our Ortho-K lenses are individually designed using the latest generation, fully-customisable 3D Ortho-K technology, delivering superior results and the ability to correct more complex prescriptions and eye shapes, compared to older Ortho-K systems with limitations in lens parameters.

Is orthokeratology lens safe?

All contact lenses carry the potential for complications and OK lenses are no exception. Ortho-K is a safe form of vision correction when properly prescribed by a trained practitioner and worn as instructed with due care by an individual. Although OK lenses are rigid, they are made from a breathable, oxygen-permeable material designed especially for night-time wear.

People who are non-compliant wearers of regular, low-oxygen soft lenses and cosmetic contact lenses are at higher risk than a diligent OK lens wearer. Cases of eye infections across all contact lens use are largely associated with poor hygiene and poor compliance such as not washing hands prior to lens handling, using tap water to rinse lenses, showering or swimming with lenses (does not happen with Ortho-K), improper lens disinfection and re-using cleaning solutions. At our office, we maintain a 100% safety record with no incidence of serious complications involving Ortho-K wear.

What are the risks of orthokeratology lenses?

Infection is the main risk of all types of contact lenses, including Ortho K. The risk of microbial keratitis in an OK lens wearer is extremely low (approximately 7 in 10,000 wearers, or just 0.07%), which is actually comparative far less than overnight extended-wear of soft lenses (0.52%). Even a daily-disposable soft lens wearer can be at risk if he or she doesn't do the right thing. So the key to minimising risk is to always follow the proper handling, hygiene and disinfection procedures for your lenses as recommended by your optometrist. There is no additional risk for a child wearing OK lenses compared to an adult.

Who is suitable for orthokeratology lenses?

Anyone who wants the freedom of clear vision without having to wear glasses or contact lenses during the day. People work in environments that may cause issues with regular day-time contact lenses — eg. eye irritation and dryness from computer screens, air-conditioning, smoky areas and dusty outdoor work sites. People with sensitive eyes and prone to allergies. Those with active lifestyles, fitness fanatics and keen swimmers. Adults considering laser eye correction but whose prescription hasn't quite stabilised enough for surgery, or are wary of the risks of permanent laser surgery.

Kids are great candidates for OK lenses — they can see clearly for school, sports, swimming and all their other activities without the inconvenience of glasses, or the risk of breaking or losing their glasses or day-time contacts. For children with myopia (short-sightedness, or near-sightedness) Ortho-K is also one of the most effective treatments for slowing their progressive vision deterioration.

What prescriptions are suitable for orthokeratology lenses?

Orthokeratology can correct most prescriptions — myopia (short-sighted), astigmatism (uneven eye shape), hyperopia (long-sighted) and even presbyopia (difficulty focusing with age). With correction for short-sightedness, Ortho-K generally works best for prescriptions between -1.00 and -6.00. Higher corrections are possible depending on the individual's eye parameters and vision expectations, and partial corrections are also a possibility for people with high degrees of myopia. With the latest, more complex lens designs, even a moderate amount of astigmatism up to around -4.00 can be treated. At this office our experienced optometrist has successfully corrected myopia up to -11.00 with Ortho-K.

Who can wear orthokeratology lenses?

There are no lower and upper age limits for OK lens wear. Children as young as 5 have been successfully fitted with OK lenses. One key advantage of OK lenses for kids is that they can effectively slow down, or even stop, their eyes from worsening as they grow up. Reducing a child's myopia (short-sighted) progression is highly beneficial for their long-term eye health — lowering the risk of developing glaucoma, retinal detachment and myopic macular degeneration associated with high degrees of myopia. We assess your suitability for OK lenses based on many factors — to best way to know if you're a suitable candidate is to visit us for a detailed Ortho-K assessment.

How effective is orthokeratology lenses for myopia control?

Orthokeratology is the most effective optical treatment for myopia control, and this is backed by numerous international research papers studying the effects of OK lenses on children's myopia progression. We can expect OK lens treatment to slow a child's myopia progression by around 50% (halving the rate of progression), and in many cases even better results have been achieved. Even at 50% progression reduction, a child who may have ended up with short-sightedness of -8.00 untreated is now around -4.00 after OK lens treatment, which is a substantially better outcome for the child's functional vision and eye health, reducing the risk of serious eye disease in life.

How does orthokeratology lenses slow myopia progression?

Ortho-K slow myopia progression by improving peripheral vision, which glasses do not. Wearing Ortho-K lenses changes the shape of the cornea — the clear part of the front of the eye — in two ways. There is a central flattening effect plus a raised effect in the mid-periphery of the cornea. This change in peripheral corneal shape improves the focusing of light onto the periphery of the retina, at the back of the eye, and in turn reduces the stimulus for the eye to grow longer. This slows the abnormal eye elongation that occurs with progressive childhood myopia.

How does orthokeratology lenses compared to other myopia control treatments?

OK lenses are considered the gold standard in optical treatment for myopia control, while atropine eye drops is a medical treatment that is also very effective in many children. These two methods work on different pathways on the eye. As every child is different, one child may respond well to one method of treatment while another doesn't. The different methods give us more options in managing your child's myopia.

​Soft contact lenses for myopia control are also available — these do not correct astigmatism as well as OK lenses and their studied effectiveness is generally slightly less — but are still an excellent options for many kids. Children with more aggressive progression may benefit from combined treatment with both contact lenses and atropine eye drops — recent published studies have shown synergistic myopic control effect when Ortho-K treatment is combined with atropine therapy.

Can I wear orthokeratology lenses if I have dry eyes?

As part of our detailed assessment of your suitability for OK lenses we will assess your eyes for dry eyes. Yes, most people can wear OK lenses even if they have dry eyes. In fact, hard lenses can be more suitable than soft lenses for people with dry eyes as soft lenses draw moisture from the eyes. Many dry eye symptoms are also caused by the environment — air conditioning and looking at a computer screen — which won't be an issue during sleep with the eyes closed. Many of our adult Ortho-K patients switch from regular contact lenses to Ortho-K because of their dry eyes with day-time contacts.

How quickly can I expect my vision to improve with orthokeratology lenses?

You will notice an improvement in your vision after the first night of OK lens wear, and further improvement and stability over the first 1-2 weeks as your eye shape settles with treatment. As part of our Orthokeratology Fitting Package we provide you with a pair of glasses or soft contact lenses at half strength to give you good functional daytime vision during the initial adaptation period. With lower prescriptions, excellent vision can usually be achieved within a week. 

Are orthokeratology lenses comfortable to wear?

During the first few nights as your eyes are becoming accustomed to the lenses, you may feel a slight sensation after lens insertion and before going to sleep. A bit like the feeling of an eyelash in your eye. That is normal and nothing to worry about. Most of the sensation comes from your eyelid moving over the lens as you blink. When you go to bed and close your eyes you won't feel anything and the lenses won't affect your sleep. After one week you will find that the lenses are quite comfortable to wear.

Can I see while wearing orthokeratology lenses?

Yes, you can see while you are wearing your lenses. We recommend that you insert your OK lenses about 10 minutes prior to bedtime to allow them to settle in your eyes. You can watch TV with the lenses in, and if you woke up the middle of the night to go the bathroom you can still see.

How long do I have to wear my orthokeratology lenses while sleeping?

The recommended wearing time each night is at least 6 hours, and optimally 8 hours, for maximum vision correction and best results.

Will my vision gets blurry at the end of the day?

Depending on your pre-treatment prescription there may be a little fade in your vision towards the end of a long day, but for most people it's not a problem. During the design of your lenses we factor in a slight amount of expected daytime regression to ensure that good vision is maintained for most of your waking hours. For lower prescriptions you should enjoy clear vision lasting one full day after lens wear, and sometimes longer.

What if I forget to put on my orthokeratology lenses for one night?

Once the Ortho-K treatment effect has stabilised, you may not have to wear your lenses every single night, depending on your level of correction and your vision needs. Many of our patients can skip a night of wear occasionally and still maintain satisfactory vision the next day. For example, kids who go on school camp for a few days can see quite clearly without bringing their Ortho-K lenses with them to camp. They simply resume OK lens wear when they return home to restore full treatment effect.

How often do I have to replace my orthokeratology lenses?

Yearly replacement of lenses is our recommendation, for best vision results, comfort and safety. Microscopic deposits, minute lens surface scratches and lens shape changes can occur with normal use, gradually reducing the effectiveness of treatment over time.

For how long can I continue with orthokeratology treatment?

You can continue with Ortho-K treatment for as long as you wish. For children using Ortho-K for myopia control, they generally wear OK lenses until their myopia has stabilised, usually in their late teens or early adulthood, however many may choose to continue using OK lenses for their vision correction instead of regular glasses and contact lenses. There are individuals who have happily and successfully worn Ortho-K lenses for over 20 years.

Will I be able to have lasik surgery later on if I wear orthokeratology lenses?

Of course. Ortho-K vision treatment is temporary and completely reversible. Your eyes will naturally return to their original shape if you stopped OK lens wear for a few weeks and there are no implications for laser surgery should you decide to have permanent vision correction later on. For children, keeping their prescription lower with Ortho-K when they are young also gives them with more options in regards to permanent laser vision correction later on as an adult, if they wish to do so.

Why is orthokeratology not common in Singapore?

Orthokeratology is a well-known form of vision correction in Asia, Europe and North America. Adults and children have been successfully treated with OK lenses for many years in countries such as China, Hong Kong and Australia — the main reason being these Asian countries have long had a much higher prevalence of myopia (short-sightedness) than the rest of the world, with greater public awareness of the importance of myopia preventation and myopia control. With the rise of myopia around the world, including in Singapore, there is an increasing interest in Ortho-K here from parents concerned about their children's worsening eyesight and wanting to do more to help them maintain good vision and eye health.

Why don't all Optometrists fit orthokeratology lenses?

Ortho-K fitting requires specialist training and technology. Not all optometrists are equipped with the necessary skills and equipment to fit OK lenses properly. As all OK lenses are custom-designed individually for each eye, this takes additional time, expertise and experience. In addition, successful orthokeratology requires close aftercare monitoring and follow-up visits ideally with the same practitioner for continuity of care and best results — this is often not possible in a retail chain store environment. Ortho-K lenses are best fitted by a practitioner with an interest in specialty contact lenses.

If you have any other questions about Ortho-K, please call us at

(+65) 9383 8569 or send us an email.

​We are more than happy to provide further information to help you decide if Orthokeratology is the right option for you or your child.

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