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EYE CARE INFO & UPDATES
If you or your child is wearing Ortho-K sleep contacts and they aren't working as well as expected, perhaps we can help.
Fitting Ortho-K lenses is much more complex than regular contact lenses and requires a high level of professional skill, expertise and technology to get right. At this practice I have seen some patients with Ortho-K lenses fitted by other practitioners who may not have the best equipment or knowledge, resulting in sub-optimal vision and unhappy experiences.
Below is an example of a 9 year old girl (-4.00 short-sighted) who was fitted with Ortho-K lenses by another Melbourne practice. She had never been satisfied with her vision from her lenses, experiences a large drop in vision from morning to evening, and despite her previous optometrist trying 4 different sets of lenses from 3 lens manufacturers she was unable to achieve 20/20 vision, hindering her vision at school. So her mum decided to seek a second opinion.
At her first visit to this practice I measured her eye surface topography and it was quite obvious that her Ortho-K lenses were not fitting her eyes properly, hence the poor visual outcome and short treatment holding time during the day. Her treated vision was 20/40, that's 3 lines worse than 20/20 vision on the letter chart. Her lenses were unstable and de-centred on her eyes (especially the left eye) as she slept with her lenses on at night.
Lens centration and treatment zone centration are key to achieving good results with Ortho-K. A well-centred Ortho-K lens places even pressure and forces across the eye surface for optimum moulding effect — essential for good vision and myopia control.
I asked her to discontinue her lens wear for one week, by which time her cornea (the front surface of the eye) had completely reversed to its normal, non-treated shape. I then designed a new set of Ortho-K lenses for her using our advanced corneal topography technology and lens design software. This more sophisticated lens design approach allows me to create fully-customised lenses to suit all individual eye shapes and prescriptions. Having full control of every parameter of the lens shape, curvature and size means better fitting lenses and vision outcomes than older, trial lens-based Ortho-K fitting systems that some optometrists use.
Within 2 weeks the new Ortho-K lenses were presented to her. At her first review, after one night of wear, she was already seeing better than her previous troublesome lenses, and one week later (when the above right-side topography maps were taken) she was achieving 20/20 vision and much happier with her vision at school. It is expected that the quality of her vision will improve further still as she wears her Ortho-K lenses into her second and third weeks and the corneal moulding and treatment zone areas stabilise.
So a very happy patient and mum and well worth the visit to see us!
Dr Philip Cheng — Melbourne Optometrist & Orthokeratologist
Member of the Orthokeratology Society of Oceania (OSO)
This follows from my last eye blog, Ortho-K: How Does It Work?
How long does Ortho-K take to correct vision?
The length of time it takes for Ortho-K overnight lenses to fully correct your vision will depend on your pre-treatment prescription and your individual eye shape. Other factors include quality and length of sleep each night (7-8 hours is ideal), consistency in wearing the lenses regularly, rigidity of the eye surface layers, the cornea, that can vary from person to person, lens design parameters, pupil size, presence of and amount of astigmatism to be corrected and the curvature of the eye surface.
In my practice, all our Ortho-K patients have enjoyed significant improvement in their vision even after just one night of lens wear. Typically a patient with a medium level of short-sightedness, say -3.00 dioptres of myopia, will have over half of this prescription (around -2.00D) corrected already at their first review, in the morning following their first overnight wear of the lenses. By the end of week 1, he or she will have about 85% (around -2.50D) of their prescription corrected, and this further improves in the 2nd week to achieve 6/6 or 20/20 vision.
Some patients experience faster vision correction progress, and some slower — this is normal as each individual's eyes are different. Some optometrists or websites may claim to be able to achieve 20/20 vision after one night of Ortho-K — while this may be possible in some cases with a simple prescription, I prefer my patients to have a realistic expectation of their treatment progress and outcome.
As part of our Ortho-K Package for first time wearers we can provide, where needed, a spare pair of glasses made with a mild correction to help you see clearly during your first few weeks of Ortho-K treatment. This pair of glasses is also helpful for those who wish to wear their Ortho-K lenses every 2nd or 3rd night, instead of every night. As the treatment effect begins to wear off the glasses help to support their vision until they resume Ortho-K lens wear. Ortho-K vision correction is flexible, not everyone will need to wear their lenses nightly, depending on their personal vision needs and the holding time of their Ortho-K treatment.
Individuals with astigmatism (uneven eye surface curvatures) tend to take a little longer to reach optimum vision. This is because the corneal reshaping involved in an eye with astigmatism is more complex. Astigmatism is corrected using customised dual-axis Ortho-K lenses. Some patients have astigmatism in one eye and not in the other, and these patients often will have faster vision correction in the eye without astigmatism, and with about 1 week difference between the two eyes in reaching the optimum vision outcome.
Higher levels of short-sightedness (high myopia of over -6.00D) will also take longer for good visual outcome to occur, as greater amounts of eye surface flattening is required. Typically around 3 weeks for full or close-to-full correction is my advice to patients with high myopia considering Ortho-K lenses. During this initial period when treatment effect is gradually building we supply temporary soft contact lenses in steps of decreasing power to support the individual's daytime vision. With higher prescriptions it is normal for an individual to experience some ghosting and halos around lights, particular in dim conditions and at night. This usually improves with time as the Ortho-K treatment effect increases across a wider area on the eye surface.
With very high prescriptions (eg. -8.00D short-sighted) it may not be possible to fully correct vision to 20/20 due to lens and biological limitations, in which case the individual may be left with a residual amount of short-sightedness (eg. -1.00D after a correction of -7.00D with Ortho-K for a -8.00D individual). This is termed 'partial correction'. Many patients with very high prescriptions are happy with a partial correction as it already significantly reduces their dependency on glasses, and if they do need to see clearer they can wear a light prescription pair of glasses during the daytime, rather than their usual thick and heavy glasses.
In summary, these are the typical timeframes for Ortho-K lenses to effectively correct vision in most individuals:
Low level myopia (less than -2.00D) — 3-4 days.
Medium level myopia (-2.00 to -4.00D) — 1 week.
Moderate level myopia (-4.00 to -6.00D) — 1-2 weeks.
High level myopia (more than -6.00D) — 2-3 weeks.
EYECARE CONCEPTS — ORTHO K PRACTITIONER — MELBOURNE
Ortho-K, short for orthokeratology, is a relatively new concept to many Australians. Most people may not have heard of it before, or know what it does, or how it works. If you're reading this page you probably want to learn more about Ortho-K and how it might help you or your child see clearer. In the next few eye blogs I will go into detail to explain everything you need to know about Ortho-K overnight contact lenses, which I believe is the future of vision correction.
What is Ortho-K?
Ortho-K is a special type of vision correction technology that uses a breathable rigid contact lens to change the shape of your eyes as you sleep. Also called Sleep Lenses or Night Contacts, you put on the lenses just before you go to bed, and when you wake up in the morning you remove your lenses and enjoy clear vision for the rest of your day, without wearing glasses or daytime contact lenses.
How does it work?
Ortho-K sounds amazing because it really is. Our Ortho-K patients find it incredible to get their clear vision back without needing to wear glasses or contacts during the day. No more dry eyes or discomfort at work, and for kids no need for the parents to worry about them losing their glasses or contacts at school. The science behind this technology is a little complex, but here's a brief explanation of how it works.
For correction of short-sightedness (blurred vision in the far distance, also known as myopia), an Ortho-K lens flattens a central 5-6mm zone of your eye's front surface, the cornea. This surface flattening is similar to what happens with laser surgery (LASIK), only that Ortho-K is a temporary and reversible process and laser surgery is permanent. Flattening the cornea by a precisely calculated amount bends light to refocus it onto the surface of your retina, restoring your vision.
An Ortho-K lens a specially designed rigid contact lens made to precisely fit the shape of your eye's surface. Every lens is tailor-made for each eye's shape and prescription. At Eyecare Concepts we use the sophisticated Medmont E300 corneal topographer (pictured below) with 102,000 individual points to scan your eyes' unique surface contours to generate 3D topographical maps of its shape. We then use this topography data and advanced computer simulation software to design your lenses to fit your eyes perfectly. The information we can capture is so precise that we can design the fitting of your lenses with an accuracy level measured in microns (0.001 mm).
The image below shows how an Ortho-K lens works on the eye to correct vision. The lens, together with the eye's natural tear layer and eyelid in its closed state during sleep, places gentle hydraulic forces on the eye's surface, to gradually mould its shape by the precise pre-determined amounts required to give clear vision. You never feel any addition pressure on your eyes while wearing the lenses during sleep as the forces are very gentle. The centre of the lens does not actually directly touch the centre of the eye's surface but rather it vaults over the centre, and supported by a very thin film of tears, by approximately 20 microns (0.02 mm) — less than half the thickness of a strand of human hair. This is the kind of precision involved.
The shape of an Ortho-K lens is different from other kinds of contact lenses. It is also technically known as a 'reverse geometry lens'. There are multiple curves on the back of the lens surface that create different pressure zones and for helping the lens to centre correctly on your eye as you sleep. The fluro-green areas on the right-side image show the areas where the shape of the lens changes from the central 'treatment zone' to the peripheral 'alignment zone'. This lens is fitting perfectly on the eye with a well-centred and even treatment zone, important for good, clear vision. The green glow is from fluorescein dye placed on the eye during the lens evaluation process. Normally the lens is completely clear.
The left-side image is a 3D topography map of an eye following Ortho-K vision correction — showing flattening of the central zone of the eye surface (circular area in green), surrounded by a peripheral band (in red) of surface elevation changes which also helps to control short-sightedness progression in children and teenagers (myopia control) using Ortho-K lenses.
Below is an example of one of our patients successfully fitted with Ortho-K lenses. The upper-left image is her natural eye surface shape before Ortho-K lens treatment. She had a prescription of -3.00 short-sighted plus a mild amount of astigmatism. The lower-left image shows the post-treatment shape of her cornea after Ortho-K lens wear. The red ring represents the positioning of her lens during sleep, showing excellent lens centration. On the right image the centre blue zone is the vision correction zone and is the ideal treatment effect that we are looking for. Her -3.00 prescription and astigmatism was fully corrected with Ortho-K, giving her 20/20 vision in just 1 week.
EYECARE CONCEPTS — MELBOURNE ORTHO K PRACTITIONER
Philip Cheng - B.Optom (Melb) Ocular Therapeutics (GCOT). Optometrist at Eyecare Concepts Kew East, Melbourne. An experienced eye care & contact lens practitioner with expertise in myopia control & orthokeratology.