The Process of Orthokeratology Treatment

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The Process of Orthokeratology Treatment

The Process of Orthokeratology Treatment

Understanding the procedure..

Orthokeratology (OrthoK) is considered a relatively new concept to many Singaporeans. Most people may not have heard of it before, or know what it does, or how it works. You probably want to learn more about OrthoK if you are reading this page. In this blog, we will go into detail to explain everything you need to know about OrthoK contact lenses, which we believe is the future of vision correction.

What is OrthoK exactly?

OrthoK is a type of hard lens with special type of vision correction technology that uses breathable material to change the shape of your eyes as you sleep. It is also called “Sleep Lenses” or “Night Lenses”. You put on the lenses just before you head to bed and when you wake up, you will enjoy clear vision for the rest of your day after removing your lenses. There is no longer a need to rely on wearing glasses or daytime contact lenses.4 steps to orthok lens wear-1

How does it work?

OrthoK sounds too good to be true because it really is. Most of our OrthoK patients find it incredible to get their clear vision back without needing to wear glasses or daytime contact lenses during the day. The incidence of dry or discomfort eyes at work has reduced. For children, there is no need for parents to worry about them losing their glasses or contact lenses at school. The science and technology can be a little complex, but this is a brief explanation of how it works.

For correction of short-sightedness (blur vision in the far distance, known as myopia), OrthoK lens flattens the central 5-6mm zone of your cornea, the outermost surface of the eye. This surface flattening is similar to what happens during laser corrective surgery (LASIK). The only difference is that OrthoK is a temporary and reversible process and laser surgery is permanent. By flattening the cornea using a precise calculated formula, it bends light to refocus it onto the surface of your retina, restoring your vision.

A specially designed OrthoK contact lens is made to fit the shape of your cornea precisely. Every lens is tailor-made for each eye’s shape and prescription. We use the sophisticated equipment to scan your eyes’ unique surface and generate 3D topographical maps of its shape. An advanced computer simulation is then used with the topography data to design your lenses to fit your eyes precisely. The information we can capture is so precise that we can design the fitting of your lenses with an accuracy level measured in microns, 0.001mm.

Medmont E300 Corneal Topography to measure the front surface of the eye

We demonstrate to you on how an OrthoK lens works on the eye to correct vision. OrthoK works together with the eye’s natural tear layer and eyelid in a closed environment during sleep, this creates gentle hydraulic forces on the cornea surface to mould its shape gradually by the precise amounts required to give clear vision. You will not feel any addition pressure on your eyes while wearing the lenses during sleep as the forces are very gentle. OrthoK lens does not come in contact directly with the centre of the eye’s surface but rather, it vaults over the centre and supported by a thin layer of tear film, approximately 20 microns (0.02mm). This is less than half the thickness of a strand of human hair. This is the level of precision involved with OrthoK lens design.

OrthoK lens design is different from other kinds of contact lenses. Technically, it is known as “reverse geometry lens”. There are various curves in the back surface of the lens that create different pressure zones to centre the lens correctly on your eye while you sleep.
During our optometrists Singapore clinic's assessment of the OrthoK lens fitting, the lens will glow in green from fluorescein dye placed on the eye. The glowing green areas in the image show the areas where the shape of the lens changes from the central to the edge. This lens is fitting perfectly on the eye with a well-centred treatment zone, which is critical for good and clear vision. We will use the lens assessment to examine whether the result is aligned to the corneal topography scan.

OrthoK lens fitting assessment

The image below is an image we use frequently to assess the eye surface shape after fitted with OrthoK lenses. By using the topographical data “before” and “after” OrthoK lens wear, we can easily determine the treatment zone and positioning of the OrthoK lens during sleep. The red ring in the centre represents an excellent lens centration. The centre blue one is the vision correction zone and is the optimal treatment effect that we are targeting for. In this case, the prescription was -2.50 myopia with -0.75 astigmatism. This young patient was fully corrected with OrthoK lenses, giving her 6/6 vision in a week.

Pre-post Orthok treatment

Comparing the topographical data “before” and “after” OrthoK lens wear