OrthoKeratology, also called Accelerated OrthoK is a non-surgical method of reshaping the outermost layer of the cornea (the clear part at the front of the eye). By temporarily reshaping this layer of epithelium it is possible to allow clear vision without the aid of spectacles or contact lenses.
It is not an invasive procedure like PRK or LASIK/LASEK, – it requires no surgery, and it is non permanent. It would therefore be suitable for people who are too young to be considered for laser corrective surgery, those who do not yet have a stable refractive error and those who would like clear vision without correction, but are hesitant about having corrective surgery.
OrthoK works by reshaping the outermost layer of the cornea using special reverse geometry Rigid Gas Permeable (RGP) contact lenses. Normally an RGP lens is fitted to align with the corneal curves centrally, and because the cornea flattens towards the periphery, so do the lenses. Reverse geometry lenses are fitted flatter centrally and steepen towards the periphery to achieve a good fit. RGP lenses are less comfortable than soft contact lenses, especially initially, when they can feel a little bit gritty to start off, but tolerance to them usually increases fairly quickly, though comfort is not usually a major issue with OrthoK, as within a few days you would only be wearing the lenses when you are sleeping!
Most people are aware that they should not sleep in contact lenses, as it can increase the risk of painful and serious eye infections. There are a number of reasons why these lenses are safe to sleep in.
- You only wear them when asleep- this is much easier of the eye compared to a person who has worn the lenses all day and then sleeps in them. Many people wear lenses (often daily disposables) than do not allow enough air through to the eye when the lenses are worn, and therefore they should allow their eyes to breath before going to sleep. The lack of air during the day, and even less at night in these wearers is why they have an increased risk of infection.
- The RGP lenses used in OrthoK have a very high Dk/t – they have extremely high Oxygen transmission, much higher even than the Silicone Hydrogel soft contact lenses we would generally recommend to our daily wear clients!