Night Lenses - Ortho-K Lenses

Also known as Ortho-K, orthokeratology was initially designed to reshape the cornea during sleep to non-permanently correct low to moderate levels of myopia during the waking hours. Simply put, 'ortho' means 'straightening' and 'keratology' refers to the cornea, so 'ortho-k' is a way to straighten the cornea to temporarily correct myopia and reduce the risk of progression. Essentially, whilst asleep, a specially shaped contact lens is used to mould the central cornea into a less steep/flatter shape, thus moving the eye's focal point back towards the retina, making vision clearer and sharper on waking after removing the lens. Every evening, the lens is put back in the eye after being cleaned during the day. Ortho-K can give many children freedom from glasses or contact lenses during the day. 

 

Now, with some newer lens designs, not only is Ortho-K more effective at correcting myopia, including higher prescriptions than previously thought possible but it has also been shown to be a highly effective way of slowing eyeball growth in progressive myopia.  

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Ultimately, vision must be corrected to the highest level possible whilst at the same time, controlling the mechanisms that seem to cause the axial length of the eye to grow. 

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In modern Ortho-K lenses for myopia management, central light is brought into focus on the retina. Peripheral light is, however, brought into focus in front of the retina. This is also known as peripheral myopic defocus, or sometimes as a peripheral myopic image shell. This phenomenon is illustrated in the diagrams below.