Orthokeratology lenses temporarily reshape the cornea to improve vision. Orthokeratology is also known as Night lenses, Ortho-K, OK, Overnight Vision Correction, Corneal Refractive Therapy (CRT), Accelerated Orthokeratology, Cornea Corrective Contacts, Eccentricity Zero Molding, and Gentle Vision Shaping System (GVSS).
Ortho K lenses are customized high-oxygen permeable rigid lenses. These lenses are worn overnight. They gently reshape the cornea so that you can see clearly during the day without glasses or contact lenses. This provides lifestyle benefits, especially for active children and adults, sports and other recreational activities.
The practitioner will measure and map the front surface of the cornea using an instrument called a corneal topographer. Depending upon the scan the lenses are tried and sent for customization. As these lenses are needed to be worn overnight, due to the lens design and pressure created by eyelids it flattens the centre portion of the cornea.
These lenses are removed in the morning. The cornea stays flat for a while and your vision is corrected without the glasses. Once you stop using the lenses at night, your cornea will return to its original shape along with your refractive error. For best results, you have to wear the lenses regularly.
Ortho-k lenses for myopia correction are designed peculiarly in that it creates a positive pressure on the centre of the cornea and negative pulling pressure on the midperiphery of the cornea. The cells are redistributed in a fashion that appears like a “volcano” pattern on the corneal topography. This reshaping of the cornea allows the light rays to fall accurately on the retina forming a clear image.
As per the theory, the light rays that enter through the peripheral cornea help in slowing down the myopia progression. Also, there will be a change in eye muscle postures which can also help in delaying myopia progression.
• Myopia correction
• To slow down the myopia progression.
• Someone who does not want to use spectacle and wants to be free from any type of correction in the daytime.
• Inflammations or infection of the eye or the cornea.
• Disease, injury or abnormality affecting the cornea, conjunctiva or eyelid, or impacting contact lens wear.
• Very dry eyes
• Low sensitivity in the cornea
• Eye-related allergies (including allergies to contact lens solutions)
• Residual power correction post LASIK.
Usually, it takes 2-3 weeks to achieve maximum vision correction, however, some people may experience significant vision improvement in just a few days. This happens because our cornea takes some time in molding and holds the shape as per the lens.
To get your desired prescription you need to undergo trials for a series of temporary ortho-k lenses. Once the perfect fit is achieved the person has to use the same shape of the lens each night to maintain the correction.
For the initial days after wearing the lens, you may feel the foreign body sensation but with time your eye gets adjusted to it and you will feel comfortable.
Research shows that Ortho-k is a safe treatment for visual correction and in delaying myopia. There may be a minimal risk of an eye infection which can happen with any kind of contact lens wear, but the risk is low. When the cleaning and maintenance are practised well the risk of such infections is further reduced.