Orthokeratology (also referred to as Ortho-K, Overnight Vision Correction and Corneal Refractive Therapy) is the use of rigid gas-permeable contact lenses, usually worn only at night, to enhance and improve vision by the reshaping of the cornea. This method can be used as another way to improve vision instead of wearing glasses, having refractive surgery, or for people who would rather not wear contact lenses in the daytime. The latter may be because of discomfort from working in air-conditioned or dusty environments, from using a computer all the time which reduces blink rates and tear film production or from displacement or loss because of playing sport.
Lenses are generally known to be not as comfortable as soft contacts and can feel almost like an eyelash getting trapped in the wearer's eye, especially when wearing them for the first time and while the eye is open or isblinking. This is because the shape requirements of the lens and edge design which have to serve more purposes than a traditional lens. Overall, the feeling is reduced as the body adjusts to the lens, however it may never become as comfortable as traditional soft or RGP contact lenses which are made to be used for active vision correction.
Tissue growth and propagation studies suggest that epithelial cells changes growth in response to the presence of foreign material. CRT lens proximity to the cells is then thought to rouse cell growth where less proximity coincides with additional growth and more proximity accords with growth repression which then creates a ‘proximal pressure’ on the epithelial cells.
There is a general consensus that overnight Ortho-K is well acceptedsince the main feeling is due the eyelids moving over the lens edges. When the eyes stay closed for sleeping, there is generally no residual feeling of the lens after the period of adjustment.
During the first month of lens wear when the treatment zone on the surface of the cornea is in the process of becoming fully formed, some users may have vision issues such as ghosting, starbursting, contrast problems and double vision, at night in particular. These problems are generally solved by the end of the first month of wearing the lenses. If these issues persist beyond this initial period, the cause may be from a lack of centration of the lens on the eye and/or overly large pupil size (in light or dark). It’s possible to resolve this issue through redesign, material changes and/or better eye moisture retention (night-eye masks, duct blocking etc. ) or other techniques. All issues should be immediately discussed with a professional eye doctor.
Leading Manly optometrist , Max Humphreys at icontact, not only specialises in Ortho-K. At icontact we also provide excellent eye care and eyewear depending on your needs and wants. Please check our services and products page for further information.