Ortho-k refers to custom-made rigid contact lenses worn overnight to gradually reshape the cornea (the transparent dome in front of the eye) so that glasses or contact lenses are no longer required during the day. In addition to correcting vision and delaying myopia progression, ortho-k offers lifestyle benefits, especially for active individuals and sports and recreational activities.
How do ortho-k lenses function?
In numerous respects, the eye functions like a camera. Instead of focusing light onto a computer processor or film, light is instead focused onto the retina.
The cornea at the front of the eye is the primary focusing lens; it has a fixed focus intensity and contributes a portion of the eye’s focus power.
The lens inside the eye compensates for the difference and is flexible enough to adapt to different distances; the lens inside your eye adapts to maintain objects in focus as they are brought closer.
Ortho-k lenses correct myopia by delicately and temporarily flattening the cornea by an amount proportional to the degree of myopia to be corrected, with greater degrees of myopia requiring greater corneal flattening.
Flattening the cornea will reduce the cornea’s focussing power. Since the eye causes myopia’s focusing power to be too strong, this neutralises the myopia and refocuses objects on the retina.
Ortho-k lenses are worn overnight, when the flattening effect occurs, and removed during the day, with the temporarily corrected myopia and clear vision resulting from the flattened corneal profile.
Is ortho-k irreversible?
The corneal flattening caused by ortho-k is not permanent, and most of its effects will diminish within the first few days after lens removal. This is because ortho-k primarily affects the cornea’s anterior surface. This front surface layer is gradually compressed in some areas and expanded in others to conform to the ortho-k lens profile. When contact lens wear is discontinued, the cornea progressively returns to its pre-ortho-k state.
Are ortho-k lenses painful?
It is understandable to believe that altering the contour of the eye will be painful, given the eye’s sensitivity. However, this is generally not the case.
Ortho-k lenses are either custom-made for each eye or very closely matched to the eye’s contours. This close alignment eliminates the majority of discomfort that could otherwise occur; however, for those new to ortho-k, there is still an initial sensation similar to having grit in the eye. This is merely due to the feeling of the upper eyelid and the emphasis of the lens on the eye.
Typically, the eye will produce tears in an attempt to remove the ortho-k lens because it perceives it as dust. Typically, after a brief period of time, this settles down until the lenses are so comfortable that they cannot be felt in the eye at all.
Is ortho-k safe?
Because of their placement on the eye, all contact lenses can increase your risk of infection. Ortho-k lenses pose an additional risk when worn during sleep with closed eyes, although they are safer than flexible contact lenses for sleeping. Blinking is a natural cleansing and defence mechanism for the eyes, and the inability to blink during sleep diminishes the effectiveness of this mechanism.
The good news is that the risk of infection can be significantly reduced if proper cleansing procedures are followed and the lenses and their cases are kept away from tap water. This final point is so crucial that it bears repeating: tap water should never come into contact with contact lenses, including ortho-k lenses, or any contact lens-related devices, such as cases or lens application receptacles.