Orthokeratology- Corneal reshaping
Orthokeratology (Ortho-K) is the use of contact lenses to remould the shape of the cornea to reduce or correct myopia(short-sightedness), hyperopia (long-sightedness) and astigmatism (irregular surface of the cornea).
Ortho-K lenses are prescribed to obtain the ideal corneal shape or maximum change for that particular patient.
The main purpose of Ortho-K is to enable wearers to be free of both contact lenses and spectacles for the majority of or possibly all of the waking hours. This is ideal for sports people, swimmers or those who work in dusty or dirty environments and patients who suffer from dry eyes, while for others it is simply the appeal of being free of visual aids during the day.
Many studies on myopia agree that extensive close work may play a significant role in the progression of short-sightedness. Some studies have stated that 85% of myopia develops from close work. Clinical reports abound of youngsters who have had increasing myopia that is slowed once they are fitted with Ortho-k contact lenses.
Specific myopia control designs now appear to slow myopia progression as long as the patient practices good visual hygiene.
First there is an initial assessment appointment. This gives the optometrist a chance to both assess the general condition and health of the eyes and also to discuss the likely effectiveness of the procedure in an individual’s case. Most of the visual changes occur rapidly in the first few days and weeks requiring frequent examinations. Stabilisation procedures then follow at a slower pace over the next few months. The program length varies between three and six months, depending upon the degree of visual error and the rates of change.
After maximum results are achieved, Ortho-K lenses are worn to stabilise the new corneal shape. These are typically worn full time initially and can be reduced to several nights wear, but this varies from patient to patient. Failure to wear the Ortho-K lens on an ongoing basis will result in the return to the pre-existing prescription. Ortho-K patients are reviewed on a six-monthly basis.
Myopia Control (short-sightedness)
In general those optometrists who practise orthokeratology believe that Ortho-K lenses can slow the progression of myopia, however there has been no authoritative scientific study that proves this.
The results of a pilot study suggested a potential slowing of myopia progression, finding an average reduction of 50%. The authors added that there was no way to predict the effect for individuals. Due to the limitations of this study these results are not definitive.