Orthokeratology is non-surgical treatment for temporary refractive error correction in which there will be using of special designed rigid contact lens called reverse geometry lens to reshape the corneal surface and make it flatter.
It is used to correct myopia and astigmatism. By making the cornea flatter, the eye will become less myopic.
This lens has three parts. The central part which is called the base curve which should be made flatter than the corneal curvature.
The second part which is steeper than the base curve and is called reverse curve. This part will prevent the lens from decentering or moving with each blinking.
The third part which is the peripheral one and it is flatter than the other two parts and it is called alignment part which will help in centration of the lens on cornea. This special lens design will allow the lens to stay in place and maintain centration.
To monitor the progress of the treatment and to change the parameters of this contact lens, the doctor will use corneal topography.
In Overnight Ortho-keratology, the patient will use rigid lens with high oxygen permeability and he can wear them during sleeping.
This overnight type is more convenient to the patient, because there will be no need to wear them during the day. He can use them before bedtime and remove them in the morning so he will have optimal results during all waking hours.
When the lens wear is discontinued, the refraction will move toward the baseline at a rate of 0.50 to 0.75 per hour.
Those patients should be monitored carefully for contact lens complications.
This type of procedure is also appropriate for children and teenagers because it is not necessary for the refractive error to be stable and in children, it was seen to be safe and effective as young as 8 years of age.
This type of procedure can correct:
1- Myopia from 1 to 6.
2- Astigmatism up to 1.5.