ORTHO-K (short for Orthokeratology) is a non surgical procedure using specially designed contact lenses to gently reshape the curvature of eyes to improve vision.
WHAT IS ORTHO-K?
Orthokeratology (ortho-k) is the process of corneal reshaping by utilising specialty contact lenses which temporarily reshape anterior cornea to reduce refractive error. However, post lens removal the cornea again regains its shape thus making this process reversible. Orthokeratology treatment uses rigid contact lenses to change the curvature of the cornea, resulting in a movement in refractive error towards plano.
Ortho-k lenses are generally worn overnight to reshape the front surface of the cornea while the patient is asleep,then the improved vision stays throughout the day and the patient can easily continue their daily activities without the lenses worn. However, the vision improvement from ortho-k lenses is reversible but can be maintained if used regularly as directed by the Optometrist.
HOW ORTHO-K WORKS?
In order to reduce the refractive power of the eye,Orthokeratology lenses flatten the anterior cornea. creates a flattening of the cornea. The ortho-k lenses presses the central cornea resulting of a mid-peripheral thickening and a central thinning. Even 15 minutes of lens wear can cause structural changes to the cornea.
The speed of ortho-k lens effect and recovery after removal of the lenses varies from patient to patient and is also dependent on corneal resistance.
Currently, orthokeratology lenses are designed to have an effective 10-12 hours of functional vision. Generally, the cornea returns to its original shape within three days, although some trace of residual corneal flattening can extend beyond two weeks of discontinuing the lens wear.
USE OF ORTHO-K IN MYOPIA CONTROL
Myopia onset can be found in newborns,but the majority is seen in school-age children particularly the pre-teens. Studies show that the younger the myopia develops,the faster it progresses. It has been observed that older children and teens show myopic progression. However, the rate of progression slows after 12 to 13 years of age. There is no minimum age for starting Ortho-K.
Ortho-K lenses provide good unaided visual acuity when prescribed for myopia. As refractive error is corrected with Ortho-K, the demonstrated myopia control effect has been a beneficial side effect. Ortho-K lenses has a significant effect in slowing myopic progression, but the results vary with individuals. Some Ortho-K patients show little or no myopic progression, while some do continue to progress.
ORTHO-K LENSES Vs LASIK
LASIK surgery works on a similar but permanent principle to orthokeratology to correct for myopia by flattening the central cornea and steepening the peripheral cornea.
However, unlike orthokeratology, myopia progression becomes common with LASIK if performed on a child who has an unstable myopic refraction.
Consequently, LASIK is generally recommended for patients over the age of 18 years, and the myopic refraction should be stable for at least 12 months.
Orthokeratology is a safe and effective method of myopia control in children.
Ortho-K is a specialized process requiring professional care hence practitioners need to seek special training, certification, and practical experience.
Ortho-K lenses require careful, regular follow-up is critical to ensure ongoing corneal health and maintenance of clean lenses. Lens care and cleaning is not difficult, but compliance with prescribed lens care products and routines is critical to maintain a clear cornea and to minimize the potential for complications.
REFERENCES
1. Lipson, M. J., Brooks, M. M., & Koffler, B. H. (2018). The role of orthokeratology in myopia control: a review. Eye & contact lens, 44(4), 224-230.
2. van der Worp, E., & Ruston, D. (2006). Orthokeratology: an update. Optometry in Practice, 7(2), 47.
3. Vincent, S. J., Cho, P., Chan, K. Y., Fadel, D., Ghorbani-Mojarrad, N., González-Méijome, J. M., ... & Jones, L. (2021). BCLA CLEAR-Orthokeratology. Contact Lens and Anterior Eye, 44(2), 240-269.
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