Orthokeratology and Myopia Progression Control
Why is Myopia a new global concern?
Myopia is one of the most common visual impairments in the world. According to the results of National Health and Nutrition Examination Survey, the estimated myopic population between ages of 12 to 54 increased from 25 % to 41.6% from 1970 to 1972 compared to 1999 to 2004 in the United States.
In addition, students aged between 5 to 17 from the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study Group in the United States revealed that the prevalence of myopia is about 18.5 % in Asians, 13.2% in Hispanics, 6.6% in African Americans and 4.4% in Caucasians. Several studies also indicated that myopia showed a higher prevalence and severity in school aged girls than boys.
High myopia (Rx over -6.00 D) presented higher risks of retinal holes, retinal detachment, lattice degeneration (retinal thinning), and glaucoma. Hence, myopia has become one of the targeted priority areas by World Health Organization in the global initiative to correct avoidable blindness by the year 2020.
What causes myopic progression?
Genetics, environment, and optics error of the eye are contributing factors for myopic progression.
Myopic progression is due to axial elongation of the eyeball. As the eyeball gets longer, the amount of nearsightness increases (i.e. the nearsightness prescription increases and lenses from eyeglasses become thicker)
Traditionally, spectacle and monofocal contacts lenses (non-bifocal/non-multifocal) are used to correct myopia; however, they do not help slow down the progression of myopia.
Research has shown that peripheral hyperopic defocus caused by regular spectacle lenses and monofocal (single vision) lenses is a contributing factor for elongation of the eyeball. Peripheral hyperopic defocus is defined as the images formed behind the peripheral retina from the light rays refracted from the edges of the spectacle lens or contact lenses.
How does Orthokeratology slow down myopic progression?
Extensive research have shown that Orthokeratology as an option in slowing down the progression of myopia. Orthokeratology helps reshape the cornea and allows optical changes in peripheral retina. These changes will bring the images (behind the retina from peripheral hyperopic defocus) forward and slow down the axial length elongation; hence, control near-sightedness progression.
What is Orthokeratology?
Orthokeratology (Ortho-K) is also known as corneal reshaping therapy (CRT). It is a reversible and non-surgical procedure to change the refractive errors on the human cornea. It is a safe and great alternative to laser eye surgery.
Orthokeratology utilizes a specialized gas permeable rigid lens to mold the cornea overnight. Ortho-K patients will insert the specialized molding lenses in their eyes before bedtime. The molding effect occurs overnight during sleep when the eyes are closed. The patient will be able to see clearly after molding lenses are removed upon waking. This corneal molding procedure may take 2-6 weeks to complete depending on the patient’s prescription, shape of the cornea, corneal rigidity and compliance from the patient.
A successful Orthokeratology results in:
- Clear vision
- Free of using eyeglasses or contact lenses during waking hours
- Slows down the progression of myopia
In addition, Ortho-K has been FDA approved as a safe procedure to correct vision overnight with special molding lenses since 2002 for all ages.
The effectiveness of myopia control using Traditional OK lens cited from studies is about 50%. Customized Ortho-K lenses show higher efficacy between 50% to 75%.
70% of patients who have used both soft contact lenses and Ortho-K lenses prefer Ortho-K.
What are the Pros and Cons of Orthokeratology?
The cost of Orthokeratology is about half of LASIK. Should patients decide to stop Orthokeratology, the molded cornea will return to its original shape after a period of time and the refractive prescription will return to its pretreatment prescription after a few weeks.
The prescription changes and myopic reduction are not permanent. Patients must use the molding lenses daily prior to bedtime to maintain the cornea reshaping. Furthermore, Orthokeratology is an ongoing treatment which requires close monitoring on the health and the fit of the molding lenses on cornea.