I remember being only 9 years old when I was first diagnosed with myopia - my eyeballs were too elongated. The cornea and lens of my eye were hence too convex in proportion to the longer length of my eyeball, and hence could not refract the parallel light rays from distant objects onto the fovea of my retina. Therefore, images of distant objects that were formed on my retina and processed by my brain were blurry.
a diagram of the human eye
a diagram of the myopic eye
In essence, I was short-sighted. I’m not alone in this struggle, especially in the country I live in. The prevalence of myopia in Singapore is amongst the highest in the world, with 65 percent of children being myopic by 12 years old, and 83 percent of young adults being myopic. To make matters worse, myopia is a progressive condition that worsens with age in children, for whom the eyeballs elongate more quickly due to natural growth. Obviously, myopia causes inconvenience. But beyond that, eyeball elongation results in a thinner retina. This puts the eye at greater risk of developing a retina tear, hole or detachment. Retinal detachment requires urgent treatment to reattach the detached layer, as this may cause permanent loss of vision in the affected eye.
This brings me to the topic of orthokeratology. Orthokeratology, also known as ortho-k, is defined as a treatment for defects of vision by altering the shape of the cornea through the application of a series of differently shaped hard contact lenses - which is why it is commonly used to treat myopia. In modern orthokeratology practice, users usually wear their ortho-k lenses at night, waking up with a less convex or more convex cornea, to treat myopia and hyperopia respectively.
the process of modern ortho-k lenses
The understanding and applications of orthokeratology have progressed leaps and bounds in the 20th and 21st centuries. The first record of trying to reduce excessive corneal curvature (a cause of myopia) was the ancient Chinese use of sandbags on the eyes at night to flatten the cornea. A novel invention created by Dr. J. Bell in 1850 was an eye cup with a spring-mounted plunger to pound the cornea flat through the closed eye. Needless to say, these methods sound slightly ridiculous have little to no practicality in the modern world, and have nearly nothing in common with orthokeratology today.
In the medical world, the reshaping of the cornea started to gain more scientific interest in the post-war 20th century. George Jessen (co-founder of Wesley-Jessen Corporation) described a process he called “ortho focus” at a 1962 contact lens specialists conference in Chicago. This process was the closest to modern orthokeratology so far, with the use of the lens to reshape the cornea by putting pressure on it. The lens designs used at this time, and for many years to come, were standard spherical lenses worn during daytime hours.
In the 1970s and 80s, orthokeratology studies increased in popularity in the world of medicine, with ophthalmologists starting to experiment with the new process of corneal reshaping, conduct clinical studies and publish their findings. But none of the results yielded were close to today’s success rates. An example is a clinical trial in 1972 by May and Grant, in which 23 orthokeratology patients and 16 cosmetic hard contact lens patients were evaluated. For contact lens patients, there was no improvement in their vision after the attempt of corneal reshaping during the study. In the ortho-k patients, the study revealed that the quality of uncorrected vision after ortho-k was worse than with contacts or glasses and that the chances of attaining 20/20 vision with this process were low. Once the lenses are removed, the corneal parameters return to pre-fit levels.
Numerous studies continued and the science of orthokeratology advanced. Up until the 1990s, daytime wear of ortho-k lenses was recommended. Stuart Grant introduced the idea of these lenses being worn in the night, as the eyelid pressure from closed eyes would increase the effectiveness of corneal reshaping while slowing down myopic progression. Since the early 2000s, hundreds of studies have been carried out on the night-time wear of ortho-k lenses, indubiously contributing to the progress, current success and popularity of these lenses. Ortho-k studies have recently increased in Asia, these studies being large-scale and involving hundreds of participants. This is because Asia, including the aforementioned example of Singapore, has seen the highest need for myopia control due to a largely myopic young population.
These numerous clinical trials have transformed modern orthokeratology to become a sophisticated fitting process that includes highly permeable lens materials, spherical and toric designs, and serial mapping of the corneal surface to note the amount and location of changes made to the cornea. This has clearly proven effective - for children and adults with a successful ortho-k treatment of at least one year of duration, 88.7% and 95.9% of eyes had a predictable refractive outcome, and efficacy was 0.98 and 1.01, respectively.
Today, ortho-k lenses have become household names, with global soft contact lens companies adopting them and selling them to millions of users. Optometrists and ophthalmologists are taught the science behind these lenses and their applications in real life, in schools all around the world. It would be prudent for us to take note that the progress in the field of orthokeratology can be attributed to the key role played by many clinical trials conducted over the decades, as we examine the increased rate of success and popularity in ortho-k lenses through this article.
As someone with a strong interest in ophthalmology and orthokeratology, I hope that more clinical trials can be conducted to pave the way for even more advancements in this field of study. As myopia becomes increasingly prevalent in Asia and in the world, I believe that there is a need to assess the modern methods of orthokeratology and improve their efficiency even further. I am also of the opinion that this venture should be done in altruism, rather than for profit, as myopia is truly a condition that many young children face today.
Written By: Gayathri Anand
1 Norman, C. W., Skoner, J., Martin, M. J., & Panzer, A. (2023, September 8). The history of orthokeratology: How far have we come? . The Ortho-K Knowledge Bank.
2 Jessen GN. (2000) Orthofocus techniques . Contacto 1962;6:200–4.
3 Perry S. Binder MD, FACS, Charles H. May OD, Stuart C. Grant OD (1980, August). Orthokeratology-control of refractive errors through contact lenses . J Am Optom Assoc, 42 (1971), pp. 1277-1283.
4 Allen, J. J. (2021, April 7). Ortho K Contact Lenses Explained (what is Orthokeratology). YouTube.
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