Today it’s possible to tailor any products to peoples’ specific needs, and contact lenses are not being overlooked. During the 2021 SOA-AOC e-Symposium Dr. Ngoc Hoang demonstrated a special orthokeratology lens (or Ortho-K) and shared results of recent studies regarding its effectiveness.
With a PhD in biotechnology from the Tokyo Institute of Technology, Dr. Hoang is currently involved in the Clinical Affairs Department at Japanese vision company SEED, where she helps facilitate clinical trials of their lenses in Japan and abroad. She has brought experience in evaluating several types of contact lenses from SEED and other manufacturers.
Let’s have a glance at how SEED’s overnight corneal shaping lens is particularly suitable for East Asian eyes, in particular.
The Rise of Myopia in Asia
Dr. Hoang reports that in 2010 about 25% of the global population had a form of myopia. With numbers increasing by 5% each decade, by 2050 half of the world is expected to be near-sighted.
Yet in Asia, the numbers are more extreme, with studies showing East Asians being more susceptible to the epidemic. In Singapore, the prevalence of myopia is among the highest in the world, with 65% of children being myopic by 6-years-old; and by 2050 it’s predicted that 80-90% of all Singaporean adults will have some form of the disease.
More alarmingly, the COVID-19 pandemic appears to have had an effect on myopia development, most notably in young children who have been forced to have more screen time per day and who are no longer spending time outside walking to and from school. Citing a 2019-2020 study from China, the biotechnology expert explained that due to children staying home for school, the rate of refractive error of children aged 6,7 and 8-years-old was significantly worse and the number of myopic children increased 3x, 2x and 1.4x respectively.
“The reason why myopia is a major public health concern,” Dr. Hoang warns, “is because myopia is not just a refractive error … there are some side threatening complications such as cataract, retinal detachment and myopic maculopathy.”
Fortunately, the use of Ortho-K lenses prevents myopia and can help prevent its associated health risks by reshaping the cornea; it’s particularly effective for children who do not yet have high myopia.
Orthokeratology lenses aren’t brand new. Still, their use hasn’t really permeated society: “There’s evidence that Ortho-K prescription is increasing in several countries but the percentage is still relatively low,” Dr. Hoang reported. “Countries like Taiwan, China, Malaysia and Japan have maybe 2-3%.”
At the same time, more and more Japanese clinics are prescribing Ortho-K, with the number more than doubling between 2013 and 2019. About 75% of the patients are children under 18-years-old. Citing a SEED study with clinician respondents, providers believe Ortho-K has a good myopia control effect, and about 27% of respondents say they began to offer such lenses because patients came in asking for them.
With the goal to provide an ideal option for those considering a nighttime lens, SEED has taken into account that Asian eyes are shallower and flatter than Caucasian eyes, which might affect lens fit.
“The normal lens was designed originally for Caucasian eyes,” Dr. Hoang explained. “There is a need for an Ortho-K specifically designed for Asians … a shallower lens with a wider treatment zone which may bring more clarity for the Asian patient.”
Dry eye is a common symptom of wearing contact lenses, and studies have shown that Asians may have more susceptibility.1
The SEED Ortho-K lens design presented by Dr. Hoang boasts a new material make up that gives it oxygen permeability that is “significantly higher than other Ortho-K lenses available on the market.”
Without enough oxygen, our eyes struggle to produce natural tears. What’s more, low oxygen leads to hypoxia which leads to corneal edema. These are frustrating experiences that could lead a patient to give up on Ortho-K treatment.
“Our material has silicone embedded in strong methyl methacrylate (MMA) molecules, so it maximizes the oxygen transmission while keeping the material high durability,” elaborated the expert.
Citing a 1984 study2, she elaborated that minimum Dk/t (ionicity and oxygen transmission) to ensure sufficient oxygen to prevent corneal edema is 75, and confidently announced that only SEED’s lens satisfies this criterion.
The composition of the lens also makes it more durable: While it’s likely none of us have or are planning to ever purposely smash something heavy on top of our contact lenses, such a test that was carried out on multiple lenses revealed that SEED’s Ortho-K variant was broken with a ball dropped from 150 cm while other lenses were destroyed from only 20-30 cm.
“This flexibility gives you confidence while washing and handling the lens; also, it provides the safety of lens wear. I have heard of other Ortho-K lenses breaking inside of patients’ eyes while they were sleeping; this never happens to our lens. When the lens is broken they have to wait 2-3 weeks while the lens arrives, so their vision gradually goes down and when the new lens comes it goes up again. This affects the quality of life of your patient during that period.”
Keeping Near-Sightedness Far Away
Studies carried out by SEED demonstrate that wearing orthokeratology lenses results in a good improvement of refractive error, stable flattening of the cornea, and low to zero occurrence of incidents. At the 12th week of lens wear, 90% of patients have excellent visual acuity of more than a 1 decimal increase.
“Our Ortho-K lens provides several benefits to patients and practitioners because it is highly suitable for Asian eyes, with high Dk and high Dk/t, providing sufficient oxygen to the cornea. [The lens] is also highly flexible and durable, ensuring [it] won’t break easily,” Dr. Hoang summarized.
These orthokeratology lenses have proven their ability to stave off myopia and improve visual acuity to near-perfect in most patients, making them an “eye-deal” option for near-sighted Asians.
- Craig J, Wang M. Factors predisposing the Asian eye to dry eye disease. Invest Ophthalmol Vis Sci. 2019;60:2746.
- O’Neal MR, Polse KA, Sarver MD. Corneal response to rigid and hydrogel lenses during eye closure. Invest Ophthalmol Vis Sci. 1984;25(7):837-42.