What is Myopia?
Myopia, commonly referred to as short-sightedness or near-sightedness, is a refractive error that is increasing in prevalence. Here a person can't see distant objects clearly. Myopia is a very common problem that can be corrected and even managed.
Affecting 21.15% of school-going children (aged between 5-15 years) in urban India, myopia (short-sightedness) is a condition of concern as compared to hypermetropia (long-sightedness). In fact, WHO has estimated that by 2050, half of the world's population would be myopic, if not addressed appropriately.
Certain studies conducted post-pandemic have reported a sudden surge in the cases of myopia in children globally, due to home confinements which lead to increased screen time. Usually, the onset of myopia is in childhood when the eyeball lengthens excessively, resulting in blurry vision for far. Additionally, because children's eyes continue their axial elongation as they age, the minus number tends to keep increasing if no intervention is made. This can significantly affect a child's daily life and occasionally cause long-term eye health issues like retinal detachment.
Lenses for myopia control can correct and control myopia. Given that wearing glasses is probably easier, this is a good option for myopia management to begin with. Spectacle lenses with DIMS and H.A.L.T. technology go beyond conventional spectacle lenses to control myopia. Imagine DIMS (Defocus Incorporated Multiple Segments) and H.A.L.T. (Highly Aspherical Lenslet Target) technologies as myopia-correcting single-vision lenses with an additional "treatment zone" on top of the regular lenses.
Based on available studies, we describe, how they help in slowing myopia progression.
Following are the features of DIMS and H.A.L.T spectacle lenses (Figure 1):
Two-year randomised clinical research was conducted by Hong Kong Polytechnic on children aged 8 to 13 with myopia of -1.00 to -5.00D and no more than 1.50D astigmatism. They made half of the children wear DIMS design and the other half wear single vision (SV) lenses. After two years, the average increase of myopia in children in DIMS and SV, respectively, was -0.41D vs. -0.85D and 0.21mm vs. 0.55mm, indicating a 50–60% control effect. The paper reported that 21.5% of children who wore DIMS had no myopia progression over two years, compared to only 7% of those who wore SV lenses.
Thus they showed that these myopia-correcting lenses slow down myopic progression.
Atropine is used for controlling myopia progression for a few decades, however, there wasn’t a long-term study available as concrete evidence. But recently a study known as ATOM (Atropine in the Treatment of Myopia) had done a 2-year-long assessment of myopia progression where they had given a set of myopic children low-concentration atropine 0.01% and a set of myopic children nothing and found that children who were given 0.01% atropine had reduced rate of myopia progression as compared to the normal no intervention group. With the lockdown imposed during the COVID-19 pandemic, there was suddenly a surge in myopia and interestingly even 0.01% atropine was found to be less effective. Thus, atropine 0.05% was then compared with 0.01% atropine to compare the efficacy and also the side effects which showed that 0.05% atropine slows myopic progression with better efficacy with minimal side effects in the children. Thus, along with 0.01% atropine, gradually 0.05% atropine is also getting into clinical practice to reduce progression in children. It's important not to use regular atropine eye drops which are 1% in concentration.
Multifocal Contact Lenses: Multifocal soft contact lenses can correct myopia in youngsters while also halting the progression of myopia by delaying pathological eye growth. They are primarily used to improve near vision in persons over the age of 40. The soft multifocal contact lenses are shaped like a bullseye and have two basic light-focusing regions. For clear distance vision, the centre of the lens corrects near-sightedness and directs light onto the retina. To focus the stray light rays in front of the retina, more plus power is added to the lens' outer section. According to studies, focusing light in front of the retina signals the eye to restrict its growth. Peripheral light is focused farther in front of the retina with higher additional power or in other words a myopic defocus. Contrarily, regular contact lenses and single-vision glasses concentrate peripheral light at a location behind the retina, which causes the eye to continue developing. The researchers looked at whether high-add-power contact lenses slowed myopia development and eye growth more effectively than medium-add-power lenses. They discovered that the only contact lenses that significantly slowed eye growth were those with a high addition power.
Orthokeratology is the process of designing stiff gas-permeable contact lenses specifically to temporarily reduce or eliminate the refractive error by reshaping the corneal curvature. It is based on the idea of reverse geometry. OrthoK lenses press against the central corneal surface, reshaping the cornea. This flattens the cornea, i.e., the front part of the eye which decreases the eye's axial length and focusing power. According to research, corneal reshaping, the lenses create a plus-powered ring in the periphery because of increased cell count and thus creating the plus-powered defocus like soft multifocal contact lenses and DIMS spectacles. OrthoK lenses are supposed to be worn by the child at night before sleeping and get a good night’s sleep with the lenses on. Best results are found in patients having myopia up to -5.00 dioptres. For refractive errors beyond -5.00, a customized OrthoK lens has to be designed. A major concern as a parent is about infections, thus Prof. Mark Bullimore had done a study to investigate the risk of infection in children due to overnight OrthoK lens wear and found the risk to be less than 1%, provided the care and maintenance regime of the lenses are followed appropriately as prescribed.
Pro Tip - These myopia control spectacle lenses are usually not available at optical shops. Please speak to your eye care provider and confirm if they can fit these lenses for you.
At Eye Solutions, we practice all the above-mentioned myopia control techniques and have been doing so for the past few years. Some of the techniques are newer and are being used since their launch in India.