Myopia refractive error is increasing in the population, especially in children in the digital age. Areas in Asian countries such as Singapore and China are places where the rate of refractive errors is increasing and accounts for a relatively large rate (80-90%). Myopia can cause visual impairment, more severe can lead to complications of other dangerous eye diseases such as retinal detachment, retinal degeneration, etc.
Facing this alarming situation, methods to control myopia have been researched and released. Myopia control is divided into two main branches: limiting the development of myopia or preventing the formation of myopia. There are different methods in each branch, and this article will introduce the main features of a few popular methods.
Limit the development of myopia
Correct myopia lower than actual degree
This is a fairly simple method used by many medical staff with the aim of slowing down the development of myopia by prescribing corrective lenses with a lower level of about 0.50 to 0.75D than real glasses. However, a lot of large studies on this method in recent years have shown that lower glasses correction does not bring any effect in limiting the development of myopia, maybe even myopia. increase faster.
Ortho Glasses – KY
This method controls myopia through the use of a hard contact lens with a special structure to flatten the central part of the cornea, thereby changing the focus of light rays when entering the eye and making temporary reduction of myopia (the cornea is the anterior and transparent part of the eyeball). Patients using this method will be assigned to wear these glasses at night before going to bed and remove them in the morning. The success rate of this method varies across different studies, with rates ranging from 30% to 65% depending on differences in study time and population sample. Average efficiency is about 41%
One of the limitations of this method is that there have not been many studies on the effects of glasses for a long time (over 5 years) as well as the consequences of increasing the level of myopia development after stopping treatment. (rebound effect). In addition, the use of Ortho-K glasses must also ensure the appropriate factors from the patient’s side such as corneal curvature, degree of myopia… The cost of this method is also relatively high.
Bifocal or multifocal glasses
Bifocal or multifocal lenses are also prescribed by experts for children with the aim of limiting the development of myopia. The principle of operation of these glasses is quite similar, which is to control myopia by limiting the effort of adjusting the eye when looking up close. Studies on bifocal lenses also show that the ability to control myopia is about 30-40%, and the type of bifocal lens used in most studies is Executive bifocal (Figure 2), with effective about 39% on average. For multifocal lenses, some studies show that the ability to control myopia of this method is not really effective (about 10% – 30%). The limitation of these methods is that the number of studies is quite small compared to other methods, so their effectiveness value is not really meaningful in clinical practice.
Peripheral Convergence Reduction Glass
A defocus lens is a type of lens specially formulated for the purpose of controlling nearsightedness. When we use conventional myopia glasses, the light rays at the periphery will focus behind the retina causing blurred images in the out-of-center areas, generating signals that stimulate the elongation of the eyeball axis. The retina is a layer at the back of the eyeball that captures light and transmits these signals to the brain for processing into the images we see. Lengthening the axis of the eyeball will cause an increase in myopia. For peripheral converging lenses, the peripheral retinal image blurring will be eliminated due to its special construction.
The effectiveness of this type of glass is still being studied further, the numbers range from 11% to 50% for different brands of glasses. The results in a few studies are still not enough to prove the real effectiveness of this method.
Contact lenses are also one of the methods of interest to experts in controlling myopia refractive error. There are two main types of contact lenses: hard contact lenses and soft contact lenses. Compared with the hard contact lens method (proven through studies on the ability to control myopia is quite low), the soft contact lenses with many areas of vision (2 lenses, multifocal, circumferential) have the following indicators: better numbers. The effectiveness of soft multifocal contact lenses can inhibit the development of myopia by about 46%, with an average value across different studies of 43%. Multi-aspect soft contact lenses come in a variety of designs, but the ones used in studies are often designed to see far from the center.
One limitation of this type of glasses is that the patient must have good glass cleaning habits as well as follow strict instructions from medical staff. Because glasses are placed directly on the eyes, the risk of infection is inevitable.
The use of drug groups to limit the development of myopia is also a trend at the moment. One of the drugs that is being studied the most is atropine low-dose eye drops. This type of eye drops works by reducing the activity of the muscles in the eye, thereby preventing accommodation. Atropine is used in myopia control at low concentrations because high concentrations, when used long-term, can cause many unwanted side effects (increased heart rate, dry eyes, etc.). The dosages used in the studies are usually 0.01%, 0.5%, 0.1%, etc. With a dosage of 0.01%, it has been proven through many studies to bring the most optimal effectiveness of myopia control. about 50-59% on the refractive index. The limitation of this method is that there are not many studies on the side effects of the drug when used for a long time.
This drug is on the prescription drug list, so its use must be prescribed by qualified medical personnel.
Combination of methods
The combination of the above methods for the purpose of controlling myopia, through many studies has shown that the effect will be better than using a single method. Some combination groups can be mentioned such as using low-dose atropine and Ortho-K, low-dose Atropine and glasses or contact lenses…