Can eyeglasses control myopia? Read on to find out.
In this article, we will be discussing Myopia (near-sightedness) in detail. This article will talk about the possible reasons for myopia development, the commercially available techniques to correct it and the available methods to prevent myopia progression.
What is myopia?
Figure 1: Image formation in a normal eye (left) and an eye with myopia(right)
In a normal-sighted person, the light from an object forms an image on the retina. In a person with myopia, the image forms in front of the retina (figure 1). Myopia is a condition where distant objects are blurred while near objects are clear. The distance at which the objects can be seen depends on the spectacle power. To correct myopia, minus lenses are prescribed.
Figure 2: Accommodation of the eye
Accommodation is the eyes’ ability to keep an object in focus (figure 2). It occurs at a near distance with the help of eye muscles. When an object is placed at 30 cm, the eye muscles have to contract to see a clear image at 30 cm. Suppose a person can clear this image at 40 cm only, while the object is placed at 30cm. This 10 cm difference is called the lag of accommodation.
The main reasons for myopia include –
i. Elongation of the eyeball
ii. Lag of accommodation
iii. Abnormal shape and/or position of the eye structures inside the eyes
What is normal myopia progression?
An increase of 0.50D or more of the minus power and/or increase in eyeball length by 0.1mm per year is defined as normal physiological progression of myopia. Anything more than this should be considered for myopia glasses.
What are the currently available solutions for myopia control?
Figure 3: Types of spectacle lenses – Single vision (Top left), Bifocal lenses (Top right) with the visible demarcation line and Progressive addition lenses (Below)- virtually identical to Single vision lenses
- Single vision eyeglasses
Spectacles or eyeglasses are the traditional method of correction but are not the control for myopia. Hence if the power or eyeball length increases more than expected, this option may not help much.
- Bifocal or Progressive eyeglasses
This type of spectacles is preferred when a lag of accommodation and eye deviation is noted, resulting in a power increase. To relax the eyes accommodation, additional near power is prescribed.
This near power is put into the eyeglasses as either bifocals or progressives (fig 3). Lenses that consist of two different powers – one for distance viewing and the other for near viewing in the same eyeglasses are called bifocals.
- Myopia control glasses or special myopia management eyeglasses
Commercially available types have shown a promising reduction in the progression of myopia. They are a non-invasive and safe option for myopia control.
How do myopia control lenses work?
Our eyes are curves at the back, and the regular spectacle lenses that we use are not made for a curved surface. The focus of peripheral rays falls behind the retina or the eyeball’s back surface. This causes blur image at the periphery.
These blur images act as a trigger for the eyeball to increase in length such that the peripheral rays fall on the retina. However, this will create a central blur, and vision will be unclear.
The myopia control lenses’ design is made to avoid this peripheral blurred image yet provide a clear central view and thus limit the progression of myopia.
Figure: Normal (Left) versus myopia control lens (Right) – The latter does not leave a blurred peripheral image unlike the normal lens
Available myopia control glasses
1. Zeiss MyoVision Pro lenses
These single vision lenses are designed and marketed by Zeiss. A study reported that the progression of myopia was reduced by 30% in Chinese children aged between 6 and 12 years with MyoVision Pro lenses. Another study in Japanese children did not show much difference in myopia progression when compared between traditional lenses and Zeiss MyoVision lenses (Older version of MyoVision Pro lenses).
2. Zeiss Myokids
These progressive addition lenses (PALs) are designed and dispensed by Zeiss. This lens was launched after its successful ability to reduce myopia progression caused due to accommodative lag by 20% when compared with single vision lenses. A study in Hongkong and Guangzhou showed that 91% of the children felt satisfied and comfortable within one week of spectacle wear.
3. Hoya’s MiyoSmart
The Defocus Incorporated Multiple Segments (DIMS) spectacles are designed and marketed by HOYA. These lenses have been effective in curbing down the progression of myopia by 52% and slow down eye elongation by 62% in children with myopia aged between 8 and 13 years in two years. It is designed to consist of 400 one-millimetre defocus segments (33 mm in diameter in total) around the 9 mm central zone of the spectacle lens.
4. Essilor’s Stellest
This aspherical lens is designed and marketed by Essilor. The Essilor’s Stellest reduces the rate of progression of spectacle power by 60% and eye elongation by 28% in myopic children aged between 8 and 13 years in one year when compared with the single vision glasses. The highly aspherical lenslet target (HALT) consists of 11 aspherical lenslets around the spectacle lens’s central clear zone.
5. Essilor’s Myopilux
These near vision addition lenses are designed and dispensed by Essilor. In a two year follow up study, the Myopilux lenses were reported to slow the progression by 37.2% to 62% in children with myopia. These lenses are available in three versions – Myopilux Lite, Myopilux Plus and Myopilux Max. Myopilux Lite has a progressive addition lens design. Myopilux Plus is an advanced version of the Lite version with specific visual ergonomic modifications. Myopilux Max is a prismatic bifocal lens.
6. SightGlass Vision DOT lenses
These light diffusion technology lenses are designed by SightGlass Vision. These lenses were found to slow progression by 59 to 74% in the spectacle power and 33 to 50% of eye elongation. These lenses consist of a clear centre aperture that is surrounded by multiple dots. These dots change the light contrast in the eye’s retinal periphery to reduce progression.
|Myopia control lenses
|Zeiss MyoVision Pro lenses
|Single vision lenses
|Designed after considering the children’s eye parameters and can be customizedEasy to use and adaptLarge range of material designs and features
|Progressive Addition Lenses (PALs)
|Designed after considering the children’s eye parameters and can be customizedEasy to use and adaptSpecially designed for near work and digital devices
|Defocus incorporated multiple segments (D.I.M.S)
|High impact resistant polycarbonate materialLight and thinUV Protection
|Highly aspherical Lenslet target (H.A.L.T.)
|Clear vision and easy to adaptVery thin lenses
|Near addition lenses
|Various designs to cater to the child’s needsUses Wavefront technology
Myopia in children is extremely common in these current times. Control of myopia progression is essential as the increase in eye power can have sight-threatening complications in late adulthood. Myopia control glasses are specially designed lenses to reduce the rate of myopia progression.
These glasses are based on two theories known to cause myopia progression: eyeball elongation and lag of accommodation. Various eye care companies like Zeiss, Hoya, Essilor and Sight Glass Vision have developed and designed glasses to reduce myopia progression.
Most of these myopia control lenses have shown a significant reduction in myopia progression in the initial reports. Many are still in a clinical trial to understand their efficiency.
Irrespective of the number of lenses in the market, it is best to consult a myopia control practitioner to assess these specialty products’ suitability. Always remember, your eye care practitioner knows best!