MYOPIA MANAGEMENT

Managing the Progression of Short-Sight

What is Myopia?

Having Myopia or being Short-sighted means that without a spectacle or contact lens correction one can not see clearly in the distance. The higher the prescription the closer things have to be in order to see them clearly. 

How Many People Suffer from Myopia?

It has been estimated that there could be as many as 2.3 billion myopic people in the world[1] (just under a third of the world population), however studies of prevalence in myopia across different races have shown that myopia has traditionally affected the Asian and Jewish communities more than Caucasian European communities, both with regards to the amount of people with the condition and also the severity of the condition.[2] [3] [4]

Conversely, people of African or African American descent tend to have a lower prevalence and lower severity of myopia than people from Europe or European descent.[5]

More recent studies have found an alarming increase in myopia across all races. In some countries in the Far-East it is estimated that 80 – 90% of the population are now short-sighted.[6][7] Among Europeans and Americans there has been a significant increase over the last 30 years in myopia, with a prevalence of 25% in the ‘70s changing to 42% at the turn of the millennium.[8]

It is statistically proven that 20% of children see print this way:

This inevitably affects their academic performance, as well as their confidence.

What causes Myopia?     

We see clear images when the rays of light from an object in the distance come to a focused point at the retina (the back of the eye). Myopia occurs when the rays are focused in front of the retina. The cause of this is either a cornea (front of the eye) that is too steeply curved or, more commonly, an eyeball that is too long, or a combination of the two. 

For centuries scientists have attempted to identify the cause, and thereby hopefully the solution, to myopia. It is clear that there is a genetic component to myopia based on the racial differences[9] and evident family inheritance.[10] Nevertheless the recent increase in myopia has clearly demonstrated that there are other factors involved. Recent studies have shown that children who spend more time outdoors are less likely to develop myopia[11] [12] and there may be a combination of reasons for this.

Children today spend a large amount of time viewing things at a close distance. Whereas TV used to provide a break from near viewing, it is very common now for children to finish their homework and then watch something on a tablet or play a game on a smart phone. It is possible that this constant accommodation (close focusing) is driving the progression of myopia. In contrast, children who spend more time outdoors viewing distant objects with relaxed accommodation are therefore less likely to become myopic.

Another possible mechanism is lighting. Studies have shown that animals that are exposed to blue light are less likely to become myopic than those exposed to red light. It has also been shown that a much brighter light can have a similar effect on the reduction of myopia.[13] Therefore children who are in bluish bright daylight are less likely to become myopic then those in redder, dimmer indoor lighting.

Emmetropisation

Recent studies have shown a further likely cause of progressive myopia. Most children are born with a refractive error (i.e. they theoretically need a prescription) and the eye has a natural process where the eyeball changes shape until the rays are focused on the retina.

By the age of 4 most children have a prescription tending towards zero.[14] There is clearly a feedback mechanism that ‘tells’ the eye how to change its size based on the information it receives. We call this process emmetropisation.

There could however be a downside to this process. The back of the myopic eye may not be perfectly spherical but rather has a more oval shape. When that eye is corrected optically, even if the rays are in focus at the centre point of the eye, they may be out of focus in the periphery.

The feedback mechanism makes the eye grow longer to put those peripheral rays on the retina but at the same time the centre of the retina also grows, causing the eye to become more myopic.[15] [16]

What is Myopia Control?

In the past many different methods to control myopia have been suggested including eye exercises, hard contact lenses and under-correcting the spectacle prescription with little evidence of myopia retardation.[17] [18] [19] There is some evidence that prescribing bifocals or progressive spectacle lenses may help in some individuals.[20] [21] [22]

Based on the current research, what is really needed is an optical system which focuses light on the central retina for good vision while keeping peripheral light rays in front of the peripheral retina in order to avoid the stimulation of eye growth which causes myopia progression.  

The ideal optical system for myopia control where the central rays are focused on the retina while peripheral rays focus in front rather than behind the peripheral retina.

Although it is possible to create a spectacle lens like this[23] it is not effective as the eye moves around and will not always be looking through the centre of the lens. A contact lens however will move around with the eye and may be more effective in generating such an optical system.

Orthokeratology

Orthokeratology, also known as Corneal Refractive Therapy (CRT) is a contact lens therapy which temporarily eliminates myopia. Specialist rigid lenses are worn overnight during sleep and removed in the morning, enabling clear vision, free from glasses and contact lens, during the day.

CRT lenses alter the shape of the front of the eye (the elastic cornea) by the generation of controlled hydro-static (liquid tears) pressure. The design of the lens means that more pressure is put on the central part of the cornea making it flatter, thereby fully correcting just the central vision. The peripheral part of the cornea becomes steeper and generates the desired peripheral optics focusing the light in front of the peripheral retina, which retards the stimulus for eye growth.  

Recent results from long-term studies using Orthokeratology for myopia management have shown significant slow-down, and sometimes a complete halt, in myopic progression. [24] [25] 

The process is safe and fully reversible: see Corneal Refractive Therapy (CRT) for more information.

Multifocal Contact Lenses

Multifocal contact lenses are manufactured in soft, rigid and hybrid forms and are worn during the day. Some of the disposable multifocal contact lenses currently mass produced work on a ‘centre distance’ concept where the central part of the lens is fully corrected and the periphery is less strong.

Studies using these sorts of lenses for myopia control show a general slow-down in the myopic progression but not as significant as with CRT.[26] [27] Two reasons have been suggested as to why the effect is not quite comparable.

Firstly with CRT there is a much greater change in prescription from the centre to the periphery than with regular ‘centre distance’ soft contact lenses and secondly the central area that is fully corrected with CRT is much smaller than that with multifocal contact lenses.

Barnard Levit Optometrists are one of only a very few Contact Lens Specialists across the world who use specially designed daily wear, non disposable, multifocal soft contact lenses that simulate the optical effect achieved with CRT lenses. In this way we aim to achieve with soft lenses the level of Myopia Control that CRT provides.                    

Medication

There is increasing evidence that atropine drops instilled in the eyes at very low concentrations (0.01%) can have significant effects in slowing the progression of myopia[28] without any symptoms or side effects.[29] At Barnard Levit Optometrists we would consider this treatment either in situations where contact lenses are not appropriate or as a dual treatment in conjunction with CRT or multifocal contact lenses, where a more aggressive approach to myopia control is needed.

Currently, Atropine 0.01% is not currently licenced in the UK. As soon as it is, we will be able to inform our patients. Further information may be found here.

What Age is Suitable for Myopia Control?

If a person’s myopia is progressively deteriorating, the earlier they start Myopia Control the better. In fact, we recommend that Myopia Control should be commenced as soon as a myopia tendency is recognised, even prior to frank myopia manifesting itself.

At Barnard Levit Optometrists we regularly and successfully fit contact lenses to children as young as six. We will consider myopia control with even younger children when parents are willing to take an active role in the therapy by performing insertion, removal and lens care for their child.

Why Do I Need Myopia Control?

Some people ask ‘Why do I need myopia control, I can just get stronger and stronger glasses as I get worse?’

The most important answer to this question is that as the myopia increases the eyeball gets longer and the retina is stretched over a larger area. As a result of this the higher a person’s myopia, the more at risk they are to eye health issues later on in life, e.g. retinal tears and detachment, retinal atrophies and degenerative disorders, optic nerve atrophies, myopic maculopathies, macula holes and vitreo-retinal disorders[30].

It has also been shown that other eye diseases such as glaucoma[31] [32] and cataract[33] are more common in people with myopia and the risk increases as the myopia increases.

With regards to glasses themselves, as the prescription increases the lenses get steadily thicker. A myopic prescription also makes the eyes look smaller than in reality and the higher the prescription the greater this minification effect.

If the myopia is halted or slowed early enough it may even be possible to keep the uncorrected prescription at a level where full time wear will not be necessary.

How Do I Book an Appointment?

To book an appointment with our specialists in Myopia Management, please contact reception on 020 8458 0599 or reception@barnardlevit.com