Myopia Or Nearsightedness
A person is myopic when their eyes are focused at a near distance and they cannot see well at far distances without the aid of glasses or contact lenses.
The greater the myopia the greater the risk of developing glaucoma, cataracts, retinal detachment and/or myopic macular degeneration. At the Downtown Vancouver Optometry Clinic, our principle work is (but not limited to) correcting for myopia and its complications.
The prevalence of myopia in North America has nearly doubled between 1971 and 2004 to where 42% of the population is now myopic. In Canada – 30%. Persons of Asian descent have an 85% probability of being myopic. This significant increase in just one generation speaks to the increasing environmental factors that stimulate myopic progression especially when there is an underlying genetic component for change.
The more up-close work a person does the more likely they are to become myopic. As a result, our downtown practice was built on accountants and lawyers – two groups that do a lot of up-close work.
In pediatric cases, the onset of myopia usually begins between the ages of six and nine. Up until grade four children “learn to read” – at grade four they “read to learn” and this is often the trigger for change as the demand on the visual system is elevated.
Today, children are put into learning and recreation environments that require more up-close work rather than playing in open fields in the sun and as a result we are likely to continue to see an increase in the prevalence of myopia for generations to come.
In our practice, a day does not go by without a mother asking what can be done to stop her child from becoming more myopic or needing stronger glasses.
Controlling The Progression Of Myopia In Children
The science has shown that there are only three proven ways to reduce the rate of progression of myopia and all them work with about the same effectiveness:
- Low dose 0.01% Atropine eye drops daily
- Multifocal Lenses
- Orthokeratology (OrthoK)
Each of these methods can reduce the rate of progression of myopia by about 40% when compared to children who do not utilize one of these tools. No studies have been published on combination therapy.
While nothing can stop myopia from progressing, each of these methods reduce myopic progression to about -0.30 diopters a year.
Low dose 0.01% Atropine – while effective, this eye drop stings upon instillation and carries the risk of causing blurred vision, increased light sensitivity, an allergic reaction, irregular heart rhythm and difficulty breathing. As a result, this is not our preferred method of treatment.
Multifocal Lenses – works best in low myopia of less than -3.00 diopters and for higher myopia of greater than -6.00 diopters by reducing accommodative stress (i.e., by reducing the amount of work on the ciliary muscle and thereby reducing the elongation of the eye’s vitreous chamber)
OrthoK – works best on an eye between 2.00 and 3.50 diopters of myopia.
Our Preferred Technique – Orthokeratology
OrthoK works overnight on both children and adults to gently reshape the surface of an eye to give vision free of the absolute need for wearing glasses or contact lenses during the day. More importantly, since 1963 OrthoK is a time honoured and scientifically proven way to reduce myopic progression by up to 63% in children between the ages of eight and eleven.
Please read our OrthoK page for more information.
The bifocal lens method does not work in all cases. Bifocal soft contact lenses are known to increase corneal thickness and in some cases promote an increase of myopia.
- There are ten interfaces where light bends in an eye, namely the:
- air/tear interface
- tear layer
- tear/cornea interface
- cornea/aqueous interface
- aqueous/lens interface
- crystalline lens
- lens/vitreous interface
- vitreous humor
- Myopia is directly related to the steepening of the corneal curvature and/or to the elongation of the vitreous chamber
- The cornea is responsible for 60% of the light bending power of an eye
- OrthoK controls changes to the curvature of the cornea thereby controlling at least 60% of the progression of myopia
- Surprisingly, two studies have shown that OrthoK also slows vitreous chamber elongation between 41% and 52%