Ask an optometrist: What is Myopia Control?

By Dr. Eric Bishop, OD

Myopia, or nearsightedness, is the most common vision concern for children today. The alarming rate at which more and more of our youth are becoming myopic is especially evident in certain parts of Asia, where depending on which research you look at, 70-80% of young adults are myopic. Current projections show that by 2050, 50% of the world’s population will be nearsighted.

What are the risks associated with Myopia?

As myopia increases, the risk for further ocular health complications also increases. These complications include conditions such as;

  • Myopic Maculopathy – also called Myopic Macular Degeneration, this condition occurs when severe myopia causes damage to the retina. Myopic Maculopathy can cause vision loss, light sensitivity, and an increased risk of developing cataracts and glaucoma. 
  • Retinal Detachment – retinal detachments occur when the retina separates from the back of the eye. If not treated immediately, retinal detachments can result in permanent vision loss. 
  • PSC Cataract – posterior subcapsular cataracts (PSC) form at the back of the lens, in front of the posterior capsule. PSC are more likely to develop in younger patients. 
  • Glaucoma – a leading cause of blindness in Canada, glaucoma leads to damage to the optic nerve, which causes a loss of vision.

Myopia measured in D (dioptre), the unit of magnifying power of a lens.

Myopia Risk Graph

Ways we can control Myopia progression

Due to the multifactorial causes of myopia progression, there are multiple ways to slow it down. Each method of myopia control has a varying amount of progression reduction. Though it needs to be researched further, it is generally accepted that combination therapies are even more effective than a single method.

  • Corneal reshaping technologies (specialized rigid contact lenses)
  • Specialized soft contact lenses
  • Specialized spectacle lenses
  • Pharmaceuticals
  • Lifestyle changes

Why does Myopia progress, and how can we slow it down?

In an eye with perfect vision, the cornea and the lens focuses the image directly on the retina. When you are nearsighted, your eyeball that is too big, and the eye’s image is focussed in front of the retina. Traditionally, we use glasses or contacts to shift the image onto the retina. Nearsighted VS Normal 01

When a child is nearsighted, it will nearly always continue to get worse, because as a child grows their eye will continue to grow as well. Multiple factors dictate how quickly this growth occurs. The ones we can affect the most and, therefore, slow down progression the best, are: Accommodative Demand and Peripheral Defocus.

Accommodative Demand
Accommodative demand refers to the amount our eye is focusing up close. This includes both the amount of time focused up close and how close that focus is. The higher the accommodative demand, the quicker the eye will grow. This is one of the easiest risk factors to manage, as less near work = less myopia progression.  Studies have also shown that increasing time spent outdoors strongly correlates to lower levels of myopia. There is no set standard of how much near work is “safe”; however, a 2015 study showed four additional hours of near work per day, after school, increased the risk of myopia by 120%.

Ways we can reduce Accommodative Demand

  • Spend time outdoors - remember your UV protection!
  • Take regular breaks from near work - at least once every 20-30 mins • When working up close use a good working distance - do not hold things too close to your face
  • Good lighting – Helps increase accommodative accuracy and decrease strain
  • Multifocal Glasses (10-35% reduction)
  • Multifocal Contacts (50-60% reduction)
  • Pharmaceutical Agents – EG. Atropine will help relax the accommodative system

Peripheral Defocus
Whenever we focus on an object, our cornea and lens try to focus that image onto our central vision, also called our macula. When the image is not on the macula, we traditionally use glasses or contact lenses to move the image to the central vision. Conventional glasses and contacts are not perfect though, and as you move farther from the central vision the image becomes increasingly unfocused.
 
In myopic cases, the image is focused behind the peripheral retina (called hyperopic defocus). This type of defocus has been associated with worsening Myopia. And research has shown that flipping the focus to be in front of the retina (Myopic Defocus) has been associated with decreased eye growth and, therefore, lowered myopia progression.

Ways we can improve peripheral defocus
PHD Diagram

  • Aspheric glasses (10-35% reduction)
  • D.I.M.S. (Defocus Incorporated Multiple Segments) technology glasses (50-60% reduction)
  • Specialized soft contact lenses (50-60% reduction)
  • Specialized rigid contact lenses worn at night only (50-60% reduction)

We are continuing to learn more and more about myopia progression as new technology comes out, and more research is made available.
 
If you have any questions about how you can slow down your or your child’s myopia, call 403.974.3937 (EYES) to book an appointment with one of our Calgary eye doctors today.

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