Refractive error

We all rely heavily on our sight, but do you know how your eyes work?

Our eyes allow us to see by detecting light from the outside world and converting this into messages that the brain can understand.

Light rays are bent (refracted) by two parts of the front of the eye called the lens and the cornea. The light is then focused on an area at the back of the eye, called the retina. The retina converts these light-rays into messages, and the optic nerve sends these messages to the brain.

If light is not focused properly on the back of the eye (the retina), vision becomes blurry. This is called refractive error. Refractive errors are the most common eye problem in the world. They are the most common cause of visual impairment, and the second most common cause of blindness.
There are four main types of refractive error:

  • Myopia (nearsightedness): causes difficulty seeing far away objects – e.g. road signs, the blackboard in a classroom, or the television screen. This is because light rays are focused in front of the retina, rather than on the retina.
  • Hyperopia (farsightedness): causes difficulty seeing objects close – e.g. reading, or fine work such as sewing. However if it is severe, vision can be blurry for objects at all distances.
  • Astigmatism: vision is blurred at all distances, and images may appear stretched out
  • Presbyopia: causes difficulty in focusing on close objects.

Myopia, hyperopia and astigmatism can occur at all ages. Presbyopia occurs in almost all older people, due to the lens becoming stiff.


In Africa, myopia affects 6% of children and 16% of adults, while hyperopia affects 3% of children and nearly 40% of adults!

However, luckily, most refractive errors can be treated easily.

Eye glasses are the simplest and safest way to correct a refractive error! An eye care professional can measure your exact refractive error and give you the right type of glasses to correct it.

Other options include contact lenses, and refractive surgery.

So get your vision checked today!


This article is part of Right for Education’s Eye Health Week.



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