In the first part, we talked about the components of a routine eye examination and your eye health and safety. In this final part, we'll be talking about refraction.
REFRACTION
What is refraction?
We are able to see the world around us just because of the way our eyes bend or refract light. So, simply put, refraction is the bending of light. Just like the camera, the human eye need light to be focused to produce sharp images. Refraction in the eye occurs when light rays pass through the curved, clear front surface of the eye which is known as the cornea and focuses on the retina. The retina then converts these light-rays into messages that are sent to the brain through the optic nerve.
What are refractive errors?
Refractive errors are caused when the shape of the eye stops light from focusing directly on the retina. Refractive errors mean that the shape of your eyes does not allow for proper bending of light resulting in blurred images.
Types of Refractive Errors
The main types of refractive errors are myopia, hyperopia, presbyopia, and astigmatism.
Myopia (close objects are clear)
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Also known as nearsightedness, it is usually inherited and is mostly discovered during childhood. It is a condition where objects up close appear clearly, while objects far away appear blurry.
Hyperopia (close objects are more blurry than distant ones)
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Known as farsightedness, it can also be inherited. In mild hyperopia condition, objects that are far away are clear while close objects appear blurry.
Presbyopia (aging of the eye lens)
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After age 40, the lens of the eye is no longer flexible enough to allow the eye to focus on close objects clearly. This aging process of the lens can also be combined with hyperopia, myopia and astigmatism.
Astigmatism
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Normally, the cornea is smooth and curved equally on all directions and light enters the cornea in all directions. In astigmatism, the front of the cornea is unequally curved i.e curved to one direction than in another. This abnormality will result to a distorted vision usually blurred at all distances.
Signs and symptoms of refractive errors:
Blurred vision is the most common symptom of refractive errors. Other symptoms may include:
- Double vision
- Haziness
- Glare or halos around bright lights
- Squinting
- Headaches
- Eye strain
How are refractive errors tested and diagnosed?
A refractive error can be diagnosed by an optician during a routine eye examination or test. During testing, the patient is usually asked to read a vision chart while a variety of lenses are tested to maximise the patient's vision.
Treatment:
Refractive errors are mostly treated using corrective lenses e.g eyeglasses or contact lenses. Refractive surgery can also be used to correct some.
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