Refractive error

What are the types of refractive errors?

Here are the most well-known types of refractive error people can suffer from:

Hypermetropia: This is also known as hyperopia or farsightedness. If you have hypermetropia objects in the distance are usually clear, but nearby objects may seem blurred.
Myopia: This is near-sightedness and makes it difficult to view objects in the distance. Depending on the level of myopia, you might even experience difficulty with objects at intermediate distance.
Astigmatism: Refractive error of this kind means that the eye’s cornea is irregularly curved, which causes blurred and/or distorted vision.
Presbyopia: This condition causes difficulty in seeing or reading objects and materials at arm’s length or closer. This condition is generally a result of aging, due to the elasticity of the lens decreasing. Usually people experience symptoms from around the age of 40 and onwards.

Causes of refractive error

Here are some of the reasons why you may have a refractive error:

Length of the eyeball: If your eyeball is either too long or too short, it can prevent the light rays that enter your eye from converging correctly on the retina.
Irregular cornea: The eye is naturally curved, but when the cornea (the transparent outer layer of the eye) is not curved equally in all directions, it cannot focus the incoming light rays onto the retina correctly. When insufficient light signals enter the retina, the retina fails to bounce back the light signals needed for the eye to see clearly.
Aged lens: The muscles surrounding the eye that help it mobilise properly can weaken, causing the eye to be slower to respond to signals. The lens, which is made up of flexible tissue, actually becomes stiff with age, which may cause the eye to struggle to change its shape and re-focus during daily activities and observations.

Who is at risk for refractive errors?

Refractive errors can affect people of any age. Anyone can have a refractive error, although these conditions are often hereditary. If you have family members who wear glasses or contact lenses, it is best to have your eyes checked regularly.

Some refractive errors, such as near-sightedness, can begin in childhood, whereas other refractive eye conditions, such as presbyopia, occur at an older age (40 and above).