Refractive Errors

What is it?

A refractive error means that the shape or length of the eye results in the light not being focused on the retina, causing a blurred image. The main types of refractive errors are myopia (near-sightedness), hyperopic (farsightedness), presbyopia (loss of near vision with age), and astigmatism.


Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. Near-sightedness can also be caused by the cornea and/or lens being too curved for the length of the eyeball. In some cases, myopia is due to a combination of these factors.

Myopia typically begins in childhood and there may be a higher risk if family members are near-sighted. In most cases, near-sightedness stabilises in early adulthood, but sometimes it progresses with age.

How is it treated?

Near-sightedness can be corrected with glasses, contact lenses or refractive surgery. Depending on the degree of the myopia, eyeglasses or contact lenses may need to be worn all the time or only when very clear distance vision is needed, like when driving, seeing a whiteboard or watching a movie.


Hyperopia, or farsightedness, is a common vision problem. People with hyperopia can see distant objects very well but have difficulty focusing on objects that are up close.

Farsighted people sometimes have headaches or eye strain and may squint or feel fatigued when performing work at close range. If these symptoms occur while wearing eyeglasses or contact lenses, then it may be necessary to undergo an eye examination and obtain a new prescription.

How is it treated?

Farsightedness can be corrected with glasses or contact lenses to change the way light rays bend into the eyes. A prescription beginning with plus numbers, like +2.50, indicates that a person is farsighted.

It may be necessary to wear glasses or contacts all the time, or only when reading, working on a computer or doing other close-up work.


Presbyopia is the normal loss of near focusing ability that occurs with age. Most people begin to notice the effects of presbyopia sometime after age 40 when they start having trouble seeing small print clearly — including text messages on their phone.

One cannot escape presbyopia, even if a vision problem has never been experienced before. Even people who are near-sighted will notice that their near vision blurs when they wear their usual eyeglasses or contact lenses to correct distance vision.

Presbyopia is caused by an age-related process. This differs from astigmatism, near-sightedness and farsightedness, which are related to the shape of the eyeball and are caused by genetic and environmental factors. Presbyopia generally is believed to stem from a gradual thickening and loss of flexibility of the natural lens inside the eye.

These age-related changes occur within the proteins in the lens, making the lens harder and less elastic over time. Age-related changes also take place in the muscle fibres surrounding the lens. With less elasticity, the eye has a challenge to focus up close.

How is it treated?

Eyeglasses with progressive lenses are the most popular solution for presbyopia for most people over age 40. These line-free multifocal lenses restore clear near vision and provide excellent vision at all distances, regardless of what other refractive errors may exist in addition to presbyopia.

Another option is eyeglasses with bifocal lenses. But, bifocals are presently less popular as they provide a more limited range of vision for many presbyopes. Also, most people do not want to show their age by wearing eyeglasses that have a visible bifocal line.

People with Presbyopia will notice that they are becoming more sensitive to light and glare due to ageing changes in their eyes. Photochromic lenses are a good choice for this reason as the lenses will automatically darken in sunlight. They are available in all lens designs, including progressive lenses and bifocals.

Reading glasses are another option. Unlike bifocals and progressive lenses, which most people wear all day, reading glasses are worn only when needed to see close objects and small print more clearly.


Astigmatism is probably the most misunderstood vision problem. To begin with, it is called “astigmatism,” not “stigmatism.” (One does not have “a stigmatism” — one has astigmatism.)

In an eye with astigmatism, the light fails to come to a single focus on the retina to produce clear vision. Instead, multiple focus points occur, either in front of the retina or behind it (or both).

Astigmatism is usually caused by an irregularly shaped cornea. Instead of the cornea having a symmetrically round shape like a soccer ball, it is shaped more like a rugby ball, with one meridian being significantly more curved than the meridian perpendicular to it.

There are three primary types of astigmatism: Myopic astigmatism, Hyperopic astigmatism and Mixed astigmatism.

How is it treated?

Astigmatism, like near-sightedness and farsightedness, usually can be corrected with eyeglasses, contact lenses or refractive surgery.