What is an uncorrected refractive error?

When there is a mismatch between the refractive components of the eye and the length of the eye ball - the result is an out of focus or blurred image. This is known as refractive error.

Refraction is when the eye bends light so that it can pass through the sections of your eye; the cornea, the lens, and eventually the retina. The retina is the thin, light-sensitive tissue at the back of the eye.

In order to process what we see every day, the brain needs to receive messages from the retina, sent through the optic nerve. If your retina doesn't receive light-rays correctly, it won't be able to pass messages to the optic nerve and then to the brain for interpretation. 

If this happens, images can appear blurred or unclear, resulting in vision loss.

When does refractive error happen?

Refractive errors can happen when the eyeball grows or reduces in length, when the cornea changes shape, or simply with age. 

Overuse of the eye does not cause refractive error. Rather, if refractive error runs in your family, you may have more chance of developing a condition.

People of all ages are affected by refractive errors, but some conditions are more common in certain populations. For example, presbyopia (loss of near vision with age) is present in most adults over 35-45, while myopia (near-sightedness or short-sightedness) is more common among people of Asian heritage.

We often use glasses to correct long or short sightedness caused by refractive error, as well as the inability to change focus properly.

What are the main types of refractive error?

Below are some of the most common types of refractive error. 

Myopia (near-sightedness or short-sightedness)

Often an inherited eye condition, myopia causes far away images to be seen blurred, while images are clear up close. 

Myopia happens because the distance between the cornea and the retina is too long. So, instead of the light focusing on the retina, it focuses in front of the retina.

Myopia is usually identified during late childhood and exacerbated during puberty, when the body goes through a lot of change.

Hyperopia/ hypermetropia (far sightedness or long sightedness)

Hyperopia - sometimes called hypermetropia - occurs when the distance between the cornea and the retina is too short. This causes the light rays to focus behind the retina, rather than on it.

We experience hyperopia on a scale; mild levels make images appear blurred close up, and clear when they're far away. For individuals with high levels of hyperopia, images can be blurry at all distances.

In childhood, hyperopia can be difficult as children may not always notice their vision problems until they are older.

Presbyopia (loss of near vision with age)

Presbyopia is one of life’s inevitable burdens brought on by the ageing process.

As we age, our lenses become more rigid, allowing less close-range focusing flexibility. Signs of presbyopia start to emerge from around 35-45 years of age. 

Presbyopia is a normal part of the ageing process, but can be corrected by using reading glasses.

Astigmatism (uneven focus)
 

When the cornea has asymmetrical curvature, we call that astigmatism.

In the case of astigmatism, rather than the equal curves of a sphere, the front surface of the eye ends up more like a rugby ball. This causes the light coming through the cornea to focus unequally on the retina, resulting in a distorted or ‘stretched out’ image. 

In most cases, a person with astigmatism will have blurred vision, whether it’s near or far.

What are the symptoms of refractive error?

How is refractive error treated?

There are a few simple solutions that are available to correct refractive error, including eyeglasses, contact lenses, or different kinds of surgery.

 

Eyeglasses are the most common and simple solution. An eye care professional can measure you for a pair of eyeglasses for effective correction.

Contact lenses are a less common, but still popular treatment for correcting refractive error. They work by placing an artificial lens on the film of tears covering the eye’s surface.

A contact lens is thin, curved and in most cases these days, soft and bendy. Like eyeglasses, you'll need to have your contact lenses fitted by an eye care  professional. Your optometrist will be able to give you lessons on safe insertion and removal of contact lenses and how to keep them clean. 

But remember, always seek out professional advice if you think you need contact lenses, as you won't be able to wear them with some eye conditions.

Corrective surgery is also necessary for some patients. Corrective surgery options include refractive (laser) surgery and intraocular lens (IOL) surgery.

Refractive surgery, of which there are many types, can be used to correct the vision of those with refractive error. Laser surgery is one type of refractive surgery.

Experts use specialised tools to measure the surface contour of your eye and then permanently reshape the cornea (front surface of the eye). They do this by vaporizing the surface tissue into a new shape, restoring the eye’s ability to focus light rays directly on the retina.

Intraocular lens (IOL) replacement surgery is another kind of refractive surgery available. Surgeons remove the natural lens from the eye and replace it with an artificial lens called an intraocular lens (IOL) or they may insert an additional lens to correct the refractive error. IOLs are also used in cataract surgeries.

How is The Fred Hollows Foundation helping people with refractive error? 

Our aim is to make effective treatment refractive error prevention and treatment accessible to all.

Access to glasses remains a global challenge and the result is that uncorrected refractive error is the second leading cause of blindness globally and the leading cause of moderate to severe vision impairment.

Most cases of refractive error are successfully treated with glasses, but if left untreated, they can have an enormous impact on educational outcomes, productivity, and overall quality of life.

 
Our Targets:

As highlighted in our 2019 - 2023 strategy, these are our three key targets:

• Build refractive error into national health plans in key countries where we work.

• Integrate eye screening into national health plans in key countries where we work.

• Increase treatment uptake and treatment compliance in our programs by 50% from 2019 baseline.
  
  Find out about other eye conditions.

DISCLAIMER: The content on this page is not intended to be medical advice. For specific medical advice, please contact your health professional. 

 

What does blindness look like?  

It's difficult to imagine what it's like to suffer from loss of vision. That's why we've launched an online Sight Simulator.



With this simulator you can get a sense of what the world might look like through the eyes of someone living with a visual impairment.