Refractive Error Management
A refractive error is the most common eye problem. When the shape of the eye is abnormal, the eye doesn't bend (or refract) light properly, and so vision is blurred.
The most common types of refractive errors are:
Short-sightedness (myopia) causing blurred long distance vision.
Long-sightedness (hypermetropia), causing blurred close and distance vision.
Astigmatism, which causes an uneven focus of light and blurred vision.
Presbyopia, When the eye lens loses flexibility, making close work difficult. This is most common with people over 40 years of age.
People with refractive errors might have one or a combination of these conditions.
These errors can be corrected with glasses or contact lenses. Surgery might also be an option.
What is short-sightedness?
Short-sightedness (also known as myopia) is a common eye condition that causes distant objects to appear blurred. Someone with myopia can achieve good vision with prescription glasses, contact lenses or laser surgery. Short-sightedness usually first appears in childhood.
How is short-sightedness caused?
When light enters the eye, it is bent by the cornea (the clear layer on the front of the eye) and the lens. If you have normal vision, the light waves are brought into focus right on the retina, the layer at the back of the eye. If you are short-sighted, the light waves from distant objects focus in front of, rather than on, the retina.
Short-sightedness usually appears in the pre-teen years and often gets worse for a few years. It can also develop later - even in early adulthood. It is becoming more common.
Myopia has been linked to spending many hours doing activities such as reading, schoolwork or using a computer, while spending less time outdoors.
You can also inherit short-sightedness from your parents.
Short-sightedness causes light to focus in front of the retina instead of on the back of the eye, causing distant objects to appear blurred.
How can I tell if I'm short-sighted?
If you are short-sighted, distant objects will appear blurred when you look at them. It can be hard to tell, but you might notice that other people can see distant objects more clearly than you can.
Children might have difficulty reading the board in class or be reluctant to play outdoor sports. Your child might squint to see things at a distance or they might sit very close to the television. Many children don't complain about blurry vision because of the gradual changes of vision and don't know their vision can be better.
If you feel that you or your child might be short-sighted, see your doctor or optometrist for an eye test.
How is short-sightedness diagnosed?
An eye test using an eye chart will allow an optometrist (primary eyecare and vision doctor, no referral is required) or ophthalmologist (eye health specialist, referrals are required) to diagnose short-sightedness.
Children should have their vision checked when they start both primary and secondary schools.
How is short-sightedness treated?
Short-sightedness is usually corrected with prescription glasses.
Contact lenses are also an option, but generally not for children. Laser refractive eye surgery can be an option for mild to moderate short-sightedness but is only appropriate for adults.
Some research suggests that certain treatments might be able to slow the progression of short-sightedness in children. If you want to know more about this, talk to your optometrist or doctor.
Even if you have no concerns about your vision, it is a good idea to have your eyes checked every 2 years.
What is long-sightedness?
Long-sightedness (also known as hyperopia) is a common eye condition that can be hard to detect. It makes close objects appear blurry, or you might be able to focus clearly but get tired eyes or headaches. For people with significant long-sightedness, vision can be blurry for things in the distance as well.
How is long-sightedness caused?
The size and shape of the eye largely causes long-sightedness.
When light enters the eye, it is bent by the cornea, the clear layer on the front of the eye, and the lens. This process is known as refraction.
If you have normal vision, the rays of light are brought into focus right on the retina, the layer at the back of the eye. If you are long-sighted, the cornea is not sufficiently curved or the eye is too short, so the light rays from close objects focus behind, rather than on, the retina when the eye is resting (not actively focusing on something).
Many people are slightly long-sighted and the lens automatically corrects for the refractive error by adjusting the focus to get a sharp image.
People who are more long-sighted, or who do a lot of near-focus activities such as reading, need more adjustment. This means their eyes can get tired by the end of the day and they might get headaches.
You have a slightly higher chance of being long-sighted if either of your parents is long-sighted.
Long-sightedness causes light to focus behind the retina when the eye is resting – rather than directly on it – so close objects appear blurred.
How can I tell if I'm long-sighted?
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Mild long-sightedness can be hard to detect because the lens automatically corrects your focus to make close objects clear. But you might find that you have strained or aching eyes or a headache or tiredness after periods of close work.
If you have more severe long-sightedness, you might find it hard to focus on close objects.
If you think that you or your child might be long-sighted, see your doctor or optometrist for an eye check.
How is long-sightedness diagnosed?
Standard vision screening tests might not detect long-sightedness, but an optometrist (primary eyecare and vision doctor, no referral is required) or ophthalmologist (eye health specialist, referrals are required) can measure how well your eye focuses as part of an eye examination.
Treatment of long-sightedness
Mild long-sightedness, especially in young people, might not need any treatment.
If moderate to severe long-sightedness is not corrected, however, the extra focusing effort required may increase the likelihood of children developing lazy eye (amblyopia) or turned eyes (also known as a squint, or strabismus).
The most common treatment is glasses, especially for reading and other near work, but sometimes also for distance. Your optometrist might recommend eye exercises.
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Laser refraction surgery can correct mild long-sightedness, and might be suitable for adults, although it is not recommended for children.
Even if you have no concerns about your vision, it is best to have your eyes checked every 1 or 2 years.
What is astigmatism?
Astigmatism is a problem with vision that is caused by the cornea or the lens of the eye not being perfectly curved. The result is blurred vision — mildly blurred for some people, severely blurred for others.
Eye check-ups can diagnose astigmatism, which can be treated with glasses, contact lenses or laser eye surgery.
What are the types of astigmatism?
There are 2 types of astigmatism:
regular — where the cornea is curved more in 1 direction (say vertically) than the other (say horizontally)
irregular — where the curvature of the cornea is uneven across the surface of the eye; it is usually associated or caused by corneal disorders or diseases.
Specialized equipment for mapping corneal topography is required to detect and confirm diagnosis of the irregular astigmatism.
What are the symptoms of astigmatism?
difficulty seeing at night
eye strain, especially after concentrating for a long time
a 'lazy eye' in children
Astigmatism involves poor focus at all distances. People who have astigmatism may also experience:
What causes astigmatism?
Astigmatism may be present at birth or develop with ageing and may have a hereditary component. It can also result from eye disease or injury.
How is astigmatism diagnosed?
Testing may include:
measurement of the curve of your corneas
measurement of how well your eyes focus light
If you have any concerns about your eyesight, see your optometrist or talk to your doctor.
Astigmatism in children
Because astigmatism can be present from birth, it is important to have your child’s eyesight checked if you are concerned about their vision.
How is astigmatism treated?
For most people, astigmatism is a mild condition and does not need treatment beyond correction with glasses or contact lenses. More severe astigmatism may need treatment.
Treatments for astigmatism include:
corrective glasses or contact lenses
orthokeratology, which uses rigid contact lenses to reshape the cornea
laser eye surgery, which reshapes the cornea
Presbyopia (Age-related Near Blur)
What is presbyopia?
Presbyopia is a condition in which your eyes become less able to focus as you get older. Usually, you notice that reading and focusing on objects close up becomes more difficult, although you will still see distant objects clearly.
Presbyopia is a natural part of ageing and is usually corrected with the use of glasses or contact lenses.
What causes presbyopia?
As you get older, the lens in your eye becomes harder and less flexible. This makes it harder to focus on close objects.
People often notice changes in their vision around the age of 40.
You might find it harder to focus to read, especially in poor light. You might also find yourself holding your book further away or needing a brighter light for detailed work such as doing a crossword or crafts.
The strain of focusing your eyes might also give you headaches.
Presbyopia usually worsens until around the age of 65. It is a natural part of ageing and there is no known way to avoid it.
Presbyopia causes light to focus behind the retina, making it hard to see close-up objects clearly.
How is presbyopia diagnosed?
Your optometrist (primary eyecare and vision doctor, no referral is required) or ophthalmologist (eye health specialist, referrals are required) will assess your eye in a comprehensive examination. If you already wear glasses or contact lenses, they will be able to tell you if you need a new prescription.
As presbyopia is a continual process, your prescription is likely to change significantly between the ages of 45 and 65. It is recommended that you have an eye test every 1 to 2 years.
How is presbyopia treated?
Presbyopia is usually corrected with the use of glasses, and sometimes with contact lenses. Many people begin with simple reading glasses, but prescription bifocals, multifocals and more specialized lenses are also available.
Wearing glasses to correct presbyopia doesn't change how quickly the condition develops and will not weaken your eyes.
A few surgical techniques are also available to improve the eyesight of people with presbyopia, but they cannot be reversed and are not totally effective over long periods of time. If you are considering surgery, discuss it first with your doctor and your ophthalmologist.