Eye Conditions - Adult Vision

What is Astigmatism?

Astigmatism is a condition where the optical power of the eye varies depending on the angle of light passing through it. Astigmatism produces blurred vision at all distances. It is usually due to the shape of the cornea (the front surface of the eye). If the curvature of the cornea is not the same in all directions (like the side of an Australian football) it will bend the light passing through it by different amounts depending on the direction of the light, producing astigmatism.

Astigmatism is a focusing error which causes asymmetric blur. Some directions in an image are more out of focus than others.

Astigmatism is not an eye disease and any changes are generally gradual and not necessarily for the worse. Most people have at least very slight astigmatism.

What does it look like?

Astigmatism causes different amounts of blur in different directions. This causes images to appear distorted, or sometimes even double. Certain letters may be more difficult to read than others, depending on the orientation of the lines within them.

One type of chart used to detect astigmatism uses a series of lines arranged in a fan shape – if you have astigmatism, some lines will appear clearer than others.

How is Astigmatism corrected?

Glasses and contact lenses (hard and soft) can correct Astigmatism. Sometimes correction of Astigmatism can cause change in the apparent size and shape of objects and may affect judgment of distance. A patient may feel taller or shorter, or walls may appear to slope and floors curve. In most cases, adjustment to these side effects takes only a week or so. Astigmatism correction may involve a compromise between optimal clarity and visual discomfort.

How is Astigmatism detected?

Some people notice blur themselves. Only a proper eye examination will determine for certain if you have Astigmatism.

What is Myopia? (Shortsightedness)

Myopia, commonly called Shortsightedness, is a condition in which light is focused in front of the retina, resulting in blurred vision. Shortsighted people can often see reasonably clearly at short distances, but will not be able to see distant objects clearly.

There is currently no cure for myopia, but spectacles, contact lenses and refractive surgery can all provide good distance vision for people with myopia.

How can I tell if I am Shortsighted?

Shortsighted people have difficulty in seeing distant objects clearly. They find it hard to read road signs and scoreboards and to play ball games. Recognising people in the distance may be a problem for many shortsighted people. Often a person will not realise that they cannot see clearly but an eye examination by an optometrist will reveal the problem.

How can I tell if my child is Shortsighted?

A complete eye test is the only sure way of determining whether your child’s vision is normal. Some clues to myopia in a child are:

  • Screwing up eyes to see distant objects.
  • Difficulty reading the blackboard at school.
  • Poor posture while reading.
  • Lack of interest in playing outdoor games.

What causes Myopia?

The exact causes of myopia are not known. At various times people have blamed excessive amounts of reading, poor metabolism, poor diet, poor light, poor posture and genetic factors. Recent research has shown that the development of myopia is influenced by both genetic and environmental factors.

Myopia is now considered a diseases as in ‘normal’ people have the size of the eye set at 12 months of age whereas in myopia the eye gets longer as we get older.

How common is Myopia?

It is a very common condition. About 15 per cent of the Australian population is shortsighted. Usually myopia begins to develop in teenage years and it may Hyperopia or long-sightedness is a condition in which the optical components of the eye are not strong enough and so light is not focused onto the retina. This results in blurred vision that is usually worse at shorter distances.

What is Hyperopia? (Longsightedness)

People with Hyperopia often have reasonable vision in the distance, but may find that their vision is blurred or that they experience feelings of eyestrain or headaches when doing near work such as reading.

The eye’s lens and cornea focus light into an image on the retina, just as a camera lens focuses light on to a film. In a resting hyperopic (longsighted) eye, the light is focused behind the retina and so the image is blurred. The perfect state of focusing exactly on the retina is unusual; the average person is a little Hyperopic.

How does Hyperopia affect vision?

A little Hyperopia is not a problem because the lens compensates easily but if there is a significant amount of Hyperopia, the effort of focusing (called accommodation) can lead to symptoms. A Hyperopic person can have normal vision but the greater the Hyperopia, the harder it is to focus. Vision may become blurry, especially for close objects, because the closer the object the more focusing is required. Hyperopic people may get tired eyes or headaches after a lot of visual work, even if their vision is clear. Reading is more difficult and school work can be affected.

What causes Hyperopia?

Hyperopia is often thought to be hereditary, but no-one is certain. The eyeball may be a little smaller than average.

Does Hyperopia change with age?

Hyperopia tends to increase with age, but not always. We all find it harder to focus on close objects as we get older. Hyperopes have trouble sooner and may need reading spectacles earlier because they have to focus more to start with.

How is Hyperopia diagnosed?

Because a Hyperopic person often can see well in the distance, a letter chart test alone may miss Hyperopia. Special tests have to be used, including retinoscopy and refraction.

What do we do about Hyperopia?

The optometrist has many things to consider when making a decision and symptoms are very important. In general, young people who are slightly hyperopic do not have problems. If they do, they may benefit from eye exercises or need spectacles, mainly for close work such as reading and using computers. Older people, or young people with significant Hyperopia, often have problems because focusing requires much effort. Their vision is more likely to be blurred, especially for close objects. They usually need spectacles for reading and sometimes for distance vision as well.

Why Hyperopia is called Longsightedness?

Hyperopic people generally can see better in the distance than close, but they cannot see better at any distance than someone who is not hyperopic and get worse over the following few years.

 

What is Presbyopia?

Presbyopia is a common condition that makes vision difficult at a normal reading distance. It is not a disease. It involves the gradual reduction in the amount that the eye can change its focus. The changes are the result of the continued growth of the biological lens inside the eye, and are a normal part of ageing. Presbyopia usually becomes noticeable between the ages of 40 and 50 as an inability to focus on near objects. People in this age group often find that they have to hold things further away to see them clearly. Presbyopia can be corrected by an optical prescription specifically designed for close work. This can be provided in many forms, including reading glasses, bifocals, trifocals and progressive lenses (multifocals).

How will Presbyopia affect my vision?

Close tasks such as reading and sewing become difficult, particularly in poor light. For example, you may find that you are holding your newspaper further away from your eyes to make the print clearer. You may also have difficulty concentrating when reading or you may find periods of close work result in sore eyes, headaches or tiredness. Presbyopia does not affect distance vision.

What causes Presbyopia?

It is important to understand how your eyes change their focus for viewing close objects. Normally they are focused for distance vision. Inside the eye there is a lens about the size of a pea. To focus on close objects, a special muscle in the eye changes the shape of the lens. This process is called accommodation. With age the lens loses its flexibility and is less able to change its shape. This is a completely normal ageing change, just like stiffening joints or greying hair. The loss in lens flexibility is the reason that close focusing becomes more difficult.

Who is likely to become Presbyopic?

Everyone experiences the ageing process that causes presbyopia. The condition cannot be prevented.

Does Presbyopia come on quickly?

No. Presbyopia is usually first noticed around the age of 40 to 45 years. Although difficulties with close work may seem to come on suddenly, the ageing process that causes presbyopia is gradual and has been going on since childhood. Between the ages of 45 and 65, the amount of presbyopia increases, making near work more difficult. From 65 years onwards, there are unlikely to be any further significant changes to vision due to presbyopia.

How is Presbyopia treated?

Presbyopia is corrected by a prescription designed especially for close distances, in the form of glasses or contact lenses. It is important that the prescription is calculated for the distance at which you do your close tasks. It is not possible to treat Presbyopia by surgery.

Through discussion with your optometrist, you will be able to decide on the best way of preparing your prescription. The correction for presbyopia will make near objects clear but distant objects blurry. This means that if you have a pair of glasses just for reading, you will not be able to watch television while wearing them.

Having different prescriptions for distance and reading can be a nuisance, especially if you have to change glasses all the time. One way around the problem is the use of bifocals. These are special lenses that have a prescription for distance vision in the top half of the lens and the prescription for near vision (reading) in the lower half. Another form of spectacles used to correct presbyopia is ‘look-overs’ (half-glasses). Other options include the use of trifocals, progressive lenses and some special contact lens prescriptions.

Does Presbyopia mean that my eyes are deteriorating?

No. Although your close focusing system is not functioning as well as it used to, once presbyopia has been corrected with spectacles you will be able to see close things as well as you always did. Presbyopia does not represent a threat to your eyes’ health.

When should I have my Prescription for Presbyopia renewed?

Between the ages of 45 and 65 years, your prescription is likely to change significantly. It is sensible to have your eyes examined every two to three years to review your correction and your general eye health. If you experience vision problems within two or three years of your previous examination, you should make a review appointment with your optometrist. Your optometrist will advise you of the most appropriate period between consultations.

Will wearing glasses weaken my eyes?

No. Presbyopia will continue regardless of whether glasses are worn. Wearing glasses will not accelerate or slow the development of presbyopia.

What is a Pterygium (pronounced: ter-idge-ee-um)?

A Pterygium (pronounced ter-idge-ee-um, plural: pterygia) is a triangular-shaped lump of tissue with blood vessels that grows from the conjunctiva (the thin membrane that covers the white of the eye) on to the cornea (the clear central part of the eye). Pterygia frequently occur in both eyes, usually on the side of the eye closer to the nose. A Pterygium is not a cancer. People sometimes confuse Pterygia with cataracts. A cataract is a clouding of the lens inside the eye and cannot be seen easily with the naked eye.

What causes Pterygia?

The development of Pterygia is strongly associated with exposure to ultraviolet radiation and hot, dry environments. In Tasmania with a reduction in the ozone layer people who spent their early childhood at outside, on or near water were found to have a higher risk of developing Pterygia.

Are Pterygia dangerous?

Pterygia are not dangerous, but they can be a problem cosmetically and can cause irritation and redness. Pterygia may also interfere with vision as their growth can cause corneal distortion. If the Pterygium grows on to the central part of the cornea it can begin to block light from entering the eye. Although a Pterygium is not dangerous, it should be checked to make sure that it is not something more serious. If you have any area of tissue on or around the eyes that changes rapidly or that you have not had checked previously you should make an appointment with an optometrist or eye surgeon (ophthalmologist).

How can Pterygia be treated?

In cases where the Pterygium is not actively growing on to the cornea, protecting the eyes from ultraviolet light will often stabilise its growth. In many cases, provided it is not threatening vision and it remains stable, this may be all that is required.

If a Pterygium causes discomfort, eye drops and artificial tears may help.

In cases where a Pterygium is actively growing on to the cornea and threatening to distort the vision, the only effective treatment is surgical removal. This surgery is usually performed under a local anesthetic. It is best to have surgery before the Pterygium progresses to the point where it interferes with vision. Your optometrist can assess the Pterygium and refer you to an eye surgeon if the Pterygium requires removal.

Can I wear contact lenses if I have a Pterygium?

Your optometrist will be able to advise you regarding the most suitable contact lens for your situation and will require you to attend for regular contact lens aftercare visits so that they can monitor changes in corneal shape that may indicate progression of the Pterygium and check the ongoing suitability of the fit of the contact lens.

How can Pterygia be prevented?

The best way to reduce your risk of developing a Pterygium, or to slow the progression of an existing Pterygium, is to protect your eyes from ultraviolet light. UV radiation can also cause cataracts and other eye diseases, as well as skin cancers, so reducing exposure is a wise move. The best ways of doing this are to:

  • Avoid the sun: UV radiation is strongest between 10 am and 3 pm. Staying out of the sun between those times will significantly reduce your UV exposure.
  • Wear a hat/cap: a broad-brimmed hat will not only protect your head from sunburn, but will reduce by at least half the amount of UV radiation reaching your eyes.
  • Wear sunglasses: a good pair of sunglasses will reduce the amount of UV reaching your eyes and cut the amount of glare. Wrap-around sunglasses are best as they block UV radiation that can slip around the sides of conventional sunglasses.

Parents should ensure that they protect the eyes of babies and children from ultraviolet light through the use of hats and children’s sunglasses that meet the Australian Standards.

Can Pterygia grow back after they have been removed?

It is uncommon for Pterygia to grow back after they have been surgically removed.