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Frequently Asked Questions

This page has a list of eye examination questions. Alternatively you can see FAQs on:

General Issues
Contact Lenses

What are you doing when you flip the lenses and ask "Is it better with 1 or 2?” ?

This is a test for astigmatism.

Why do you ask about previous eye problems?

We need to know this in order to avoid unnecessary referral to the doctor or hospital.

We will ask if you have had any accidents or injuries to your eyes, or if you have ever had any treatment on them. This includes any treatment you may have had as a child.

If you had a squint operation as a child, or had to wear an eye patch or do exercises, then you may have poor vision in one eye. If we find poor vision and we did not know your history we would be concerned by this finding. If we know that you have a lazy eye then we know that it is normal for you.

If you had an injury that could have left a scar then we will know what it is we are looking at. If we have no explanation to account for a scar or damage then we may refer you.

Some injuries can cause problems many years after the initial injury has healed. For example a bad blow to the eye can cause traumatic cataract decades later.

A recent injury to the eye could cause damage that you may not be aware of.

Some forms of surgery mean that we have to be particularly careful about what examinations we perform.

What are the red and green circles for?

This is a test to make sure that the final prescription is balanced.

If the circles on the red are much clearer you may find that distance vision is not very good.

If the circles on the green are much clearer you may find that your close vision is not very good.

It is not always possible to balance the colours perfectly and we will leave one colour clearer depending on what the final spectacles or contact lenses are to be used for.

Some people find this test very difficult but this does not mean that your spectacles will be wrong. We have other methods of making sure that you get the best correction for your eyes.

Why are some of the lenses in different coloured holders?

One set of lenses is used to correct for short sightedness and one for long sightedness.

The colour coding is simply to make identification easier for the optometrist. You may have a combination of different coloured holders if you have astigmatism.

Not all lens sets have the same colour coding so do not be alarmed if your previous optometrist used one colour and we use another.

Why do you want a photograph of the back of my eyes?

"A picture tells a thousand words"

A photograph is a much better record of the health of your eyes than a written record. If we see you regularly we can compare current photographs with old ones and any changes are immediately obvious.

The photographs also give us much more detail than we can obtain by other methods and we can examine them more thoroughly without causing you discomfort.

They are also very useful for referral. If we see a problem we can send a copy of the photograph to the specialist so that they know exactly what we are concerned about.

Photographs allow us to show you what we are looking at. If we see a problem we can show you exactly what we are talking about and explain it properly rather than your imagination creating some horrible picture for you.

You can have a copy of the picture if you want one. We can e-mail it to you for free (broadband only – they are very big files) just ask and give us your e-mail address.

Why do I need a copy of my prescription?

The simple answer is that we are required, by law, to give you a copy. A spectacle prescription is a medical document and should be kept in a safe place.

We can give you a second copy if you lose yours one but a charge may be made for this.

You are free to take your prescription to any optician to have your spectacles made up. You will also need it if you want contact lenses.

It is useful to carry with you if you go on holiday just in case you break your spectacles or lose a contact lens. Prescriptions are recognised world wide.

Old prescriptions provide a useful record of the changes that have occurred in your prescription. This is particularly useful if you move house and go to a new optometrist.

You may have to take your prescription with you if you have to go to hospital about your eyes.

How often should I have my eyes tested?

That depends!

Everyone should have an eye examination at least every two years, even if you don’t need glasses.

If you are over 40 years of age and have a relative with glaucoma – every year

Under 16 years of age – at least once a year

Contact lens wearers – at least once a year

Your optometrist will tell you when your next examination is due. A number of factors will be taken into account when deciding the appropriate interval and you could be advised to come back be within 3 months or allowed to "escape" for as long as 2 years.

What is the test with all the flashing dots for?

This is called a field test and is used to test your peripheral vision.

Peripheral vision means what you see “off to the edges” rather than straight ahead.

It is this peripheral vision that is damaged by glaucoma. It is therefore one of the tests used to determine if someone is developing glaucoma.

You would not necessarily notice a loss of peripheral vision as it often happens slowly, and humans are very adaptable creatures.

Glaucoma is not the only cause of peripheral vision loss. Other causes include Stroke, eye injury, haemorrhages and tumours.

If we do a field test it does not necessarily mean that we think you have any of these conditions. It is done routinely as part of a normal eye examination, although you may not have it done every time.

Migraine can also cause temporary loss of peripheral vision.

What are you looking for when you shine the light into my eyes?

We are looking at the health of your eyes.

We make sure that your pupils are reacting to light as they should do.

We look at the front of your eyes to make sure that they are normal.

We check to see if you have any cataract or other similar problems.

We look at the retina to make sure that it is healthy and normal.

We can also take a photograph of the retina which is a much better way of recording the health of your eyes. We can compare photographs at each visit and make sure that nothing has changed.

What is the pressure test for?

This is one of the tests for glaucoma.

The eyes are filled with fluid which stops them from collapsing. Some of this fluid is constantly produced and drained away. If this mechanism is faulty the pressure in the eye can rise and can cause damage to the nerves. This leads to sight loss and, if this happens, it is called glaucoma. High pressure does not always lead to glaucoma but needs to be monitored regularly.

Moderate high pressure does not cause any symptoms so you would not necessarily know that you had a problem. This is why we recommend regular eye examinations.

Some other conditions can cause the pressure to fall below a healthy level.