Why should I have an eye examination?
Eye examinations are important because more than 80% of the information you take in is visual. That means if you aren’t seeing as well as you should be then you are potentially missing out on quite a lot.
Also could you imagine not being able to see? That is a very important reason why regular eye health examination are important. We want to pickup small issues before they become big problems later.
The worst time to pickup an eye problem is when you have had it for many years. Prevention is better than any cure and many eye conditions can be treated if picked up early.
Who should have their eyes examined?
Everyone. Especially if you have never had an eye examination then now is the best time to start. For children they should have their first examination well before school so any problems can be identified and treated. Particularly if they have a lazy eye the sooner that we can start treating it the faster it can be fixed.
What are the things that are checked during an eye examination?
The two major things we do during an eye examination is to measure your vision checking for refractive errors such as short sightedness (myopia) long sightedness (hyperopia) and astigmatism. The second is to check your eye health in detail with our slit lamp microscope, retinal camera and other high tech devices.
What can I expect during my eye examination?
If it is your first time to see us we will ask you to fill in a new details form which includes many questions about your vision, eye health, medical history and family medical history. This makes it much easier for us to give you the best possible eye examination.
The first step in the eye examination is a mesurement of the focus of your eyes. This is done using an auto-refractor which uses infra-red light to measure the focus of your eyes all without you saying anything. Whilst it doesn’t entirely replace the “which is better one or two?” it does get us about 90% there.
The second test is a puff of air to measure the fluid pressure in your eye (intra-ocular pressure). This air-puff device is called a non-contact tonometer and it is an important screening tool for Glaucoma. The air pull slightly presses on your eye until it has equalised the air puff pressure with your eye pressure, then it displays a result.
The eye pressure measued with a non-contact tonometer is almost the same as that measure by an ophthalmologist with a contact device called a Goldmann tonometer. Whilst there might be a small difference at very high or very low pressures for the majority of people with normal eye pressures this is not an issue.
The next step is to measure your current spectacles (using a vertometer) and any other glasses you might have brought along.
We will then go through your medical history and any current problems you might be having.
Then we measure your spectacle prescription using the old ‘which is better one or two?” to refine the answer given from the auto-refractor. This shouldn’t take too long and don’t worry its not a test you can get wrong. We then check your reading and computer vision. It is up to us to make sense of your answers and to convert that into a spectacle prescription that gives clear and comfortable vision.
We measure the way that your eyes work together and make sure you are getting stereo vision (3D) and the eyes don’t need exercises or prism to help realign them.
We then use a slit lamp biomicroscope to examined the front and back of your eyes in detail.
When we are looking at the front of your eyes we start on the eye lids and lashes before moving onto the tear film on the very surface of your eye. We then check the cornea, conjunctiva, iris, pupil, lens, anterior chamber as well as the drainage angle of your eye.
When we look at the back of your eyes we hold up a small lens that allows us to focus on your retina. We are then checking the vitreous jelly of your eye as well as your optic nerves and macula as well as the arteries, veins and nerves that are found on your retina.
When all of this is combined with your eye pressure and medical history we then discuss our findings in detail. For most people their eyes are healthy and they just need new glasses or a regular follow up visit. For some people we might need to send you onto see an eye doctor (ophthalmologist) to further examine any issues.
How often should I have an eye examination?
As a general rule of thumb about every 2 years is a good schedule for eye examination. However if your eyes are changing or if we want to monitor any small issues with your vision we would recommend seeing you more often, sometimes every 6 or 12 months.
For children we often see them about every 6 months if their eyes are changing or 12 months for those who are not.
For older people with eye diseases such as macula degeneration or glaucoma the review period can be much shorter than this. If you notice any small changes to your vision we want to see you as soon as possible so we can determine if you need a referal to see an eye specialists or if it is something we can help with.
What is 20/20 vision?
20/20 vision means that you can see at 20 feet what the “normal” person can see at 20 feet. In Australia we use the metric system so the equivalent is 6/6 vision.
There are many different types of eye charts that measure either Snellen (20/20) visual acuity or LogMar (1.0) visual acuity. What they are trying to measure is the same but it is easier to compare vision for research using LogMar notation however it doesn’t mean as much to the general public.
To measure your vision at 6 metres would either require a very long room or more commonly a mirror that doubles the distance from the test chart. That is why you find most optometrists use a mirror on the wall and you view the chart in that.
Colour vision testing
We have a number of excellent tests for colour vision including:
Ishihara colour vision test book
The Ishihara colour vision test book includes a number of coloured plates with numbers on them that are confused if you have particular types of colour vision problems. This is considered a screening colour vision test as it will tell you if you have a problem but not exactly which type of colour vision problem or how severe it is.
The pages consist of a circular ring which is filled with colour dots of different sizes, brightness and colours. For people with normal colour vision they see one number and those with colour vision problems can see a different number or nothing at all. Also there are some plates that if you see nothing you are normal and if you see a number you have a colour vision problem.
It is known as a pseudoisochromatic test as the colours appear the same but are actually different.
Farnsworth Munsell D15 Test
The farnsworth munsell D15 test is a test using coloured paint chips that need to be arranging in changing hue order. This test can indicate a bit more information about the severity of the defect and the type of colour vision problem (Red/Green, Blue/Yellow etc).
Should everyone have a colour vision test?
Yes, especially if you have never had one before. Because the rate of colour vision problems is much higher in males all boys should have their colour vision tested at an early age. This allows them to be aware of any occupations which might not be available to them because of their colour vision problems (such as electricians, signallers, painters etc)
Peripheral visual field testing
Sometimes it is important to measure how far out you can see. We use a humphrey field analyser to measure the sensitivity to your vision across your visual field.
This is a great tool to take a baseline measure of how well you see today and then monitor it for changes over time. This is especially important in Glaucoma detection and monitoring. Glaucoma is a condition that affects your peripheral vision so it is important to detect small losses early.
Many brain and eye conditions can cause a loss of peripheral vision or vision abnormalities that can be detected using a field analyser.
The Zeiss humphrey field analyser works by keeping your head and eye still (looking straight ahead with your chin on a rest) and then projecting lights of different brightness across a white dome that you are looking at. You are required to press a button everytime you see a light flash or every time you ‘think’ you see a light flash.
We also have a Zeiss matrix field analyser that uses frequency doubling technology to pick up early changes in visual field. Sometimes we will use this machine to screen people who are suspicious for Glaucoma or for a baseline measurement.
Contrast sensitivity and vision
Sometimes you will be able to see very well on the black and white eye chart but you find your vision is just not as good as it should be.
This can sometimes be due to reduced contrast sensitivity. What this means is that you can’t tell small differences between shades of grey/black as well as you used to. This can manifest as increasing difficulties driving, particularly at night or when it is raining. Also you might feel you just aren’t seeing as well as you used to or not feel as confident when driving.
Contrast sensitivity is very important when driving in the rain or anytime when the lighting is not quite good enough. PIlots who land planes on a grey aircraft carrier on a dark ocean in a grey sky have been shown to have amazing contrast sensitivity. For them it is all about shades of grey as the ocean moves, the aircraft carrier moves and their plane moves.
If you have increasing cataract you are seeing the world through a bit of frosted glass so nothing is quite as black on white as before. Once this starts to affect your vision or driving then it is time to see an eye doctor to discuss possible cataract surgery.
There are many ways to measure contrast sensitivity. Our computerised eye chart allows us to measure it exactly and we can compare it between visits.
Sometimes we find that prescribing a specific yellow tinted lens especially for driving makes a big difference to your comfort and safety.