An eye test reveals much more about you than most people realise. Indeed, the information gleaned could save your life, as Judy Hobson reports
Not only can an eye examination diagnose eye disease and assess whether you need glasses, it can also detect life-threatening brain tumours and heart disease, enabling these to be picked up in their early stages and treated.
Dr Susan Blakeney, clinical adviser to the College of Optometrists, says: “If someone is developing a brain tumour and it’s starting to press on their optic nerve, then this may cause blind spots in certain areas of their vision. This may not be apparent to the patient, but we may be able to pick it up during a visual field test.”
This test is used to assess peripheral vision. One way of doing it is for the person being tested to look down a tube at a screen and keep gazing at a central spot. Then whenever they see pinpricks of light flash around the outside, they press a button and a graph of the results is printed out.
Visual field testing, according to Sonal Rughani, health adviser to the Royal National Institute of Blind People (RNIB) and a practising optometrist, is a particularly important part of an eye examination for those complaining of unexplained headaches.
The eye is the only transparent organ in your body, enabling us to see into it
She says: “The test tracks the pathway through the optic nerve to the back of the brain and provides essential clues about any lesions or tumours affecting the visual pathway. By careful interpretation of the results, it’s possible for us to locate the lesion.
“Eye examinations are a very accurate indicator of health. The blood vessels that nourish the eye are delicate and thin. Changes where they become more ‘wiggly’ or tortuous can be a sign of raised blood pressure.”
Dr Blakeney says: “The eye is the only transparent organ in your body. It enables us to see into it, allowing us to see whether there’s been any haemorrhaging which could indicate diabetes. If we see this we would advise you to see your GP.”
Having your eyes examined regularly is important because in some conditions they do not hurt even when something is wrong. People with glaucoma, for example, often have no symptoms until they have lost quite a lot of sight.
Those over 40, the age when the disease often starts to develop, should have regular eye tests so that it can be detected as soon as possible and they can get treatment to slow down its progression. This is especially important for people of African and Caribbean origin because they are at greater risk of developing glaucoma and at an earlier age. After 40, those with a family history of the disease are entitled to free NHS eye examinations along with people aged 60 and over.
“Sadly, some people leave it too late,” says Larry Benjamin from the Royal College of Ophthalmologists. “Glaucoma is a slow, silent disease and by the time they go for an eye examination they will have lost most of the vision in one eye. One in 100 people develop glaucoma, but we don’t know who they’re going to be, which is why it is so important everyone has their eyes examined regularly.”
An eye examination takes around 30 minutes. The sharpness and clarity of your vision are assessed by asking you to read letters of different size on a lit screen 20 feet away.
If you need glasses or already wear them and the optometrist thinks they need changing, you will be asked to look through different lenses at letters on the chart and then a prescription will be written.
To check your eyes work well together, the optometrist will look to see how your pupils react to light and, by covering each of your eyes in turn, watch how the covered eye reacts when it is uncovered and fixates on a target.
To measure the pressure in your eyes, a small probe will gently touch the cornea after a drop of local anaesthetic and some yellow dye has been put into your eyes. But in a routine examination, pressure in the eyes will simply be measured by blowing a puff of air into each eye in what is known as the “puffer test”.
An instrument called a biomicroscope will be used to examine the front and back of your eyes, and assess overall health. If the optometrist needs to make a closer inspection of the back of your eye, special drops will be inserted to increase the size of the pupil enabling the optometrist to get a full view of the retina.
Captured by the camera
DIGITAL RETINAL PHOTOGRAPHY State-of-the-art digital photography is helping eye doctors to detect problem conditions and keep an accurate record of patients’ health, writes Judy Hobson
The detailed pictures digital photography provides of the macula, retina and optic nerve are enabling optometrists and ophthalmic surgeons to detect subtle changes in the eyes that might otherwise be missed.
Another advantage is that the images serve as a photographic record of what is going on in the eye and can be used for comparison during subsequent examinations.
Ophthalmic scientist Richard Hildred, whose medical imaging company Medical Imaging UK is the biggest independent provider of diabetic screening equipment in the country, says digital retinal photography has come into its own during the past decade.
“In the 1960s and ‘70s, pictures of the eye were taken with a film camera,” he says. “Then in the early-1990s digital chips were put in the cameras instead. From 2000 the quality of the digital chips and equipment has improved dramatically, providing instant results for patients and eye doctors.”
It’s a great educational tool and helps me explain eye conditions to patients
Digital retinal photography is now being offered by many leading high street optometrists for a fee of £10 as an add-on to an NHS eye check. It is provided free as part of the annual NHS retinal screening of diabetic patients.
Larry Benjamin, consultant ophthalmic surgeon at Stoke Mandeville Hospital and spokesman for the Royal College of Ophthalmologists, says: “The traditional back-of-the-eye cameras produced pretty good pictures, but the resolution you get with a digital camera is much better and the equipment is easier to use.
“The picture is produced in an instant. In my diabetes eye clinic this allows me immediately to show a patient exactly what’s wrong with their eyes. They can see where blood vessels are leaking and this helps them understand why they need to have laser treatment. It’s a great educational tool and helps me explain eye conditions to patients.”
Having the technology in the high street helps optometrists to diagnose disease in its early stages which allows early referral to a hospital eye clinic where it can be monitored and managed.
Dr Susan Blakeney, a practising optometrist and spokesperson for the College of Optometrists, says: “Years ago, all we had to rely on were handwritten notes of what we saw when we examined someone’s eyes. We described what we saw as best we could, but having a photographic record makes spotting any changes so much easier.”