Research shows that more than 90 per cent of us are more scared of losing our sight than any of our senses. Yet many of us still take our eyesight for granted. Liz Bestic looks at how the eye works, what can sometimes go wrong and how best to care for our vision
Seeing can be likened to the process of taking pictures on a film with a camera which you then get developed. The retina is like a camera film which stores an image of what we are looking at. The image directed on to the retina is then sent to the brain where it is processed, like developing a camera film.
Therefore, we actually “see” in our brain with the light information sent to it from our eyes. This whole process happens very quickly so that everything we see is in focus.
Familiarity with the symptoms of common eye conditions can help you to prevent an initially minor infection or problem from becoming a major health issue.
Some eye conditions can be indicators of deeper, underlying health problems such as diabetes or high blood pressure, which with the right treatment can be managed or even eradicated.
However, it is essential that you have regular general health checks, as well as regular eye tests to ensure a healthy lifestyle.
Cataracts are the leading cause of impaired vision throughout the world. Around one in three people over 65 has a cataract, although they can develop at any age.
Men and women are affected equally and one eye is usually more affected than the other. Although most cataracts are age-related, some may occur earlier in life with illnesses, such as diabetes, or with eye injuries, long-standing inflammation and also with some drug treatments.
The symptoms of age-related cataracts develop gradually, getting worse over many months. Some people describe having a cataract as a bit like having a dirty windscreen on a car making the vision cloudy, foggy or sometimes blurry.
“Changes in focus are also likely, and common complaints include problems with glare, particularly from oncoming car headlights, and misty vision,” says Bruce Allan, consultant ophthalmic surgeon at Moorfields Eye Hospital in London.
Lifestyle modifications can reduce the risk of cataract development, and include not smoking and good blood sugar control in diabetic patients.
Cataract surgery can be performed equally successfully at any age and with either advanced or early-stage cataracts. It involves replacing the misty lens with an artificial lens.
Surgery is carried out under local anaesthetic and usually takes around 20 minutes. A key-hole technique is used in which a probe is inserted through a tiny, self-sealing, valve-type entry into the eye. The probe breaks up and vacuums out the hardened, misty lens using ultrasound energy.
A soft plastic lens is then injected within the lens capsule just behind the pupil. The operation is not painful and vision normally recovers substantially within two days, once the strong pupil-dilating drugs, used before surgery, wear off.
AGE-RELATED MACULAR DEGENERATION
By the year 2020, it is predicted that more than 750,000 people in the UK will have age-related macular degeneration (AMD), which is the leading cause of sight loss in the Western world.
AMD is more common in the over-60s, but it can occur in people in their 40s and 50s. There are two different types of AMD – wet and dry. The condition affects a small part of the retina at the back of the eye, known as the macula, causing blurred vision and leading to potential sight loss.
Symptoms include distorted vision, such as straight lines becoming wavy, or objects appearing the wrong size. Blurry or blank patches in central vision are also common and people may have difficulty reading, recognising faces, driving, looking at small objects and watching television.
Although the exact cause of AMD is unknown, risk factors include smoking, poor diet and old age.
There is currently no cure for either type of the condition, but early diagnosis and treatment of wet AMD – which is acute – is crucial in order to prevent vision loss. Dry AMD, which is more common but develops gradually, is not treatable. However, there are services available to support people with sight problems caused by the condition.
AMD may normally be associated with older age, but there are steps you can take earlier in life to minimise your risk.
Research suggests that a diet rich in leafy, green vegetables, brightly coloured fruit and vegetables, and oily fish may help prevent AMD. “Smoking doubles your chances of developing the condition, so quitting can reduce your risk,” says Dr Susan Blakeney, optometric adviser to the College of Optometrists.
Some experts recommend supplements of lutein, zeaxanthin and meso zeaxanthin. “There is a growing body of evidence that antioxidant supplements containing these macular carotenoids may prevent or delay the onset or progression of AMD,” says Dr John Nolan, programme director at the Macular Pigment Research Group, Waterford Institute of Technology, Ireland.
One of the most serious complications of diabetes is the development of diabetic retinopathy. Some 40 per cent of people with type 1 diabetes and 20 per cent with type 2 diabetes will develop this condition during their lifetime.
Diabetes affects the tiny blood vessels of the eye so, if they become blocked or leak, the retina and vision are affected. The extent of these changes determines the type of diabetic retinopathy.
Background diabetic retinopathy is the most common type where the blood vessels in the retina are only mildly affected. When diabetic retinopathy progresses, however, it can cause the larger blood vessels in the retina to become blocked.
This can either affect the sight directly or stimulate the formation of abnormal new blood vessels – a process known as proliferative diabetic retinopathy. This can result in large haemorrhages over the surface of the retina or into the vitreous gel, totally obscuring the vision in the affected eye.
Extensive haemorrhages can lead to scar tissue forming which pulls and distorts the retina. This type of advanced diabetic eye disease can result in the retina becoming detached with the risk of serious sight loss.
Regular diabetic eye screening at least once a year can help discover any changes in the blood vessels of the retina which can then be treated with a laser to stop sight loss.
Looking after your diabetes with good sugar and blood pressure control can help avoid the potential changes to the eye and maintain vision. Regular retinal screening will keep a close check on early changes and ensure that any signs of progression to more serious stages of retinopathy are detected early.
Not everyone who has diabetes develops an eye complication. Of those who do, many have a very mild form of retinopathy which may never progress to a sight-threatening condition.
Silent thief stealing sight
GLAUCOMA The incidence of glaucoma is set to rise by 33 per cent in the UK over the next decade. Although a cure may not be on the horizon, groundbreaking research is giving reason for hope, as Liz Bestic reports
Glaucoma affects around 5 per cent of people over the age of 65. Primary open angle glaucoma (POAG) is the most common type and becomes more prevalent with age.
It results in a narrowing of the field of vision, due to pressure on the optic nerve, caused by a build-up of the fluid that supplies the eyes with oxygen and nutrients, and removes waste.
As many as 250,000 people may be going undiagnosed each year because the deterioration of sight is slow, with virtually no symptoms
Initially, only peripheral vision is affected, with the centre of the visual field affected last, resulting in so-called tunnel vision, likened to looking through a long tube.
Glaucoma is genetic so those with close blood relatives with POAG are four times more at risk of developing the condition. People of African origin are also more at risk, along with those with diabetes, very short sight, high blood pressure and hypothyroidism.
As many as 250,000 people may be going undiagnosed each year because the deterioration of sight is slow, with virtually no symptoms. However, detected early, glaucoma is simple to treat with eye drops.
New technology has helped in the detection of glaucoma. A puff-of-air test can gauge the pressure in the eye and perimetry, which shows sight loss in peripheral vision, can help to spot early signs.
Early detection is really important in glaucoma, as most of the sight loss is preventable. If the disease is detected late, it is much harder to treat and the risk of vision loss is much higher.
Professor David Garway-Heath, consultant ophthalmologist at Moorfields Eye Hospital NHS Foundation Trust, London, is leading the UK Glaucoma Treatment Study.
“Although high eye pressure is the major risk for glaucoma, other factors may make patients more susceptible to glaucoma,” says Professor Garway-Heath. “Our study is looking at what may make patients more or less susceptible to this condition.”
Also at Moorfields NHS Trust, a brand new test for field of vision, which can be run on a laptop computer, could revolutionise the way glaucoma is detected. Each eye is tested separately; the patient is asked to look at a central spot on the computer screen and to press the mouse each time a line on the screen is seen to move.
“We are hoping that this test will make a real difference in both the developed and developing world, and reduce unnecessary blindness from glaucoma which results from late diagnosis,” says Professor Garway-Heath.