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GLAUCOMA

Glaucoma is the name for a group of eye conditions in which the optic nerve is damaged at the point where it enters the eye. This nerve carries information from the retina to the brain where it is perceived as a picture.

Your eye needs a certain amount of pressure to keep the eyeball in shape so that it can work properly. In some people, the damage is caused by raised pressure – which is why our optometrist will check your eye pressure (intraocular pressures) during your sight test. Other glaucoma patients may have pressures within normal limits but damage can still occur as a result of a weakness in the optic nerve. Eye pressure is largely independent of blood pressure.

 

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A layer of cells behind the iris produces a watery fluid called aqueous. The fluid passes through the pupil, a hole in the centre of the iris. It leaves the eye through tiny drainage channels called the trabecular meshwork. They are in the angle between the front layer of the eye (the cornea) and the iris and return the fluid to the blood stream. Normally the fluid produced is balanced by it draining out, but if it cannot escape, or too much is produced, then the eye pressure can rise.

If the optic nerve comes under too much pressure then it can be damaged. How much harm is done depends on the level and duration of the raised pressures – and whether there is a poor blood supply or other weakness of the optic nerve. A very high pressure can damage the optic nerve in a short period of time. Normal tension glaucoma can cause a gradual loss of sight if not treated.

There are four main types of glaucoma, the most common being chronic glaucoma. The eye pressure rises very slowly and there is no pain to show a problem, but the field of vision gradually becomes impaired. Acute glaucoma is much less common. This happens when there is a sudden and more complete blockage to the flow of aqueous fluid to the eye. This is because the narrow ‘angle’ closes to prevent fluid ever getting to the drainage channels. This can be quite painful and will cause permanent damage to your sight if not treated urgently.
In the UK, some form of glaucoma affects about 2 in 100 people over the age of 40.
Age, race, short sight, diabetes and a close family history of glaucoma can increase the risks of glaucoma.

Some people will notice sight is poorer in one eye than the other. The early loss in the field of vision is usually in the shape of an arc a little above and/or below the centre when looking straight ahead. If glaucoma is left untreated, it will spread outwards and inwards. The centre of the field is the last affected so that eventually it becomes like looking through a long tube. (See figure 1) Over time even this sight would be lost.
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During a sight test, our optician will check for signs of glaucoma by checking the optic nerve, measuring the eye pressures and checking the field of vision using a visual field machine. All of these tests are straightforward, do not hurt and are vital in maintaining healthy vision. Glaucoma can be treated by the use of drops – to lower the pressures. There are also treatments which aim to improve the blood supply of the optic nerve. This can be done in hospital with regular check-ups afterwards. Although glaucoma cannot be repaired, with early diagnosis and careful regular observation and treatment, damage can usually be kept to a minimum and good vision can be enjoyed indefinitely.
Symptoms include red eye, sight deterioration and black outs. There may also be nausea and vomiting. In early stages you may see misty rainbow coloured rings and white lights. If you should suffer any of these symptoms contact your optician or your Doctor immediately.

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CATARACTS

If you have been advised you have a cataract, don’t be alarmed. Over half of those over 65 have some cataract development and most cases can be treated successfully with treatment.
Some people believe that a cataract is a ‘skin that grows over the eye’. This is not the case. A cataract is a clouding of the part of your eye called the lens. Your vision becomes blurred or dim because light cannot pass through the clouded lens to the back of the eye. (See figure 2)
Figure 2
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Cataracts can form at any age but most often develop as people get older. Symptoms include vision appearing blurred round the edges or that glasses feel ‘dirty’ or ‘scratched’.

Cloudiness in the lens may occur in more than one place meaning light rays which reach the retina are split – causing a double image. You may also find that bright light or very sunny days make it more difficult to see. As the cataract develops its centre becomes more and more yellow giving everything a yellowish tinge. (See figure 3)

Figure 3
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Our optometrist or your Doctor can make a referral to the cataract clinic for you. The most effective treatment for cataracts is a small operation to remove the cloudy lens. This cannot be performed by laser, although laser treatment is sometimes needed afterwards. The cloudy lens will usually be replaced by a plastic lens so the eye can focus properly. Occasionally a doctor or another care professional will decide that someone’s eye is not suitable for a lens implant. There is usually a waiting list for cataract surgery. Most people usually undergo cataract surgery and go home the same day. It doesn’t take long and is painless. Drops will be inserted to enlarge the pupil and you will be given a local anaesthetic . This numbs the area being operated on. You will be wide awake but will feel nothing. The operation is performed with the aid of a microscope through a small cut in the top of the eye. The operation generally takes up to 30 minutes. Your sight will improve over the next few days after the surgery, although complete healing may take several months.

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MACULAR DEGENERATION

The retina is made up of delicate tissue that is sensitive to light, rather like the film of a camera. The macula is found at the centre of the retina where the incoming rays of light are focused. The macula is very important and is responsible for what we see in front of us, the vision needed for detailed activities such as reading and writing and our ability to appreciate colour. Sometimes the delicate cells of the macula become damaged and stop working. We do not know why this is, although it tends to happen as people get older. This is called age-related macular degeneration. Because macular degeneration is an age-related process it usually involves both eyes, although they may not be affected at the same time. With many people the visual cells simply cease to function, like the colours fading in an old photograph – this is known as dry degeneration. Sometimes several members of a family will suffer from this and if this is the case in your family, it is very important that you have your eyes checked regularly. Macular degeneration is not painful and never leads to total blindness. It is the most common cause of poor sight in people over 60 but never leads to complete sight loss because it is only the central vision that is affected. Macular degeneration is diagnosed as either dry or wet. The dry form is more common than the wet, with about 90% of AMD patients diagnosed with dry AMD and 10% with wet AMD. However, 90% of severe vision loss comes from the wet form and only 10% from the dry form.

 

Macular degeneration never affects vision at the outer edges of the eye. This means that almost everyone with macular degeneration will have enough side vision to get around and keep their independence.


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The symptoms may include central vision being blurred or distorted with things looking unusual in size or shape. This may happen quickly or develop over several months. You may be very sensitive to light or actually see lights that are not there. This may cause some discomfort occasionally, but otherwise macular degeneration is not painful. People with the advanced condition will often notice a blank patch of dark spot in the centre of the vision. (SEE FIG 1) This makes activities such as reading, writing and recognising small objects very difficult.
If you suspect that you may have macular degeneration but there are no acute symptoms you should contact us or your Doctor who will refer you to an eye specialist. If you have acute symptoms then you should consult your doctor or local casualty department immediately. If macular degeneration has already been diagnosed in one of your eyes and your other eye is getting acute symptoms then you should go to the hospital that would usually look after you, or your local casually department as soon as possible. Unfortunately, with most people the areas of degeneration are in the middle of the macula at its focal point. This means that treatment cannot be given as the scars produced by the laser would make central vision worse rather than better. There is as yet no cure for AMD, but some treatments can delay the progression, or even in some, improve vision. Treatments vary depending on whether the disease is the dry or wet form. There is currently no treatment for dry AMD but there are now medicines that can be used to treat the more severe wet AMD.

Amsler Grid

The Amsler grid, used since 1945, is a grid of horizontal and vertical lines used to monitor a person’s central visual field. It is a diagnostic tool that aids in the detection of visual disturbances caused by changes in the retina, particularly the macula. Viewing the Amsler grid separately with each eye helps to monitor vision. The Amsler grid is a very sensitive test that can reveal clinical changes before other visual symptoms develop. With new and reliable treatments for wet AMD, the tool is important for the early detection of wet AMD. After being diagnosed with macular degeneration, you will have regular visits to your ophthalmologist. Your doctor may ask you to test your sight at home daily with an Amsler grid. The Amsler grid will help you identify if any changes in your vision are taking place. If you see black spots or wavy lines during your daily test, you should contact your ophthalmologist.

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DIABETIC RETINOPATHY

Roughly one person in fifty in the UK is affected by diabetes mellitus or ‘sugar diabetes’. This means that the body cannot cope normally with sugar and other carbohydrates in the diet. Diabetes can cause complications which affect different parts of the body – both types affect the eyes in the same way.

If you have diabetes, it does not necessarily mean that your sight will be affected, but there is a higher risk. If your diabetes is well controlled then you are less likely to have problems, or they may be less serious. However, if there are complications which affect the eyes then this can result in loss of sight.

Most sight loss from diabetic retinopathy can be prevented – but early diagnosis is vital. You may not realise there is anything wrong with your eyesight which is why regular eye examinations are extremely important.

Your eye has a lens and an aperture (opening) at the front, which adjust to bring objects into focus on the retina at the back of the eye. The retina is made up of a delicate tissue that is sensitive to light, rather like the film in a camera. At the centre of the retina is the macula which is a small area about the size of a pinhead. This is the most highly specialised part of the retina and it is vital because it enables you to see fine detail and read small print. The other parts of the retina give you side vision (peripheral vision). Filling the cavity of the eye in front of the retina is a clear jelly-like substance called the vitreous humour.

Diabetes can affect the eye in a number of ways. These usually involve the fine network of blood vessels in the retina – hence the term diabetic retinopathy.

Your vision may become blurred for a few days or weeks while your diabetes is first being controlled. This is due to the swelling of the lens inside the eye and will soon clear without treatment after the diabetes is controlled.

Young people with diabetes very occasionally develop a special type of cataract. Although their vision gets worse, it can be restored by surgery. Older people with diabetes can be especially prone to developing cataracts. Cataracts can be successfully removed by surgery and usually it is possible to insert a lens implant. However this is unsuitable for some people and you will be told if this is the case.

The most serious diabetic eye condition involves the retina and is called diabetic retinopathy. This condition is very common in people who have had diabetes for a long time. Your optician or doctor may be able to see abnormalities in your eyes but there is no threat to your sight.

There are two types of diabetic retinopathy which can damage your sight. Both involve the fine network of blood vessels in the retina. They are described below.

Maculopathy – This happens when the blood vessels in the retina start to leak. If the macula is affected you will find that your central vision gradually gets worse. You may find it difficult to recognise faces in the distance or to see detail such as small print. The amount of central vision that is lost varies from person to person. However the vision which allows you to get around at home and outside (navigation vision) will be preserved. It is very rare for someone with maculopathy to lose all their sight.

Proliferative diabetic retinopathy – Sometimes diabetes can cause the blood vessels in the retina to be become blocked. If this happens then new blood vessels form in the eye. This is natures’ way of trying to repair the damage so that the retina has a new blood supply. Unfortunately these new blood vessels are weak. They are also in the wrong place – growing on the surface of the retina and into the vitreous jelly. As a result these blood vessels can bleed very easily and cause scar tissue to form in the eye. The scarring pulls and distorts the retina. This condition is rarer than background retinopathy and is more often found in people who have been insulin dependent for many years.

The new blood vessels will rarely affect your vision but their consequences, such as bleeding or retinal detachment, can cause your vision to get worse suddenly. Your vision may become blurred and patchy as the bleeding obscures part of your vision. (See image below) Diabetic retinopathy.jpg

 

 

 

 

 

 

Without treatment, total loss of vision can happen in proliferative retinopathy. With treatment most sight threatening diabetic problems can be controlled if detected early enough.

Although your vision may be good, changes can take place in your retina that may require treatment. Because most sight loss in diabetes is preventable, early diagnosis is vital. Full eye examination should be carried out yearly. DO NOT wait until your vision has deteriorated to have an eye examination.

Your optometrist or doctor can examine for diabetic retinopathy. You should also attend any diabetic screening clinic appointments. If a problem is found, you will be referred to a consultant ophthalmologist, at a hospital eye clinic. However, if your vision is getting worse – it does not necessarily mean you have diabetic retinopathy. It may simply be a problem that can be corrected by glasses.

Most sight-threatening diabetic problems can be prevented by laser treatment if it is given early enough. It is important to realise however that laser treatment aims to save the sight you have – not to make it better. The laser can be focused with extreme precision. So the blood vessels that are leaking fluid into the retina can be sealed.

If new blood vessels are growing, more extensive laser treatment has to be carried out. In eight out of ten cases laser treatment causes the new blood vessels to disappear.

All treatment is carried out in an outpatient clinic and you will not have to stay in. Eye drops are used to enlarge the pupils so that the doctor can look into your eye. The eye is then numbed with drops and a small contact lens is put onto the eye to stop it blinking. The treatment for sealing blood vessels doesn’t usually cause any discomfort. However, the treatment to remove new blood vessels can be a bit uncomfortable so you may be given a pain relieving tablet at the same time as the eye drops. If the treatment does become painful then it is possible to have an injection around the eye to numb the pain. Don’t be afraid to ask for this infection, especially if you have found a previous session of laser treatment distressing.

The treatment for sealing blood vessels has few side effects, although you may lose a little central vision or notice the laser burns as small blank spots. The risks of laser treatment are far less than the risks of not having treatment