A B C D E F G H I J K L M N O P R S T U V W

DIABETIC RETINOPATHY - DIABETIC EYE DISEASE

What is Diabetic Retinopathy ?

Diabetes can affect the eye in several ways. Fluctuation in the level of sugar (glucose) in the blood can result in blurring of vision: the lens and cornea change their shape as the blood glucose levels rise and fall.. This can be an important sign of hitherto-undiagnosed diabetes. Cataract often develops at a much younger age than in the normal population. Anyone developing a cataract in youth or middle age should have diabetes excluded by blood test. The most important way that diabetes affects the eye is by disturbance of the circulation to the seeing part of the eye (retina). If undetected or untreated, this condition (called retinopathy) can result in serious loss of vision and even blindness. There are basically two ways in which the circulation in the retina is affected. The first results from fluid and lipid (fat) leaking from the capillaries in the retina. If this happens at the centre of the retina (the macula), it results in loss of the detailed vision needed for reading: only the outside field of vision is retained. This is called DIABETIC MACULOPATHY or macula oedema. The second way that the retina is affected is a result of reduced oxygen supply to the retina, resulting from blood vessels (capillaries) becoming blocked or thickened. This process is called retinal ischaemia. It leads to reduced vision, particularly an inability to adjust normally to different light conditions. People with diabetes are often troubled by "glare". In some cases, the process of ischaemia can lead to a much more serious problem: the lack of oxygen causes abnormal blood vessels to grow over the retina. These are called new vessels and the condition is called PROLIFERATIVE RETINOPATHY. Such vessels can bleed, resulting in sudden and often complete loss of vision. This is because blood fills the jelly-like space in the back of the eye, a process called vitreous haemorrhage. Such an event must be seen by a specialist urgently. Proliferative retinopathy that is neglected and untreated leads to scar tissue forming between the retina and vitreous jelly. This causes the retina to become detached from the back of the eye (traction retinal detachment). Total loss of vision may then occur. New blood vessels may also grow on the surface of the iris at the front of the eye, resulting in very high pressure developing in the eye (rubeotic glaucoma). Fortunately, most people with diabetes only have mild forms of retinopathy (BACKGROUND RETINOPATHY). This consists of small haemorrhages and microaneurysms (sac like swellings on the capillaries) in the retina and small collections of lipid (exudates). These collections do not affect the vision unless they form in the centre of the retina, the macula. Background retinopathy can however develop into proliferative retinopathy or maculopathy, particularly if your diabetes is not well controlled. Regular, and at least annual eye examination is therefore essential for ALL people with diabetes. All people with diabetes should be screened annually. Screening for retinopathy can be achieved in a number of ways. Retinal photography is being increasingly employed. However examination by your doctor, a designated optician or by the diabetic specialist are all valid methods.

How does Diabetic Retinopathy occur ?

Uncontrolled high levels of glucose in the blood result in the damage to the walls of the capillary blood vessels. They leak and fail to supply sufficient oxygen to the retina.

Why does Diabetic Retinopathy occur ?

Diabetic retinopathy is usually only picked up after diabetes has been present for many years. However we know that the actual damage can begin much sooner, if diabetic control is poor. In children or teenagers, retinopathy is rare within ten years of diagnosis. A small percentage (about 2%) will have signs of serious retinopathy at 15 years, Thereafter, the risk increases with each year. People who develop diabetes later in life (type 2 diabetes) may have retinopathy already at the time of diagnosis. Many such patients will have had the condition for a number of years, before it is discovered. The risk of developing significant retinopathy increases when diabetes is poorly controlled. It can be largely prevented by good blood glucose control. Keeping blood pressure to low-normal levels also reduces the risk markedly. During pregnancy, retinopathy can become temporarily worse. Patients with kidney (renal) failure due to diabetes also tend to have more serious retinopathy. Cigarette smoking also worsens retinopathy by reducing oxygen supplies to the retina. There may be an inherited (genetic) factor as well. Some people even with poor blood glucose and blood pressure control seem to be protected against retinopathy.

Treatment Involved for Diabetic Retinopathy

Once discovered, diabetic retinopathy must be either monitored very closely or actively treated. Most importantly, blood glucose, blood pressure and blood fat levels (cholesterol and other so-called lipids) need to be controlled as well as possible. The intervals between examinations will depend on the severity of the retinopathy. If more serious retinopathy is found, a special test to examine the retinal circulation (a fluorescein angiogram) may be required. This involves a special dye being injected into the circulation through a vein of the arm. The pupil is dilated and the patient sits in front of a camera. The transit of the dye is monitored as it passes around the retina, The image is recorded either digitally or on film.. This test identifes areas of leakage and abnormal blood vessels in the retina, and is often useful in planning appropriate laser treatment. Laser treatment is the mainstay of treatment of both diabetic maculopathy and proliferative retinopathy. Laser treatment is generally given via a contact lens, placed on to the cornea after applying a local anaesthetic eye drop. Occasionally it is given directly into the eye from a laser source attached to a helmet worn by the specialist and focused with a hand-held lens (indirect laser). Brief shots of laser light pass into the retina producing small round burns which later turn into scars. So-called focal treatment is used for treating maculopathy, directing the laser at areas of retina affected by fluid and lipid. This treatment is generally not painful. However it is very precise and the patient must keep the eye very still to prevent the laser hitting the very centre of the macula (the fovea). This would result in serious damage to central vision. The laser is also often delivered in a grid pattern for fluid leakage affecting the macula. Treatment of proliferative retinopathy involves treating large areas of the retina with a scatter of laser burns. This is called panretinal photocoagulation. Initial treatment involves up to 2000 laser shots over one or two sessions. The treatment is often uncomfortable and sometimes painful. It is possible to numb the pain by giving injections of anaesthetic around the eye before treatment. This is not usually necessary. Following treatment, the abnormal "new vessels" usually disappear within 4-6 weeks. However in more severe cases repeated application of laser are necessary and continued until new vessels shrink. Rarely even extensive laser does not control the growth of vessels and surgery is necessary to remove the vitreous jelly which forms a scaffold for the new vessels. This operation (vitrectomy) is for treating severe forms of diabetic retinopathy. The operation is necessary when a vitreous haemorrhage fails to clear on its own. The blood-stained gel is then removed from the eye with restoration of vision. Vitrectomy is usually advised if a vitreous haemorrhage has shown no sign of clearing after 2-3 months. When the centre part of the retina becomes detached in association with vitreous haemorrhage (traction retinal detachment), vitrectomy combined with separation of scar tissue is necessary as a matter of urgency. Unfortunately not all cases of serious retinopathy are treatable or respond to treatment. This is particularly true of macula disease due to poor circulation (ischaemic maculopathy). However, retinopathy identified and treated early will generally do better. Regular eye examination as part of overall diabetic care is therefore of the utmost importance.

After Treatment for Diabetic Retinopathy

Patients who have had their eyes treated will need frequent checks to be sure that treatment has been effective: it may need to be repeated. Panretinal photocoagulation can result in disturbance of near focus. This is usually temporary. The ability to see at night may be affected after extensive treatment for proliferative retinopathy . A temporary blurring of vision is common after laser treatment, usually lasting a few days only. Grid laser treatment for maculopathy sometimes leaves the patient with a visual impression of the grid pattern. Unfortunately, vision in some patients continues to deteriorate despite laser treatment. It is therefore not at all uncommon for patients to blame the treatment for the worsening of the vision. You must be realistic in your expectations and outlook.

If Diabetic Retinopathy is Left Untreated

Poor blood glucose and blood pressure control can cause or worsen retinopathy. Lack of laser treatment at the correct time can lead to blindness.

Effects on Family of Diabetic Retinopathy

Support by the family is important particularly for the more elderly with poor vision. It is important that patients are registered as having a visual handicap, if vision worsens. This involves either blind or partially-sighted registration, depending on how bad the eyesight is. The eye specialist will advise and arrange this. The family can also play an important role by encouraging you to have the all-important regular checkups.