Mr Nicholas Glover  - Consultant Cataract Surgeon
Diabetes and your eye 

Diabetes can affect your eye in a number of ways:  

The most serious eye condition involves the blood vessels supplying the retina. This is called diabetic retinopathy.   

The blood sugar levels can affect the lens, especially when diabetes is uncontrolled. This can result in blurring of vision which fluctuates, depending on your blood sugar levels.  

A longer-term effect of diabetes is that the lens can go cloudy, this is called a cataract.     

Not everyone with diabetes develops a complication, many people have a very mild form of retinopathy which may never progress to a sight threatening condition.    

Diabetic retinopathy 

The most serious complication of diabetes for your eye is the development of diabetic retinopathy. Diabetes affects the tiny blood vessels of your eye and if they become blocked or leak then your vision may be affected. Forty per cent of people with type 1 diabetes and 20 per cent with type 2 diabetes will develop some sort of diabetic retinopathy. 

Background diabetic retinopathy 

This is the most common type of diabetic retinopathy. The blood vessels in the retina bulge slightly (microaneurysm) and may leak blood (haemorrhages) or fluid (exudates). As long as the macula is not affected, vision remains  normal and you will not be aware that anything is wrong. Your retinal screening test will check for these early changes and monitor for any signs of progression    

Proliferative diabetic retinopathy 

If diabetic retinopathy progresses, it can cause the blood vessels in the retina to become blocked. These can result in areas of the retina becoming starved of oxygen. (ischaemia) and the eye is stimulated into growing new vessels, a process called neo-vascularisation.   

Unfortunately, these new blood vessels are weak, and grow in the wrong place - on the surface of the retina and into your vitreous gel. These blood vessels can bleed very easily and  result in large bleeds over the surface of the retina or into the vitreous gel.   

These can totally obscure vision in the affected eye as the blood blocks light. For many people, with time, the blood can be reabsorbed and their sight can improve. But for others these bleeds may keep happening and can lead to permanent loss of sight.   

Extensive bleeding can lead to scar tissue forming which distorts the retina resulting in a tractional retinal detachment with the risk of blindness.   

Only 10 per cent of all people with diabetes develop proliferative retinopathy.    

Diabetic maculopathy   

Diabetic maculopathy may occur either with background, or proliferative retinopathy. If this happens, your central vision will be affected and you may find it difficult to see detail such as recognising people's faces in the distance or reading small print.   

However, the vision that allows you to get around at home and outside (peripheral vision) is not affected. Most diabetic maculopathy can be treated with a laser, and more recently injections, with the aim of preserving as much vision as possible, although vision may improve in 25% of treated eyes.    

Reducing risk 

Good diabetic control significantly lowers your risk of retinopathy. The following actions reduce your risk of developing retinopathy or help to stop it from getting worse:

 •   Controlling your blood sugar (glucose levels). 

 •   Tightly controlling your blood pressure.

 •   Controlling your cholesterol levels. 

 •   Keeping fit, maintaining a healthy weight and giving up smoking are all part of good diabetes control. Nerve damage, kidney and cardiovascular disease are more likely in smokers with diabetes. 

 •   Regular retinal screening. Early detection and treatment prevents sight loss. 

Risk factors that cannot be controlled: 

 •   The length of time you have had diabetes. This is a major risk for developing diabetic retinopathy.

 •   Your age affects the progression of diabetic retinopathy. 

 •   Your ethnicity. If you or your family are from India, Pakistan, Bangladesh or Sri Lanka you are more at risk of developing diabetes and the sight-threatening complications.   

 If you have diabetes and plan to have a child, retinal screening is carried out more often during pregnancy and for a while after you have had your baby.

Annual diabetic eye screening  

Most of the complications that diabetes causes in the eye can be treated, but it is vital that they are diagnosed early. If you have diabetes you will have annual retinal screening.  A picture is taken using a digital retinal camera and this is looked at in detail to see if there are any changes caused by diabetes.   

If retinopathy is identified early, through retinal screening, and treated appropriately, blindness can be prevented in 90 per cent of those at risk.     

Treatment for diabetic retinopathy 

Most sight-threatening problems caused by diabetic retinopathy can be managed by laser treatment if detected early enough. The aim of laser treatment is to prevent bleeding or to prevent the growth of new blood vessels. The laser can be used in two ways:    

Focal Laser Treatment   

When individual vessels are leaking, laser treatment can seal them. This type of treatment is quick, painless and performed in the outpatient clinic, sometimes taking only a few minutes. Vision is not affected by this type of treatment.   

Pan retinal Laser Treatment   

 If new vessel growth (neo-vascularisation) has been detected you may need more extensive laser treatment. The aim is to treat the peripheral retina with the laser. This treatment stops the retina from producing the growth factors that stimulate new blood vessels to grow. Treatment causes the new vessels to shrink and disappear over a few months.   

This treatment is identical to focal laser but may be divided into a number of sessions as treatment time is significantly longer   

When new vessels are first detected your vision may still be very good. After the treatment your peripheral vision may be affected. You may feel that the laser has made your sight worse. The difficult issue is, that if left untreated, the new vessels will soon bleed and cause serious loss of vision. The laser treatment is the best option for preventing this.   

It is important to remember that laser treatment aims to prevent your vision from getting worse. It cannot make your vision better. 

How is treatment carried out   

You can usually be treated in an outpatient clinic and do not need to stay in hospital. Eye drops enlarge your pupils so that the eye specialist can look into your eye. Your eye is then numbed with drops and a small contact lens is put onto your eye to stop it blinking.   

When treatment is first suggested, ask how long each session is likely to last. Some people need more than one treatment session.    

Is it painful   

Local treatment for sealing blood vessels does not usually cause discomfort. Pan retinal treatment can be uncomfortable, so you may need a pain-relieving tablet at the same time as the eye drops:    

•   tell your eye specialist if the treatment is hurting   
•   tell the eye specialist if you have found a previous session of laser treatment uncomfortable.   

Does laser treatment have any side effects   

No treatment is possible without some side effects, but the risks to your vision of laser treatment are far fewer than the risks of not having laser treatment. The short-term effects of the laser treatment are due to the brightness of the laser used. It can cause a temporary reduction of sight which may last an hour or two after the treatment. You may also lose a little central vision which may improve with time or notice the after effects of the laser as small black spots in your vision.  

The local treatment has little long-term effect, as it only treats a very small area of the retina. 

The more extensive pan retinal treatment can have more lasting effects on your vision: 

 •   It is quite common to lose some vision to the sides (peripheral vision) and this may affect your ability to drive safely. 

 •   Night and colour vision may also be affected. 

 •   Occasionally your central vision may not be as good as before so that, for example, print is not as easy to see.   

 If you drive and have had laser treatment in both eyes or your one remaining eye you must inform the Driver and Vehicle Licensing Agency (DVLA). They may ask that you have an examination to make sure your central and peripheral vision are good enough for safe driving.   

What if my eye becomes painful after treatment, or if my vision gets worse   

After lengthy treatment, some people may develop a headache, paracetamol can be taken for this. However, if the pain is severe, or if your eyesight gets worse, you should contact your eye specialist immediately. 

If this is not possible, go straight to the Accident and Emergency department at your nearest hospital.    

Treatment for diabetic macular oedema 

Diabetes can cause fluid to collect on or under your macula which is known as "oedema".    Macular oedema may make your central vision distorted or blurry and, over a period of time, it may cause a blank patch in the centre of your vision. 
When the macular oedema does not involve the centre of the macula (called fovea), laser treatment can reduce the leakage and prevent any more blurring. However, when the oedema affects the centre, then laser treatment offers no benefit.   

Treatment is now available for this type of diabetic macular oedema.   

Lucentis, an anti-vascular endothelial growth factor (anti-VEGF) treatment. Research has shown that Lucentis can reduce the macular swelling caused by diabetic macular oedema, and reduces the blurred central vision. 
 Lucentis is given by an injection into the white of your eye and you may need to have more than one injection over a period of months to get the best effect.    

Other ways diabetes can affect your eyes 

Temporary blurring   

The changes in blood sugar levels resulting from diabetes can affect the lens inside your eye, especially when diabetes is uncontrolled. This can result in blurring of vision which comes and goes across the day. This blurring may be one of the first symptoms of diabetes although it may also occur at any time when your diabetes is not well controlled. Once your diabetes is controlled most people find this variable blurring goes away.    

A cataract is a clouding of the lens of your eye, which causes the vision to become blurred or dim because light cannot pass easily to the back of your eye. This is a very common eye condition that  develops as we get older, but people with diabetes usually develop cataracts at an earlier age.   

Important points to remember 

 •   Early diagnosis of diabetic retinopathy is vital.   

 •   Attend your annual diabetic eye screening appointment. 
 •   Speak to your doctor if you notice changes to your vision.  
 •   Sight-threatening diabetic problems can be managed by laser if treatment is early   

 •   Good control of sugar, blood pressure and cholesterol reduces the risk of diabetes-related sight loss. 
 •   Smoking increases your risk of diabetes-related sight loss.