Diabetes can affect the eye in a number of ways:
- The most serious eye condition associated with diabetes involves the network of blood vessels supplying the retina. This condition is called diabetic retinopathy.
- The unusual changes in blood sugar levels resulting from diabetes can affect the lens inside the eye, especially when diabetes is uncontrolled. This can result in blurring of vision which comes and goes over the day, depending on your blood sugar levels.
- A longer term effect of diabetes is that the lens can go cloudy and this is called a cataract.
Not everyone who has diabetes develops an eye complication. Of those that do, many people have a very mild form of retinopathy which may never progress to a sight threatening condition.
Annual retinal screening
Most diabetic eye complications can be treated, but it is vital that they are diagnosed early. They can only be detected by a detailed examination of the eye carried out at a specialist screening centre. One should have an annual retinal screening. Retinal screening is carried out more often during pregnancy and for a while after you have had your baby.
At this visit you will have eye drops put into your eyes which dilate the pupil and allow the specialist a good view of the retina. Pictures may be taken using a digital retinal camera and this is looked at in detail to see if there are any changes caused by diabetes.
As you may not be aware that there is anything wrong with your eyes until it is too late, having this regular test is essential. Research shows that if retinopathy is identified early, through retinal screening, and treated appropriately, blindness can be prevented in 90 per cent of those at risk. If you have not had this type of test, ask your GP or diabetic clinic as soon as possible. You should also go for an annual eye test with the optometrist as the retinal screening test does not replace the regular eye examination.
Diabetes affects the tiny blood vessels of the eye and if they become blocked or leak then the retina and possibly your vision will be affected. The extent of these changes determines what type of diabetic retinopathy you have. Forty per cent of people with type 1 diabetes and twenty per cent with type 2 diabetes will develop some sort of diabetic retinopathy.
This is the most common type of diabetic retinopathy and many people who have had diabetes for some time will have this early type. The blood vessels in the retina are only very mildly affected, they may bulge slightly (microaneurysm) and may leak blood (haemorrhages) or fluid (exudates). As long as the macula is not affected, vision is normal and you will not be aware that anything is wrong.
Maculopathy means that your macula is affected by 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 seeing detail such as small print. Most maculopathy can be treated with laser with the aim of preserving as much vision as possible. The amount of central vision that is lost varies from person to person. However, the vision that allows you to get around at home and outside (peripheral vision) is not affected.
Proliferative diabetic retinopathy
If diabetic retinopathy progresses, it can cause the larger blood vessels in the retina to become blocked. These blockages can result in areas of the retina becoming starved of oxygen. This is called ischaemia. If this happens the eye is stimulated into growing new vessels, a process called neo-vascularisation. This is the proliferative stage of diabetic retinopathy, and is nature’s way of trying to repair the damage by growing a new blood supply to the oxygen starved area of your retina.
Unfortunately, these new blood vessels are weak, and grow in the wrong place – on the surface of the retina and into the vitreous gel. As a result, these blood vessels can bleed very easily which may result in large haemorrhages over the surface of the retina or into the vitreous gel. These types of haemorrhages can totally obscure the vision in the affected eye as light is blocked by the bleed. With time the blood can be reabsorbed and vision can improve.
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.
Only between 5 and 10 per cent of all diabetics develop proliferative retinopathy. It is more common in people with type 1 diabetes than type 2. Sixty per cent of type 1 diabetics show some signs of proliferative disease after having diabetes for 30 years.
Good diabetic control significantly lowers your risk of retinopathy.
The following action reduces your risk of developing retinopathy or helps to stop it from getting worse:
- controlling your blood sugar (glucose levels), having an HBA1C <7%
- tightly controlling your blood pressure
- controlling your cholesterol levels
- keeping fit( doing approximately 150 minutes cardiovascular exercise per week), 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. Smoking increases your blood pressure and raises your blood sugar level which makes it harder to control your diabetes
- See a dietician annually
- regular retinal screening . The most effective thing you can do to prevent sight loss due to diabetic retinopathy is to attend your retinal screening appointments. Early detection and treatment prevents sight loss.
We recommend you join the Diabetic Association :
Diabetes South Africa Durban Branch
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:
Localised Laser Treatment
When individual vessels or small groups of vessels are leaking, the laser can seal them. This stops the bleeding and helps reduce the swelling of the retina. This type of treatment is quick, sometimes taking only a few minutes. Localised laser treatment is used when early proliferative retinopathy or maculopathy has been detected. Vision is not usually affected by this type of treatment because only a very localised area of the retina is treated.
Pan retinal Laser Treatment
If new vessel growth (neovascularisation) has been detected you may need more extensive laser treatment. The aim is to treat large areas of the peripheral retina with the laser. This treatment stops the retina from producing the growth factors that stimulate new blood vessels to grow. If the treatment is successful, the new vessels shrink and disappear over a few months.
Because large areas of the peripheral retina are lasered, the effects on your vision may be significant. It is quite common to permanently 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.
When new vessels are first detected your vision may be very good and you may not have noticed any changes to the way you see. This is because, in the initial stages, new vessels have very little effect on the vision. After the treatment your vision may be very different for example your peripheral vision may be quite poor. You may feel that the laser has made your sight much 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 the ophthalmologist’s rooms and do not normally 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. During the treatment you will be asked to move your eyes in certain directions and you will be able to do this easily with the contact lens in place.
Is laser treatment 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.
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.
What if my eye becomes painful after treatment, or if my vision gets worse?
After lengthy treatment, most people develop a headache so a headache tablet can be taken for this.
However, if the pain is severe, or if your eyesight gets worse, you should contact your ophthalmologist immediately.
Treatment for advanced diabetic retinopathy
If your eye condition becomes more severe and the gel inside your eye becomes cloudy due to haemorrhages, or if scar tissue forms causing retinal detachment, it may be possible for you to have an operation called a vitrectomy. This procedure involves the vitreous gel being removed and replaced with a clear solution that light can pass more easily through.
A vitrectomy is a specialised and complicated operation and you need to discuss with your specialist the advantages and disadvantages of the procedure for your vision.
Other ways diabetes can affect your eyes
The unusual changes in blood sugar levels resulting from diabetes can affect the lens inside the 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 the eye, which causes the vision to become blurred or dim because light cannot pass easily to the back of the eye. This is a very common eye condition that often develops as we get older, but people with diabetes sometimes develop cataracts at an earlier age. An operation can remove the cloudy lens, which is usually replaced by a plastic lens, helping the eye to focus properly again.