Diabetic retinopathy is a complication of diabetes that affects the retina. The retina is the layer at the back of the eye which is sensitive to light and to function properly, light must be able to pass through the eye uninterrupted to reach the retina. Light passes through the cornea, lens and vitreous (a jelly-like substance in the eye) to reach the retina in the same way that light rays pass through the lens of a camera to reach the film. The focused light or images are then relayed to the brain by the optic nerve. The macula is the area of the retina concerned with central detailed vision especially for reading. Diabetes causes the capillaries (tiny blood vessels in the retina) to become blocked, this may then lead to leakage in the central retina (diabetic maculopathy) or result in the growth of the new vessels which may bleed and fill the eye with blood (vitreous haemorrhage). Both conditions are treatable by laser in the early stages but may require surgery.
Can any diabetic develop retinopathy?
Yes. Diabetics of all types:
- The young and insulin dependent.
- Those on diet only.
- Diabetics on hypoglycaemic tablets.
- The well controlled can develop it if they have had diabetes long enough.
Is there any way to prevent it?
No. But good diabetic control can slow down the rate of the progression of complications.
You should:
Control your diet.
Always take your diabetic treatment. NOT taking treatment is harmful.
- Avoid becoming overweight.
- Avoid smoking completely
- Avoid excessive alcohol, but a small amount is fine
- Have blood pressure checks and treat any hypertension
- Check your cholesterol level and take tablets to reduce it if high
Improving diabetic control can have an effect on diabetic retinopathy itself, and should be maintained to try to prevent any further deterioration.
Would eye checks have prevented it?
No. They would not have prevented disease but would enable early diagnosis and early treatment and this would benefit your eyesight. Adult Insulin dependent diabetics needs to have their eyes examined every year. Patients diagnosed in childhood should be checked annually following the onset of puberty and diabetic women should be checked several times during pregnancy as this can make the vessels grow. Other diabetics (not on insulin) should have an eye examination every year by their diabetic specialist, GP, ophthalmologist or optician. Sight tests are FREE for diabetics.
HOSPITAL TESTS
What does the eye examination involve?
You will have a sight test (using those familiar charts) and then a full eye examination. Instruments such as an ophthalmoscope and slip lamp are used to give a good view inside the eye. Eye drops are put in your eyes to make the pupils bigger. The ophthalmologist must examine the back of your eye through the dilated pupil. Your vision will be blurred temporarily preventing you from reading and there may be difficulty driving for a few hours. Avoid driving yourself to hospital or the local railway station whenever you come to have your retina examined because your pupils will always need to be dilated.
Will I need any further tests?
Yes: colour photographs taken with a special camera and using ‘flash’. These enable the doctor to see and keep an accurate record of what is going on at the back of the eye. They are kept in your records and can be used for later comparisons.
Fluorescein angiogram.This is a test used for a few patients for one of 3 reasons:
- To establish the diagnosis.
- So that the doctor can see the exact area to direct laser treatment.
- To enable the doctor to see why patients my have lost any vision.
Your pupils will be dilated (as above). A small injection of yellow dye is injected into a vein in your arm. This dye circulates throughout the body and to the retinal blood vessels so that the network of capillaries can be seen. A series of flash photos will be taken while you are sitting at the slit lamp to show the passage of dye through the vessels in the retina. The dye will not leak out of normal capillaries; if it is leaking it means the vessels are diseased or new vessels have developed.
The results and appropriate treatment will be discussed with you. During angiography some 10% of patients will develop nausea and occasionally sickness that soon passes. Allergic reactions rarely occur. The dye has the effect of yellowing the skin for 3-6 hours and urine for 24 hours. Continue to test your urine in the normal way but test your blood sugar as well because the dye may affect the result of the urine test (by turning it dark orange).