Diabetic retinopathy (kinonga karu nā te matehuka) is damage to the retina, a structure at the back of your eye, which is caused by diabetes.
Key points about diabetic retinopathy
- Diabetic retinopathy is a common cause of visual impairment and blindness in New Zealand.
- If it is picked up early, treatment can help prevent or slow vision loss.
- Good blood glucose control, regular diabetes eye examinations (even if your vision seems normal), good blood pressure, cholesterol management and avoiding smoking can reduce your risk of developing diabetic retinopathy.
What are the vision problems in diabetes?
Diabetes can increase your risk of several eye conditions, including diabetic retinopathy, cataract and glaucoma. Diabetes is the commonest cause of blindness and vision impairment in people aged 20–60 years.
- Compared to the general population, people with diabetes have about 25 times greater risk of vision impairment.
- At least one-third of people with diabetes have retinopathy.
- Retinopathy threatens vision, or has already destroyed sight, in 10% of people with diabetes.
Early detection of eye conditions means treatment can be given to slow or prevent vision loss.
Read more about eye problems and diabetes.
What happens in diabetic retinopathy?
Diabetes damages the blood vessels that supply the retina of your eye. When signs of damage are detected, you have retinopathy.
The retina is a very thin and complex layer that lines the back and inner wall of your eye. It contains photoreceptor cells, which convert light to chemical and electrical energy. This is then conveyed to your brain via other retinal cells, the optic nerve and the visual nerve pathways to produce your sense of vision.
If the retina is damaged, especially in its central area, the macula, there is a loss of sight that can't be regained.
Diabetes causes the small blood vessels within the retina to occlude (close up) and/or leak blood, fats and fluid. There are toxic to your retina and cause 2 types of major damage:
What is retinopathy?
Closure of small blood vessels leads to rapid growth of abnormal blood vessels which are fragile and may bleed into the vitreous, the ‘jelly’ of the eye which fills the space between the retina and the lens, and may eventually cause the retina to detach.
What is maculopathy?
Leakage within the macula, especially of fluid and fat, destroys the retinal photoreceptor and nerve cells, and reduces vision.
Who is most likely to develop retinopathy?
Those most likely to develop retinopathy are people:
- who have had diabetes for many years – the risk increases progressively each year from the time of diagnosis, and after 15 years, 3 out of 4 people will have retinopathy
- whose diabetes is poorly controlled – strict blood glucose control is the most important factor in the prevention of both the development and progression of retinopathy
- with hypertension (high blood pressure) and abnormal blood fats
- with kidney disease.
Also be aware that retinopathy can get worse more quickly for people with diabetes who also:
- are pregnant
- have poor glucose control
- have high blood pressure.
How is retinopathy diagnosed?
Diabetes eye checks every 2 years are an important part of your diabetes care, as treatment is possible if these conditions are found in the early stages. However, if you notice any changes in your vision, see your doctor or optometrist right away.
A diabetes eye check looks at the back of your eyes (the retina) rather than testing your vision for glasses or driving. It is done by a specially trained health professional either looking at, or photographing, the back of your eyes (retinas).
If they diagnose retinopathy, it will be graded according to severity:
- minimal/ mild/ moderate – no immediate threat to sight
- pre-proliferative, proliferative/pre-maculopathy/maculopathy – sight threatened or already lost
- advanced – irretrievable sight loss.
How is retinopathy treated?
Laser treatment is aimed at reducing the demands of the ‘sick’ retina on the eye. As such, there is a smaller risk of new blood vessels forming or blood vessels leaking.
Macula laser treatment
This ‘dries up’ the fluid and exudates – but may take several months, and two to three treatments to be effective.
Overall retinal laser treatment
A laser burns throughout the retina, causing the fragile abnormal blood vessels to disappear, or never develop. Again, several treatments may be necessary for each eye. Where treatment has to be extensive there will be some loss of side vision and night vision.
You may be offered injections of medicines that reduce the swelling and leakage of blood vessels. This is usually offered as a course of treatment and, in some instances, could be performed as a monthly injection. Common medicines include Avastin, Lucentis, Eyelea and Triamcinolone. Your eye doctor will discuss the side effects of medicines and the treatment regimen.
How can I protect my vision with diabetes?
Measures to preserve eyesight include the following:
- Minimise the risk of retinopathy by strict control of blood glucose.
- Have treatment for abnormal blood pressure and fats in the blood (lipids) which cause additional harm to the eyes if not controlled. See also high blood cholesterol
- Once someone is diagnosed with diabetes, you need a retinal eye screen test at least every 2 years.
- Once changes are found, this may become every year or less. Remember, vision may be normal, but retinopathy could be present.
- Follow medical advice about diet, exercise, medications for diabetes, blood pressure and abnormal blood lipids.
- Do not smoke – this causes strokes, heart attacks and poor circulation in the legs which may result in amputation. See also quitting smoking
Regular eye examinations for retinopathy
Once you have diabetes, make sure you get regular retinal examinations at least every 2 years because there is no other way of detecting retinopathy.
- For type 2 diabetes, eye checks start from the time of diagnosis. This is because some people may already have signs of diabetes eye disease by this time.
- For type 1 diabetes, eye checks tend to start 5 years after diagnosis, but this can vary depending on your age when first diagnosed.
- If you have any type of diabetes and become pregnant, have an eye check in the first trimester.
- If you have no damage to your retina, you will be offered an eye screen every 2 years.
If there are any signs of eye disease, the eye team will explain what further tests, treatment and follow up is needed. You may also need eye checks more often than every 2 years. Do not wait until you have any eye symptoms or vision problems. This can be too late.
Benefits of regular eye examinations include:
- picking up retinopathy early
- making sure you get treatment at the right time to prevent visual loss or blindness
- with early detection and adequate treatment, up to 98% of severe vision loss (bilateral blindness) can be prevented.
- The national diabetes retinal screening grading system and referral guidelines Ministry of Health, NZ, 2006
- Quality standards for diabetes care toolkit Ministry of Health, NZ, 2014
- Diabetic retinopathy screening in New Zealand requires improvement: results from a multi-centre audit, Australian & NZ Journal of Public Health, 2012
- Management of diabetic retinopathy NZ Society for the Study of Diabetes and Ministry of Health, NZ, 2021
Dr Divya Perumal works at the Eye Institute and Auckland public hospital. She has expertise in performing eye surgery, including advanced glaucoma surgery and cataract surgery. She is a senior lecturer at the University of Auckland and is actively involved in teaching junior doctors and research, as well as conducting public lectures.