What is Diabetic Retinopathy?
Diabetic retinopathy is a complication of diabetes and a common cause of vision impairment in people with diabetes. Diabetes has a significant impact on the small and larger blood vessels within the body, including the eye. It occurs when diabetes damages the fine blood vessels within the retina, the light-sensitive nerve tissue at the back of the eye. A heathy retina is necessary for good vision.
The macula is a small area (5mm) located in the very central part of the retina. It provides us with sharp central vision as well as recognition of colours. Another potential complication of diabetes is swelling at the macular, known as diabetic macular oedema.
Diabetic retinopathy usually affects both eyes, although one eye may be affected first or to a greater extent.
What are the stages of Diabetic Retinopathy?
- Mild Non-Proliferative Diabetic Retinopathy
At this early stage, there are tiny blow-outs in the blood vessels known as microaneurysms.
- Moderate Non-Proliferative Diabetic Retinopathy
As diabetic disease progresses, some of the retinal blood vessels become blocked, causing haemorrhages and hard exudates.
- Severe Non-Proliferative Diabetic Retinopathy
An increasing number of blood vessels are blocked, further depriving the retina of its blood supply.
- Proliferative Diabetic Retinopathy
At this end stage of diabetic retinopathy, the retina forms new blood vessels in an attempt to overcome the interrupted blood supply. This is known as neovascularisation.
These new blood vessels are abnormal and tend to leak into the retina and/or vitreous (the gel-like substance that fills the cavity of the eyeball), causing significant vision loss.
Who is at risk of Diabetic Retinopathy?
Diabetic retinopathy is a complication of both Type I and Type II diabetes. The risk of diabetic retinopathy increases with the duration of time that the diabetes has been present. Control of blood sugar levels can also influence the risk significantly. Patients who control their BSLs and maintain a stable healthy HbA1C often succeed in limiting the severity of the disease.
Additionally, pregnant women with underlying or gestational diabetes are more at risk of developing and/or having rapidly progressive diabetic retinopathy.
What are the symptoms of Diabetic Retinopathy?
If you have early diabetic retinopathy, you may initially notice no changes in your vision. Patients may have minimal evidence of diabetic retinopathy at clinic reviews.
Over time, however, the retinopathy can progress and ultimately cause vision loss. Don’t wait for symptoms before going for a comprehensive eye examination.
Vision loss from diabetic retinopathy can be due to either:
1. Proliferative Retinopathy
As blood leaks from the abnormal vessels in the retina, people will often see specks or spots of blood “floating” in their vision. These spots can sometimes clear without treatment. However, bleeding can recur and cause a significant reduction in vision. If you experience early symptoms, it is important to see your eye care practitioner to discuss treatment options and to prevent more serious bleeding from occurring.
2. Diabetic Macular Oedema
Fluid leaks under the macula, causing distortion and blurring of the central vision. Diabetic macular oedema can occur at any stage of diabetic retinopathy, although it is more likely in the advanced stages. Approximately half of people with proliferative retinopathy also have diabetic macular oedema.
How is Diabetic Retinopathy detected?
Regular screenings with your eye care practitioner will allow early signs of diabetic retinopathy to be detected. Often, earlier treatment leads to a better visual prognosis. Patients with moderate-to-severe diabetic retinopathy and pregnant women with diabetes may be recommended to have more frequent examinations.
Testing may include:
- Visual acuity: a measurement of vision on a letter chart
- Retinal examination: your eye care practitioner will dilate (enlarge) your pupil and use a slit lamp microscope to assess the optic nerve, blood vessels and macula for signs of diabetic damage. These drops will blur your vision for 2-3 hours and it is recommended that you do not drive on the day of your eye exam
- Tonometry: an instrument used to measure the pressure inside the eye. This can aid in the diagnosis of glaucoma, which tends to be more prevalent in diabetics
Optical Coherence Tomography
Optical coherence tomography (OCT) allows non-invasive imaging of the macula in cross-section. It can identify if macular oedema is present, and it is useful in quantifying the degree of fluid present as well as the response to treatment.
In fluorescein angiography, fluorescein dye (vegetable based) is injected into a vein in the arm via a cannula, which then travels to the eye via the circulatory system. A series of photographs are taken as the dye passes through the blood vessels in the retina.
Fluorescein angiography will highlight abnormal vessels that are leaking and causing damage in the retina. It will also show any leakage caused by macular oedema.
What treatments are available for Diabetic Retinopathy?
During the first three stages of diabetic retinopathy, treatment is not usually required. To prevent progression of diabetic retinopathy, people with diabetes should develop and maintain a Diabetic management plan with their General Practitioner and/or Endocrinologist to maintain adequate control of blood sugar, blood pressure and cholesterol levels.
Proliferative retinopathy is treated with laser, using a procedure known as panretinal photocoagulation (PRP). The laser targets and shrinks abnormal leaky blood vessels. Approximately 1000-2000 laser burns (which appear as white spots) are made in the peripheral retina.
Because a high number of laser burns are necessary, more than one session may be required to complete treatment. PRP laser can result in some reduced peripheral and/or night vision.
PRP laser works best if the new vessels have not yet started to leak. If the abnormal vessels have already started bleeding into the vitreous (causing a vitreous haemorrhage), vision will be reduced and a surgical procedure known as a vitrectomy may be required.
Vitrectomy surgery is performed under local anaesthesia and copious sedation. Three small instrument ports are inserted through the white of the eye (the sclera) at the front of the eye, each approximately half a millimeter wide. Very fine surgical instruments are inserted via these ports and the vitreous and haemorrhage is removed under microscopic guidance.
A short-acting gas bubble is inserted at the end of the vitrectomy to replace the vitreous. It may take several weeks for the gas to dissipate. The eye may be temporarily red and gritty. Ultimately, however, there is a significant improvement in vision.
Both PRP laser and vitrectomy have high success rates and are very effective at reducing vision loss. People with proliferative diabetic retinopathy have less than a 5% chance of becoming blind within five years if they get timely and appropriate treatment. However, these treatments do not cure diabetic retinopathy.
Once you have proliferative retinopathy, you will always be at risk for new growth of leaky blood vessels and repeat treatments may be required.
What treatments are available for Diabetic Macular Oedema?
Early diabetic macular oedema is commonly treated with a specialized macular laser. Multiple burns are placed around the macula to seal focal points of leakage. Treatment is usually completed in one session, although repeat treatments may be required to control recurrent fluid leakage.
In some cases, macular laser may be performed in conjunction with an injection of medication into the eye (an intravitreal injection). This is commonly done if vision has already been affected by the diabetic macular oedema, since combination therapy is highly effective at restoring vision.
The eye is numbed with local anaesthetic before receiving the injection. Again, ongoing treatment may be required to control the oedema.
Finally, patients with macular oedema who do not respond to laser or medication may also require vitrectomy surgical intervention.
What happens during and after laser treatment?
Both macular and PRP laser treatment are performed in a retinal specialist’s rooms. Prior to the laser treatment, the pupil is enlarged (dilated) and anaesthetic drops are applied to numb the eye. A special lens is held to the eye to allow accurate placement of the laser burns.
During the procedure, you may see flashes of light which can create a mildly uncomfortable stinging sensation. Your pupil will remain dilated for a few hours. For this reason, it is recommended that you bring a pair of dark sunglasses and have someone drive you home after treatment. You may also see a few bright “after-images” after the procedure which usually dissipate within a few days.
What can I do to protect my eyes from diabetic damage?
- Yearly dilated eye examinations: If you have diabetic retinopathy, you may need more frequent eye examinations. Approximately 40-45% of Australians with diabetes have some stage of diabetic retinopathy. Early detection and treatment usually results in a better visual outcome. Patients with proliferative retinopathy can reduce their risk of blindness by 95% with timely treatment and appropriate follow-up.
- Control blood sugar levels: A major study has shown that good control of blood sugar levels can slow the onset and progression of diabetic retinopathy. In the study, diabetics who kept their blood sugar levels as close to normal as possible had lower incidences of kidney and nerve
disease, as well as a lower requirement for retinal eye treatment. Be sure to ask your GP or endocrinologist about a control program that is right for you.
- Control blood pressure and cholesterol: Studies have also shown that good control of blood pressure and cholesterol improved overall health and helped to reduce the risk of vision loss from diabetic eye disease.
- Monitoring between eye appointments: If you notice an increase in distortion (straight lines appearing bent on an Amsler grid) or blurred/dark patches in your vision then you should see your retinal specialist earlier than scheduled.