Diabetic retinopathy is a complication of diabetes, caused by high blood sugar levels damaging the back of the eye (retina). It can cause blindness if left undiagnosed and untreated. But how does diabetic retinopathy come about, what are the symptoms and how can it be treated? We speak to leading eye expert at The Holly, Mr Hadi Zambarakji (Consultant Ophthalmologist), about the condition.
What is Diabetic retinopathy?
If you have diabetes mellitus, your body does not use and store sugar (glucose) properly. High blood-sugar levels can damage the blood vessels in the retina, the nerve layer at the back of the eye that senses light, which sends images to the brain. The damage to the retinal vessels and the retina is referred to as diabetic retinopathy.
In the early stage of diabetic retinopathy, the tiny blood vessels within the retina leak blood or fluid. The leaking and haemorrhage causes the retina to swell or to form deposits called exudates. Many people with diabetes have a form of mild diabetic retinopathy (also called background diabetic retinopathy or non-proliferative diabetic retinopathy), which usually does not affect their vision. When the vision is affected, it is the result of macular oedema and/or macular ischemia. Macular oedema refers to the swelling to the retina, and macular ischaemia refers to the reduction in the blood supply and nutrients to the retina. Both oedema and ischaemia subsequently affect the vision.
Proliferative diabetic retinopathy (PDR) however, is said to be present when abnormal new vessels (neovascularization) grow on the surface of the retina or optic nerve. The main cause of PDR is widespread closure of retinal blood vessels, preventing adequate blood flow. This growth of blood vessels on the retina is the body’s attempt to supply blood to the area where the original vessels closed. Unfortunately, the new abnormal blood vessels do not supply the retina with normal blood flow, and are often accompanied by scar tissue that may cause wrinkling or detachment of the retina.
What are the symptoms of diabetic retinopathy?
A medical eye examination is the only way to detect changes inside your eye. However, when diabetic retinopathy affects the macula, this could result in macular oedema and as a result the vision may deteriorate.
If your ophthalmologist finds diabetic retinopathy, he or she may order colour photographs of the retina, Optical Coherence Tomography (OCT) scans of the retina or a special test called fluorescein angiography to find out if you need treatment. As part of this test, a dye is injected into one of the veins in your arm and photos of your eye are taken to detect where fluid is leaking. The OCT scan however, does not involve any injections and gives the Ophthalmologist additional information about assessing and monitoring diabetic macular oedema.
Am I at risk of diabetic retinopathy?
All diabetic patients are at risk of diabetic retinopathy. This risk increases the longer the person has diabetes – so it’s important to have regular eye examinations.
How can I reduce the risk?
You can reduce the risk by keeping your blood glucose well controlled (glucose under 7 mmol/L and HbA1c under 7% are recommended), keeping your cholesterol and blood pressure within the normal range, avoiding smoking and keeping a normal weight (your GP can provide more information).
When should I see a Consultant?
You should see a Consultant if your visual acuity is reduced (less clarity or sharpness of vision), or if your Optometrist or the diabetic screening service (where you have your yearly retinal photographs) have identified sight-threatening diabetic retinopathy in your eyes.
What treatments are available?
While laser treatment does not cure diabetic retinopathy or restore vision that has already been lost, it has been shown to reduce the chance of severe vision loss and blindness. It is applied at the slit lamp (the microscope with a bright light that is used during an eye exam) in the clinic and takes approximately 10-20 minutes.
VEGF stands for “vascular endothelial growth factor”. Several studies have demonstrated that treatment with anti-VEGF injections can reduce vascular leakage and improve vision secondary to diabetic macular oedema.
There are three anti-VEGF agents in use for diabetic macular oedema.
These are Bevacizumab (Avastin) Ranibizumab (Lucentis) and Aflibercept (Eylea). Lucentis and Eylea are the only licensed agents for diabetic macular oedema, but all three agents have been used extensively for this purpose. Current data suggests that all three are effective and relatively safe. On average, when visual acuity loss is mild, all three agents appear similar, however, when visual acuity loss is more severe, Eylea appears more effective at improving vision.
Other treatments for diabetic macular oedema
Options for macular oedema treatment include intraocular steroid injections with a steroid including a dexamethasone implant called Ozurdex, and another long-acting Fluocinolone steroid implant called Iluvien. Both have received marketing authorization for the management of chronic diabetic macular oedema. Iluvien is particularly interesting because it can be effective for up to three years!
Anti-VEGFs and intraocular steroids are given as an intraocular injection into the vitreous cavity (the back of the eye) as a day case procedure under local anaesthesia. The procedure sounds complex but is very well received by patients on the whole. After the injection the eye is usually a little red and uncomfortable but this feeling soon subsides.
In patients with vitreous haemorrhage and/or traction retinal detachment, a surgical procedure called a vitrectomy may be needed. During this microsurgical procedure (performed in the operating room under local anaesthesia), the blood-filled vitreous is removed and replaced with a clear solution. In general, I would tend to wait for 2-3 months to see if the blood clears on its own before planning vitrectomy surgery. Vitrectomy often prevents further bleeding by removing the abnormal vessels that caused the bleeding in the first place. If the retina is detached, it can be repaired during vitrectomy surgery, in which case surgery is usually done early because macular distortion or traction retinal detachment will cause permanent visual loss.