How does diabetes affect the eye?
Diabetes is a disease that affects the blood vessels and the nerves in the body. The eye contains a structure called the retina which works in a similar manner to the photographic film in a camera; it captures light and converts it into electrical signals that are transmitted to the brain through the optic nerves. Diabetes can damage these fine nerves and blood vessels, and this can result in a reduction in your eyesight. It is estimated that about 40% of people with Type 1 Diabetes Mellitus and 20% with Type 2 Diabetes Mellitus will develop some sort of diabetic retinopathy.
Early changes consist of small areas of bleeding (haemorrhages) on the retina. There may be leakage of fluid that affects the central part of the retina, the macular and this is known as diabetic maculopathy. The leakage can cause swelling of the retina, also known as macular oedema.
In the more advanced stages, the small blood vessels can be permanently damaged and can disappear. This is known as retinal ischaemia. As the disease progresses further, abnormal blood vessels can grow on the retinal surface (proliferative retinopathy) and need to be treated urgently as they can bleed and cause permanent structural damage to the retina. If these bleed, you may notice a sudden increase in floaters or the vision may suddenly become very blurred or dark. You will need to contact a retina specialist for urgent treatment.
Diabetes is also associated with other eye disorders that can affect sight. People with diabetes usually develop cataracts at an earlier age and are also at higher risk of developing glaucoma.
What are the symptoms of diabetic eye disease?
Most people do not have any problems with their vision in the early stages of the disease. We are very fortunate to have a comprehensive diabetic retinopathy screening programme in the UK that will pick up the disease at an early stage.
It is important to seek help if you develop any problems with your eyesight.
Diabetic retinopathy can develop slowly and affects your central vision. You may find it difficult to see detail such as recognising people’s faces in the distance or small print when reading.
What treatment is available if I develop diabetic eye disease?
Diabetic retinopathy develops much more commonly than proliferative retinopathy. The early stages can be observed (depending on the extent and location of the macular oedema). This can even be reversed by improving overall glucose control, blood pressure, blood cholesterol and increasing activity.
When diabetic retinopathy is considered clinically significant, it is treated with either retinal laser or injections of drugs into the eye. Injections will normally be given a course of injections and most patients will need between 3-9 in the first year.
The different drugs that are used to treat macular oedema include anti-vascular endothelial growth factor (Anti-VEGF) drugs – Lucentis, Eylea or Avastin – and steroid implants such as Ozurdex or Iluvien. They have different advantages and side effects and choosing the right drug for you will depend on your individual needs. Your doctor will advise you of this.
Having an injection is not painful. The eyelids are cleaned with Iodine and local anaesthetic eye drops will be applied to the eye surface. A speculum is used to keep the eye open and the injection is given with a very fine needle (almost as thin as an eyelash). You will feel a sensation of pressure (like a finger pressing on the eye) but this will not feel sharp or painful. The whole process takes less than 10 minutes. Most patients will require a course of injections.
What to expect after the injection:
The eye will feel like it has a small piece of grit under the lids. This is where the needle entered the eye. This sensation will usually pass within a day and can be easily managed by using artificial tear drops.
There may be a small blood spot on the eye surface where the needle entered the eye. This is harmless and will disappear after about a week.
Immediately after the injection, your vision may be blurred. This will resolve within a few hours.
You can assume all normal tasks after an injection. However, it is important to avoid contaminating the eye surface with unclean water or dirt. Patients are advised not to perform tasks such as gardening or swimming for 1 week.
If you were treated with a steroid implant, you may notice a floater in the shape of a line. This is the shadow that is cast from the implant if it is floating near the centre of the eye. This is a temporary symptom and will usually fade with time.
There is a 1:1000 risk of developing a sight-threatening infection after an injection into the eye. This is very rare but needs to be treated urgently. If you develop either worsening pain, worsening redness of the eye or worsening vision in the first 10 days after an injection, you must contact your doctor immediately.
A laser is a highly focussed beam of light that is used to reduce the leakage from damaged blood vessels in the retina. A special contact lens is placed on the eye surface to help focus the laser to the correct area of the retina. It is performed as an outpatient procedure.
Laser treatment cannot be used effectively to treat macular oedema that involves the fovea (the specialised part of the retina that is used to determine fine detail in vision, such as reading). Laser still can offer some advantages over intravitreal injections such as requiring less frequent treatment and it is not a surgical procedure, so there is no risk of infections that can cause blindness.
Laser remains the main form of treatment for proliferative retinopathy. This form of laser requires a greater intensity of energy and can be a little painful during the treatment. In our clinic in London, Miss Sivagnanavel will use local anaesthetic injections around the eye to avoid such treatment being painful. This form of laser can result in a restriction of your peripheral vision and difficulty with night vision (depending on the extent of treatment required). Some people also experience a reduction in their central or reading and distance vision, but this is rare and affects less than 10% of patients undergoing treatment.
Important points to remember:
Diabetic eye disease develops to a variable extent depending on the duration of time a person has had diabetes and the severity of the underlying diabetes.
Improving the control of the blood glucose levels, blood cholesterol and blood pressure is extremely important in preventing visual loss from diabetic eye disease. Smoking is also a significant risk factor for visual loss.
Attending diabetic retinopathy screening is important in preventing visual loss as this will detect diabetic eye disease at a much earlier stage.
Most sight loss due to diabetic retinopathy is preventable if treatment is given early. The earlier the treatment is given the more effective it is.
If you develop problems with your vision such as slowly progressive blurring, there is no need to panic as this may be resolved by a simple change in your glasses. Seek help early.
If you develop a sudden reduction in your vision or floaters (dark spots that move around in your vision), you must seek help urgently as there could be a bleed in the eye from proliferative retinopathy. This needs immediate treatment.