What is Diabetic Retinopathy ?
Diabetic retinopathy is damage to the retina, specifically blood vessels in the retina, caused by complications of diabetes mellitus. The retina is the light-sensitive membrane that covers the back of the eye. Diabetic retinopathy can eventually lead to blindness if left untreated. Approximately 80% of all patients who have had diabetes for at least ten years suffer from some degree of diabetic retinopathy.
If diagnosed and treated early blindness is usually preventable. Diabetic retinopathy generally starts without any noticeable change in vision. However, an eye doctor (ophthalmologist) can detect the signs. The risk is greater the longer a patient has diabetes and the less controlled his/her blood sugar is. Hence, it is important for diabetes patients to have an eye examination at least once or twice annually.
The retina - this is a nerve layer that lines the inside of the back of the eye. It senses light and creates impulses that are sent through the optic nerve to the brain. At the centre of the retina is a small area of very specialized and sensitive tissue called the macula - the macula allows us to see fine details clearly. The macula is used for activities which require careful focusing, such as writing and reading. It also helps us distinguish colors.
There is a network of tiny blood vessels which supply blood to the retina - without them it would not survive. Experts believe that these tiny blood vessels become damaged because of high glucose levels linked to diabetes, resulting in poor blood supply to the retina.
Early diabetic retinopathy (Non-proliferative diabetic retinopathy) - the walls of the blood vessels weaken and microaneurysms develop; these are tiny bulges in the walls of the blood vessels. Sometimes they leak blood and fluid - this does not generally affect vision. Eventually, however, the tiny blood vessels that nourish the macula may become damaged, leading to varying degrees of vision loss - the patient may find it hard to see things clearly at a distance and/or in fine detail, such as small print on paper.
Advanced diabetic retinopathy (Proliferative diabetic retinopathy) - in the more advanced stages of diabetic retinopathy the blood vessels that nourish the retina may become blocked. The body tries to make up for this by producing new blood vessels in the area. These new blood vessels may be unstable and can bleed into the clear, jelly-like substance (vitreous) that fills the centre of the eye, causing blurred and patchy vision as leaking blood obscures the patient's sight. In time the bleeding can result in the formation of scar tissue which may pull the retina out of position (retinal detachment) - vision gets darker, more floaters appear and the patient eventually loses his/her sight if the condition is left untreated.
What are the signs and symptoms of diabetic retinopathy?
A symptom is something the patient senses and describes, while a sign is something other people, such as the doctor notice. For example, drowsiness may be a symptom while dilated pupils may be a sign.
Diabetic retinopathy typically has no symptoms during the early stages. Unfortunately when symptoms become noticeable the condition is often at an advanced stage. Sometimes the only detectable symptom is a sudden and complete loss of vision. The only way patients with diabetes can protect themselves is to attend every eye examination their doctor tells them to go to.
Signs and symptoms may include:
- Blurred vision
- Both eyes are usually affected
- Colour vision becomes impaired Floaters - transparent and colourless spots that float in the patient's field of vision. Sometimes they may appear as dark strings (see picture).
- Patches or streaks block the person's vision; sometimes described as empty or dark areas
- Poor night vision
- Sudden total loss of vision
What are the risk factors for Diabetic Retinopathy?
Anybody who has diabetes is at risk of developing diabetic retinopathy. However, there is a greater risk if the patient:
- Does not control blood sugar levels properly
- Suffers from hypertension (high blood pressure)
- Has high cholesterol
- Is pregnant
- Smokes regularly
- Has had diabetes for a long time
What are the treatment options for Diabetic Retinopathy?
Treatment options depend on several factors, including the type of diabetic retinopathy, how severe (advanced) it is and how the patient may have responded to previous treatments.
Treatment options for early diabetic retinopathy (nonproliferative diabetic retinopathy) - the patient may not need treatment straight away. The doctor may decide just to monitor the patient's eyes closely (watchful waiting).
Patients with poor blood sugar control will need to work with their doctor to seek ways of better controlling the diabetes. Good blood sugar control can significantly slow down the development of diabetic retinopathy.