Diabetic retinopathy is an eye disease found in people with diabetes. It is caused by damage to the retina, and if left untreated can cause blindness.
What is the retina?
The retina is the light-sensitive film on the back of our eyes. The retina is responsible for sensing light that enters our eye and transmitting these signals via the optic nerve to our brain. The brain is then able to generate an image. Damage to the retina (without inflammation) is referred to as retinopathy.
Diagram showing the position of the retina relative to the other structures in the eye.
What is diabetes?
Diabetes mellitus is a disease in which blood sugar (glucose) levels are high. Most often, this is due to low levels of the hormone insulin. Insulin is important in the uptake of sugars from the bloodstream into our tissues.
The two major forms of diabetes are type 1 diabetes and type 2 diabetes.
In type 1 diabetes, the organ that produces insulin (the pancreas) is destroyed by our own immune system, decreasing the amount of insulin and therefore increasing blood sugar.
In type 2 diabetes, cells throughout our body become less responsive to insulin. This means that more insulin is required than normal to keep blood sugar levels down.
What are the complications of diabetes?
Both type 1 and type 2 diabetes can cause a variety of complications. These include heart disease, stroke, nerve damage, kidney damage and eye damage.
What are the ocular manifestations of diabetes?
There are many changes to the eye that can occur with diabetes, especially if the diabetes has been present for a long time. These can include cornea problems, glaucoma or cataracts. However, the most serious complication of diabetes to the eye is diabetic retinopathy. Most people having had diabetes more than 20 years will develop diabetic retinopathy.
How does diabetes damage the retina?
All tissues in our body require oxygen and nutrients in order to survive. In most cases, this is supplied by our blood vessels.
In diabetes, the high sugars in the blood can damage blood vessels. In the retina, this means that certain parts can become deprived of oxygen. These vessels can also leak, causing swelling in the back of the eye.
As the disease progresses, fragile new blood vessels can grow into areas of the retina deprived of oxygen. These new blood vessels can bleed into the eye and obscure vision.
What are the stages of diabetic retinopathy?
Diabetic retinopathy is usually classified into either non-proliferative diabetic retinopathy (NPDR) or proliferative diabetic retinopathy.
In non-proliferative diabetic retinopathy, there is damage to the blood vessels of the retina but no overgrowth of new blood vessels. Commonly, this stage of the diseases is asymptomatic; in other words, there are no visual changes yet.
In proliferative diabetic retinopathy, there is an overgrowth of new, fragile blood vessels into areas of the retina deprived of oxygen. These new blood vessels cause problems, as they can obscure vision and leak fluid into the eye. As well, proliferative diabetic retinopathy can lead to retinal detachments or glaucoma.
Diagram showing proliferative diabetic retinopathy. When blood leaks into the vitreous ("vitreous hemorrhage"), vision will be obscured.
What are the symptoms of diabetic retinopathy?
Symptoms of diabetic retinopathy can include: • Decreased vision • Blurred vision • Floaters
Unfortunately, diabetic retinopathy usually does not cause vision problems until its later stages. This means that by the time vision changes do occur, there has already been much damage to the retina.
Is there screening for diabetic retinopathy?
It is very important that people with diabetes be monitored regularly by both a doctor specializing in diabetes (typically an endocrinologist) as well as an ophthalmologist. If diabetic retinopathy is “caught” early, there will be a better long term outcome.
How is diabetic retinopathy diagnosed?
Diabetic retinopathy is diagnosed by a full eye exam by an ophthalmologist. The full eye exam includes direct visualization of the retina (with an ophthalmoscope), visual acuity tests and eye pressure measurements.
Sometimes, the ophthalmologist may request more extensive imaging with a technology called fluorescein angiography, in which fluorescent dye is injected into the blood vessels to help visualization of the retina.
How is diabetic retinopathy treated?
Treatment of diabetic retinopathy is usually delayed until later stages of the disease (but before significant damage). There are 3 common forms of treatments:
Laser treatment: In laser treatment, the ophthalmologist uses lasers to destroy areas of the retina deprived of oxygen. This helps to prevent the growth of new blood vessels into these areas.
Vitrectomy: vitrectomy is a surgical procedure in which the fluid in the back of the eye is replaced by a saline fluid. This may be the treatment of choice if there has been extensive bleeding into the eye. To read more about a vitrectomy, click here.
Steroid injection: injection of the steroid triamcinolone into the eye can also be beneficial for some patients with diabetic retinopathy.
The choice of treatment depends on the stage of the disease, the age of the patient and the recommendations of the ophthalmologist. It is important that treatment be prompt before extensive damage has occurred.
Can treatment regain vision loss?
For patients who have already lost vision from the disease, treatment usually does not regain that vision. However, vision loss from complications such as bleeding into the eye, retinal detachments or cataracts can be regained.
Can diabetic retinopathy be prevented?
There is evidence that good blood sugar (glucose) control can delay the progression and limit the complications of diabetic retinopathy for people with diabetes.
Diabetes itself can also be prevented with a healthy lifestyle. This involves maintaining a healthy weight, avoiding junk foods and exercising regularly.
