Diabetic retinopathy: Causes, symptoms, and treatments
The condition can lead to blindness if left untreated. Early blindness due to diabetic retinopathy (DR) is usually preventable with routine checks and effective management of the underlying diabetes.
- Diabetic retinopathy (DR) is blood vessel damage in the retina that happens as a result of diabetes.
- It is the leading cause of blindness in the United States (U.S.).
- Symptoms include blurred vision, difficulty seeing colors, floaters, and even total loss of vision.
- People with diabetes should have their vision checked at least once annually to rule out DR.
- There are retinal surgeries that can relieve symptoms, but controlling diabetes and managing early symptoms are the most effective ways to prevent DR.
What is diabetic retinopathy?
Diabetic retinopathy is a complication of diabetes that can lead to total blindness without treatment.
DR is a complication of diabetes and a leading cause of blindness in the United States (U.S.).
The retina is the membrane that covers the back of the eye. It is highly sensitive to light.
It converts any light that hits the eye into signals that can be interpreted by the brain. This process produces visual images, and it is how sight functions in the human eye.
Diabetic retinopathy damages the blood vessels within the retinal tissue, causing them to leak fluid and distort vision.
There are two types of DR:
- Non-proliferative diabetic retinopathy (NPDR): This is the milder form of diabetic retinopathy and is usually symptomless.
- Proliferative diabetic retinopathy (PDR): PDR is the most advanced stage of diabetic retinopathy and refers to the formation of new, abnormal blood vessels in the retina.
Approximately 5.4 percent of people in the U.S. aged over 40 years have DR.
Worldwide, one-third of the estimated 285 million people with diabetes show signs of DR.
Diabetic retinopathy typically presents no symptoms during the early stages.
The condition is often at an advanced stage when symptoms become noticeable. On occasion, the only detectable symptom is a sudden and complete loss of vision.
Signs and symptoms of diabetic retinopathy may include:
- blurred vision
- the impairment of color vision
- floaters, or transparent and colorless spots and dark strings that float in the patient's field of vision
- patches or streaks that block the person's vision
- poor night vision
- sudden and total loss of vision
DR usually affects both eyes. It is important to make sure that the risk of vision loss is minimized. The only way people with diabetes can prevent DR is to attend every eye examination scheduled by their doctor.
Possible complications associated with diabetic retinopathy include the following:
Vitreous hemorrhage: A newly formed blood vessel leaks into the vitreous gel that fills the eye, stopping light from reaching the retina. Symptoms include loss of vision and sensitivity to light, or floaters in milder cases. This complication can resolve itself if the retina remains undamaged.
Detached retina: Scar tissue can pull the retina away from the back of the eye. This usually causes the appearance of floating spots in the individual's field of vision, flashes of light, and severe vision loss. A detached retina presents a significant risk of total vision loss if left untreated.
Glaucoma: The normal flow of fluid in the eye may become blocked as new blood vessels form. The blockage causes a buildup of ocular pressure, or pressure in the eye, increasing the risk of optic nerve damage and vision loss.
Causes and risk factors
Anybody with diabetes is at risk of developing diabetic retinopathy. However, there is a greater risk if the person:
- does not correctly control blood sugar levels
- experiences high blood pressure
- has high cholesterol
- is pregnant
- smokes regularly
- has had diabetes for a long time
Damage to the network of blood vessels that nourish the retina is the key cause of diabetic retinopathy.
High glucose levels damage these vessels and restrict the flow of blood to the retina. The problems with the blood vessels can be as mild as tiny bulges in the vessel wall that occasionally leak blood without affecting vision.
However, in the advanced stages of the condition, these blood vessels may become completely blocked. The eye then produces new, less stable blood vessels. The new vessels break easily and leak into the vitreous gel of the eye. The bleeding causes blurred and patchy vision by further blocking the retina.
This bleeding, on occasion, forms scars that can separate the retina and the eye, leading to a detached retina. As symptoms develop, a person with DR becomes increasingly likely to experience complete vision loss.
Diabetic retinopathy may be diagnosed using an optical coherence tomography (OCT) scan.
Diabetic retinopathy generally starts without any noticeable change in vision. However, an ophthalmologist, or eye specialist, can detect the signs.
It is crucial for people with diabetes to have an eye examination at least once or twice annually, or when recommended by a physician.
The following methods are commonly used to diagnose diabetic retinopathy:
Dilated eye exam
The doctor administers drops into the patient's eyes. These drops dilate the pupils and allow the doctor to view the inside of the eye in a more detailed way.
Photographs are taken of the interior of the eye. During the eye examination, the doctor can detect the presence of:
- abnormalities in the blood vessels, optic nerve, or retina
- changes in eye pressure or overall vision
- new blood vessels
- retinal detachment
- scar tissue
These drops may sting, and the bright lights of the photographs can startle the person receiving the test. In high-risk individuals, the eye drops may cause an increase in ocular pressure.
Drops are used to dilate the pupils, and a special dye called fluorescein is injected into a vein in the patient's arm. Pictures are taken as the dye circulates through the eyes. The dye may leak into the retina or stain the blood vessels if the blood vessels are abnormal.
This test can determine which blood vessels are blocked, leaking fluid, or broken down. Any laser treatments can then be accurately guided. For around 24 hours after the test, the skin may turn yellowish, and urine dark orange, as the dye exits the body.
Optical coherence tomography (OCT)
This noninvasive imaging scan provides high-resolution cross-sectional images of the retina, revealing its thickness. After any treatments, scans may be used later to check how effective treatment has been.
OCT is similar to ultrasound testing but uses light rather than sound to produce images. The scan can also detect diseases of the optic nerve.
Treating DR depends on several factors, including the severity and type of DR, and how the person with DR has responded to previous treatments.
With NPDR, a doctor may decide to monitor the person's eyes closely without intervening. This is known as watchful waiting.
Individuals will need to work with their doctor to control diabetes. Good blood sugar control can significantly slow the development of DR.
In most cases of PDR, the patient will require immediate surgical treatment. The following options are available:
Focal laser treatment, or photocoagulation
The procedure is carried out in a doctor's office or an eye clinic. Targeted laser burns seal the leaks from abnormal blood vessels. Photocoagulation can either stop or slow down the leakage of blood and buildup of fluid in the eye.
People will usually experience blurry vision for 24 hours following focal laser treatment. Small spots may appear in the visual field for a few weeks after the procedure.
Scatter laser treatment, or pan-retinal photocoagulation
Scattered laser burns are applied to the areas of the retina away from the macula, normally over the course of two or three sessions. The macula is the area at the center of the retina in which vision is strongest.
The laser burns cause abnormal new blood vessels to shrink and scar. Most patients require two or three sessions for the best results.
Individuals may have blurry vision for 24 hours following the procedure, and there may be some loss of night vision or peripheral vision.
This involves the removal some of the vitreous from within the eyeball. The surgeon replaces the clouded gel with a clear liquid or gas. The body will eventually absorb the gas or liquid. This will create new vitreous to replace the clouded gel that has been removed.
Any blood in the vitreous and scar tissue that may be pulling on the retina is removed. This procedure is performed in a hospital under general or local anesthetic.
The retina may also be strengthened and held in position with tiny clamps.
After surgery, the patient may have to wear an eye patch to gradually regain use of their eye, which can tire after a vitrectomy.
If gas was used to replace the removed gel, the patient should not travel by plane until all gas has been absorbed into the body. The surgeon will tell the patient how long this should take. Most patients will have blurry vision for a few weeks after surgery. It can take several months for normal vision to return.
Surgery is not a cure for diabetic retinopathy. However, it may stop or slow the progression of symptoms. Diabetes is a long-term condition, and subsequent retinal damage and vision loss may still occur despite treatment.
For the majority of people with diabetes, DR is an inevitable consequence.
However, patients with diabetes who successfully manage their blood sugar levels will help to prevent the onset of a severe form of DR.
- eating a healthy and balanced diet
- regularly exercising
- maintaining a healthy body weight
- smoking cessation
- strictly controlling alcohol intake
- taking any antihypertensive measures according to their doctor's instructions
- attending regular screenings
Early detection of symptoms increases the effectiveness of the treatment.
Written by Christian Nordqvist