Diabetic retinopathy causes, symptoms and how diabetes affects the eye
According to the International Diabetes Federation (IDF):
- Approximately 425 million adults (20-79 years) were living with diabetes in 2017; and by the year 2045, this number is expected to increase to 629 million.
- Another 325 million people in 2017 were at risk of developing type 2 diabetes.
- The proportion of people with type 2 diabetes is increasing in most countries throughout the world.
- The greatest number of people with diabetes in 2017 were between 40 and 59 years of age.
- 1 in 2 (212 million) people with diabetes are unaware they have the disease.
Because of these facts and projections, diabetic retinopathy may soon become a major worldwide health crisis.
Risk factors for type 2 diabetes include obesity, an unhealthful diet and physical inactivity.
Generally, diabetics don't develop diabetic retinopathy until they have had diabetes for at least 10 years. But it is unwise to wait that long for an eye exam.
If you are at risk of diabetes or have been diagnosed with the disease, it’s important to see your eye doctor for an annual comprehensive eye exam. In some cases, your doctor may recommend more frequent exams to monitor the health of your retina.
How does diabetes cause diabetic retinopathy?
Diabetes mellitus (DM) causes abnormal changes in the blood sugar (glucose) that your body ordinarily converts into energy to fuel different bodily functions.
Uncontrolled diabetes allows unusually high levels of blood sugar (hyperglycemia) to accumulate in blood vessels, causing damage that hampers or alters blood flow to your body's organs — including your eyes.
There are two main types of diabetes:
- Type 1 diabetes. Insulin is a natural hormone that helps regulate the levels of blood sugar needed to help "feed" your body. When you are diagnosed with type 1 diabetes, you are considered insulin-dependent and you will need insulin injections or other medical treatment to supply the insulin your body is unable to produce on its own. When you don't produce enough of your own insulin, your blood sugar is unregulated and levels are too high.
- Type 2 diabetes. When you are diagnosed with type 2 diabetes, you generally are considered non-insulin-dependent or insulin-resistant. With this type of diabetes, you produce enough insulin, but your body is unable to make proper use of it. Your body then compensates by producing even more insulin, which can cause an accompanying abnormal increase in blood sugar levels.
With both types of diabetes, abnormal spikes in blood sugar increase your risk of diabetic retinopathy.
Eye damage occurs when chronically high amounts of blood sugar begin to clog or damage blood vessels within the eye's retina, which contains light-sensitive cells (photoreceptors) necessary for good vision.
Symptoms of diabetic retinopathy and other diabetic eye disease
Symptoms of diabetic retinopathy (DR) and other diabetes-related eye disease include:
- Fluctuating vision
- Eye floaters and spots
- Development of a scotoma or shadow in your field of view
- Blurry and/or distorted vision
- Corneal abnormalities such as slow healing of wounds due to corneal abrasions
- Double vision
- Eye pain
- Near vision problems unrelated to presbyopia
During an eye examination, your eye doctor will look for other signs of diabetic retinopathy and diabetic eye disease. Signs of eye damage found in the retina can include swelling, deposits and evidence of bleeding or leakage of fluids from blood vessels.
Your eye doctor will use a special camera or other imaging device to photograph the retina and look for telltale signs of diabetes-related damage. In some cases, he or she may refer you to a retinal specialist for additional testing and possible treatment.
For a definitive diagnosis, you may need to undergo a test called a fluorescein angiography. In this test, a dye is injected into your arm intravenously and gradually appears in the blood vessels of the retina, where it is illuminated to detect diabetes-related blood vessel changes and blood leakage in the retina.
One sometimes overlooked symptom of diabetic eye disease is nerve damage (neuropathy) affecting ocular muscles that control eye movements. Symptoms can include involuntary eye movement (nystagmus) and double vision.
Types of diabetic eye disease
Once high blood sugar damages blood vessels in the retina, they can leak fluid or bleed. This causes the retina to swell and form deposits in early stages of diabetic retinopathy.
In later stages, leakage from blood vessels into the eye's clear, jelly-like vitreous can cause serious vision problems and eventually lead to blindness.
Diabetic macular edema. This swelling of the macula more commonly is associated with type 2 diabetes. Macular edema may cause reduced or distorted vision.
Diabetic macular edema (DME) typically is classified in two ways:
- Focal, caused by microaneurysms or other vascular abnormalities sometimes accompanied by leaky blood vessels.
- Diffuse, which describes dilated or swollen tiny blood vessels (capillaries) within the retina.
Non-proliferative diabetic retinopathy (NPDR). This early stage of DR — identified by deposits forming in the retina — can occur at any time after the onset of diabetes.
Often no visual symptoms are present, but examination of the retina can reveal tiny dot and blot hemorrhages known as microaneurysms, which are a type of out-pouching of tiny blood vessels.
In type 1 diabetes, these early symptoms rarely are present earlier than three to four years after diagnosis. In type 2 diabetes, NPDR can be present even upon diagnosis.
Proliferative diabetic retinopathy (PDR). Of the diabetic eye diseases, proliferative diabetic retinopathy has the greatest risk of visual loss.
PDR is characterized by these signs:
- Development of abnormal blood vessels (neovascularization) on or adjacent to the optic nerve and vitreous.
- Ischemia from decreased or blocked blood flow, with accompanying lack of oxygen needed for a healthy retina.
These abnormal blood vessels formed from neovascularization tend to break and bleed into the vitreous humor of the eye. Besides sudden vision loss, more permanent complications can include tractional retinal detachment and neovascular glaucoma.
Macular edema may occur separately from or in addition to NPDR or PDR.
You should be monitored regularly, but you typically don't require laser treatment for diabetic eye disease until the condition is advanced.
Who gets diabetic retinopathy?
Beyond the presence of diabetes, how well your blood sugar is controlled is a major factor determining how likely you are to develop diabetic retinopathy with accompanying vision loss
Uncontrolled high blood pressure (hypertension) has been associated with eye damage related to diabetes. Also, studies have shown a greater rate of progression of diabetic retinopathy in diabetic women when they become pregnant.
Of course, the longer you have diabetes the more likely you are to have vision loss. Nearly all diabetics who have the disease long enough eventually will develop at least some degree of diabetic retinopathy, though less advanced forms of the eye disease may not lead to vision loss.
Remember: Routine eye exams are the best way to protect your eyes from vision loss caused by diabetic retinopathy and other diabetic eye disease.