Diabetic Retinopathy: Causes and Diagnosis

Diabetic retinopathy is an eye disease that is a complication of diabetes. It is closely related to the duration of diabetes, retinopathy status at diagnosis, and level of glycemic control. Other factors associated with the disease include high blood pressure (hypertension), nephropathy (kidney disease), and dyslipidemia.

Diabetic retinopathy is diagnosed by a comprehensive dilated eye exam by an ophthalmologist or optometrist with experience in diabetic eye disease. Early detection and treatment can reduce complications and slow the progression of the disease.

Causes of Diabetic Retinopathy

The most common causes of diabetic retinopathy include chronically elevated blood sugar (hyperglycemia), the duration of diabetes, and blood pressure levels.

high blood sugar

There are many reasons why people with diabetes experience elevated blood sugar, including inadequate medication (timing, dose, cost), difficulties with self-management, poor diet, or high carbohydrate intake.

When sugar (glucose) cannot be absorbed into cells for energy, the excess sugar remains in the bloodstream, causing damage to the body.

Diabetic retinopathy occurs when the tiny blood vessels in the retina are damaged by excess sugar. The buildup of sugar disrupts the ability of blood vessels to carry blood and nutrients to the optic nerve.

This blockage of blood vessels can cause the balloon pocket to leak fluid and blood into the retina, which can lead to macular edema. The macula is the part of the eye that helps focus. When it fills with fluid, vision becomes blurred.

If too many blood vessels are affected and shut down, the body will compensate by growing new, weaker blood vessels. When this happens, diabetic retinopathy is called proliferative retinopathy, which is a more advanced stage of the disease.

New blood vessels continue to ooze fluid and blood and may also lead to scar tissue formation. The buildup of scar tissue can lead to retinal detachment.

Diabetes course

Retinopathy can occur even before diabetes is diagnosed. The longer you have diabetes, the more likely you are to develop retinopathy.

But there is good news. Many people do not experience symptoms of diabetic retinopathy, and the more severe forms that can lead to vision loss are very rare. This is especially true today due to earlier detection and better treatment options.

The American Diabetes Association recommends a dilated eye exam for all people with diabetes. Adults with type 1 diabetes should have an initial dilated eye exam within five years of diabetes onset, while those with type 2 diabetes should have their first eye exam at diagnosis.

High blood pressure

There is an association between blood pressure control and diabetic retinopathy. Some studies suggest that elevated blood pressure increases the risk of diabetic retinopathy as well as disease progression. It is hypothesized that elevated blood pressure damages retinal capillary endothelial cells.

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kidney disease

People with diabetes who have kidney disease (kidney disease) are more likely to develop diabetic retinopathy. In patients with type 1 diabetes, retinopathy has been established to precede nephropathy. However, this relationship is poorly understood in type 2 diabetes. Some studies suggest that kidney disease precedes retinopathy.

pregnancy and puberty

Pregnancy and puberty may accelerate diabetic retinopathy. With pre-existing type 1 or type 2 diabetes, it occurs when a pregnant woman’s blood sugar is not well controlled at the time of conception.


Some people with diabetes may have a genetic predisposition to develop diabetic retinopathy. Researchers have identified about 65 genes associated with the disease. These genes play roles in insulin signaling, angiogenesis (the process of forming new blood vessels), inflammation, neurogenesis, and the regulation of endothelial cells.

cardiovascular risk factors

Certain cardiovascular risk factors are associated with retinopathy and may contribute to the etiology.

Lipid abnormalities

Elevated blood lipids, also known as dyslipidemia, are associated with diabetic retinopathy. Specifically, dyslipidemia is known to cause hard exudates, which occur when blood vessels in the eye leak lipids into the retina. People with type 2 diabetes and hyperlipidemia appear to have an increased risk of diabetic macular edema.

Metabolic syndrome

The researchers found a correlation between the development of diabetic retinopathy and metabolic syndrome. Metabolic syndrome is characterized by central obesity, hyperlipidemia, insulin resistance, and hypertension. The mechanism by which this occurs is thought to be due in part to the body’s chronic inflammatory state.

Lifestyle Risk Factors

Smoking exacerbates blood vessel damage in people with diabetes. A meta-analysis of the literature showed that smokers with type 1 diabetes had a significantly increased risk of diabetic retinopathy, whereas smokers with type 2 diabetes had a significantly lower risk.

Although retinopathy is reduced in smokers with type 2 diabetes, smoking causes many other complications of diabetes and is not recommended.


All people with diabetes should have a full dilated eye exam by an ophthalmologist or optometrist who knows how to treat diabetic eye disease. For people with type 1 diabetes, this should happen within five years of the onset of diabetes. For those with type 2 diabetes, this should happen shortly after diagnosis.

Further testing and follow-up will depend on whether retinopathy is present, whether you have any symptoms, and how well you control your blood sugar.

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Self-examination and home assessment

There is no way to self-check for diabetic retinopathy. And because most people don’t even know they have it, they’re less likely to be screened. It is especially important to perform a dilated examination for all people with diabetes. Adequate and timely screening can prevent or delay disease development and progression.

Comprehensive dilated eye exam

The American Diabetes Association reports that as many as one in five people with type 2 diabetes have some form of retinopathy at the time of diabetes diagnosis, especially if the newly diagnosed person has diabetes that has been undiagnosed for many years.

In addition, many patients with retinopathy may be asymptomatic, so adequate screening before retinopathy progresses is essential to identify and treat retinopathy.

A comprehensive mydriatic exam uses drops to dilate the pupil so that the retina can be seen. Drops make the pupil (the black part of the eye) larger to expand the retina’s field of vision. Next, the healthcare provider will shine a bright light (slit lamp) into the pupil to see the retina.

If retinopathy is found, you may need more tests. The test can also be used to diagnose diabetic macular edema, glaucoma and cataracts – common eye diseases associated with diabetes.

indirect ophthalmoscope

In this exam, the examiner wears an optical device on the top of the head that contains special lenses that magnify the eyes. Lenses and lights allow the examiner to see more retinal detail.

optical coherence tomography

Optical coherence tomography (OCT) is commonly used to examine optic nerve diseases such as diabetic macular edema (DME) and glaucoma. It is considered one of the best tests for diagnosing and evaluating DME and can also be used to monitor response to DME-related treatments such as anti-VEGF injections.

This is a non-invasive test that uses light waves to assess a cross-section of the retina and measure its thickness. OCT machines scan your eyes without touching them. The exam usually takes five to ten minutes.

Fluorescein Angiography

This test is used to see if there are any leaks or microaneurysms in the retinal blood vessels. It is also used to track changes in the eye and target treatment area. The test is done by dilating your eye and then injecting a dye into your vein. The dye illuminates the small blood vessels in the eye. Your healthcare provider will take a picture of your eye while the dye is active.

Your eyes may be sensitive to light and your skin may turn yellow after the test. In rare cases, you may have an allergic reaction to the dye. If you have any signs of an allergic reaction, such as itching, hives, or trouble breathing, you should let your healthcare provider know right away.

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digital retinal imaging

The American Diabetes Association says retinal photographs have great potential as a screening resource when high-quality eye professionals are not readily available. These digital photos can take pictures of the retina, blood vessels, and optic nerve, and help evaluate diabetic eye disease.

It should be noted that they are not a substitute for a comprehensive eye exam, but can be used as an additional diagnostic tool to detect most clinically significant diabetic retinopathy.


Assessing glycemic control can help professionals assess the risk of diabetic retinopathy and prevent disease progression.

The Diabetes Control and Complications Trial (DCCT) determined that intensive glycemic control in people with diabetes reduces the development or progression of diabetic retinopathy by 35% to 76%. Early treatment of hyperglycemia and lowering of hemoglobin A1C has also been shown to reduce the progression of retinopathy.

Therefore, your healthcare provider may want to assess your hemoglobin A1C (three-month average blood sugar). Most people with diabetes should have a hemoglobin A1C of 7% or less, but the goal should vary from person to person. If your A1C is above target, a 10% reduction may help reduce the progression of retinopathy.

Your healthcare provider can assess your hemoglobin A1C using a phlebotomy or a finger stick (if they have an instant A1C machine on site).

Other laboratory markers may include blood and urine collections to assess your kidney function, cholesterol and triglyceride levels. Abnormal results are not sufficient to diagnose retinopathy, but they may indicate an increased risk of the disease.

VigorTip words

There are many causes of diabetic retinopathy, some of which are manageable. Optimizing blood sugar, blood pressure and lipids; smoking cessation; early detection and screening can prevent or delay the development and progression of diabetic retinopathy.

Improvements in diagnostic assessment tools can help reveal asymptomatic disease and provide accurate assessments for treating and preventing serious complications.

If you have diabetes, the most important thing to do to protect your eyes is to work hard to control your blood sugar and make sure you get a full dilated eye exam. If you do not have a reputable eye doctor, seek advice from your primary care provider, endocrinologist, or certified diabetes care and education specialist.