Diabetic Retinopathy: Symptoms, Causes & Treatment Guide

What Is Diabetic Retinopathy?

Diabetic retinopathy is damage to the retina caused by high blood sugar levels over time. The condition progresses through stages, from mild non-proliferative changes to severe proliferative disease where abnormal blood vessels grow and can lead to blindness. It affects approximately 35% of people with diabetes and is the leading cause of preventable blindness in working-age adults.

Diabetic retinopathy develops when chronically elevated blood sugar levels damage the tiny blood vessels that nourish the retina, the light-sensitive layer of tissue at the back of the eye that converts light into neural signals sent to the brain. The retina is extremely sensitive to changes in blood flow and oxygen supply, making it particularly vulnerable to damage from diabetes.

The condition typically develops gradually over many years. In the early stages, the damaged blood vessels may leak fluid, blood, or fatty deposits (called exudates) into the retina. This leakage can cause the retina to swell, particularly in the macula - the central part of the retina responsible for sharp, detailed vision. This swelling, known as diabetic macular edema, is a common cause of vision loss in diabetic retinopathy.

As the disease progresses, areas of the retina may become deprived of oxygen due to blocked or damaged blood vessels. In response, the body attempts to grow new blood vessels to supply oxygen to the retina - a process called neovascularization. However, these new vessels are fragile and abnormal. They grow in the wrong places, leak easily, and can bleed into the clear, gel-like substance (vitreous) that fills the center of the eye, causing floaters, vision obstruction, or sudden vision loss.

The abnormal blood vessels can also form scar tissue, which may pull on the retina and cause it to detach from the back of the eye - a sight-threatening condition called tractional retinal detachment. Additionally, abnormal vessels can grow on the iris and block the normal drainage of fluid from the eye, leading to a form of glaucoma called neovascular glaucoma.

Types of Diabetic Retinopathy

Diabetic retinopathy is classified into two main types based on disease severity and the presence of abnormal blood vessel growth:

Non-Proliferative Diabetic Retinopathy (NPDR) is the early stage of the disease. In NPDR, the walls of the retinal blood vessels weaken, and tiny bulges (microaneurysms) protrude from the vessel walls. These microaneurysms may leak fluid and blood into the retina. Small hemorrhages (dot and blot hemorrhages), fatty deposits (hard exudates), and areas of swelling may develop. NPDR is further classified as mild, moderate, or severe based on the extent of these changes. Many people with mild to moderate NPDR have no symptoms and may be unaware they have the condition.

Proliferative Diabetic Retinopathy (PDR) is the advanced stage where the disease has progressed to the point where new, abnormal blood vessels begin growing (proliferating) on the surface of the retina or the optic nerve. These fragile vessels can bleed into the vitreous, causing sudden floaters or complete vision obstruction. The scar tissue associated with neovascularization can contract and pull on the retina, causing distortion, retinal tears, or detachment. PDR is a serious condition that requires prompt treatment to prevent permanent vision loss.

What Are the Symptoms of Diabetic Retinopathy?

Early diabetic retinopathy often has no symptoms at all. As the disease progresses, symptoms may include blurred vision, floaters (dark spots or strings floating in your vision), difficulty seeing at night, dark or empty areas in your vision, and sudden vision loss. Symptoms can fluctuate with blood sugar levels.

One of the most dangerous aspects of diabetic retinopathy is that it typically causes no symptoms in its early stages. You can have significant retinal damage without noticing any changes in your vision. This is why regular screening eye exams are so critical for everyone with diabetes - by the time symptoms appear, the disease may have already progressed substantially.

When symptoms do develop, they can vary depending on which part of the retina is affected and what type of damage has occurred. Some people experience gradual changes that develop over months or years, while others may have sudden, dramatic symptoms if bleeding occurs into the vitreous.

Sudden Vision Changes

A bleed from newly formed abnormal blood vessels can cause sudden, noticeable vision changes. When blood leaks into the vitreous (the clear gel filling the eye), you may notice:

• Moving shadows or spots in your vision (floaters)
• Cobweb-like or string-like shapes drifting across your field of view
• A dark, smoky appearance to your vision
• Sudden, severe vision obstruction if the bleeding is significant

These symptoms often appear suddenly and can be alarming. While the blood may clear on its own over weeks to months if the bleeding is minor, significant vitreous hemorrhage requires medical evaluation and may need treatment to restore vision.

Gradual Vision Changes

Swelling of the macula (diabetic macular edema) typically causes more gradual changes to vision. The macula is responsible for central vision - the sharp, detailed vision you use for reading, recognizing faces, and driving. When the macula swells, you may experience:

• Blurred or hazy central vision
• Difficulty reading or recognizing faces
• Colors appearing washed out or faded
• Difficulty seeing fine details
• Problems with distance vision, which may affect driving

These changes may develop over weeks to months or even years. Because they happen gradually, some people may not notice the changes or may attribute them to normal aging or needing new glasses.

Signs of Retinal Detachment

If scar tissue from proliferative diabetic retinopathy pulls on the retina, it can lead to retinal detachment - a serious condition where the retina separates from the back of the eye. Warning signs include:

• Flashes of light, especially in peripheral vision
• A sudden increase in floaters
• A dark shadow or "curtain" moving across your field of vision
• Sudden decrease in vision

What Causes Diabetic Retinopathy?

Diabetic retinopathy is caused by chronically elevated blood sugar levels damaging the tiny blood vessels in the retina. Over time, high glucose damages vessel walls, causes inflammation, and leads to vessel leakage and blockage. The retina responds to oxygen deprivation by growing abnormal new blood vessels, which can bleed and cause scarring.

Understanding the causes of diabetic retinopathy requires understanding how diabetes affects blood vessels throughout the body. The retinal blood vessels are particularly vulnerable because they are very small (some are just one cell thick) and the retina has extremely high metabolic demands - it consumes more oxygen per gram of tissue than most other organs.

When blood sugar levels remain elevated over extended periods, a cascade of damaging processes begins. Glucose molecules bind to proteins in blood vessel walls through a process called glycation, forming harmful substances called advanced glycation end products (AGEs). These AGEs cause structural damage to vessel walls, make them leaky, and trigger inflammation.

The elevated blood sugar also activates biochemical pathways that produce oxidative stress and inflammation in retinal tissues. Important cellular processes become disrupted, including the ability of blood vessel cells to regulate blood flow, respond to changing oxygen demands, and maintain the blood-retinal barrier that normally prevents fluid and proteins from leaking into retinal tissue.

As damage accumulates, small areas of the retina become deprived of their normal blood supply. The retina releases chemical signals, including vascular endothelial growth factor (VEGF), that stimulate the growth of new blood vessels in an attempt to restore oxygen delivery. However, these new vessels grow abnormally - they have weak walls, grow in the wrong locations (on the retinal surface or into the vitreous), and leak easily. Rather than solving the oxygen problem, they create new complications through bleeding and scarring.

Risk Factors for Developing Diabetic Retinopathy

While anyone with diabetes can develop diabetic retinopathy, several factors significantly increase your risk or accelerate disease progression:

Duration of diabetes: The longer you have had diabetes, the greater your risk. After 20 years with diabetes, nearly all people with type 1 diabetes and more than 60% of people with type 2 diabetes have some degree of retinopathy. This is why screening is recommended earlier and more frequently for those who have had diabetes longer.

Poor blood sugar control: Higher average blood sugar levels (measured by HbA1c) strongly correlate with risk and progression of diabetic retinopathy. The landmark DCCT and UKPDS studies showed that intensive blood sugar control reduces the risk of developing retinopathy by 40-76% and slows progression of existing disease. Each 1% reduction in HbA1c reduces retinopathy risk by approximately 40%.

High blood pressure: Hypertension damages blood vessels throughout the body, including in the retina. High blood pressure adds stress to already weakened retinal vessels, accelerating damage and increasing the risk of bleeding. Studies show that good blood pressure control (maintaining levels below 140/80 mmHg) significantly reduces diabetic retinopathy progression.

High cholesterol and lipid levels: Abnormal blood lipids contribute to vascular damage and may worsen macular edema. The fatty deposits (hard exudates) seen in diabetic retinopathy are partly composed of leaked lipoproteins. Lipid-lowering treatment has been shown to reduce these deposits.

Pregnancy: Pregnancy can accelerate diabetic retinopathy progression, particularly if retinopathy is already present. The hormonal changes, increased blood volume, and metabolic demands of pregnancy put additional stress on retinal blood vessels. Women with diabetes who become pregnant need more frequent eye exams during pregnancy - typically every trimester, or more often if retinopathy is present.

Smoking: Tobacco use accelerates vascular damage throughout the body and is associated with faster progression of diabetic retinopathy. Smoking reduces oxygen delivery to tissues and increases inflammation and oxidative stress.

How Is Diabetic Retinopathy Diagnosed and Screened?

Diabetic retinopathy is diagnosed through a comprehensive dilated eye examination. Eye drops are used to widen the pupils, allowing the ophthalmologist to examine the retina. Additional tests may include fundus photography (pictures of the retina), optical coherence tomography (OCT) for detailed retinal imaging, and fluorescein angiography to assess blood vessel leakage.

Because diabetic retinopathy often has no symptoms in its early stages, regular screening examinations are essential for everyone with diabetes. Early detection allows treatment before significant vision loss occurs. Studies consistently show that regular screening and timely treatment can prevent more than 90% of severe vision loss from diabetic retinopathy.

Who Needs Screening and How Often?

All people with diabetes need regular eye examinations. The specific recommendations depend on the type of diabetes and findings from previous exams:

• Type 1 diabetes: First comprehensive dilated eye exam within 5 years of diagnosis, then annually
• Type 2 diabetes: Comprehensive dilated eye exam at the time of diagnosis (many people have had undiagnosed diabetes for years), then annually
• Pregnancy with pre-existing diabetes: Eye exam before conception or in the first trimester, then each trimester and for one year postpartum
• No retinopathy present: May be able to extend screening interval to every 2 years if blood sugar is well-controlled
• Mild to moderate NPDR: Every 6-12 months
• Severe NPDR or PDR: Every 3-6 months or as recommended by your ophthalmologist

The Dilated Eye Examination

The cornerstone of diabetic retinopathy screening is the dilated eye examination. During this exam, your eye care professional places drops in your eyes that widen (dilate) your pupils. This allows a clear view of the retina and optic nerve at the back of your eye.

Before the photographs are taken, dilating drops are instilled. These typically take 10-30 minutes to fully widen your pupils. The examination itself takes only a few minutes, but the entire visit may take longer due to the time needed for dilation.

After the exam, your vision will be blurry and you will be sensitive to light for several hours - typically 4-6 hours, but occasionally up to 24 hours. You should not drive after a dilated eye exam. Bring sunglasses to wear afterward, as bright light may be uncomfortable.

Fundus Photography

Fundus photography uses a specialized camera to take detailed pictures of the retina. These photographs document the current state of your retina and serve as a baseline for comparison at future visits. By comparing images over time, your doctor can detect subtle changes that might indicate disease progression.

Modern retinal photography systems can capture high-resolution images and may use advanced imaging techniques like ultra-widefield photography to image a larger area of the retina. Some screening programs use digital photography with remote reading, where images are captured at one location and interpreted by specialists at another.

Optical Coherence Tomography (OCT)

OCT is a non-invasive imaging technique that uses light waves to create detailed cross-sectional images of the retina. It can measure retinal thickness and detect even small amounts of macular edema (swelling) that might not be visible on regular examination. OCT is particularly useful for monitoring diabetic macular edema and assessing response to treatment.

The OCT scan is quick and painless. You simply look into the machine while it scans your retina. No dilation is required specifically for OCT, although it may be done as part of a comprehensive exam.

Fluorescein Angiography

Fluorescein angiography provides detailed information about blood flow in the retina and can reveal areas of vessel leakage, blockage, or abnormal new vessel growth. During this test, a fluorescent dye is injected into a vein in your arm. As the dye circulates through the retinal blood vessels, rapid sequential photographs are taken.

The dye highlights blood vessels and any areas where they are leaking or blocked. This test is particularly useful for planning laser treatment and assessing the extent of vessel abnormalities. Side effects are usually minor - the dye may temporarily turn your skin yellowish and your urine bright yellow for 24-48 hours. Allergic reactions are rare but possible.

How Is Diabetic Retinopathy Treated?

Treatment for diabetic retinopathy depends on the stage and severity. Options include anti-VEGF injections (medications injected into the eye to reduce swelling and prevent abnormal vessel growth), laser photocoagulation (using laser light to seal leaking vessels or destroy abnormal ones), and vitrectomy surgery (removing blood and scar tissue from inside the eye). All treatments work better when combined with good diabetes management.

The treatment approach for diabetic retinopathy depends on the type and severity of disease, the presence of macular edema, and individual patient factors. In early stages, treatment may primarily focus on optimizing diabetes control and monitoring for progression. More advanced disease requires specific interventions to prevent vision loss.

Anti-VEGF Injection Therapy

Anti-VEGF (anti-vascular endothelial growth factor) injections have revolutionized the treatment of diabetic retinopathy and diabetic macular edema. VEGF is a protein that drives both the growth of abnormal blood vessels and the leakage that causes macular swelling. By blocking VEGF, these medications can reduce macular edema, cause abnormal vessels to regress, and in many cases actually improve vision.

The medications are injected directly into the vitreous (the gel-like substance filling the eye) in a procedure that takes only a few minutes. While the idea of an eye injection may sound frightening, the procedure is performed with numbing drops and is generally well-tolerated. Most people report feeling only pressure, not pain.

Common anti-VEGF medications include ranibizumab (Lucentis), aflibercept (Eylea), and bevacizumab (Avastin). These medications typically need to be given repeatedly - often monthly at first, then less frequently as the condition stabilizes. The treatment schedule is individualized based on response.

Anti-VEGF therapy is now considered first-line treatment for diabetic macular edema and is also effective for proliferative diabetic retinopathy. Studies have shown that these treatments not only prevent vision loss but can improve vision in many patients - something that was rarely possible with older treatments.

Laser Photocoagulation Treatment

Laser treatment has been the standard treatment for diabetic retinopathy for decades and remains an important option, particularly for proliferative disease. The laser creates small burns on the retina that have therapeutic effects.

Focal laser treatment is used to treat specific leaking blood vessels in the macula. The laser precisely targets and seals individual leaking vessels, reducing macular edema.

Panretinal photocoagulation (PRP) is used for proliferative diabetic retinopathy. This treatment applies laser burns across the peripheral retina, destroying areas of oxygen-deprived tissue. This reduces the stimulus for abnormal vessel growth and causes existing abnormal vessels to shrink. PRP is highly effective at preventing severe vision loss - studies show it reduces the risk of blindness by more than 90%.

Laser treatment is usually performed in an outpatient setting. The eye is numbed with drops, and a special contact lens is placed on the eye to focus the laser. The procedure typically takes 15-30 minutes. Multiple sessions may be needed to complete treatment.

Side effects of laser treatment can include temporary blurred vision, mild pain during treatment, and, particularly with PRP, some reduction in peripheral vision and night vision. Despite these side effects, the benefits of preventing severe central vision loss usually far outweigh the risks.

Vitrectomy Surgery

Vitrectomy is a surgical procedure that may be needed when bleeding into the vitreous does not clear on its own, or when scar tissue threatens or has caused retinal detachment. During vitrectomy, the surgeon removes the blood-filled or scarred vitreous gel and replaces it with a clear solution. Any scar tissue pulling on the retina can be carefully removed, and additional laser treatment can be applied if needed.

Vitrectomy is performed under local or general anesthesia, typically as an outpatient procedure. Recovery time varies but usually involves several weeks of restricted activities and positioning requirements. While vitrectomy is a more invasive procedure than injections or laser, it can be sight-saving when other treatments are not sufficient.

Corticosteroid Treatments

Corticosteroids can reduce inflammation and macular edema. They can be delivered by injection into or around the eye, or through sustained-release implants that release medication over months. Corticosteroids are typically used when anti-VEGF therapy alone is not sufficient or for patients who cannot use anti-VEGF medications. Side effects can include cataract formation and increased eye pressure, so careful monitoring is required.

How Can You Prevent Diabetic Retinopathy?

You can significantly reduce your risk of diabetic retinopathy through excellent blood sugar control (target HbA1c below 7%), maintaining healthy blood pressure (below 140/90 mmHg), managing cholesterol levels, not smoking, and attending regular eye screening appointments. Good metabolic control can prevent retinopathy from developing and slow its progression if already present.

While not everyone with diabetes will develop retinopathy, taking proactive steps can dramatically reduce your risk. The landmark DCCT (Diabetes Control and Complications Trial) and UKPDS (United Kingdom Prospective Diabetes Study) demonstrated that intensive diabetes management substantially reduces the risk of developing diabetic retinopathy and slows progression in those who already have it.

Optimize Blood Sugar Control

Maintaining blood sugar levels as close to normal as safely possible is the most important step you can take to protect your eyes. Studies show that each 1% reduction in HbA1c (a measure of average blood sugar over 2-3 months) reduces the risk of diabetic retinopathy by approximately 40%.

Work with your healthcare team to establish target blood sugar levels that are appropriate for you. For most people with diabetes, aiming for an HbA1c below 7% (53 mmol/mol) helps prevent complications, including retinopathy. Monitor your blood glucose regularly, take your diabetes medications as prescribed, and make lifestyle modifications to support good control.

Be aware that rapidly improving blood sugar control after a period of poor control can temporarily worsen retinopathy in some cases. If you have existing retinopathy and plan to significantly intensify your diabetes treatment, discuss this with your ophthalmologist so more frequent monitoring can be arranged if needed.

Control Blood Pressure

High blood pressure puts additional stress on blood vessels throughout the body, including the delicate vessels in the retina. Studies have shown that good blood pressure control reduces the risk of diabetic retinopathy progression and vision loss.

The target blood pressure for most people with diabetes is below 140/90 mmHg, though your doctor may recommend a lower target. If you have been prescribed blood pressure medications, take them consistently. Lifestyle measures such as reducing sodium intake, maintaining a healthy weight, exercising regularly, and limiting alcohol can also help control blood pressure.

Manage Cholesterol and Lipids

Abnormal blood lipid levels contribute to vascular damage and may worsen diabetic macular edema. The fatty deposits seen in the retina (hard exudates) are partly composed of leaked lipids. Studies have shown that treatment with lipid-lowering medications (statins and fibrates) can reduce these deposits and may slow retinopathy progression.

Follow your healthcare provider's recommendations for cholesterol management, which may include dietary changes, exercise, and medications if needed.

Stop Smoking

Smoking accelerates damage to blood vessels throughout the body and is associated with faster progression of diabetic retinopathy. If you smoke, quitting is one of the best things you can do for your overall health and specifically for protecting your vision.

Talk to your healthcare provider about smoking cessation resources and support. Many effective treatments are available, including counseling, nicotine replacement therapy, and prescription medications.

Attend Regular Screening Appointments

Regular eye examinations allow detection of diabetic retinopathy in its earliest stages, when treatment is most effective. Do not wait for symptoms to develop - remember that early retinopathy usually causes no symptoms. Keep track of when your next eye exam is due and make it a priority.

Manage Diabetes Holistically

Eye health is connected to your overall health. Steps that are good for your general health are also good for your eyes:

• Maintain a healthy weight
• Eat a balanced diet rich in fruits, vegetables, and whole grains
• Exercise regularly - aim for at least 150 minutes per week of moderate activity
• Limit alcohol consumption
• Take all prescribed medications consistently
• Attend regular check-ups with your diabetes care team

Living with Diabetic Retinopathy

If you have been diagnosed with diabetic retinopathy, following your treatment plan, attending all follow-up appointments, and maintaining excellent diabetes control are essential. Report any new vision changes promptly. Many resources are available if vision loss affects daily activities, including low vision aids and rehabilitation services.

A diagnosis of diabetic retinopathy can be concerning, but with proper management, many people maintain good vision throughout their lives. The key is working closely with your healthcare team, staying engaged with your treatment, and taking proactive steps to protect your remaining vision.

Following Your Treatment Plan

If treatment has been recommended, follow through with it. This may mean scheduling regular injection appointments, laser treatment sessions, or surgical procedures. It is natural to feel apprehensive about eye treatments, but remember that these interventions can prevent blindness and, in many cases, improve vision.

Anti-VEGF injection therapy often requires ongoing treatment over months or years. Missing appointments can allow the disease to progress. If you are having difficulty keeping up with treatment - whether due to cost, transportation, time constraints, or other factors - talk with your healthcare team about possible solutions.

Monitoring for Changes

Be aware of your vision and report any changes promptly. Some changes require urgent attention:

• New floaters or a sudden increase in floaters
• Flashes of light
• A shadow or curtain affecting any part of your vision
• Sudden decrease in vision

These symptoms may indicate vitreous hemorrhage or retinal detachment and require immediate evaluation. Do not wait for your next scheduled appointment - contact your eye doctor right away or go to an emergency room if your doctor is not available.

Vision Rehabilitation

If vision loss has affected your daily activities, vision rehabilitation services can help you maximize your remaining vision and maintain independence. Low vision specialists can assess your specific needs and recommend:

• Magnifying devices and glasses
• Large-print materials and electronic magnification
• Proper lighting strategies
• Techniques for daily tasks
• Resources for transportation and other practical needs