How Does Diabetes Affect the Retina?

Diabetic retinopathy is a complication of diabetes (type I or type II) that affects the blood vessels and nerve tissues of the eyes.

Two stages of diabetic retinopathy include:

1. Early diabetic retinopathy or nonproliferative diabetic retinopathy
   • The most common type (an early stage) of retinopathy, is in which the walls of the blood vessels in the retina become weakened, leading to tiny bulges protruding from the walls of the smaller vessels, which results in fluid and blood leaking into the retina. 
   • Larger retinal vessels dilate and become irregular in diameter, causing edema (accumulation of fluid) in the macula (central portion of the retina).
2. Advanced diabetic retinopathy or proliferative diabetic retinopathy
   • A severe type (an advanced stage), wherein the damaged blood vessels close off, causing the growth of new, abnormal blood vessels in the retina. 
   • These new blood vessels are fragile and can leak into the vitreous (the clear, jellylike substance that fills the center of the eye).
   • The scar tissue formed due to the growth of new blood vessels can cause the retina to detach from the back of the eye. 
   • If these new blood vessels interfere with the normal flow of fluid, pressure can build in the eyeball, causing damage to the optic nerve (which carries images from the eye to the brain), resulting in glaucoma.

Over time, excess sugar in the blood (uncontrolled diabetes) can lead to the blockage of the tiny blood vessels that nourish the retina, cutting off its blood supply.

As a result, the eye attempts to grow new blood vessels, which may not develop properly or leak easily.

Although anyone with diabetes can develop diabetic retinopathy, the risk of this eye complication increases dramatically as a result of the following:

• Having diabetes for a long time
• Poor control of the blood sugar levels
• High blood pressure
• High cholesterol
• Pregnancy (due to gestational diabetes)
• Smoking
• Tobacco use
• Being African American, Hispanic, or Native American

Initially, the early stages of diabetic retinopathy might not cause any symptoms or may cause only mild vision problems, but eventually, it can lead to blindness.

As the condition progresses, a person might develop the following:

• Floaters (spots, dark strings, or streaks floating in the vision)
• Blurred or double vision
• Fluctuating, spotty, or hazy vision
• Dark, blank, or empty spots in the vision
• Pain or pressure in one or both the eyes
• Trouble reading
• Difficulty seeing faraway objects
• Partial or complete vision loss

Apart from the vision symptoms, diabetic retinopathy is best diagnosed through the following:

• Visual acuity test: To measure the central vision ability at variable distances.
• Comprehensive dilated eye examination: The doctor will look for abnormalities inside the eyes using eye drops to widen (dilate) the pupils for a better view.
• Tonometry: To check the intraocular pressure inside the eye.
• Ophthalmoscopy: A close examination of the retina using a special magnifying glass.
• Fluorescein angiography: After the eyes are dilated, a dye is injected into a vein in the arm, and pictures are taken as the dye circulates through the blood vessels.
• Optical coherence tomography: Cross-sectional images of the retina are taken to visualize the thickness of the retina.

Depending on the type and severity of diabetic retinopathy, treatment is geared to slow down or stop the progression of the condition.

Early diabetic retinopathy

In cases of mild to moderate diabetic retinopathy, good blood sugar control by oral medications or injectables can usually help to slow the progression.

Advanced diabetic retinopathy

Depending on the specific issues with the retina, treatment options might include:

• Vascular endothelial growth factor inhibitors
  • These medications are injected into the vitreous of the eye using topical anesthesia to help stop the growth of new blood vessels and decrease fluid accumulation.
  • Drugs approved by the FDA for the treatment of diabetic macular edema:
    • Lucentis (ranibizumab)
    • Eylea (aflibercept)
• Photocoagulation
  • A focal laser treatment that can stop or slow the leakage of blood and fluid in the eye.
• Panretinal photocoagulation
  • A scatter laser treatment can help shrink abnormal blood vessels.
• Vitrectomy
  • Blood and scar tissue from the vitreous (a jellylike substance that fills the middle of the eye) on the retina is removed through a tiny incision in the eye using local or general anesthesia.

Diabetic retinopathy can lead to serious eye and vision complications, such as:

• Vitreous hemorrhage
• Retinal detachment
• Glaucoma
• Blindness

Although to a lesser extent, diabetic retinopathy can be prevented through regular eye examination, good control of blood sugar and blood pressure, and early intervention for vision problems.

The risk of getting diabetic retinopathy can be reduced by:

• Managing diabetes through healthy eating, regular physical activity, and taking oral diabetes medications or insulin as directed by the physician.
• Monitoring your blood sugar levels regularly.
• Keeping your blood pressure and cholesterol under control (through healthy eating, exercising regularly, and losing excess weight).
• Quitting smoking or use of any other types of tobacco products.
• Paying complete attention to vision changes (if any).
• Having regular eye checkups (at least six per month).