Diabetic Eye Disease: Causes and Symptoms

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By Debra A. Sokol-McKay,
MS, CVRT, CDE, CLVT, OTR/L, SCLV

Diagnosing Diabetic Eye Disease
How Diabetes Affects the Eyes and Vision: Diabetic Retinopathy
Eye Examination Guidelines

Diagnosing Diabetic Eye Disease

Diabetic retinopathy usually has no early warning signs. It can be detected only through a comprehensive eye examination that looks for early signs of the disease, including:

  • Leaking blood vessels
  • Macular edema (swelling)
  • Pale, fatty deposits on the retina
  • Damaged nerve tissue
  • Any changes to the retinal blood vessels

To diagnose diabetic eye disease effectively, eye care specialists recommend a comprehensive diabetic eye examination that includes the following procedures:

  • Distance and near vision acuity tests
  • A dilated eye (or fundus) examination, which includes the use of an ophthalmoscope. In a dilated eye examination, it is the pupil that is dilated—not the entire eye. This allows the examiner to see through the pupil to the retina. Visual acuity tests alone are not sufficient to detect diabetic retinopathy in its early stages.
  • A tonometry test to measure fluid pressure inside the eye.
  • A fluorescein angiography test, if more serious retinal changes, such as macular edema, are suspected. Fluorescein angiography is an eye test that uses a special dye and camera to look at blood flow in the retina.
  • Optical coherence tomography (OCT) testing may be used to gain a clearer picture of the retina and its supporting layers. OCT is a type of medical imaging technology that produces high-resolution cross-sectional and three-dimensional images of the eye.
  • Also, an Amsler Grid test can detect early and sometimes subtle visual changes in a variety of macular diseases, including diabetic macular edema.

The first image below shows an Amsler Grid as seen with unimpaired vision. The next image gives an example of an abnormal Amsler Grid, as seen by a person with eye disease. These images of the grids are much smaller than normal size so that we can show them to you on this website. If you have been diagnosed with diabetic retinopathy or any eye disease, ask your eye care professional for a real Amsler Grid you can use at home.

Amsler Grid as seen with normal vision
As seen with normal vision

Amsler grid as seen by person with eye disease
An example of an abnormal
Amsler Grid

How Diabetes Affects the Eyes and Vision: Diabetic Retinopathy

Although individuals with diabetes are more likely to develop cataracts at a younger age and are twice as likely to develop glaucoma as are non-diabetics, the primary vision problem caused by diabetes is diabetic retinopathy, the leading cause of new cases of blindness and low vision in adults aged 20-65:

  • "Retinopathy" is a general term that describes damage to the retina.
  • The retina is a thin, light-sensitive tissue that lines the inside surface of the eye. Nerve cells in the retina convert incoming light into electrical impulses. These electrical impulses are carried by the optic nerve to the brain, which interprets them as visual images.
  • Diabetic retinopathy occurs when there is damage to the small blood vessels that nourish tissue and nerve cells in the retina.
  • "Proliferative" is a general term that means to grow or increase at a rapid rate by producing new tissue or cells. When the term "proliferative" is used in relation to diabetic retinopathy, it describes the growth, or proliferation, of abnormal new blood vessels in the retina. "Non-proliferative" indicates that this process is not yet occurring.

Four Stages of Diabetic Retinopathy

According to the National Eye Institute, diabetic retinopathy has four stages:

  • Mild non-proliferative retinopathy: At this early stage, small areas of balloon-like swelling occur in the retina's tiny blood vessels.
  • Moderate non-proliferative retinopathy: As the disease progresses, some blood vessels that nourish the retina become blocked.
  • Severe non-proliferative retinopathy: Many more blood vessels become blocked, which disrupts the blood supply that nourishes the retina. The damaged retina then signals the body to produce new blood vessels.
  • Proliferative retinopathy: At this advanced stage, signals sent by the retina trigger the development of new blood vessels that grow (or proliferate) in the retina and the vitreous, which is a transparent gel that fills the interior of the eye. Because these new blood vessels are abnormal, they can rupture and bleed, causing hemorrhages in the retina or vitreous. Scar tissue can develop and can tug at the retina, causing further damage or even retinal detachment.

In addition, fluid can leak into the macula, the small sensitive area in the center of the retina that provides detailed vision. This fluid can cause macular edema (or swelling), which can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses.

During the non-proliferative stages, your eye care physician may notice changes in your eyes due to retinopathy. It is unlikely that you will notice any changes in your vision until the proliferative stage is reached.

Symptoms of diabetic retinopathy can include:

  • Blurry vision or double vision
  • Flashing lights, which can indicate a retinal detachment
  • A veil, cloud, or streaks of red in the field of vision, or dark or floating spots in one or both eyes, which can indicate bleeding
  • Blind or blank spots in the field of vision
Simulation of the effects of diabetic retinopathy

A simulation of the ocular and functional effects of diabetic retinopathy
Henry Ford Center for Vision Rehabilitation and Research

Ocular and functional effects of diabetic retinopathy can include any or all of the following:

  • Fluctuating vision in response to changing blood glucose levels; vision can change from day to day, or from morning to evening.
  • Blurred central vision from macular edema can interfere with reading.
  • Decreased visual acuity can interfere with seeing the markings on an insulin syringe or the display on a standard blood glucose monitor.
  • Irregular patches of vision loss or "blind spots" can make it difficult to judge the size of food portions on a plate.
  • Decreased depth perception, in combination with decreased visual acuity, can make it difficult to see curbs and steps, or walk to the diabetes clinic.

Eye Examination Guidelines

The American Association of Diabetes Educators provides the following eye examination guidelines for individuals with diabetes:

  • At minimum, individuals with type 1 and type 2 diabetes should schedule an annual diabetic eye exam.
  • Individuals with mild non-proliferative retinopathy should schedule an annual diabetic eye exam.
  • Individuals with moderate to severe non-proliferative retinopathy should schedule a diabetic eye exam every 6 to 12 months.
  • Individuals with macular edema or proliferative retinopathy should schedule a diabetic eye exam as frequently as every 4 months, if indicated.
  • Individuals with proliferative retinopathy and high-risk complications, such as the growth of new blood vessels in the optic disc area [the entry point of the optic nerve] or recent bleeding in the retina or vitreous, should schedule diabetic eye exams as frequently as needed.

Personal Stories

  • Vivian, Living with Diabetes and Visual Impairment
    Vivian was diagnosed with diabetes twenty years ago, at age 58. Ten years later, she was diagnosed with diabetic retinopathy and spinal stenosis. She talks about how she is living and coping with her diabetes and some of the tools and techniques she uses.

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