How Doctors Diagnose Diabetic Retinopathy

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unidentifiable eye doctor holding lens up to female patient's eye to perform indirect ophthalmoscopy


In diabetic retinopathy, excessive blood sugar causes tiny blood vessels in the retina to leak fluid or to close off and prevent blood flow. Many people with diabetes have diabetic retinopathy, but don’t know it because it isn’t yet causing symptoms. Typical early symptoms of diabetic retinopathy include subtle difficulty reading or seeing distant objects. Later symptoms can include “cobwebby” vision. Because diabetic retinopathy ultimately can cause blindness, getting an accurate diabetic retinopathy diagnosis (before you experience symptoms) is crucial to preserving your vision when you have diabetes.

Diabetic Retinal Exams: A Crucial Screening Test

If you have diabetes, you should get regular vision exams whether or not you wear glasses. As part of your general vision screening, your eye doctor will conduct an initial diabetic retinal exam by dilating your pupils and looking for changes in your retinal tissue.

To perform this test, your eye doctor will place a few drops of medicine into each eye. This medicine causes the pupils to dilate widely. After a few minutes, your eye doctor will be able to use a handheld lens and a headlamp to perform indirect ophthalmoscopy to view the inside of your eye. He or she will closely examine the retina for changes that could indicate diabetic retinopathy. Both optometrists and ophthalmologists perform diabetic retinal exams.

Additional Diabetic Retinopathy Tests

If your eye doctor suspects you have diabetic retinopathy, he or she may want to perform additional tests. These exams not only can confirm a diabetic retinopathy diagnosis, but they track ongoing changes to your retinas. The most common advanced tests for diabetic retinopathy include:

  • Fluorescein angiography. In this test, the doctor—an ophthalmologist—injects a small amount of dye into a vein in the arm. Then, a special camera tracks the flow of the dye through the blood vessels in the eye. The doctor will be able to see if any of the dye leaks from the vessels near the retina, which would indicate diabetic retinopathy. The dye also will show any abnormal growth of blood vessels around the retinal tissue, which also can occur in diabetic retinopathy.
  • Optical coherence tomography (OCT). This noninvasive imaging test creates a three-dimensional “topographical” type map of your retinal tissue. OCT reveals any swelling of the tissues at the back of the eye. Doctors can use OCT to create sequential images of the inner eye and then compare prior images to look for signs the disease is worsening. Some eye and vision practices perform retinal scans as part of an annual eye exam, but it may not be covered by vision insurance.

These tests can also determine the severity of diabetic retinopathy. Non-proliferative retinopathy is when there is blood vessel damage but new blood vessel growth (proliferation) has not yet occurred. There are mild, moderate or severe stages of non-proliferative retinopathy. The fourth stage is proliferative retinopathy, where new, but abnormal blood vessels are forming.

Better diabetes management can help mild diabetic retinopathy from worsening. Moderate to severe non-proliferative retinopathy and proliferative retinopathy require treatment to reduce blood vessel proliferation. Eye surgery may be necessary.

Preventing Diabetic Vision Loss

You can reduce your risk of developing advanced diabetic retinopathy by closely managing your blood sugar levels and getting routine vision exams. Controlling your blood sugar will help avoid damage to the retinal tissues, and regular eye checkups can lead to early diagnosis and treatment. Taking these simple precautions can help you preserve your vision as you live with diabetes.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Jun 10
  1. Diabetic Retinopathy. MedlinePlus, U.S. National Library of Medicine. https://medlineplus.gov/diabeticeyeproblems.html
  2. Diabetic Retinopathy. U.S. National Eye Institute. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/diabetic-retinopathy
  3. Diabetic Retinopathy Diagnosis. American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/diabetic-retinopathy-diagnosis
  4. What is Optical Coherence Tomography? American Academy of Ophthalmology. https://www.aao.org/eye-health/treatments/what-is-optical-coherence-tomography
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