Diabetic retinopathy can be detected during a dilated eye exam by an ophthalmologist or optometrist. An exam by your primary doctor, during which your eyes are not dilated, is not an adequate substitute for a full exam done by an ophthalmologist. Eye exams for people with diabetes can include:
• Visual acuity testing. Visual acuity testing measures the eye’s ability to focus and to see details at near and far distances. It can help detect vision loss and other problems.
• Ophthalmoscopy and slit lamp exam. These tests allow your doctor to see the back of the eye and other structures within the eye. They may be used to detect clouding of the lens (cataract), changes in the retina, and other problems.
• Gonioscopy. Gonioscopy is used to find out whether the area where fluid drains out of your eye (called the drainage angle) is open or closed. This test is done if your doctor thinks you may have glaucoma, a group of eye diseases that can cause blindness by damaging the optic nerve.
• Tonometry. This test measures the pressure inside the eye, which is called intraocular pressure (IOP). It is used to help detect glaucoma. Diabetes can increase your risk of glaucoma.
Your doctor may also do a test called an optical coherence tomography (OCT) to check for fluid in your retina. Sometimes a fluorescein angiogram is done to check for and locate leaking blood vessels in the retina, especially if you have symptoms, such as blurred or distorted vision, that suggest damage to or swelling of the retina.

Fundus photography can track changes in the eye over time in people who have diabetic retinopathy and especially in those who have been treated for it. Fundus photography produces accurate pictures of the back of the eye (the fundus). An eye doctor can compare photographs taken at different times to watch the progression of the disease and find out how well treatment is working. 

Early detection and treatment of diabetic retinopathy can help prevent vision loss. For people in whom diabetic retinopathy has not been diagnosed, the American Diabetes Association recommends that screening be done based on the following guidelines:1
• People with type 1 diabetes who are age 10 and older should have a dilated eye exam within 5 years after diabetes is diagnosed and then every year.
• People with type 2 diabetes should have an exam as soon as diabetes is diagnosed and then every year.
• If your eye exam results are normal, your doctor may consider follow-up exams less often. For example, you may have an exam every 2 years. But if you are diagnosed with retinopathy, you may need frequent eye exams.
• Women who have type 1 or type 2 diabetes and who are planning to become pregnant should have an exam before becoming pregnant, if possible, and then once during the first 3 months (first trimester) of pregnancy. The eye doctor can decide whether you need further screening for retinopathy during pregnancy based on the results of the first-trimester exam.

Note: Pregnant women who develop gestational diabetes are not at risk for diabetic retinopathy and do not need to be screened for it. (But women who develop gestational diabetes during pregnancy have a greater chance of developing type 2 diabetes later in life, which can put them at increased risk for retinopathy and other eye problems.)