Diagnosing Diabetic Retinopathy

You've come a long way, baby. Thirty years ago, your chances of going blind within five years of being diagnosed with severe diabetic retinopathy were no better than 50/50. Today, the same diagnosis gives you a 90% chance of saving your sight.

There's just one little catch: If you have type 1 or type 2 diabetes (visit What is Diabetic Retinopathy to learn about the differences) you must have a comprehensive dilated eye examination every year even if you have no symptoms. Preserving your sight is a gamble that depends more on strategy than on luck—but it's a game you simply must not walk away from.

Screening

Remember, adults and children age 10 and older who have diabetes should have a comprehensive dilated eye examination every year even if they have no symptoms. An immediate eye exam is in order if you recognize yourself below:

  • You've had Type 1 diabetes for a year or more and have not had an exam in over a year
  • You have Type 2 diabetes and have not had an exam in a year or longer
  • You have a child with diabetes who has reached puberty
  • You're pregnant or are planning to become pregnant and have diabetes

Retinal imaging

The Retasure retinal imaging device is a new tool that allows you to be screened for diabetic retinopathy at a primary care physician's office. The device takes a quick, painless digital photo of the macula and optic nerve. This photo is transmitted via a secure network to an ophthalmologist at an accredited reading center. Results are available within a few days, and you'll be referred to an ophthalmologist for a complete examination and possible treatment if signs of retinopathy are discovered.

However, the Retasure network is limited to several hundred primary care offices that subscribe to the service and have the necessary camera and hardware on the premises; unless you live in a rural area, far from a vision care provider's office, the system offers little advantage except that your pupils don't have to be dilated. For that very reason, though, the system could fail to discover any diseased areas on the periphery (edges) of the retina.

Comprehensive Examination

After asking you about your symptoms, family history, medications, surgical and medical history, and general health, your eye doctor will give an eye examination. A comprehensive examination to detect diabetic retinopathy and macular edema consists of three parts:

Visual acuity testing. Most of us are familiar with the “big E” eye chart, so named for the large block letter at the top. This visual acuity chart measures how well you see at various distances. From a specified distance, usually 20 feet, your vision care provider will ask you to read aloud progressively smaller rows of capital letters.

Ophthalmoscopy and slit-lamp examination. Your vision care provider will assess the retina using a hand-held, microscope-like viewing instrument called an ophthalmoscope to look for the following signs of diabetic retinopathy:

  • Leaking blood vessels
  • Swelling and inflammation (edema)
  • Fatty yellow deposits called exudates
  • Cotton-wool spots, so named for their fuzzy white appearance; they indicate areas where tissue has died and become opaque

First, eye drops will be instilled to dilate your pupils, revealing the internal structures of the eye. After this examination, a slit lamp, which is a high-intensity light source combined with a low-power microscope, will be used to examine the frontal structures of the eye.

Tonometry. A tonometer is an instrument that measures intraocular pressure (the pressure of fluids inside the eye) after anesthetic (numbing) drops have been instilled. This test is performed to rule out glaucoma.

Supplemental Testing

Optical coherence tomography

Optical coherence tomography (OCT) is a safe, painless test that produces high-resolution images of three-dimensional cross-sections of the retina, allowing its thickness to be measured. This test can also show abnormal fluid build-up in and under the retina. OCT works like ultrasound, except that it measures scattered light instead of sound waves.

Angiography

If you have macular edema, you will probably also undergo a fluorescein angiogram.

Fluorescein is a yellow dye injected into a vein that's taken up by vessels of the eye, allowing your vision care provider to visualize any leaking vessels in your retina (see Overview of Diabetic Retinopathy). A similar dye called indocyanine green may also be used to obtain additional information about the vasculature (vessel structure) of your eye. Eye diseases other than diabetic retinopathy can cause edema, so your vision care provider must carefully consider your signs and symptoms.

When to Seek Care

If you have diabetic retinopathy, don't put off having the treatment recommended by your vision care provider. Once the disease reaches the proliferative stage, vision loss occurs rapidly and is likely to be permanent.

Current screening recommendations are as follows:

  • If you have type 2 diabetes, you should have a comprehensive dilated eye examination shortly after diagnosis and once a year after that.
  • If you have type 1 diabetes, you should have a comprehensive dilated eye examination within three years after the onset of diabetes and once a year after that.
  • Women with type 1 diabetes should be screened while planning their pregnancy and during every trimester after becoming pregnant. They should also be screened periodically for one year postpartum.
  • If you have nonproliferative diabetic retinopathy, you should receive a comprehensive eye examination every three to six months, depending on severity, if you have no new symptoms.
  • You should visit a vision care specialist with 24 hours of the onset of any new symptoms (see Symptoms of Diabetic Retinopathy).

A Positive Diagnosis

It's distressing to learn you have diabetic retinopathy, as if diabetes weren't enough to deal with. But the mere fact that you've been diagnosed means you've already beat the house odds. Instead of feeling unlucky, think of yourself as a high roller. Now all you have to do is seek treatment, and you can sally over to the cashier's window to collect a prize no one can put a price on—the preservation of your sight.

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