Retinal Imaging

Test Overview

Retinal imaging uses special cameras and scanners to make magnified images, or pictures, of the back of your eye. This includes the retina. It's the part of the eye that's most responsible for your vision.

Common imaging methods include:

• Colour and black-and-white photography. A camera magnifies the back of your eye and makes pictures.
• Optical coherence tomography, or OCT. A scanner uses light waves to form an image of the retina on a computer screen.
• Ultrasound. This test uses sound waves to form the image.
• Angiogram. A dye is injected into your arm. It flows through your blood to the blood vessels in your eye. The dye makes the blood vessels in your eye easier to see as your doctor looks at your eyes through the camera.

A test called fundus autofluorescence is sometimes used. Special lighting lets the doctor see microscopic changes in your eye that are caused by certain conditions.

Why It Is Done

These tests help doctors find and treat eye problems. Doctors can see if a disease is getting worse or if treatment is working.

You may need retinal imaging if:

• You have diabetes or

  diabetic retinopathy

  . These conditions can lead to poor vision and even blindness. A test can help your doctor see if treatment is working.
• Your doctor thinks you have

  wet macular degeneration

  . It can lead to vision loss. Tests can help find leaky blood vessels in your eye or blood vessels that are not normal, which are part of this disease.
• Your vision is getting worse and your doctor wants to find out why.

Eye examinations, including retinal imaging, may help your doctor find a problem before it has a chance to get worse. And this gives you a better chance of protecting your vision. Retinal imaging should not take the place of a complete eye examination.

How To Prepare

If you know that the doctor will use drops to widen, or dilate, your pupils, think about having someone else drive you home. The drops make your eyes very sensitive to light. You may not be able to see well for a few hours. If you have sunglasses, take them with you to wear on the way home.

If you wear contact lenses, you may want to take your eyeglasses with you.

How It Is Done

Retinal imaging tests are done in a hospital or doctor's office.

For some tests, the doctor will first use eyedrops to widen, or dilate, your pupils. You'll sit and wait for about half an hour for the drops to take effect.

For most tests, you'll sit in a chair facing the camera. You'll place your chin on a chin rest. And you'll brace your forehead against a bar to keep it still.

Keep your mouth closed, open your eyes as wide as you can, and stare straight ahead. You can breathe and blink normally while the camera photographs or scans your eyes.

It only takes a few minutes to take the pictures.

Angiogram

Before an angiogram, a dye is injected into your vein.

• An

  IV

  needle is placed in a vein in your arm, and the dye is injected. It takes only a few seconds for the dye to be visible in the blood vessels in your eyes.
• Photos are taken as the dye enters the eyes.
• This test usually takes about 30 minutes.

Eye ultrasound

Eyes closed: You sit in a chair with your eyes closed. The doctor puts ultrasound gel on your eyelid. Then the doctor gently moves a small ultrasound wand against your eyelid.

Eyes open: Eyedrops are used to numb your eyes. The doctor moves the ultrasound wand against the front surface of your eye.

How It Feels

The tests themselves don't cause pain or discomfort. For some tests, very bright light may shine in your eye.

If your eyes have been dilated, they will be very sensitive to light for several hours. Your vision may be a little blurry.

The dye used in an angiogram may cause a metallic taste in your mouth. You may also have mild nausea and a brief feeling of warmth. Your urine may be orange for a day or two.

Risks

In some people, the dilating eyedrops can cause an allergic reaction.

The dye used in an angiogram may upset your stomach. You may feel flushed. These symptoms pass quickly. If you're pregnant, talk to your doctor about possible risks to your baby.

Some people are allergic to the dye. Tell your doctor if you feel light-headed, need to vomit, or feel itchy after the dye is injected. Very rarely, a person may have a serious allergic reaction (anaphylaxis) and need emergency care.

Results

Normal:

The retina looks healthy.

Abnormal:

• There is a mole, cyst, or some other problem on the back of the eye.
• There are blocked or leaking blood vessels in the eye.
• The layer of nerves called the retinal nerve fibre layer is injured or getting thin.
• There are changes in the natural colouring of the back of the eye.

Credits

Author: Healthwise Staff
Medical Review:
Patrice Burgess MD - Family Medicine
Adam Husney MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine