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.
Tell your doctor if:
- You are or might be pregnant or are breastfeeding. The dye used in an angiogram may harm the fetus. The dye also can pass to a baby in breast milk.
- You have any health problems, including glaucoma.
- You are taking any medicines, including over-the-counter medicines and natural health products.
- You are allergic to any medicines, including dilating eyedrops.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information form ( What is a PDF document? ).
How It Is Done
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.
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.
Eyes closed: You sit in a chair with your eyes closed. The doctor puts ultrasound gel on your eyelid. Then he or she 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.
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.
The pictures from retinal imaging tests help your doctor look for problems and decide on treatment.
The retina looks healthy.
What Affects the Test
You may not be able to have the test, or the results may not be helpful, if:
- You have cataracts.
- The dilating drops don't widen your pupils enough.
- You aren't able to keep your eyes wide open and to stare straight ahead during the test.
- You aren't able to hold still during the test.
What To Think About
The dyes used in angiograms can be passed on through breast milk. This means that moms will need to stop breastfeeding for a day or two after the test. Use a breast pump to empty your breasts and get rid of the milk until it's safe to start breastfeeding again.
Other Works Consulted
- Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Current as ofJuly 17, 2018
Author: Healthwise Staff
Medical Review: Patrice Burgess, MD, FAAFP - Family Medicine
Adam Husney, MD - Family Medicine
E. Gregory Thompson, MD - Internal Medicine
Christopher Joseph Rudnisky, MD, MPH, FRCSC - Ophthalmology