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Electroretinography
ERG · electroretinogram · retina function test
A device records weak electrical signals from your retina while you look at flashes of light.
For poor vision in the dark, inherited retinal diseases, and when a normal eye exam does not explain poor vision.
⏱ Duration: usually 30 to 90 minutes; the report is ready right away or in a few days
Be sure to tell your doctor
How to prepare
- Pupils. Drops are usually put in to widen your pupils. For several hours afterward, things will look blurry.
- Getting home. Do not drive after the test. Have someone take you home.
- Lenses. Take out your contact lenses. Bring the case with you.
What to bring
- Your referral
- Sunglasses
- Your glasses, if you wear them
- Someone to go with you
How it goes
- Drops are put in your eyes to widen the pupils
- Sometimes you sit in the dark for a while so your eyes adjust
- Numbing drops are put in
- An electrode is placed on or under your eye
- You look into a device with flashing light
- The electrodes are removed
What you'll feel
- The drops sting for a few seconds
- The electrode on your eye feels strange but does not hurt
- The flashes are bright
Afterwards
- For several hours: blurry vision and sensitivity to light
- Do not rub your eyes while the drops are working
- The report is ready right away or in a few days
Contact a doctor straight away if
- Severe eye pain or a sudden drop in vision
- The eye is very red and watering for more than a day
Common questions
Can I drive right after?
No. Your pupils stay wide for several hours. Have someone drive you.
Does it hurt?
No. After the numbing drops, you can hardly feel the electrode.