The ERG Test for a Child: Does My Child Need to Be Put to Sleep for It?
Your Child's ERG and the Sleep Question at a Glance
You are here for one worry: will my child be put to sleep for this eye test? Here is the short answer. Many children have an ERG while awake. Sleep, meaning general anesthesia, is used mainly for a young child or one who cannot stay still. When a child cannot hold still for the electrodes and the flashes of light, the test may be best done under anesthesia1. So the answer depends on your child's age and how well they can sit through it, not on the test always needing sleep.
This page walks you through what the ERG is, how the awake and asleep versions differ, what the day looks like, and what the results can and cannot tell you.
The test looks at how well the retina is working, not at how it looks. An electroretinogram measures the electrical activity of the retina's rod and cone cells in response to light2. It monitors whole-retina function, giving a signal of the eye much like an EKG gives a signal of the heart3. That electrical signal is something a regular eye exam cannot capture, which is why the doctor asked for it.
Ask the eye clinic which version your child will have, awake or under anesthesia, and why. If anesthesia is planned, ask for a pre-anesthesia consultation so you know how to prepare. Bring the referral details and any earlier eye or genetic test results, because the ERG is used alongside other findings to establish a clinical diagnosis of retinal disease3.
What an ERG Is and Why Your Child Needs One
The retina is the light-sensing film at the back of the eye. It contains rod cells, which help us see in dim light, and cone cells, which help us see in daylight, and the ERG measures the electrical activity of these cells in response to light2. Small sensors pick up those tiny signals while lights flash. Your child does not have to do anything except keep their eyes open toward the light.
An ERG is ordered when the doctor needs to know how the retina is functioning across its whole surface. The test helps identify inherited and acquired retinal disorders, injury from certain drugs, and foreign bodies in the eye2. In inherited retinal disease, the ERG is integral to establishing a good clinical diagnosis3. A worrying reason for the test does not mean a worrying result is certain; the ERG is how the team gets a clear answer rather than guessing.
How the sensor contacts the eye differs between clinics, and this affects comfort. At some centers a contact-lens-type electrode rests on the surface of the eye1. At others, a skin electrode is placed on the skin under the eyes, or a thin thread electrode is tucked under the lower eyelid, which is not painful but can feel like an eyelash in the eye2. Skin electrodes are gentler, which is one reason they are often chosen for children.
Getting Ready, and the Anesthesia Decision
This is the decision most parents care about, and it comes down to whether your child can cooperate. When a child cannot hold still for the electrodes and the flashes, the ERG may be best done under anesthesia1. The full standard ERG is hard to do awake in non-compliant children roughly 2 to 5 years old, so for that age it is often done under anesthesia or left out4. Older, cooperative children commonly do the test awake. The clinic decides with you based on your child.
Awake testing has become easier with shorter methods. An abbreviated skin-electrode protocol developed at Great Ormond Street Hospital takes only 5 to 10 minutes, uses natural pupils and minimal time in the dark, and allows testing in alert children of all ages4. Ask whether your clinic offers a shorter awake protocol. Practicing at home by pretending to watch flashing lights, and bringing a favorite comfort item, can help a nervous child sit through it.
If the team recommends general anesthesia, it is usually because the standard recording needs stillness your child cannot manage while awake. Anesthesia is not without risk, so an anesthesia team reviews your child's health with you beforehand and gives fasting instructions to follow exactly. Ask for a pre-anesthesia consultation, tell them about any medicines, allergies, or breathing problems, and confirm who will be with your child during and after. This is a planned, supervised step, not an emergency one.
What Happens During the Test
Most ERG visits start with eye drops. Drops are placed in each eye to dilate the pupils, which causes blurred vision and sensitivity to light for a while5. To test the rod cells, a child may sit in a very dark room for about 20 minutes first, so the eyes adjust to the dark2. Some shorter awake protocols skip most of this waiting.
Once the sensors are in place, the actual recording is quick. The ERG measures the retina's electrical activity in response to flashes of light5. Your child watches a series of light flashes in a bowl-shaped device or on a screen while the sensors record. There are no needles and no shocks; the electricity is coming from the eye, not going into it.
What the Results Can and Cannot Tell You
The ERG tells the doctor how well the retina responds to light. It measures the electrical activity of the retina's rod and cone cells in response to light and helps identify inherited and acquired retinal disorders2. A reduced or absent response can point to a problem, while a normal response is reassuring for retinal function. The doctor reads the wave patterns to see whether rods, cones, or both are affected, which helps narrow down the cause.
An ERG is powerful but narrow. It measures retinal function, so it does not by itself name a specific gene, measure your child's eyeglass prescription, or rule out problems outside the retina. That is why it is combined with other findings, such as family history and imaging, to reach a diagnosis rather than used alone3. A normal ERG is reassuring for the retina but does not clear every possible eye or vision concern.
Some results come quickly, others take review. Ask when and how you will get the findings, and what the plan is for each possible outcome. Because the ERG helps identify inherited and acquired retinal disorders2, an abnormal result often leads to further testing, such as genetic testing or imaging, rather than an immediate treatment decision. Bring your questions to the follow-up visit.
Safety, Comfort, and What to Expect Afterward
The recording part is very low risk. There are no needles for the ERG, the electrodes rest on the surface of the eye or on the skin, and a thread electrode is not painful though it can feel like an eyelash2. The flashes are bright but not harmful. The most common bother is the dilating drops, which sting briefly and blur vision for a few hours.
When general anesthesia is used, that, not the ERG itself, is the part worth weighing. Anesthesia is reserved for children who cannot cooperate with the awake test1. General anesthesia has its own risks, which the anesthesia team reviews with you, and part of why shorter awake skin-electrode methods exist is to spare younger children from needing it. If awake testing is an option for your child, it avoids the anesthesia question entirely.
After an awake test, expect blurred vision and light sensitivity from the drops for a few hours, so bring sunglasses or a hat. The dilating drops cause blurred vision and light sensitivity until they wear off5. After anesthesia, your child may be groggy, and the care team will watch them until they are awake enough to go home. Follow the discharge instructions you are given.
When to Call the Doctor
An ERG is not an emergency test, but general anesthesia comes with routine aftercare. Call your care team the same day, or seek urgent help, if after anesthesia your child has trouble breathing, will not wake up normally or stays unusually drowsy, has repeated vomiting, a high fever, or seems very unwell. These are the standard post-anesthesia cautions your team will also review; when in doubt, call. Acting early is simply the safe habit, not a sign something has gone wrong.
For the eye findings themselves, follow the timeline the clinic gives you for results and the next visit. If your child had dilating drops, the blur and light sensitivity should fade within a few hours; call if they last much longer than expected. Keep any scheduled genetic or imaging appointments, since the ERG is usually one piece of a larger workup.
An ERG is not part of a routine glasses check. It is a specialized test performed in a visual electrophysiology lab, typically arranged through a pediatric ophthalmologist or a retina specialist. Because the ERG is integral to diagnosing inherited retinal disease, it is ordered and interpreted by specialists who manage these conditions3. If you were referred, that referral is the right pathway.
Common Questions Parents Ask About a Child's ERG
Often, no. Many children, especially older and cooperative ones, do the ERG awake. Anesthesia is used mainly when a child cannot hold still for the electrodes and flashes of light1. For non-compliant children about 2 to 5 years old the full standard test is often done under anesthesia, but shorter awake skin-electrode methods can test alert children of all ages4. Ask which your clinic offers.
It should not be painful. A skin electrode sits on the skin under the eye, and a thread electrode tucked under the lower eyelid is not painful although it can feel like an eyelash in the eye2. At some centers a contact-lens-type electrode rests on the surface of the eye1. The dilating drops sting for a moment, but the recording itself does not hurt.
Plan for a longer visit than the recording alone. Including dilation, the visit is often about an hour or more5. The actual ERG recording takes roughly 20 to 30 minutes1. An abbreviated awake protocol can take just 5 to 10 minutes of testing4. If anesthesia is used, add time for preparation and recovery.
The drops open the pupil so the light can reach the whole retina. Drops are placed in each eye to dilate the pupils, which causes blurred vision and light sensitivity for a while5. Some shorter awake protocols use natural pupils and skip the drops. Bring sunglasses for the ride home, since the eyes stay light-sensitive until the drops wear off.
Yes. The ERG only records signals the eye already makes. There are no needles, and the electrodes rest on the eye's surface or the skin2. The flashes are bright but not harmful. The main things to plan for are the temporary blur from the drops and, if used, the separate considerations of anesthesia.
Sometimes part of the picture is available soon, but a full read takes review. The ERG produces wave patterns a specialist interprets, and it is combined with other findings like family history and imaging to reach a diagnosis3. Ask the clinic when to expect results and who will explain them. An abnormal result usually leads to more testing rather than an on-the-spot answer.
More Questions About the ERG
Possibly. If your child can sit still with support, an awake test may work, especially a shorter method. An abbreviated skin-electrode protocol allows testing in alert children of all ages in about 5 to 10 minutes4. Tell the clinic your child is anxious but cooperative and ask about the awake option. A child-life specialist, where available, can also help your child through it.
It is used across a range of retinal problems. The ERG helps identify inherited and acquired retinal disorders, injury from certain drugs, and foreign bodies in the eye2. It is especially valuable in inherited retinal disease, where it is integral to a clinical diagnosis3. Your child's doctor ordered it to answer a specific question about how the retina is working.
That is a fair question to ask the team directly. Anesthesia is chosen only when a reliable recording cannot be obtained awake, because a child who cannot stay still for the electrodes and flashes may need the test done under anesthesia to get usable results1. Weigh it against how much the answer will change your child's care, and ask whether a shorter awake protocol could work first.
- Will my child be tested awake or under anesthesia, and why that choice for my child?
- Does your clinic offer a shorter, skin-electrode awake protocol?
- If anesthesia is needed, can we have a pre-anesthesia consultation first?
- What specific question are you hoping this ERG will answer?
- When and how will we get the results, and what happens next for each outcome?
- Boston Children's Hospital, Department of Ophthalmology (2024). Common Eye Tests and Procedures (Electroretinogram).
- UPMC Children's Hospital of Pittsburgh, Visual Electrophysiology Diagnostic Lab (2024). Electroretinogram.
- American Academy of Ophthalmology (EyeNet Magazine) (2023). Inherited Retinal Diseases.
- Diagnosys LLC (describing the ISCEV Standard and the GOSH-ERG protocol) (2023). ERG for Children.
- Nationwide Children's Hospital (2024). Visual Electrophysiology.