top of page


What is Electroretinogram?

The electroretinogram (ERG) test is an eye test that aims to assess how well the retina and optic nerve at the back of your eye is working, and whether it has any kind of disease.

The electrical signal generated by the retina and optic nerve is detected by the special skin electrodes and analysed to assess the health of your eye.  This test is less affected by cataracts or other opacity obscuring vision such as vitreous haemorrahge.

Time to take the test?

The ERG test is very helpful in assessing any problems with your retina and optic nerve that you may have inherited, such as retinitis pigmentosa, or acquired such as glaucoma or diabetic retinopathy.

Good reasons why?


The test gives the ophthalmologist vital information to help them decide the best way to treat your eye.

When light falls on the retina it stimulates many different types of cells which in turn produce a variety of electrical responses. Studying these responses can help us detect which cells are healthy and which are not.  For the retina, important electrical responses include a-wave, b-wave, oscillatory potential, and for the optic nerve it includes PhNR (photopic negative response) and nSTR(negative scotopic threshold response).

Your retina has cells called rods and cones which process light. During the ERG test, these cells release tiny amounts of electricity in response to flashes of light. If we know exactly how much light enters the eye and how much electricity comes out, we can figure out how the rods and cones are working.

During the procedure

At the start of the procedure, a technician will place electrodes on your skin to record the electrical signals generated from light stimulus.  Please let your technician know whether you suffer from epilepsy as the test involves flashes of light in front of your eyes.  Each eye is tested separately.  A series of blue and red lights is recorded and will be repeated.

Your doctor will then interpret the findings of the test with you.

Dr George Kong is an expert in retinal electrophysiology with his PhD thesis examining the electroretinography responses in the setting of eye pressure.  His work was awarded the Prestigious Eberhard Dodt Memorial Award from International Society for Clinical Electrophysiology of Vision (ISCEV) . 

Fluorescein angiography: Feature
bottom of page