ERG (Electroretinography)

Listening to the Electrical Language of Your Retina

Your retina does not just see — it generates electrical signals every time light falls on it. These signals travel along the optic nerve to the brain, where they are interpreted as vision. Electroretinography — ERG — is a specialised test that measures these electrical responses, giving our specialists a unique and detailed picture of how well the cells of your retina are functioning. It is one of the most informative diagnostic tests available for retinal disease.

What Is Electroretinography?

ERG is an electrophysiological test that records the electrical activity generated by the retina in response to flashes of light. Small electrodes are placed on or near the eye, and the retina’s electrical response to controlled light stimuli is measured and recorded. The resulting waveforms reveal whether the photoreceptors — the rods and cones — and the other retinal cells are functioning normally, and if not, which specific cell types are affected and to what degree.

What Conditions Can ERG Diagnose?

• Retinitis Pigmentosa — a hereditary condition causing progressive loss of rod and cone function
• Cone and rod dystrophies — inherited disorders affecting specific retinal cell types
• Unexplained vision loss where the cause is not apparent on examination or imaging
• Night blindness — assessing rod function in patients who struggle to see in low light
• Assessment of retinal function before and after surgery or treatment
• Toxic retinopathy — retinal damage caused by medications or substances
• Evaluation of retinal function in young children who cannot describe their vision

What Happens During the Test?

Step 1 — Dark Adaptation

You will sit in a darkened room for a period of time — typically 20 to 30 minutes — to allow your eyes to adapt fully to the dark. This ensures that the rods, which are responsible for night vision, are in their most sensitive state and can be tested accurately.

Step 2 — Electrode Placement

After numbing drops are applied, a small, soft contact electrode is placed on the eye surface, along with skin electrodes near the eye. These are connected to the recording equipment and are comfortable to wear throughout the test.

Step 3 — Light Stimulation and Recording

You are asked to look at a screen or into a bowl that produces precisely controlled flashes of light at different intensities and colours. The electrical responses generated by your retina are recorded automatically as each stimulus is delivered.

Step 4 — Analysis and Results

The recorded waveforms are analysed by your specialist and compared to normal values. The results help identify which retinal cell populations are affected, the severity of any dysfunction, and whether the condition is likely to be hereditary, acquired, or toxic in origin.

Why Patients Trust RGC Eye Hospital

• Specialist electrophysiology equipment for accurate and reproducible ERG recordings
• Experienced clinicians who interpret ERG results in the context of your full clinical picture
• ERG findings combined with other investigations for the most complete diagnosis possible
• Clear explanation of what the results mean for your condition, your vision, and your future care