What is an electroretinogram?

An electroretinogram, or electroretinogram, is a diagnostic test used to measure the electrical response of the cells of the retina (the back wall of the eye) when exposed to light.

The rod and cone cells that make up the retina are sensitive to light and are essential to our ability to see. They react to light and cause an electrical signal to be sent through adjacent ganglion cells via the optic nerve to the brain. There, the brain interprets the signal as visual information, and that is how we see what we see. There are approximately 120 million rods and 6 to 7 million cones in the human eye.

An electroretinogram examines the rods and cones and their connecting ganglia to check that the visual information sent from these cells reaches the brain correctly.

What does electroretinography consist/imply?

Electroretinography involves placing an electrode on the cornea (the front of the eye) to measure electrical signals and then presenting the eye with stimuli, such as flashes of light and frame reversal patterns.

Electroretinography diagnostic test used to measure the electrical response of retinal cells.

Why is electroretinography performed?

An ERG can be used to diagnose a number of retinal conditions, such as:

  • Retinitis pigmentosa
  • Macular degeneration
  • Retinoblastoma (a cancer of the retina)
  • Retinal detachment
  • Cone-rod dystrophy (CBD).

It may also be helpful in evaluating whether eye surgery is needed.

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Preparation for electroretinography

The patient’s eyes should first be dilated with normal dilating eye drops. The eyes are then numbed with anesthetic drops. The patient is placed in a comfortable position, either lying down or sitting up.

What to expect during the test

Once the patient is ready, with the eyes numbed by the anesthetic drops, a speculum is used to hold the eyelids open. Next, an electrode is gently placed on each eye through what resembles a contact lens and one more electrode is placed on the skin. The patient then observes light stimuli, such as flashes, and the electrodes monitor the retina’s response to light.