Ophthalmic electrodiagnostic tests provide information about the function of the visual system from the retina at the back of the eye, through the visual pathways to the visual centre in the brain.

This information helps the ophthalmologist make a diagnosis and recommend treatment for patients with retinal and visual pathway disorders.

Tests take between 30 and 60 minutes. Many people will need a combination of electrodiagnostic tests to give complete information about their visual problem.

Electroretinogram (ERG)

The electroretinogram is an electrodiagnostic test for evaluating the function of the retina. Electrodes are place on the skin around the eye and a soft gold foil electrode is placed over the lower lid so that it is in contact with the cornea through the tear film. The ERG responses to flashes of light give the ophthalmologist information about any retinal abnormalities.

If the flashes of light are changed to a flickering pattern on a TV monitor screen, the resulting ERG waveform gives information about macular disease.

Electro-oculogram (EOG)

The electro-oculogram tests abnormalities of the outermost layer of the retina, the retinal pigment epithelium, allowing the early diagnosis of some inherited macular diseases such as Bests disease.

Cortical Visual Evoked Potential (VEP)

The cortical visual evoked potential provides information about the health and function of the visual pathways from the optic nerve as it leaves the back of the eye, to the visual centre in the brain.