ERGundersøkelse

ERG examination, or electroretinography, is a diagnostic test that records the retina’s electrical responses to light. It provides an objective measure of retinal function, especially the activity of photoreceptors, bipolar cells, and Müller cells. The test can be performed as full-field ERG (ffERG), which assesses the global retina, or in targeted forms such as multifocal ERG (mfERG) and pattern ERG (pERG) for localized or pathway-specific testing.

Procedure: After dilation and placement of an electrode on the eye, scotopic responses are recorded following dark adaptation, and then photopic responses are recorded under light adaptation. A series of light flashes or pattern stimuli is delivered, and the resulting electrical potentials are recorded. The main components are the a-wave (photoreceptor origin) and the b-wave (bipolar/Müller cell origin); oscillatory potentials and c-waves may also be observed. Results are compared with normative data and reported as amplitudes and implicit times.

Indications: ERG is used to evaluate suspected hereditary retinal diseases (e.g., retinitis pigmentosa, cone-rod dystrophy), Leber congenital amaurosis, congenital stationary night blindness, and other retinal dysfunctions. It helps distinguish retinal from optic nerve disorders and can monitor retinal toxicity from certain medications. In children, testing may require cooperation that can necessitate sedation or anesthesia.

Risks and limitations: ERG is noninvasive with minimal risk; transient irritation from electrodes and bright light exposure can occur. Limitations include variability due to fixation, media opacities, and inadequate adaptation, and sometimes reduced or absent responses that limit interpretation.