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Electroretinography
Introduction
- Measures the potential difference generated across the retina when stimulated by light.
- This provides a means of measuring retinal function.
- The electroretinogram (ERG) consists of a negative 'a' wave, positive 'b' wave and a positive 'c' wave which correspond to the photoreceptors, Muller's cells and retinal pigment epithelium respectively.
- Many modifications possible to distinguish between rod and cone response.
- Pattern electroretinograhy is used in research settings to investigate retinal ganglion cell function within the inner retina in cases of glaucoma.
- Visual evoked potentials are used in a research setting to investigate the central visual pathways.
Uses
- The most common indication in clinical practice is evaluation of retinal function prior to cataract surgery, where fundus assessment is not possible due to the lens opacity.
- Investigation of sudden onset blindness when the fundus looks normal; most often to distinguish sudden acquired retinal degeneration syndrome Retina: sudden acquired retinal degeneration syndrome from retrobulbar (brain or optic nerve disease) blindness Blindness.
- Investigation or early detection of various inherited retinopathies (dystrophy or degeneration).
Advantages
- Objective, repeatable test.
- Non-invasive.
- Equipment becoming more affordable and portable systems available.
Disadvantages
- Specialized equipment and training required.
Technical problems
- Specialist knowledge required.
- Artifacts can arise, such as electrical noise interference from electrical equipment in the room.
Requirements
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Preparation
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Technique
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Aftercare
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Outcomes
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