Electroretinography measures the summed electrical responses of retinal cells to light stimuli, providing information about global or local retinal function. Different protocols isolate rod, cone, and macular activity.
Technique
Electrodes are placed on or near the eye, such as corneal contact lenses or skin electrodes, while flashes or patterned stimuli are presented under dark- and light-adapted conditions. The resulting waveforms are recorded and analysed.
- Full-field ERG assesses overall rod and cone function
- Pattern ERG focuses on macular and ganglion cell function
- Multifocal ERG maps responses from many small retinal regions simultaneously
- Testing follows standardised protocols for reliable comparison
Clinical Applications
Electroretinography is central in diagnosing inherited retinal dystrophies, distinguishing generalised from focal retinal disease, and monitoring retinal toxicity. It can reveal dysfunction before visible structural changes appear.
- Guides counselling about prognosis in progressive conditions
- Helps differentiate retinal from optic nerve or cortical causes of poor vision
- Used in surveillance for drugs with potential retinal side effects
- Results are interpreted against normative ranges and clinical findings
