electroretinography measures the electric responses of numerous cell sorts in the retina, together with the photoreceptors (rods and cones), internal retinal cells (bipolar and amacrine cells), and the ganglion cells. electrodes (dtl silver/nylon fiber string) are commonly located at the surface of the cornea for complete subject/international/multifocal erg's and brass/copper electrodes are placed on the skin near the attention for eog kind checking out. throughout a recording, the affected person's eyes are exposed to standardized stimuli and the ensuing signal is displayed displaying the time direction of the sign's amplitude (voltage). signals are very small, and usually are measured in microvolts or nanovolts. the erg consists of electrical potentials contributed by way of different cellular types within the retina, and the stimulus situations (flash or pattern stimulus, whether or not a background mild is present, and the colours of the stimulus and heritage) can elicit stronger reaction from sure components.
if a dim flash erg is executed on a darkish-adapted eye, the response is more often than not from the rod system. flash ergs executed on a light adapted eye will replicate the activity of the cone device. sufficiently bright flashes will elicit ergs containing an a-wave (initial negative deflection) followed with the aid of a b-wave (tremendous deflection). the main edge of the a-wave is produced by way of the photoreceptors, even as the the rest of the wave is produced via a combination of cells such as photoreceptors, bipolar, amacrine, and muller cells or muller glia. the pattern erg (perg), evoked via an alternating checkerboard stimulus, mostly reflects hobby of retinal ganglion cells.
clinically used especially by using ophthalmologists and optometrists, the electroretinogram (erg) is used for the analysis of various retinal sicknesses.
inherited retinal degenerations wherein the erg can be beneficial encompass:
retinitis pigmentosa and associated hereditary degenerations
retinitis punctata albescens
leber's congenital amaurosis
gyrate atrophy of the retina and choroid
congenital stationary night time blindness - ordinary a-wave indicates regular photoreceptors; absent b-wave shows abnormality inside the bipolar mobile region.
x-connected juvenile retinoschisis
problems mimicking retinitis pigmentosa
different ocular problems wherein the standard erg offers useful statistics include:
other ischemic retinopathies including valuable retinal vein occlusion (crvo), branch vein occlusion (bvo), and sickle cellular retinopathy
toxic retinopathies, consisting of the ones due to plaquenil and vigabatrin. the erg is likewise used to display retinal toxicity in many drug trials.
autoimmune retinopathies such as cancer related retinopathy (vehicle), cancer related retinopathy (mar), and acute zonal occult outer retinopathy (azoor)
assessment of retinal function after trauma, particularly in vitreous hemorrhage, dense cataracts, and other situations wherein the fundus can't be visualized.
the erg is also used notably in eye studies, as it gives facts about the characteristic of the retina that isn't in any other case to be had.
different erg checks, together with the photopic bad reaction (phnr) and sample erg (perg) may be useful in assessing retinal ganglion cellular characteristic in diseases like glaucoma.
the multifocal erg is used to file separate responses for distinct retinal locations.
the worldwide frame concerned with the scientific use and standardization of the erg, eog, and vep is the worldwide society for the clinical electrophysiology of vision (iscev).