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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/05/02 12:21:42」(JST)

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An electroretinogram (ERG) test performed in 2014.

A historical photo of a patient undergoing an electroretinogram.

Electroretinography measures the electrical responses of various cell types in the retina, including the photoreceptors (rods and cones), inner retinal cells (bipolar and amacrine cells), and the ganglion cells. Electrodes are usually placed on the cornea and the skin near the eye, although it is possible to record the ERG from skin electrodes. During a recording, the patient's eyes are exposed to standardized stimuli and the resulting signal is displayed showing the time course of the signal's amplitude (voltage). Signals are very small, and typically are measured in microvolts or nanovolts. The ERG is composed of electrical potentials contributed by different cell types within the retina, and the stimulus conditions (flash or pattern stimulus, whether a background light is present, and the colors of the stimulus and background) can elicit stronger response from certain components.

If a dim flash ERG is performed on a dark-adapted eye, the response is primarily from the rod system. Flash ERGs performed on a light adapted eye will reflect the activity of the cone system. Sufficiently bright flashes will elicit ERGs containing an a-wave (initial negative deflection) followed by a b-wave (positive deflection). The leading edge of the a-wave is produced by the photoreceptors, while the remainder of the wave is produced by a mixture of cells including photoreceptors, bipolar, amacrine, and Muller cells or Muller glia.^[1] The pattern ERG (PERG), evoked by an alternating checkerboard stimulus, primarily reflects activity of retinal ganglion cells.

Clinically used mainly by ophthalmologists and optometrists, the electroretinogram (ERG) is used for the diagnosis of various retinal diseases.^[2]

Inherited retinal degenerations in which the ERG can be useful include:

Retinitis pigmentosa and related hereditary degenerations
Retinitis punctata albescens
Leber's congenital amaurosis
Choroideremia
Gyrate atrophy of the retina and choroid
Goldman-Favre syndrome
Congenital stationary night blindness - normal a-wave indicates normal photoreceptors; absent b-wave indicates abnormality in the bipolar cell region.
X-linked juvenile retinoschisis
Achromatopsia
Cone dystrophy
Disorders mimicking retinitis pigmentosa
Usher Syndrome

Other ocular disorders in which the standard ERG provides useful information include:

Diabetic retinopathy^[3]
Other ischemic retinopathies including central retinal vein occlusion (CRVO), branch vein occlusion (BVO), and sickle cell retinopathy
Toxic retinopathies, including those caused by Plaquenil and Vigabatrin. The ERG is also used to monitor retinal toxicity in many drug trials.
Autoimmune retinopathies such as Cancer Associated Retinopathy (CAR), Melanoma Associated Retinopathy (MAR), and Acute Zonal Occult Outer Retinopathy (AZOOR)
Retinal detachment
Assessment of retinal function after trauma, especially in vitreous hemorrhage, dense cataracts, and other conditions where the fundus cannot be visualized.

The ERG is also used extensively in eye research, as it provides information about the function of the retina that is not otherwise available.

Other ERG tests, such as the Photopic Negative Response (PhNR) and pattern ERG (PERG) may be useful in assessing retinal ganglion cell function in diseases like glaucoma.

The multifocal ERG is used to record separate responses for different retinal locations.

The international body concerned with the clinical use and standardization of the ERG, EOG, and VEP is the International Society for the Clinical Electrophysiology of Vision (ISCEV) ^[4]

In addition to its clinical diagnostic purpose, the ERG can be used during the course of drug development and in clinical trails for testing ocular safety and efficacy of new or existing drugs and treatment modalities ^[5]

References

^ Webvision at University of Utah
^ Electroretinography, U.S. National Library of Medicine, 11 April 2005 (accessed 19 January 2007)
^ Maa; et al. (2015). "A novel device for accurate and efficient testing for vision-threatening diabetic retinopathy". Journal of Diabetes and its Complications. doi:10.1016/j.jdiacomp.2015.12.005. PMID 26803474. Retrieved 3 February 2015.
^ ISCEV Website
^ Brigell; et al. (2005). "An overview of drug development with special emphasis on the role of visual electrophysiological testing". Doc Ophthalmol. 110 (1): 3–13. doi:10.1007/s10633-005-7338-9. PMID 16249953. Retrieved 12 August 2014.

UpToDate Contents

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English Journal

Functional validation of a human CAPN5 exome variant by lentiviral transduction into mouse retina.

Wert KJ1, Skeie JM, Bassuk AG, Olivier AK, Tsang SH, Mahajan VB.Author information 1Bernard and Shirlee Brown Glaucoma Laboratory, Department of Pathology and Cell Biology, College of Physicians and Surgeons.AbstractExome sequencing indicated that the gene encoding the calpain-5 protease, CAPN5, is the likely cause of retinal degeneration and autoimmune uveitis in human patients with autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV, OMIM #193235). To explore the mechanism of ADNIV, a human CAPN5 disease allele was expressed in mouse retinas with a lentiviral vector created to express either the wild-type human (h) CAPN5 or the ADNIV mutant hCAPN5-R243L allele under a rhodopsin promoter with tandem green fluorescent protein (GFP) expression. Vectors were injected into the subretinal space of perinatal mice. Mouse phenotypes were analyzed using electroretinography, histology and inflammatory gene expression profiling. Mouse calpain-5 showed high homology to its human ortholog with >98% sequence identity that includes the ADNIV mutant residue. Calpain-5 protein was expressed in the inner and outer segments of the photoreceptors and in the outer plexiform layer. Expression of the hCAPN5-R243L allele caused loss of the electroretinogram b-wave, photoreceptor degeneration and induction of immune cell infiltration and inflammatory genes in the retina, recapitulating major features of the ADNIV phenotype. Intraocular neovascularization and fibrosis were not observed during the study period. Our study shows that expression of the hCAPN5-R243L disease allele elicits an ADNIV-like disease in mice. It further suggests that ADNIV is due to CAPN5 gain-of-function rather than haploinsufficiency, and retinal expression may be sufficient to generate an autoimmune response. Genetic models of ADNIV in the mouse can be used to explore protease mechanisms in retinal degeneration and inflammation as well as preclinical therapeutic testing.
Human molecular genetics.Hum Mol Genet.2014 May 15;23(10):2665-77. doi: 10.1093/hmg/ddt661. Epub 2013 Dec 30.
Exome sequencing indicated that the gene encoding the calpain-5 protease, CAPN5, is the likely cause of retinal degeneration and autoimmune uveitis in human patients with autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV, OMIM #193235). To explore the mechanism of ADNIV, a human C
PMID 24381307

Best vitelliform macular dystrophy in a Swedish family: genetic analysis and a seven-year follow-up of photodynamic treatment of a young boy with choroidal neovascularization.

Frennesson CI1, Wadelius C, Nilsson SE.Author information 1Department of Ophthalmology, Linköping University, Linköping, SwedenDepartment of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.AbstractPurpose: To determine the mutation in a Swedish family with Best disease (vitelliform macular dystrophy; VMD) and to investigate the short- and long-term effects of photodynamic treatment (PDT) on subretinal neovascularization in a young boy. Methods: The five members of three generations of a family with VMD underwent a thorough ophthalmological examination, including best-corrected visual acuity (VA), visual field, colour vision, biomicroscopy of the posterior segment (dilated), fundus photography and electro-oculography (EOG). For the proband, an eleven-year-old boy, his father and grandfather, dark adaptation test, angiography and electroretinography (ERG) were also performed. After PCR amplification, the genotype was determined by cleavage with restriction enzyme, specific for the W93C allele. Results: Four family members had an abnormal EOG response. All showed the W93C mutation in the VMD2 gene. Visual acuity ranged from 20/20 to 20/250. The fundus manifestations varied from minor pigmentary changes over egg yolk-like lesions to chorioretinal atrophy, and fluorescein angiography showed corresponding pathology. In the proband, VA decreased during follow-up from 0.5 (20/40) to 0.08 (20/250) due to a subfoveal neovascularization with haemorrhage, and PDT with visudyne was begun. The haemorrhage resolved within 2 months, and after three treatments, VA had increased to 0.25 (20/80). One year later, acuity had improved to 0.5 (20/40), and this result was stable throughout the 7 years of the follow-up. Conclusion: The mutation was determined to be W93C, the most common mutation in VMD in Sweden. In an eleven-year-old boy with subretinal neovascularization, PDT seemed to be beneficial also in a long-term follow-up.
Acta ophthalmologica.Acta Ophthalmol.2014 May;92(3):238-42. doi: 10.1111/aos.12142. Epub 2013 Apr 26.
Purpose: To determine the mutation in a Swedish family with Best disease (vitelliform macular dystrophy; VMD) and to investigate the short- and long-term effects of photodynamic treatment (PDT) on subretinal neovascularization in a young boy. Methods: The five members of three generations of a
PMID 23617333

Transgenic Expression of Constitutively Active RAC1 Disrupts Mouse Rod Morphogenesis.

Song H1, Bush RA, Vijayasarathy C, Fariss RN, Kjellstrom S, Sieving PA.Author information 1Section for Translational Research in Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, United States.AbstractPURPOSE: Dominant-active RAC1 rescues photoreceptor structure in Drosophila rhodopsin-null mutants, indicating an important role in morphogenesis. This report assesses the morphogenetic effect of activated RAC1 during mammalian rod photoreceptor development using transgenic mice that express constitutively active (CA) RAC1.
Investigative ophthalmology & visual science.Invest Ophthalmol Vis Sci.2014 Apr 25;55(4):2659-68. doi: 10.1167/iovs.13-13649.
PURPOSE: Dominant-active RAC1 rescues photoreceptor structure in Drosophila rhodopsin-null mutants, indicating an important role in morphogenesis. This report assesses the morphogenetic effect of activated RAC1 during mammalian rod photoreceptor development using transgenic mice that express constit
PMID 24651551