Electroretinography (ERG) Explained
Why is Electroretinography Important?
What is electroretinography (ERG)?
Electroretinography is an electrophysiological test of the retina, the layer of the eye which detects light. The electroretinogram (ERG) is to the retina what the electrocardiogram (ECG) is to the heart. Just as an ECG is crucial to diagnosing illness and monitoring the heart’s function, ERG plays a critical role in the care of the eye, and is instrumental in the early detection of retinal dysfunction.
Why does ERG matter?
Electroretinography provides a wealth of objective, vital information about retinal function and health. ERG plays a vital role in the diagnosis of acquired and inherited eye diseases, as well as fuel research into the factors that affect the health of the retina or the visual pathways.
What is an Electroretinogram?
The electroretinogram (ERG) is an examination that evaluates the function of the eye’s retinal cells. Patients’ eyes are stimulated with light and the resulting electrical activity from their retinal cells is measured by skin or corneal electrodes. Dependent on the type, intensity and colour of the light stimulus information on different areas and types of cells can be obtained.
3 Types of ERG Tests
There are 3 main types of ERGs: full-field flash ERG (ffERG), pattern ERG (PERG), and multifocal ERG (mfERG). Each has different applications and benefits. Determining the functional status of the retina with different typs of ERG testing allows clinicians and researchers to evaluate patients for retina-related conditions, reliably monitor retinal function over time, and evaluate the efficacy of retinal treatments. ERGs are used in human care, veterinary practices, and medical research.
Full-field ERG
(ffERG)
In full-field ERG (ffERG), electrodes record the summed electrical response of the retinal cells. The summed electrical response is a blend of the results from a range of different cells and regions in the retina, meaning that full-field ERG shows the status of the retina as a whole. The handheld and portable RETeval® device is capable of performing ffERG.
Pattern ERG
(PERG)
In pattern ERG (PERG), the light stimulus is an alternating checkerboard pattern which evokes electrical responses from the ganglion cells composing the inner retina. PERG is commonly used as a test for disorders affecting ganglion cells, as well as many neurodegenerative disorders.[8]
Multifocal ERG
(mfERG)
Multifocal ERG (mfERG) is performed with a similar protocol to the PERG, but the light stimulus displays an array of hexagons that flicker between white and black in a pseudo-random sequence. The mfERG is best for measuring dysfunction of the central retina area and is not sensitive to abnormalities in the ganglion axon.[9]
Detect Functional Stress
Anticipate Structural Damage
How is ERG different than structural imaging?
Electroretinography objectively evaluates the functional abnormalities of the retina, while structural imaging shows the anatomy of the retinal tissue. While both functional and structural assessments have their benefits, functional changes generally appear well before structural changes. Catching retinal abnormalities quickly is critical for minimizing damage and maximizing vision retention, so functional assessments like ERG are important tools in the ophthalmic diagnostic suite.
Handheld ERG as a practical & effective diagnostic tool
Recent studies comparing ERG to structural imaging techniques show that ERG is an effective diagnostic tool. In studies comparing ERG and structural imaging’s abilities to evaluate sight-threatening diabetic retinopathy, the handheld and portable RETeval device’s ERG results outperformed the traditionally-used imaging technique in predicting which patients would later need medical intervention.[13],[14] In an assessment of RETeval’s ability to evaluate diabetic retinopathy, the advantages of RETeval included earlier detection of retinal dysfunction, lower investment costs, and less required reading knowledge than the traditionally-used imaging technique.[15] An assessment of RETeval’s ability to evaluate central retinal vein occlusion found that RETeval ERGs are less invasive, easier to perform, and give more reliable predictions than the traditionally-used imaging technique.[16]
Advantages of ERG testing
The ease and sensitivity of ERGs performed with the handheld RETeval is highly preferred over imaging techniques in certain situations. Patients who have media opacities, poor cooperation, or small pupils are better able to be evaluated for retinal abnormalities with the RETeval[14].
Non-invasive ERG testing
In an independent study comparing RETeval ERGs to conventional digital retinal photographs, the RETeval was chosen by patients as the method preferred over photography.[14] While many children need to be sedated to undergo conventional ERG, children as young as six months old have been able to remain calm during ERGs performed with RETeval.[18] The non-invasive nature of the ERG and the ease of the hand-held, non-mydriatic RETeval makes the ERG device a valuable screening tool for many ophthalmic pathologies.
RETeval, ERG Testing Made Simple
Applications of Electroretinography
Electroretinography has an impressive range of human and animal applications, for both clinical and research uses. Our technology provides reliable, repeatable, and effective ERG solutions in all of these categories.
More about ERG/VEP
Popular Topics: Detect and Track Diabetic Retinopathy | Glaucoma Evaluation with RETeval PhNR Test | RETeval Device Reference Data | RETeval in Optometry
Case Studies: Routine ERG Use Supports Complex Patient Management | ERG Alters Follow-up Schedule and Education for Patient with Diabetes | Using ERG for Management of Birdshot Chorioretinopathy | Using ERG to Monitor Glaucoma | Comprehensive Pediatric Assessment Using ERG in Challenging Cases | ERG Above and Beyond Retinal Imaging | ERG’s Role in Diabetic Retinopathy Progression Monitoring | ERG-based Risk Assessment in CRVO | ERG Supports Diagnostic Accuracy in a Pediatric Patient
Ebooks: Modern Fundamentals of Diabetic Retinopathy Management in Optometry
Articles: The Ultimate Guide to Diabetic Retinopathy in Primary Eyecare | What Type of Functional Testing Do You Prefer for Patients with Diabetes? | Major Milestone: RETeval Referenced in over 200 Publications | Collaboration to Elevate the Standard of Care for DR | Is ERG Needed if You Have Access to a Good Structural Imaging Device? | A Straightforward Approach to Managing and Supporting Patients with Diabetes | Simplify Grading and Risk Assessment in Diabetic Retinopathy | Simplify Daily Decision-Making with Modern ERG | Objective Functional Testing Needs in Diabetes and Glaucoma | Why Modern ERG is Re-Defining Diabetes Management | Diabetic Retinopathy Management Protocols for Optometry
Videos: Advice for Optometric Colleagues about Handheld ERG | Making a Difference in Diabetic Retinopathy Care | Changing the Way We Think About Electrodiagnostics | ERG Testing Made Simple | VEP Testing Made Simple | ERG Waveform | Introduction to Visual Electrophysiology | A Superior DR Progression Risk Assessment with the RETeval Device | Improve Glaucoma Management with the RETeval Handheld ERG Device | Reshaping the Retinal Diagnostic Landscape | New Solutions for Infants with ROP | Using the RETeval in Myopia Research