Frequently Asked Questions about Visual Electrophysiology and Eye Diseases
These FAQs are provided for general information. For questions about Diopsys® ERG or VEP vision tests, please ask the eye care specialist in charge of your vision care.
Eye and Vision Disorders
What is a Diopsys® ERG vision test?
A Diopsys® ERG vision test is a painless, safe, non-invasive way for your eye care provider to objectively measure the function of your retina – the light-sensitive layer at the back of your eye.
When light from an image enters your eye, it is turned into electrical energy by cells in the retina. Pattern ERG, or electroretinography, uses visual stimuli from a computer screen in different patterns and contrasts to elicit that electrical response. The electrical energy created is measured by the Diopsys® ERG vision test, and used to create a report for your doctor. It is similar to an EKG, but for your eyes..
What is a Diopsys® ffERG vision test?
A Diopsys® ffERG vision test is a painless, safe, non-invasive way for your eye care provider to objectively measure the function of cells in your retina – the light-sensitive layer at the back of your eye.
When light from an image enters your eye, it is turned into electrical energy by cells in the retina. The full field electroretinography (ffERG) vision test, sometimes referred to as flash ERG or flicker ERG, uses flashes of light as a visual stimulus to elicit an electrical response from those cells. The electrical energy created is measured by the Diopsys® ffERG vision test, and used to create a report for your doctor. It is similar to an EKG, but for your eyes.
What is a Diopsys® VEP vision test?
A Diopsys® VEP vision test is a painless, safe, non-invasive way for your eye care provider to objectively measure the function of your entire vision system.
When light from an image enters your eye, it is turned into electrical energy by cells in the retina – the light-sensitive layer at the back of your eye. These cells send the electrical energy back to the visual cortex, the part of your brain where the image is processed.
VEP, or Visual Evoked Potential, uses visual stimuli from a computer screen in different patterns and contrasts to elicit the electrical response from your retina. The electrical energy is then sent to your visual cortex, where the Diopsys® VEP vision test records the electrical signal, and creates a report for your doctor. It is similar to an EKG, but for your entire vision system.
Which test will I need?
Your test will be ordered by your ophthalmologist or optometrist prior to your appointment. The type of test you need will be determined by the vision disorder that your doctor suspects. It is possible that multiple tests may be ordered on the same day or at separate visits.
Are these vision tests covered by my insurance?
Many insurance policies do cover these tests, as they are accepted as an additional, alternative testing method when more in-depth measures of visual function are required for diagnosis, treatment and management of disorders that affect vision.
Your eye doctor’s office can help to verify coverage by your insurance plan.
Will this replace any other eye tests I take?
No. Other tests such as the Visual Field and OCT may still be performed. Electroretinography and visual evoked potential provide a different view into your overall eye health. The more information your doctors have, the better they can direct your care.
Who will perform the test?
The test is typically performed by an ophthalmic technician. Diopsys Clinical Application Specialists train and certify technicians to perform the tests safely, accurately, and in a timely manner.
How long does the test take?
The test itself does not take long. However, there is some preparation involved in order to get quality test results. To get a more accurate time frame, Diopsys recommends you contact your doctor’s office directly.
How should I prepare for the test?
All medications should be taken as usual unless otherwise directed by your doctor. Hair should be clean, dry, and free of any gels, sprays, or oils. We also recommend that you do not wear ponytails or braids to the appointment as they may need to be taken down.
It is important that you feel relaxed and comfortable so the test results are accurate. For young children, it may be helpful to bring a favorite item such as a blanket, pacifier, or toy that will make them feel more comfortable. Smaller children may also sit in their parent’s lap during testing if this is calming for them.
How is the test performed?
Each test uses three (3) small sensors for testing. The placement and type of sensor depends on the test ordered by your doctor. The technician will attach the small sensory pads to your face and/or head using a washable gel material.
For Diopsys® ERG and Diopsys® VEP vision tests, you will be seated in front of a computer screen and asked to look at the center of the monitor. The screen will display different size patterns that appear to “flip” quickly. One eye may be covered while the other eye is tested. A computer records your response.
For Diopsys® ffERG vision tests, you will be handed a small dome, and asked to cover your right eye. Lights will flash in the dome during the test, and half way through, you’ll be asked to switch to your left eye. A computer records your response.
To watch a brief video of setup and testing, please click on the links for Diopsys® ERG, Diopsys® ffERG, or Diopsys® VEP.
Should I bring my glasses or contacts if I do not wear them regularly?
It is always recommended that you bring your eyewear. Depending on your refraction and ordered test, they may be helpful for your technician to have. If needed, the technician may have you wear a trial frame and lenses during the test.
Can my family member be present during testing?
It is important for you to be relaxed and able to focus during the test. It is for this reason that we request family members wait outside the testing room.
For young children, they may sit in their parent’s lap during testing if this is calming for them.
Will I be dilated for my ERG or VEP vision test?
Dilation is not indicated prior to pattern or full field (flicker) electroretinography, nor visual evoked potential vision testing. Dilation is required for multifocal ERG (mfERG) vision testing. Your doctor may decide to dilate your eyes after testing for other reasons. Your doctor’s office can tell you if dilation will be done during your appointment.
What can I expect after the test?
The technician will remove the sensory pads and use a small amount of water to remove any gel residue. The ERG and/or VEP test results will then be read and interpreted by your ophthalmologist or optometrist.
What else do I need to know?
- You must sit still as relaxation is an important part of testing.
- If you wear makeup, we suggest that you do not apply it prior to your visit. If you must wear makeup to your visit, you may want to bring it with you to touch up after testing. The technician must remove some makeup to ensure proper sensor connection to your skin.
- Supplies provided by Diopsys for testing are latex free, hypo-allergenic, and water soluble. If you have specific topical allergies, please consult your doctor prior to testing.
- Seizure disorders are contraindicated for VEP, ERG, and ffERG vision testing.
- People who are pregnant or wear a pace-maker are safe to be tested. However, we suggest you consult your doctor prior to testing.
- Please advise your doctor of any new eye complaints prior to testing. Severe seasonal allergies or certain ocular surface disorders can leave the eye dry, itchy and irritated, which can affect your ability to test.
- Diopsys kindly requests that you turn off your cell phone prior to testing to avoid any interruptions during these important vision tests.
What is glaucoma? What causes glaucoma?
According to the Glaucoma Research Foundation, glaucoma is a group of eye diseases that gradually steal sight without warning. In the early stages of the disease, there may be no symptoms. Experts estimate that half of the people affected by glaucoma may not know they have it.
Vision loss as the result Glaucoma may be the due to damage to the optic nerve. This nerve acts like an electric cable with over a million wires. It is responsible for carrying images from the eye to the brain. There is no cure for glaucoma today. However, medication or surgery can slow or prevent further vision loss. Early detection is vital to stopping the progress of the disease.
Signs and Symptoms of Glaucoma
Persons with glaucoma may experience a gradual loss of peripheral vision, tunnel vision, halos around lights, blurred vision, severe eye pain, sudden onset of visual disturbance, and reddening of the eye.
Do not wait to visit your eye doctor until you have a problem because in the early stages of the disease, there may be no symptoms. Regular eye exams are the key to detecting glaucoma early enough for successful treatment.
What is diabetic retinopathy?
The National Eye Institute defines diabetic retinopathy (DR) as an eye disease that causes changes in the blood vessels of the retina that results as a complication of diabetes. In some people with diabetic retinopathy, blood vessels may swell and leak fluid. In other people, abnormal new blood vessels grow on the surface of the retina.
In the early stages of the disease, there may be no symptoms; but, over time, diabetic retinopathy can get worse and cause vision loss. Diabetic retinopathy usually affects both eyes.
Signs and Symptoms of Diabetic Retinopathy
Blurred vision may occur when the macula—the part of the retina that provides sharp central vision—swells from leaking fluid. This condition is called macular edema. If new blood vessels grow on the surface of the retina, they can bleed into the eye and block vision. You may see a few specks of blood, or spots, “floating” in your vision.
Do not wait to visit your eye doctor until you have a problem because there are often no symptoms in the early stages of the disease. Be sure to have a comprehensive dilated eye exam at least once a year.
Signs and Symptom of Cataracts
According to the American Academy of Ophthalmology, most age-related cataracts develop gradually. Patients may notice blurry vision, double-vision, light sensitivity, and trouble seeing well at night. The National Eye Institute says that by age 80, more than half of all Americans either have a cataract, or have had cataract surgery.
What is multiple sclerosis (MS)?
According to the National Multiple Sclerosis Society, MS is a chronic, unpredictable disease of the central nervous system (the brain, optic nerves, and spinal cord). It is thought to be an autoimmune disorder. This means the immune system incorrectly attacks the person’s healthy tissue.
Signs and Symptoms of Multiple Sclerosis
Symptoms of multiple sclerosis (MS) are unpredictable, vary from person to person, and from time to time in the same person. MS can cause blurred vision, loss of balance, poor coordination, slurred speech, tremors, numbness, extreme fatigue, problems with memory and concentration, paralysis, and blindness and more. These problems may be permanent or may come and go.
Most people are diagnosed with MS between the ages of 20 and 50, although individuals as young as 2 and as old as 75 have developed it. Multiple sclerosis is not considered a fatal disease as the vast majority of people with it live a normal life-span. But they may struggle to live as productively as they desire, often facing increasing limitations.
What is traumatic brain injury (TBI)?
The National Institute of Neurological Disorders and Stroke say traumatic brain injury (TBI), a form of acquired brain injury, occurs when a sudden trauma causes damage to the brain. TBI can result when the head suddenly and violently hits an object, or when an object pierces the skull and enters brain tissue.
Signs and Symptoms of Traumatic Brain Injury
Symptoms of TBI can be mild, moderate, or severe, depending on the extent of the damage to the brain. A person with mild TBI may remain conscious or may experience a loss of consciousness for a few seconds or minutes. Other symptoms of mild TBI include headache, confusion, lightheadedness, dizziness, blurred vision or tired eyes, ringing in the ears, bad taste in the mouth, fatigue or lethargy, a change in sleep patterns, behavioral or mood changes, and trouble with memory, concentration, attention, or thinking. A person with a moderate or severe TBI may show these same symptoms, but may also have a headache that gets worse or does not go away, repeated vomiting or nausea, convulsions or seizures, an inability to awaken from sleep, dilation of one or both pupils of the eyes, slurred speech, weakness or numbness in the extremities, loss of coordination, and increased confusion, restlessness, or agitation.