Overview of Pattern Electroretinogram

The pattern electroretinogram (PERG) is a test for the eyes that is done by doctors to understand how well the central part of your retina is functioning. The retina is the part of the eye that captures and processes light to enable you to see. This test is non-invasive, which means it doesn’t need any surgical procedures, and provides measurements that help your doctor know if there’s any loss or recovery happening in your retinal function.

The PERG test is done by showing a constantly changing black-and-white checkerboard or striped pattern to your eyes. This causes your retina to respond, and these responses are what doctors measure.

Importantly, the PERG test assesses the functioning of the macula and the retinal ganglion cells. The macula is a small area in the retina that is responsible for your central, sharp, detailed vision, and the retinal ganglion cells are the cells that transmit the visual information from your eyes to your brain.

This analysis can be really useful for doctors to figure out whether any issues you’re having with your vision are related to problems with your macula or with the optic nerve (the nerve that carries visual information from the retina to the brain). This is especially useful when the cause of vision problems is not clear after the usual checks and examinations.

Anatomy and Physiology of Pattern Electroretinogram

The retina is a part of the eye that is like a screen where everything you see is projected. It is made up of ten layers with different types of cells and links that help with seeing. The inner part of the retina has nerve fibers, ganglion cells (a type of nerve cell), and their connections, along with a type of cell called amacrine cells. The outer part of the retina has rod and cone cells that are responsible for detecting light and color.

These rod and cone cells send the visual information to the next set of cells, called bipolar cells, in the central part of the retina. Once the visual information is transformed into electrical information by the outer retina (a process called phototransduction), the inner retinal ganglion cells then pass this information to the brain through the optic nerve. This is how the images and scenes we see are processed and understood by the brain.

Why do People Need Pattern Electroretinogram

The Pattern Electroretinogram (PERG) is a test that goes beyond usual eye checks by an ophthalmologist. This test measures the electrical activity of your eye, providing information about your optic nerve and macular function. You might need a PERG test in several situations:

1. If your doctor suspects that there might be an issue with your optic nerve or macula (the part of your eye responsible for sharp, central vision), a PERG test can help diagnose and manage these conditions.

2. If you are taking medication that might harm the retina (the inner layer at the back of your eye that helps you see), a PERG test can monitor for any signs of damage.

3. If you’ve had an injury to your eye, or if there’s inflammation or pressure on your retina, a PERG test can be used to assess the extent of the damage.

When a Person Should Avoid Pattern Electroretinogram

The PERG, which is a test used to measure the electrical activity of certain cells in the eye, doesn’t have any specific conditions that would prevent an individual from undergoing the test. Even those who have conditions like epilepsy, where seizures occur, can have the PERG safely. This is because the frequency of the stimulus used in the test does not generally trigger most types of epileptic seizures.

However, if a person has seizures triggered by certain light patterns, known as photosensitive seizures, they need to be carefully evaluated before having the PERG. This is particularly important if the frequency that triggers their seizures is around 30 Hz, or if the triggering frequency is not known.

Equipment used for Pattern Electroretinogram

To perform a pattern electroretinogram (PERG), an eye test that evaluates the function of the retina (the light-sensitive tissue at the back of the eye), certain tools are needed. These include:

* Electrodes – small devices that measure electrical activity in the eye.

*An amplification system – a device that increases the small electrical signals from the eye so they can be accurately analyzed.

*A data recording system – a device or platform for storing and preserving the information collected during the test.

Who is needed to perform Pattern Electroretinogram?

Trained technicians carry out a special test called a pattern electroretinogram (PERG). This test, commonly performed in big specialized medical centers with equipment for studying the function of the nerves, helps doctors understand how well your eyes are working. Doctors who specialize in the retina (the part of your eye that senses light) and nerve-related eye conditions usually review the results of this test. They understand how to read the data and can explain what it means for your eye health.

Preparing for Pattern Electroretinogram

When using electrodes to record eye activity, the placement of these electrodes depends on their type. Some are placed on the surface of the cornea, while others may be placed on the part of the eye called the bulbar conjunctiva, which is near the lower edge of the cornea.

However, the International Society for Clinical Electrophysiology of Vision (ISCEV) suggests that these electrodes, particularly those placed on the skin, should not regularly be used to record a specific type of eye test (known as the standard pattern electroretinogram or PERG). That’s because when placed on the lower eyelid, they record a weaker PERG signal than those touching the eye. Nonetheless, they could be useful in certain situations, such as when a corneal electrode is not suitable, or in children. When topical anesthesia (numbing medicine) is applied on the eye, it helps minimize any discomfort when using corneal contact electrodes.

In addition, separate electrodes may be placed on the skin near the outer corner of each eye that is on the same side (ipsilateral). If recording an eye test from just one eye (monocular), then the eye that is covered (contralateral) could bear the reference electrode. Areas such as the forehead, earlobe, or mastoid are not recommended due to potential interference from the other (fellow) eye.

An electrode used as a reference point or “ground” is typically placed on the forehead and connected to the recording device’s input.

Before the procedure, the ISCEV recommends several steps for patients:

  • An electrically isolated recording environment
  • Recording without pupil dilation to ensure a good quality image
  • Taking a recovery break of at least 30 minutes in normal room light when using strong light imaging techniques such as fundus photography or fluorescein angiography
  • Instructing patients to focus on a target within the stimulator, minimizing eye movement. If patients are unable to see the fixation point, they can look straight ahead while maintaining a steady gaze.
  • Recording from both eyes (binocular recording) as it improves focus and shortens examination time
  • However, recording should be done from one eye when dealing with eye misalignment issues.

How is Pattern Electroretinogram performed

The pattern electroretinogram (PERG) is a test that records the electrical response of your retina (a layer at the back of your eye that sends visual information to the brain) to different stimulus patterns. There are two types of responses this test can show: a transient response and a steady-state response.

The transient response shows up when the test uses low-frequency stimuli (1-2 Hz) and breaks the response into separate waves. The steady-state response, on the other hand, appears when we use higher frequency stimuli (8 Hz) during the test. However, the steady-state response is a bit harder to understand, as it doesn’t allow for direct measurements of individual waves. Despite this, it does help counter some of the effects of poor eye fixation during the test. This means that the readings from repeated tests will be more consistent. Steady-state PERG tests are especially useful for detecting early signs of glaucoma, an eye condition that damages the optic nerve in your eye.

When we look at the transient response, we see different wave components, including a negative wave around 35 milliseconds (called N35), a positive wave at roughly 50 milliseconds (P50), and a large negative wave at about 95 milliseconds (N95).

Let’s take a closer look at these waves:

P50: The P50 wave is the first positive wave we see and it comes from the retina cells, as well as the cone cells in your macula (an area in the center of the retina). This wave mainly measures how the outer part of your retina is working.

N95: The N95 wave is the negative wave that comes after the P50 wave. This wave comes from the inner part of your retina and mainly measures how the retinal cells are working.

When analyzing these waves, we check a few different things. We check for the amplitude, which measures the maximum electrical response from the retina cells. We can calculate the amplitude of each wave, allowing us to then check the ratio of the N95 to P50 wave amplitudes. This ratio can give us an idea of the balance between the functioning of the inner and outer parts of the retina. We also look at the implicit time, which measures how long it takes for the electrical response to reach the maximum amplitude. Finally, we’ll also look at latency, which measures the time from when the stimulus starts to when the response starts.

In order to ensure consistency and accuracy in these tests, there are special protocols that labs follow. These include specifications for the size and brightness of the test stimuli and how the test is displayed and recorded. Following these protocols helps make sure that the data from these tests is reliable and can be compared across different labs.

Possible Complications of Pattern Electroretinogram

The pattern electroretinogram (PERG) is a simple and safe test. During this test, you might feel slight discomfort in your eyes. In very rare instances, the surface of your eye might get scratched, depending on the tool used. There are several factors that can interfere with the results of this test.

These factors include:

* Not following the exact testing conditions (for example, the surrounding light, the brightness of the flash, the place where the test is done, the duration of staying in light or dark, and the size of your pupils).
* Problems with the electrode (the device that picks up the electricity in your eyes) such as not enough contact with the skin or eye surface, incorrect placement, shaky position, and high electrical resistance.
* Blinking or moving your eye.
* Uncorrected vision errors or blurred vision.
* Less electric response as you age.
* Cloudiness in your eye’s lens or other parts that light has to pass through.
* The time of day the test is done.
* Reduced response if you’re given anesthesia.
* Differences in the results when using different testing devices.

What Else Should I Know About Pattern Electroretinogram?

Problems with your vision can often occur because of abnormalities in your eye’s electrical activity before you even start seeing physical changes in your eye. One way of checking your eye’s electrical activity is through a pattern electroretinogram (PERG), a test that’s very helpful for detecting issues when your eye looks normal or when you’re experiencing a loss of vision for no apparent reason.

When it comes to checking for problems with the optic nerve, the part of your eye that sends visual information to your brain, versus the macula, the part of your eye responsible for fine vision, the PERG test can give different results. In optic nerve problems, the test might show normal or decreased activity, particularly a reduction in a reading called the N95 amplitude. In contrast, when the macula isn’t functioning well, the test could show a severe reduction or complete absence of the PERG, particularly in a reading called the P50 amplitude.

There are also certain inherited diseases like Leber’s Hereditary Optic Neuropathy and Dominant Optic Atrophy that primarily affect the optic nerve and can be detected through specific patterns in the PERG test. The same goes for other diseases such as Multiple Sclerosis and Glaucoma that can cause inflammation and damage to the optic nerve, respectively.

In addition, conditions like Nonarteritic anterior ischemic optic neuropathy, which can cause sudden onset of vision loss in the elderly due to insufficient blood flow to the optic nerve, can also be detected through a specific PERG response.

Even neurodegenerative diseases which are usually not associated with vision, like Alzheimer’s and Parkinson’s, can lead to specific changes in your eye’s electrical activity according to the PERG test. Alzheimer’s can cause a decrease in both N95 and P50 amplitudes, while Parkinson’s mostly reduces N95 amplitude.

In summary, the PERG test is a very useful tool in detecting vision problems early and can help in diagnosing a range of conditions from eye-specific ones to more general diseases.

Frequently asked questions

1. How does the Pattern Electroretinogram (PERG) test assess the functioning of my macula and retinal ganglion cells? 2. In what situations would I need a PERG test? 3. Are there any conditions or factors that would prevent me from undergoing the PERG test? 4. What tools are used during a PERG test and what can I expect during the procedure? 5. What specific information can the PERG test provide about my optic nerve and macular function?

Pattern Electroretinogram (PERG) is a test that measures the electrical activity of the retina in response to visual stimuli. It can help diagnose and monitor certain eye conditions, such as glaucoma and optic nerve damage. By analyzing the PERG results, doctors can gain insights into the health and function of the retina, which can ultimately guide treatment decisions and improve visual outcomes.

You may need a Pattern Electroretinogram (PERG) if you have certain conditions or symptoms related to your eyes or vision. The PERG is a test that measures the electrical activity of specific cells in the eye, and it can help diagnose and monitor conditions such as glaucoma, optic nerve damage, and certain types of retinal diseases. Additionally, the PERG can be used to evaluate the function of the retina and optic nerve in individuals with epilepsy. It is generally safe for individuals with epilepsy to undergo the PERG, as the frequency of the stimulus used in the test does not typically trigger seizures. However, if you have a specific type of epilepsy called photosensitive seizures, where seizures are triggered by certain light patterns, you may need to be carefully evaluated before having the PERG. This is especially important if the frequency that triggers your seizures is around 30 Hz or if the triggering frequency is unknown.

You should not get a Pattern Electroretinogram (PERG) if you have photosensitive seizures triggered by certain light patterns, especially if the triggering frequency is around 30 Hz or if the triggering frequency is unknown.

The text does not provide information about the recovery time for Pattern Electroretinogram.

To prepare for a Pattern Electroretinogram (PERG) test, patients should follow several steps recommended by the International Society for Clinical Electrophysiology of Vision (ISCEV). These steps include ensuring an electrically isolated recording environment, recording without pupil dilation, taking a recovery break of at least 30 minutes in normal room light before the test, instructing patients to focus on a target within the stimulator, and recording from both eyes (binocular recording) unless there are eye misalignment issues. It is important to follow these steps to ensure accurate and consistent test results.

The complications of Pattern Electroretinogram (PERG) include discomfort in the eyes, rare instances of eye surface scratching, factors that can interfere with the test results such as not following testing conditions, problems with the electrode, blinking or moving the eye, uncorrected vision errors or blurred vision, reduced electric response with age, cloudiness in the eye's lens, the time of day the test is done, reduced response with anesthesia, and differences in results when using different testing devices.

There are no specific symptoms mentioned in the text that would require a Pattern Electroretinogram (PERG) test. The test is used in situations where there might be issues with the optic nerve or macula, when taking medication that could harm the retina, or after an eye injury or inflammation.

There is no specific information provided in the given text about the safety of Pattern Electroretinogram (PERG) during pregnancy. It is recommended to consult with a healthcare professional or ophthalmologist for personalized advice regarding the safety of PERG during pregnancy.

Join our newsletter

Stay up to date with the latest news and promotions!

"*" indicates required fields

This field is for validation purposes and should be left unchanged.

We care about your data in our privacy policy.