Electrophysiology
PricelistGENERAL INFORMATION
Electrophysiology refers to a group of tests that trace the electrical activity of both the retina and the optic nerve. They provide valuable data needed for making diagnosis. Electrophysiology also allows to control the treatment of many ophthalmic diseases and systemic diseases that give ocular manifestations.
There are three types of electrophysiological tests:
- Electroretinography (ERG), which measures the electrical activity of the retina.
- Electrooculography (EOG), which measures the function of the retinal pigment epithelium and photoreceptors.
- Visual Evoked Potentials/Responses (VEP/VER), which reflect the electrical signal generated at the visual cortex of the brain in response to visual stimulation.
All electrophysiological tests are performed at the Retina Ophthalmological Hospital.
PRACTICAL INFORMATION
What happens during an electrophysiological test
Electrophysiological tests are painless. The duration depends on the type of test – it can take from 15 to 60 minutes. No special preparation is required.
Patients with neurological diseases (e.g., epilepsy) must have a referral from their neurologist or internist. The document should state the exact type of test the patient is referred to and the purpose of the referral. The referral should be submitted to the Hospital in person, or sent by email to: a.kowalik@retina.pl
Pupil dilation is not always required, it depends on the type of test.
Attention! Patients who had their pupils dilated should not drive for about 3 hours after instillation of the drops.
Important! To ensure correct interpretation of the test results, we need to see additional medical records, such as:
– a photo of the fundus (taken not earlier than 6 months before the appointment),
– the results of OCT of the macula and optic nerve,
– past medical history (if the patient was treated elsewhere).
Patients who cannot provide the listed test results can make an appointment and have the required examinations performed at the Retina Ophthalmological Outpatient Clinic and Hospital (see the price list).
What happens during the particular electrophysiological test
ERG
Badanie elektroretinograficzne (ERG) pozwala na uzyskanie informacji o funkcjonowaniu poszczególnych warstw siatkówki. Siatkówka oka jest wypustką mózgu, potrafiącą zamieniać światło w sygnał elektryczny, który dociera do mózgu drogą nerwu wzrokowego.
Badanie polega na pomiarze przepływu prądu między elektrodą umieszczoną na rogówce, a elektrodą umieszczoną na czole. Przepływ prądu przedstawiony jest w postaci wykresu zwanego elektroretinogramem, przypominającym nieco wykres EKG.
Badanie czynności elektrycznej siatkówki przeprowadza się zarówno w ciemności, jak i w świetle. Na początku oko adaptuje się do ciemności przez około 20–30 minut. Po tym czasie przeprowadza się badanie. Następnie pacjent czeka około 10 minut w oświetlonym pomieszczeniu, tak żeby oko przystosowało się do światła. Potem ponownie wykonuje się pomiary. Pozwala to na zmierzenie czynności obu typów fotoreceptorów; pręcików odpowiedzialnych za widzenie w ciemności pręcików i czopków odpowiedzialnych za widzenie w świetle.
PATTERN ERG
Celem badania Pattern ERG (PERG) jest określenie funkcji komórek zwojowych siatkówki, ma to znaczenie w chorobach nerwu wzrokowego takich jak jaskra.
Badanie Pattern ERG wykonuje się w oświetlonym pomieszczeniu, źrenic się nie rozszerza. Tak samo, jak w przypadku badania ERG, po wcześniejszym znieczuleniu kroplami rogówki, pacjentowi zakładane są elektrody.
EOG
Electrooculography (EOG) is used for a similar purpose as ERG – to evaluate certain macular diseases, in particular Best disease (vitelliform macular dystrophy).
Pupil dilation is required. Before the test the patient adapts to the light for about 30 minutes.
Electrodes are placed near the outer corners of the eyes, two for each eye. One grounding electrode is placed in the centre of the forehead. The patient sits forward, with his chin resting on a centered chin rest in the Ganzfeld bowl, and follows with his eyes the sequential displacement of red dots.
The test takes about 30 minutes and consists of 2 parts: about 15 minutes in the light and about 15 minutes in the dark.
Visual Evoked Potentials/Responses (VEP/VER)
Visual Evoked Potentials/Responses (VEP/VER) provide information about the entire visual pathway, starting with the retina and ending with brain structures. Visual Evoked Potentials are used to assess whether a patient can see at all. This is especially important when damage to the visual pathway in the brain is suspected.
Pupil dilation is not required. The examination is performed separately for each eye. The unexamined eye is blindfolded and three electrodes are placed in appropriate locations on the head.
VEP Pattern
A patient sits 80 cm away from a computer screen displaying a black and white checkerboard. During the test the checkerboard moves. There is a red cross in the center of the board, which is a fixation target, and the patient is supposed to fix their gaze at that.
If the patient wears glasses, they are not removed for the test (the unexamined eye is covered under the glasses). The examination takes about 15 minutes.
VEP Flash
The test uses flashes of light for stimulation.
The patient sits forward, with his chin resting on a centered chin rest in the Ganzfeld bowl, and keeps looking at the flashing light, which is similar to the flash made by a photo camera.
Young patients can be seated a little bit farther from the bowl.
During the test the patient looks ahead and blinks naturally when necessary.
The test takes about 10-15 minutes, depending on the patient’s cooperation.
Learn more about electrophysiological tests by watching the linked video: