Electroretinography - Causes, symptoms and treatment. MF.
Electroretinography is a method of research in ophthalmology, which is a graphic representation of the bioelectrical activity of retinal cells, which arises from the stimulation of the retina by light rays. This method is used to assess the functional state of both the retina as a whole and its various departments;to clarify the localization of the pathological process for various diseases of the reticular membrane. And this method allows you to identify early violations of the function of the retina before the appearance of visual changes. This method is especially indispensable for the opacification of the transparent eyes. The recording is performed using the electrode of the contact corneal lens. The data is displayed as a graph having several waves, which in turn are characterized by two parameters: the amplitude expressed in microvolts and the latency, i.e. The time elapsed from the moment of stimulation to the peak of the development of the wave, expressed in milliseconds. A negative a-wave and positive b-, c- and d-waves are singled out.a-wave displays the activity of photoreceptors( ie cells of the first level of the retina), the b-wave characterizes the electrical activity of cells of the second level of the retina. Reduction of the b-wave is one of the main signs in diseases of the retina of various origins. In some cases, a c-wave originating from the retinal pigment layer is recorded, but it is unstable and, therefore, has not found application in clinical practice. The d-wave represents the final response of retinal cells at the moment of switching off the long-term light stimulus.
There are several types of electroretinography: general, local, rhythmic and pattern-electroretinography.
With the help of general retinography, the total bioelectric potential is determined, which results from the illumination of the entire area of the retina. The light is produced by white light with a flash lamp.
Local electroretinography is a record of the bioelectric potential that occurs when light is stimulated by individual areas of the mesh shell.
Rhythmic( flashing) electroretinography is a graphical representation of the potentials in the retina when it is stimulated with light that flashes at a different frequency.
The pattern-electroretinography displays the electrical activity of ganglion cells( the third cellular level of the retina), which arises from the constant average illumination of the retina.
Apparatus retinograph
Indications:
1. Pigment retinitis.
2. Partial or complete color blindness.
3. Night blindness.
4. Congenital amaurosis of Leber.
5. Occlusion of the central artery( or vein) of the retina.
6. Toxic retinal damage.
7. Hypovitaminosis A.
8. Mucopolysaccharidosis.
9. Siderosis.
10. Retinopathy of prematurity.
11. Cataract.
12. Full hemophthalmus.
Contraindications:
1. Acute diseases of the cornea.
2. Acute diseases of the conjunctiva.
3. Acute diseases of the eyelids.
4. Allergy.
Procedure
Before testing, 1-2 drops of lidocaine solution are instilled in the eye. Then a contact lens with an electrode is put on the eye. Another electrode is attached to the ear lobe of the patient.
Retinography
During the procedure, the patient puts his chin on a special stand, and his forehead rests against the bar from above and looks at the light stimulus, which sends short flashes on the patient's retina. In this case, the device records the emerging electrical potentials through the electrodes and displays them on the screen.
Retinogram
The procedure is absolutely painless, but during and for some time after the procedure the patient may experience slight discomfort in the eyes, tears, foreign body sensation in the eye( as if an eyelash had entered the eye).
Procedure lasts no more than 1 hour.
Doctor ophthalmologist Odinochko EA