Electrooculography

Electrooculography - registration of the permanent potential of the eye with the help of skin electrodes applied to the area of the outer and inner margins of the lower eyelid. This method allows to reveal pathological changes of retinal pigment epithelium and photoreceptors. The method is based on the fact that the eye is a dipole: the cornea has a positive charge, the pigment epithelium is negative, and the available constant potential varies with the movement of the eye under various adaptation conditions.

The study is carried out in a state of light and dark adaptation.

1. Electrodes are applied to the skin in the medial and lateral margins.
2. The patient is offered to rhythmically move the gaze from side to side with the same amplitude. With each movement of the eyeball, the electrode closest to the cornea becomes active with respect to the other.
3. The potential difference passes through the amplifier and is recorded.

Necessary conditions for normal light and dark fluctuations of the constant potential is the normal functioning of photoreceptors and pigment epithelium, contact between these layers, and adequate blood supply to the choroid. On electrooculography, the following indicators are noted:

• the basic potential is a constant potential, measured in a patient who is permanently in an environment of constant illumination;
• potential of light rise: with a sudden change in light conditions from moderate illumination to bright light, a characteristic increase in the basic potential of the retina occurs (light rise);
• the potential of the tempo decline: a sharp transition from moderate illumination to darkness leads to the appearance of a series of damped oscillations of the base potential (dark fall), reaching a minimum at the 10th-12th minute of dark adaptation.

For clinical purposes, the ratio of the potential of the light peak to the potential of the dark decline is calculated. The result is multiplied by 100 and the so-called Arden's coefficient (KA) is obtained, which is considered normal if it exceeds 185%. In order to assess the pathological conditions of the retina, the KA is subdivided into subnormal (135-185%), abnormal (110-135%), extinguished (100-110%), perverted (below 100%).

Electrooculography is used in the diagnosis of various diseases of the retina dystrophic, inflammatory and toxic nature, with circulatory disorders and other pathologies in which photoreceptors and the choroid are involved in the pathological process .

[1], [2], [3], [4], [5]