Retinal correspondence

With retinal correspondence is referred to in ophthalmology a functional relationship system between both eyes, which forms the basis for binocular vision ( binocular vision ). While looking at the picture of a fixed object takes on interconnected with one another and identically localized retina of the right and left eye, which perceive it in the same location of the space and overlap so. This is known as a normal Sehrichtungsgemeinschaft, normal retinal correspondence ( NRC ) or a normal retinal correspondence. Since this state is coupled to the foveae of both eyes in the normal case, this is referred to as bifoveale Sehrichtungsgemeinschaft. The fovea as motor zero point represents the straight direction value, also called main Ehrich Tung. As a result, generally has at any point peripheral retina of one eye, a corresponding part of the retina with the same sense of direction in the other eye, and according to many side Ehrich directions. Depending on the prevailing conditions correspond to the quality of binocular vision is present.

The set of points in the outdoor space that fall on corresponding retinal points in the fixation of an object, called horopter. This horopter is a line that is similar, slightly curved parabola. Objects that are close in front or behind this horopter are not usually seen twice, although they fall on non-corresponding retinal points. This area is called Panumareal or Panumraum. In this zone through the pictures slightly offset ( lateral disparity ) is produced spatial vision. When the limits of Panumareals exceeded the so-called physiological diplopia occurs.

Pathology

Deviations from a normal retinal correspondence are caused by strabismus and are the result of permanent shifts in Figure Panumareal during the early development phase. They can lead to an abnormal Sehrichtungsgemeinschaft, which is referred to as anomalous retinal correspondence ( ARC ). This is divided into harmonious anomalous correspondence ( HARK ) and discordant anomalous correspondence ( Dhark ). This is the phenomenon that occurs during the fixation of an object to stimulant physiologically identical localizing retinal points of the eyes, which can nevertheless lead to an abnormal superposition of the images. It correspond this is usually the fovea of one eye with a non- foveal eccentric retina of the other eye. As a result of HARK can develop so-called subnormal, that is qualitatively different inferior, binocular vision. Express themselves doing this, for example, in a small fusion width or only roughly pronounced spatial vision.

The basis for the development of a ARK, a relatively small squint angle, which just allows the development of these sensory abnormalities. With increasing degree of squint angle decreases the likelihood of ARK.

Investigation

The diagnostic assessment of the correspondence relations belongs in the ophthalmic field of orthoptics.

The procedures for correspondence examination based on two principles, the detection of a normal retinal correspondence or evidence of abnormal retinal correspondence. A statement on the existing bifoveale Sehrichtungsgemeinschaft or a foveal - peripheral localization relationship can take place only if the retinal points are known to be stimulated in the fixation of an object. Indispensable in both cases, the cooperation of the patient and his information about the location of objects. A stimulation of the fovea is achieved with color filters, afterimages or the Haidinger - tufts, in the case of eccentric fixation of the squinting eye only ophthalmoscope with the latter two methods.

To assess the correspondence prisms are held in front of the squinting eye and adjusted according to the information of the patient until a superposition of fixed objects takes place to compensate for the squint angle as long. The amount of prism power corresponds to the so-called subjective squint angle. Now it checked by means of unilateral Abdecktests the healthy eye, whether a setting movement of the other takes place. If this is not the case (and is a central fixation before ), so it is a normal correspondence ( NRK), otherwise an anomalous correspondence ( ARC ), stating a corresponding adjustment movement that allows the determination of the so-called objective squint angle. The difference between objective and subjective angle is called the angle of anomaly. It therefore does the following rule:

• NRK: subjective angle = angle objective, anomaly angle = 0 °
• HARK: subjective angle = 0 °, anomaly angle = angle of objective
• Dhark: subjective angle ≠ 0 °, angle anomaly ≠ objective angle.

Depending on the condition study the fluctuations in the values ​​of subjective angle and angle anomaly.

There is a general in assessing the correspondence arising out of the fact that the main Ehrich Tung " straight " is principally associated with the fovea centralis. However, there is the case that the main Ehrich Tung the fovea is lost and transferred to a peripheral part of the retina, which is now also used for the eccentric fixation. In this case, the extent of the eccentric fixation is exactly the squint angle and the anomaly angle. We call this disease a microstrabismus with identity.