Confusion and Diplopia

For binocular vision, simultaneous bifovel fixation by both eyes is necessary, i.e. Each eye separately perceives the object of fixation, taking part in the formation of the image. Conditions necessary for binocular vision:

• Overlay of fields of view.
• Proper neuromuscular development and coordination with the direction of the visual axes on the object.
• Normal visual pathways.
• Approximately the same image clarity and size in both eyes.
• Corresponding retinal points, "cyclopean" eye.

1. Confusion - the simultaneous perception of two superimposed, but different images, caused by the stimulation of the corresponding points (usually in the background) by various objects.
2. Diplomacy is the simultaneous perception of two images of one object. Occurs when the visual images of one object are projected onto non-intersecting retinal points. Simultaneous vision is the ability to perceive an object with both eyes simultaneously.
3. The visual direction is the projection of a given element of the retina in a special direction of subjective space.
   • the main visual direction is the direction in the outer space, interpreted as the line of sight. It is usually the visual axis of the fovea;
   • secondary visual directions - projected directions of extra-foveal points relative to the main direction of the fovea.
4. Projection is the interpretation of the position of an object in space on the basis of stimulated retinal elements.
   • If the red object stimulates the right foveol and the black object located in the nasal half of the field stimulates the elements of the temporal half of the retina, then the red object is interpreted by the brain as directly projected in the forward position of the head, and the black object as the arched and nasal half of the field of view. Similarly, the nasal elements of the retina are projected onto the temporal half of the view. Upper - on the lower half and vice versa.
   • With two open eyes, the red object stimulates both fovea, the corresponding retinal points. The black object stimulates not only the temporal elements of the retina of the right eye, but also the retinal elements of the left eye located nasally. Thus, the objects are projected into the nasal half of the field of vision of the right eye and the temporal half of the field of vision of the left eye. However, most of these retinal elements are the corresponding points, so the object is projected to the same position of space (left).
5. Retino-motor values. The image of the object in the peripheral field of view falls on the extra-foveal element. To establish the fixation of an object, a saccade of a certain amplitude is required. Each extra-foveal element of the retina has, therefore, a retino-motor value proportional to the distance from the fovea, which determines the required saccade amplitude for precise focusing of the object. The retino-motor value in the center of the foveola corresponds to zero and increases toward the periphery.
6. Corresponding points are areas of the retina with the same subjective visual direction (for example, a direct projection in the fovea). Points of the nasal retina of one eye correspond to the corresponding points on the temporal half of the retina of the other eye. This is the basis of normal correspondence of the retina. For example, an object whose images are projected onto the nasal half of the retina of the right eye and the temporal half of the retina of the left eye is projected onto the right half of the visual space.
7. The Goropter is an imaginary plane in the outer space, all points of which are stimulated only by the corresponding elements of the retina and are therefore perceived by two eyes as one point. This plane passes through the intersection of the visual axes and thus includes a fixation point with binocular vision.
8. Fusional zone Ranum of binocular vision is the area in front of and behind the gopher, within which the object is seen single, although there is no precise stimulation of the corresponding elements. Objects outside the Panum zone are perceived as twofold. This is the basis of physiological diplopia. The Panum Zone is narrow in the fixation zone (6 arc seconds) and expands to the periphery, so objects within the grinder are seen as single. Objects within the Panum fusion zone are perceived singly and stereoscopically. Objects outside the Panum fusion zone are perceived as twofold.
9. Sensory fusion is the combination of two sensory images from each eye in the visual cortex into one visual image. Central sensory fusion combines images projected on the fovea, and peripheral - outside the fovea.
10. Motor fusion is a function of maintaining the correct position of the eyes in order to achieve a bifofial fixation. The stimulus to motor fusions is the retinas of the retinal image, which stimulates the fusional vergenia.
11. Fusional vergenia includes disjugate eye movements to overcome the disparity of the retinal image. Fusional reserves can be measured with prisms or synoptophore. Normal reserve values:
    • Convergence: about 15 D (fixation of a distant object) and 25 D (fixation of a nearby object).
    • Divergence: about 25 D (fixation of the distant object) and 12 D (fixation of a nearby object).
    • Vertical: 2-3 D.
    • Cyclostergence: about 2.

Through fusional convergence, exophoria is controlled, and fusional divergence helps to control esophoria. Fuzzy mechanisms of vergence can be weakened by fatigue or illness, transforming the fury into a tropy. The width of fusional vertex mechanisms can be increased with the help of orthoptic exercises, such as fusional convergence when fixing a nearby object with weak convergence.

12. Stereopsis - the perception of depth (the third dimension, the first two - the height and width). Occurs with simultaneous stimulation of horizontally disparate points by objects anteriorly and posteriorly from the fixation point, but within the Panum fusion zone. The merging of such disparate images leads to the perception of a single image in depth. The object is perceived stereoscopically (3D), as each eye sees different aspects of the object.

[1], [2], [3], [4], [5], [6]