?Were not the eye made to receive the rays of the sun, it could not behold the sun; if the peculiar power of God lay not in us, how could the godlike charm us?"
J.W. Goethe
30.1 General characteristics of the visual system
30.2 Dioptric apparatus of the eye
30.3 Receptor apparatus of the visual system
30.4 Conductive division of the visual system
30.5 Cortical division of the visual system
30.6 Color perception
30.7 Adaptation of the visual system
30.8 Protective reflexes
30.9 Eye movement
30.10 Visual sensory system study methods
Profile materials Control questions Situational tasks
30.1. General characteristics of the visual system
The visual sensory system perceives electromagnetic radiation with wavelengths of the visible range (400- 760 nm) and forms sensations of light. This phylogenet-ically young system provides about 90% of information about the external environment to the brain.
The main visual functions: 1) photosensitivity, an ability to distinguish between different intensities of diffuse lighting; 2) color vision, an ability to distinguish wavelengths within the visible spectrum; 3) spatial vision re-quiresfocusing of the subject on the retina; 4) motion perception performsreproduction of a moving object on the receptor field like on screen; five) depth perception is based on integrating information from two eyes.
Parts of the visual system. Similar to other sensory systems, the visual system consists of peripheral, conductive and cortical division. The peripheral division includes auxiliary structures (eyelids, lacrimal glands, etc.), the dioptric apparatus of the eye, and the receptor part, which is the retina of the eye.
30.2. Dioptric apparatus of the eye
The dioptric apparatus of the eye is a lens system that forms an inverted and reduced image of objects of the external world on the retina (Fig. 30.1). Light flux passes through the cornea moistened with lacrimal fluid, the chambers of the eye, the pupil of the iris, the lens and lens capsule, and the vitreous. The refractive power of the cornea together with the anterior chamber is ≈43 D, the flattened lens is ≈19 D, the total eye is ≈59 D, which allows focusing parallel beams of light on the retina in the region of the yellow spot, the distance from which to the cornea is 24 mm. The cornea and lens do not transmit ultraviolet rays.