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HUMAN EYE AS AN OPTICAL SYSTEM. CONSTRUCTION OF THE IMAGE ON THE RETINA. DISADVANTAGES OF THE OPTICAL SYSTEM OF THE EYE AND THE PHYSICAL BASIS OF THEIR ELIMINATION. Completed: Student orgma 123 gr. to treat.fak. Kochetova ChristinaSlide 2
HUMAN EYE AS AN OPTICAL SYSTEM. A person perceives objects of the external world by analyzing the image of each of the objects on the retina. The retina is the light-receiving department. The images of objects around us on the retina are rendered with the help of the optical system of the eye. The optical system of the eye consists of: Cornea Lens Vitreous humor
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HUMAN EYE AS AN OPTICAL SYSTEM. The cornea, the cornea (lat. Cornea) is the anterior most convex transparent part of the eyeball, one of the light-refracting media of the eye. The cornea in humans occupies about 1/16 of the area of the outer shell of the eye. It looks like a convex-concave lens, with its concave part facing backwards, it is transparent, due to which light passes into the eye and reaches the retina. Normally, the cornea is characterized by the following features: sphericity specularity transparency high sensitivity absence of blood vessels. Functions: protective and supporting functions (provided by its strength, sensitivity and ability to quickly recover) light conduction and light refraction (provided by the transparency and sphericity of the cornea).
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HUMAN EYE AS AN OPTICAL SYSTEM. In the cornea, six layers are distinguished: the anterior epithelium, the anterior border membrane (Bowman's), the main corneal substance, or the stroma Dua layer, the posterior border membrane (Descemet's sheath), the posterior epithelium, or the corneal endothelium.
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HUMAN EYE AS AN OPTICAL SYSTEM. The lens (lens, lat.) Is a transparent biological lens that has a biconvex shape and is included in the light-conducting and light-refracting system of the eye, and provides accommodation (the ability to focus on objects at different distances). There are 5 main functions of the lens: Light conduction: The transparency of the lens ensures the transmission of light to the retina. Refraction: As a biological lens, the lens is the second (after the cornea) refractive medium of the eye (at rest, the refractive power is about 19 diopters). Accommodation: The ability to change its shape allows the lens to change its refractive power (from 19 to 33 diopters), which ensures focusing of vision on various distant objects. Dividing: Due to the peculiarities of the location of the lens, it divides the eye into the anterior and posterior sections, acting as an "anatomical barrier" of the eye, keeping the structures from moving (prevents the vitreous from moving into the anterior chamber of the eye). Protective function: the presence of the lens makes it difficult for microorganisms to penetrate from the anterior chamber of the eye into the vitreous body during inflammatory processes.
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HUMAN EYE AS AN OPTICAL SYSTEM The structure of the lens. The lens is similar in shape to a biconvex lens, with a flatter anterior surface. The lens diameter is about 10 mm. The main substance of the lens is enclosed in a thin capsule, under the anterior part of which there is an epithelium (there is no epithelium on the posterior capsule). The lens is located behind the pupil, behind the iris. It is fixed with the help of the finest threads ("zinn ligament"), which are woven into the lens capsule at one end, and connected to the ciliary (ciliary body) and its processes at the other. It is due to the change in the tension of these threads that the shape of the lens and its refractive power change, as a result of which the process of accommodation takes place. Innervation and blood supply The lens does not have blood and lymphatic vessels, nerves. Metabolic processes are carried out through the intraocular fluid, which surrounds the lens on all sides.
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HUMAN EYE AS AN OPTICAL SYSTEM. The vitreous body is a transparent gel that fills the volume of the entire cavity of the eyeball, the area behind the lens. Functions of the vitreous body: conduction of rays of light to the retina, due to the transparency of the medium; maintaining the level of intraocular pressure; ensuring the normal location of intraocular structures, including the retina and lens; compensation for intraocular pressure drops due to sudden movements or injuries due to the gel-like component.
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HUMAN EYE AS AN OPTICAL SYSTEM. The structure of the vitreous body The volume of the vitreous body is only 3.5-4.0 ml, while 99.7% of it is water, which helps to maintain a constant volume of the eyeball. The vitreous body in front is adjacent to the lens, forming a small depression in this place, on the sides it borders on the ciliary body, and along its entire length - on the retina.
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The rays of light that are reflected from the objects under consideration necessarily pass through 4 refractive surfaces: the back and front surfaces of the cornea, the back and front surfaces of the lens.
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CONSTRUCTION OF THE IMAGE ON THE RETINA. Each of these surfaces deflects the light beam from its original direction, which is why a real, but inverted and reduced image of the observed object appears in the focus of the optical system of the organ of vision.
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Johannes Kepler (1571 - 1630) was the first to prove that the image on the retina is inverted by constructing the path of rays in the optical system of the eye. To test this conclusion, the French scientist René Descartes (1596 - 1650) took the eye of a bull and, scraping off an opaque layer from its back wall, placed it in a hole made in a window shutter. And right there, on the translucent wall of the fundus, he saw an inverted image of the picture observed from the window.
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Why then do we see all objects as they are, i.e. not inverted? The fact is that the process of vision is continuously corrected by the brain, which receives information not only through the eyes, but also through other senses. In 1896, the American psychologist J. Stretton performed an experiment on himself. He put on special glasses, thanks to which the images of surrounding objects on the retina turned out not to be reversed, but straight. He began to see all objects upside down. Because of this, there was a mismatch in the work of the eyes with other senses. The scientist developed symptoms of seasickness. For three days he felt nauseous. However, on the fourth day, the body began to return to normal, and on the fifth day Stretton began to feel the same way as before the experiment. The scientist's brain got used to the new working conditions, and he again began to see all objects straight. But when he took off his glasses, everything turned upside down again. Within an hour and a half, vision was restored, and he began to see normally again.
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The process of refraction of light in the eye's optical system is called refraction. The theory of refraction is based on the laws of optics, which characterize the propagation of light rays in a variety of media. The straight line that passes through the centers of all refractive surfaces is the optical axis of the eye. Light rays, incident parallel to this axis, are refracted and collected in the main focus of the system. These rays emanate from infinitely distant objects, therefore the main focus of the optical system is the place on the optical axis, where the image of infinitely distant objects appears. Diverging beams, which come from those objects that are located at a finite distance, are collected already in additional foci. They are located farther than the main focus, because additional refractive power is required to focus the diverging rays. The more the incident rays diverge (the proximity of the lens to the source of these rays), the more refractive power is required.
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DISADVANTAGES OF THE OPTICAL SYSTEM OF THE EYE AND THE PHYSICAL BASIS OF THEIR ELIMINATION. Thanks to accommodation, the image of the objects in question is obtained just on the retina of the eye. This is done if the eye is normal. An eye is called normal if, in a relaxed state, it collects parallel rays at a point lying on the retina. The two most common eye defects are myopia and hyperopia.
Eye as optical
system
Prepared by class 9 student Mikhalchenko Varvara
Sclera-protection from damage
Cornea protection and support. Functions
light conduction and light refraction
ensured by transparency and
enchanting cornea.
Iris - eye color detection
Pupil - regulation of the beam flow
light entering the eye and falling on
retina. Illumination control
retina.
Lens-provides
light conduction, light refraction, akko
modulation, protection.
Vitreous - fills the volume
the entire cavity of the eyeball.
Retina - lines the cavity of the eye
apples from the inside and performs the functions
perception of light and color
signals.
Optic nerve - Provides transmission
nerve impulses of light
irritation. Image view
The optical system of the eye consists of the cornea, anterior chamber, lens and
vitreous. The image of an object appearing on the retina of the eye is
real, reduced and inverted. Visual acuity
Visual acuity is the ability to distinguish between boundaries and details.
visible objects. It is determined by the minimum angular
the distance between two points at which they are perceived
apart. Farsightedness and myopia
Farsightedness - lack of vision, with
which parallel rays after
refractions are collected not on the retina, but behind
her.
Myopia is a lack of vision in which
parallel beams are not collected on
the retina, but closer to the lens. Treatment methods
There are currently three recognized methods of correction
myopia and hyperopia, namely:
Glasses
Contact lenses
Laser correction of myopia or hyperopia Binocular vision
Binocular vision - the ability to see clearly at the same time
image of an object with both eyes; in this case, the person sees one
the image of the object that is looking at, that is, this vision of two
eyes, with a subconscious connection in the visual analyzer (cortex
brain) images obtained by each eye into a single image.
Creates a three-dimensional image. Binocular vision is also called
stereoscopic.
Many people have binocular vision
animals, fish, insects, birds.
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The structure of the eye A person sees not with his eyes, but through the eyes, from where information is transmitted through the optic nerve, chiasm, visual tracts to certain areas of the occipital lobes of the cerebral cortex, where the picture of the external world that we see is formed. All these organs make up our visual analyzer or visual system. The presence of two eyes allows us to make our vision stereoscopic (that is, to form a three-dimensional image). The right side of the retina of each eye transmits through the optic nerve the "right side" of the image to the right side of the brain, similarly to the left side of the retina. Then the brain connects the two parts of the image - the right and the left - together. Since each eye perceives "its own" picture, if the joint movement of the right and left eyes is disturbed, binocular vision can be impaired. Simply put, your eyes will start to see double or you will see two completely different pictures at the same time.
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The main functions of the eye: an optical system that projects an image; a system that perceives and "encodes" the received information for the brain; "service" life support system.
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The pupil is a hole in the iris. Its dimensions usually depend on the level of illumination. The more light, the smaller the pupil. The pupil is a hole in the iris. Its dimensions usually depend on the level of illumination. The more light, the smaller the pupil. The lens is the "natural lens" of the eye. It is transparent, elastic - it can change its shape, almost instantly "directing focus", due to which a person sees well both near and far. Located in a capsule, held by the ciliary band. The lens, like the cornea, is part of the optical system of the eye. The vitreous is a gel-like transparent substance located in the back of the eye. The vitreous body maintains the shape of the eyeball, participates in intraocular metabolism. It is included in the optical system of the eye.
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The epithelial layer is a superficial protective layer that is restored if damaged. Since the cornea is an avascular layer, it is the epithelium that is responsible for "oxygen delivery", taking it from the tear film that covers the surface of the eye. The epithelium also regulates the flow of fluid into the eye. The epithelial layer is a superficial protective layer that is restored if damaged. Since the cornea is an avascular layer, it is the epithelium that is responsible for "oxygen delivery", taking it from the tear film that covers the surface of the eye. The epithelium also regulates the flow of fluid into the eye. Bowman's membrane - located just below the epithelium, is responsible for protection and is involved in nourishing the cornea. If damaged, it is not restored. The stroma is the most voluminous part of the cornea. Its main part is collagen fibers arranged in horizontal layers. Also contains cells responsible for recovery.
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Descemet's membrane - separates the stroma from the endothelium. It has a high Descemet's membrane - it separates the stroma from the endothelium. Possesses high Endothelium - is responsible for the transparency of the cornea and participates in its nutrition. It recovers very badly. It performs a very important function of an "active pump", which is responsible for preventing excess fluid from accumulating in the cornea (otherwise it will swell). In this way, the endothelium maintains the transparency of the cornea.
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