Vision sensory organ. - PowerPoint Presentation

Slide1

Vision

sensory

organ.

absorbs

light rays from our environment and transforms them in such a way that the information in the brain can be processed further.

The

eye and brain form a unit that has developed together in the course of evolution (visual system).

The

process of processing is called

"seeing", "watching"

or "looking

".

The visual impression is essentially generated from visual memory, in which only little new information from the eye is incorporated.

anatomy

cornea

The

front side of the eye is the cornea.

slightly

thinner in the centre than the outer areas.

covered

with tear fluid, which is formed in the tear glands and serves to supply and protect the eye 

Anterior and posterior chamber, intraocular fluid

Behind the cornea is the anterior eye chamber, which is filled with intraocular fluid. It contains nutrients to

supplies

the eye lens and cornea.

I

mmune

factors are floating in intraocular fluid, which serve to render potentially damaging foreign bodies and germs harmless

.

maintain

a constant intraocular pressure.

Behind the iris the posterior chamber of the eye begins. The intraocular fluid is produced and released at the ciliary processes. It then slowly flows through the pupil into the anterior chamber of the eye.

Iris

The iris is located in the

centre

of the cornea

.

It consists of many fine muscle pathways that can contract or expand.

The resulting round opening in the centre is called the pupil.

The

darker it is, the more light is needed for vision - the pupil becomes correspondingly larger in darkness.

In very bright light, the pupil is only small. The iris is coloured by certain pigments (blue, brown, green, grey or corresponding mixed values)

lens

Behind the pupil is the eye

lens.

The

eye lens is a kind of liquid sphere. They can be compared to a water-filled balloon.

In

the middle - on the so-called lens equator - the lens is hung up on the zonula fibres, which originate from the ciliary muscle.

The lens fluid solidifies over the decades. It is thus the cause of widespread presbyopia.

P

rotein

structures in the lens of the eye increasingly clump together over time, clouding the image. This deterioration in visual quality is also known as cataract.

Ciliary muscle

The ciliary muscle is located behind the cornea in a ring-shaped shape inside the eye.

influence the curvature of the eye lens

.

In a relaxed state, the lens is flat and drawn out - so you can see well in the distance.

if the ciliary muscle tightens (contract tone), the diameter of the ring becomes smaller. The zonula fibres relax and the lens takes on a rather bulbous, spherical shape. This changes the refractive power of the lens so that you can see well in the vicinity. This process is called accommodation

Vitreous chamber

The inner space of the eyeball is filled by the vitreous body. It consists of a gel-like clear liquid and is especially important for the stability of the eyeball: the liquid generates a pressure, the so-called

intraocular pressure.

This

ensures that the surrounding layers do not peel off and collapse. In addition, without intraocular pressure, the eye would be much more sensitive to external pressure influences that affect the cornea from the outside. An abnormal intraocular pressure is the cause of many eye diseases, such as glaucoma.

Sclera

The eyeball is surrounded by three layers. The outer shell is called sclera.

The

dermis has a whitish colour - in the front, open part of the

eye.

It encloses the eyeball almost completely and protects the eye.

The dermis is interrupted only in two places: in the front by the circular, transparent cornea (Cornea) and in the back of the eye by the optic nerve coming from the inside of the eye.

Choroid

Inside the protective sclera follows the choroid, which, as the name suggests, is permeated by numerous blood vessels and capillaries.

The

blood supplies the retina with nutrients and oxygen

.

The choroid is dark pigmented and ensures that unprocessed light is absorbed (instead of being reflected into the inside of the eye).

The

effect of the "red eyes on photos" is related to this: the flash is so intense that it brightens up the inner eye. The red blood vessels of the choroid are then visible in the

phone

Retina

The retina is located on the back / inside of the eye.

The

choroid contains blood vessels that supply the retina with nutrients and oxygen and remove its waste

products.

There are two types of photoreceptor cells in

Retina

— rods and cones.

Rod photoreceptors detect motion, provide black-and-white vision and function well in low light. Cones are responsible for central vision and

color

vision and perform best in medium and bright light.

Rods are located throughout the retina; cones are concentrated in a small central area of the retina called the 

macula. At the center of the macula is a small depression called the 

fovea

. The fovea contains only cone

photoreceptor.

Three

different cone cells are required for

colour

vision:

Cones

for

red-visibility

Cones for green vision Cones for blue vision

The yellow spot:

Makula

and Fovea

The area where the light information is concentrated on the retina is the area of "sharpest vision". It is called macula (yellow spot).

Here

, the photoreceptors are particularly densely packed. Practically all refractive errors (short-sightedness, long-sightedness, astigmatism and presbyopia) are based on the fact that the bundled light rays are not focused exactly on the macula. But: All these defective vision problems can be compensated by visual aids,

i

. e. optically correcting lenses

Blind spot

The

nerve endings of the approximately 1 million ganglion cells must leave the retina in one place and lead as an optic nerve into the brain.

This

position is slightly below the macula and slightly inward (towards the nose

).

It is called a blind spot because there are no photoreceptors in the area - therefore, everything projected into the region cannot be seen. Everything depicted in this area is "invisible". Thus, in a small part of the field of vision, one is virtually blind.

Light rays enter the eye through the cornea, the clear front “window” of the eye. The cornea’s refractive power bends the light rays in such a way that they pass freely through the pupil the opening in the

center

of the iris through which light enters the eye.

The iris works like a shutter in a camera. It has the ability to enlarge and shrink, depending on how much light is entering the eye.

After passing through the iris, the light rays pass

through lens

. This clear, flexible structure works like the lens in a camera, shortening and lengthening its width in order to focus light rays properly

Light rays pass through a dense, transparent gel-like substance, called the vitreous that fills the globe of the eyeball and helps the eye hold its spherical shape.

In a normal eye, the light rays come to a sharp focusing point on the retina. The retina functions much like the film in a camera. It is responsible for capturing all of the light rays, processing them into light impulses through millions of tiny nerve endings, then sending these light impulses through over a million nerve

fibers

to the optic

nerve

The retina receives the image that the cornea focuses through the eye’s internal lens and transforms this image into electrical impulses that are carried by the optic nerve to the

brain.

No

matter how well the rest of the eye is functioning, if the cornea is scarred, clouded or distorted, vision will be affected.

Most common eye defect

1. Myopia or near sightedness

Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface If you're

nearsighted

.

2.hyperopia or far sighted

This vision problem occurs when light rays entering the eye focus behind the retina, rather than directly on it. The eyeball of a farsighted person is shorter than normal

Farsightedness can be corrected with glasses to change the way light rays bend into the eyes

3. Astigmatism

Astigmatism usually causes vision to be blurred or distorted to some degree at all distances. Symptoms of uncorrected astigmatism are eye strain and headaches, especially after reading or other prolonged visual tasks

Astigmatism is usually combined with Myopia or

Hyperopia

4.

Presbyopia generally

is believed to stem from a gradual thickening and loss of flexibility of the natural lens inside your eye

Presbyopia usually occurs beginning at around age 40, when people experience blurred near vision when reading, sewing or working at the computer

.