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Irene Nausa Fernández

on 15 October 2015

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Transcript of Sight

Eye parts
how do we can see?
the eyes
The act of seeing starts when the lens of the eye focuses an image of its surroundings onto a light-sensitive membrane in the back of the eye, called the

The retina is actually part of the brain that is isolated to serve as a transducer for the conversion of patterns of light into neuronal signals.

These signals are processed in a hierarchical fashion by different parts of the brain, from the retina upstream to central ganglia in the brain.
Occur when sending the cornea images converge outside the retina rather than on it as it should be.

: The length of the eye is longer than normal.Las distant images are blurred while the nearby display correctly.

: The eye is smaller than usual and vision both distance and near vision is blurred.

: Occurs when there is an irregularity in the curvature of the cornea. In these cases the view of both distance and near vision is defective and deformed objects are perceived.

Treatment for these problems is to wear glasses, contact lenses or refractive surgery called.
The lens is a transparent lens positioned within the eye. Its function is to
change the focus
of the eye for distant and near objects.

Cataracts occur when the lens opacity is dense enough to obscure vision and are the leading cause of blindness in the world. People with cataracts reduce vision, do not appreciate the vibrancy of the colors and have night vision problems.

Treatment is exclusively surgical discarded lenses and medications.

Glaucoma is caused by excessive pressure of a fluid called aqueous humor inside the eye. This pressure damages the structure of the eye, especially the optic nerve to not repair cause blindness.

the sight
The conjunctivitis causes swelling, itch, ardor, watering and reddening of the conjunctive one, the thin and translucent membrane that covers the white part of the eye and the interior of the eyelids. The conjunctivitis transmits to one person to another and it disappears with out treatment
The reasons CAN be

Infection bacterial or viral

Allergies Substances that cause irritation

Products that are used for the contact lenses, drops for the eyes or salves.

The daltonism is a genetic illness of the sight that impade to see the colors, confusing with another. The daltonism appears when the chromosome X is modified. The problem is in the photosensory cells called
, managers of us to provide the differences of color.

There are three types of daltonism:
Trichromatic anomalous.
Retina's detachment he separation of the retina of his normal position due to a tear. It can happen to persons of all the ages but it is more common in major persons of 40. This condition affects more the men than to the women and more whites that Afro-American.
The people that are more vulnerable than the others are:

-People that have a short vision
-People that have a retina's detachment in the other eye
-People that their familiars haven
-People that have others sight's diseases
-People that haven had cataracts
-Small points or spots that appear in the vision of a person

-Sparkles of light in the eyes

-The sensation that, there are something that impede you to see something

The retina's detachment is a medical emergency. It can produce the lose of the total vision

Pupil & Iris
The iris is a circular diaphragm that regulates the quantity of light that enters in the eye.
Has a central hole, of about 3mm of diameter that is the pupil
The cornea is the transparent hemispherical structure located in front of the eye that allows the passage of light and protects the iris.
Into the retine there are the visual cells, causing it to become to a photosensitive film
The sclerotic is a membrane, thick, resistant and rich of white color in fibers of collagen that constitutes the most external cap of the eyeball. His function is it of giving him FORM and protecting to the internal elements
Is the small pink, globular nude at the inner corne of the eye. It's made of skin covering sebaceous and sudoriferous
The IRIS...?
The iris has 4 layers:
pigment epithelium
(arrowed above)
(from the arrow in the middle to bottom)
two layers
, this is where the muscles are .

Why do we have different iris colours?
It's due to the
amount of the pigment melanin
, which is present in the part of the eye called the
Genetic factors influence the colouring.
The Ishihara Color Test is an example of a color perception test for red-green color deficiencies. It was named after its designer, Dr. Shinobu Ishihara, a professor at the University of Tokyo, who first published his tests in 1917.
The test consists of a number of colored plates, called Ishihara plates, each of which contains a circle of dots appearing randomized in color and size.

Depending on the type of glaucoma, various treatments are applied . Primary open angle glaucoma ( 90 percent of cases) usually occurs among people over 55 years , diabetics or myopic . Treatment of primary glaucoma can be controlled with topical medication or laser surgery or valve implantation to facilitate drainage. The angle closure glaucoma ( chronic or simple) is less common and can manifest with eye pain, headaches , blurred vision, nausea and vomiting. The final treatment consists in the use of laser , even if also require chronic administration of topical drugs .
Vertebrates (such as humans and dogs ) have in the retina photoreceptor cells each ( sellaman so that are sensitive to light)

These cells are responsible for capturing light coming from the object and send the information to the brain , which is what really " see " things. There are two types of photoreceptors and are called rods and cones precisely because they are cone-shaped and cane.

the rods are responsible for vision in black and white and cones color vision humans have three types of cones, each is very sensitive to one of the three primary colors blue , green and red . Loa dogs have also cones but only two types therefore can not see all the colors are blind to green to red and can see basically in black and white
The fish can not close their eyes.
Squid eyes are about the size of a watermelon .
Ostriches eyes are bigger than its brain.
Some people can hear how your eyeballs move .
Butterflies can see ultraviolet light .
Chameleons can see in all directions at once.
The sun can get to burn your eyes.
Dolphins sleep with one eye open .
People blink over 10,000 times a day.
Flashing equivalent to two-fifths of a second.

We've learned a lot doing this presentation.
We hope you too!
Optic Nerve
It transmits visual information from the retina to the brain. The optic nerve is composed of retinal ganglion cell axons and glial cells.
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