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Transcript

Leonardo da Vinci -The VisionaryThe Human Eye

Group B1

INDEX

1.The Ocular Adnexa2.The 3 Layers Of The Eye3.Cornea, Aqueous Humor, Lens, Vitreous Body4.How the does the eye work?5.Acomodation of the lens

6. Pupil constriction7.Myopia, Hyperopia8.Astigmatism, Presbyopia9.Why do your legs look crooked under water?10.A scketch/A model of the eye

The Ocular adnexa

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The lacrimal glands

1. The ocular adnexa

= The adjacent structures of the eye such as the lacrimal apparatus (a), the extraocular muscles (b) and the eyelids (c), eyelashes (d), eyebrows (e) and the conjunctiva (f).

The Extraocular Muscles

The Eyelids

Inside of the orbit, but outside of the eyeball itself, are the extraocular muscles.These help the eyeball move up, down, left, right, and rotate every which way.They also control the movement of the upper (superior) eyelid.

The lacrimal glands are serous type exocrine glands that secrete lacrimal fluid onto the surfaces of the conjunctiva and cornea of the eye.The lacrimal gland is located anteriorly in the superolateral aspect of the orbit, within the lacrimal fossa – a depression in the orbital plate of the frontal bone.The lacrimal gland is approximately 2cm long. It can be divided into two main parts: orbital and palprebral.

An eyelid is a thin fold of skin that covers and protects the eye.The superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily.Its key function is to regularly spread the tears and other secretions on the eye surface to keep it moist.

1. The ocular adnexa

The Eyelashes

The Eyebrows

The Conjunctiva

= The adjacent structures of the eye such as the lacrimal apparatus (a), the extraocular muscles (b) and the eyelids (c), eyelashes (d), eyebrows (e) and the conjunctiva (f).

The eyebrow is an area of thick, delicate hair above the eye that follows the shape of the lower margin of the brow ridges of some mammals.The main function of the eyebrow is to prevent moisture, mostly salty sweat and rain, from flowing into the eye.The most recent research suggests that in humans its primary function is to allow for a wider range of ‘non-verbal’ communication.

The conjunctiva is the clear, thin membrane that covers part of the front surface of the eye and the inner surface of the eyelids. It has two segments: Bulbar conjunctiva and Palpebral conjunctiva.The primary functions of the conjunctiva are: keep the front and inner surfaces of the eye moist and lubricated so they open and close easily without friction or causing eye irritation; protect the eye from dust, debris and infection-causing microorganisms.

An eyelash is one of the hairs that grows at the edge of the eyelid. It grows in 2-3 layers on the edge of the eye lids. Eyelashes protect the eye from debris, dust and small particles and they are sensitive to being touched, thus providing a warning that an object (such as an insect) is near the eye (which then closes reflexively).Life span : 3 to 4 month

Corneea, Aqueous Humor, Lens, Vitreous Body

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The Corneea

The Corneea is the transparent front part of the eye that covers the iris, pupil and aterior chamber. The corneea refracts approximately two-thirds of the eye's total optical power.

The Aqueous Humor

The aqueous humour is a thin, transparent fluid similar to plasma. It’s made up of 99.9% water ­­– the other 0.1% consists of sugars, vitamins, proteins etc. This fluid nourishes the cornea and the lens, and gives the eye its shape.The aqueous humour fills the anterior and posterior chambers of the eye.

The Lens

The lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances.

The Vitreous Body

The vitreous body is the clear gel that fills the space between the lens and the retina of the eyeball.

How does the eye work?

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Light rays enter the eye through the cornea. 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. Then the light rays go trough the lens, the Vitreous Body to the retina. 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.

We could see how the image formed in the retina is inverted. Then the brain makes it normal.

Accommodation of the lens

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Distant focus

When you focus far away the light rays comes parallel into your eyes and gets converted into a point on the retina. The large reality of the world has to be projected on a small retina.

Pupil constriction

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Close focus

When you focus closeby the light comes into your eyes diverted. So the light gets converted back into a point on the retina. Also here the large world needs to be projected on a small retina.

Pupil constriction

Constriction of the pupil occurs when the circular muscle contracts. The pupil is an adjustable opening that controls the intensity of light permitted to strike the lens.

Myopia, Hyperopia

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Myopia, also known as near-sightedness, is an eye disorder where light focuses in front of, instead of on, the retina. This causes distant objects to be blurry while close objects appear normal.Near-sightedness can be corrected with eyeglasses, contact lenses, or surgery.

7. Myopia

Other symptoms may include headaches and eye strain.The underlying cause is believed to be a combination of genetic and environmental factors.Risk factors include doing work that involves focusing on close objects, greater time spent indoors, and a family history of the condition.

Hyperopia,also known as far-sightedness, is a condition of the eye in which light is focused behind, instead of on, the retina. This results in close objects appearing blurry, while far objects may appear normal.As the condition worsens, objects at all distances may be blurry.Management can occur with eyeglasses, contact lenses, or surgery.

7. Hyperopia

Other symptoms may include headaches and eye strain.The cause is an imperfection of the eyes. Often it occurs when the eyeball is too short, or the lens or cornea is misshapen.Risk factors include a family history of the condition, diabetes, certain medications, and tumors around the eye.

Astigmatism, Presbyopia

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8. Astigmatism

Astigmatism is a common vision condition that causes blurred vision. It occurs when the cornea (the clear front cover of the eye) is irregularly shaped or sometimes because of the curvature of the lens inside the eye.An irregularly shaped cornea or lens prevents light from focusing properly on the retina, the light-sensitive surface at the back of the eye. As a result, vision becomes blurred at any distance.

Astigmatism frequently occurs withother vision conditions like myopia (nearsightedness) and hyperopia (farsightedness). Together these vision conditions are referred to as refractive errors because they affect how the eyes bend or "refract" light.There are many causes to astigmatism. It can be hereditary and is usually present from birth. It can decrease or increase over time.

8. Presbyobia

Presbyopia is the normal loss of near focusing ability that occurs with age.Most people begin to notice the effects of presbyopia sometime after age 40. You can't escape presbyopia, even if you've never had a vision problem before.

Why do your legs look crooked under water?

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Because the light can't travel as quickly in the water as it does in the air, the light bends around the straw, causing it to look bent in the water. Basically, the light refraction gives the straw a slight magnifying effect, which makes the angle appear bigger than it actually is, causing the straw to look crooked.Exactly same thing happens with our legs, while they are underwater.

9. Why do your legs look crooked under water?

This is where the light refracts.

Part of the straw under the water is skewed and looks thicker than the part above the water.

Sketches Of The Eye

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Mireia-SP

Jason-BE

Roxana-RO

Alexia-RO

TEAM - Group B1

Ruxandra -RO