Transcript: HOW DOES LIGHT REACH RETINA? HOW DOES THE LENS FOCUS LIGHT FROM DIFFERENT DISTANCES? The blind spot is the result of no light receptors at the area where the optic nerve joins the retina. You won't notice the blind spot because the eyes help each other. The iris is a thin and circular thing in the eye that controls the size of the pupil and controls the amount of light. Introduction The eye is structurally designed to detect and process light. The cornea and the crystalline lens are both important for the eye to focus light. The eye focuses with the light to focus, and that happens in the retina. HUMAN EYE BY: KAZUHIRO How does the human eye works? WHAT IS THE FUNCTION OF THE IRIS? http://library.thinkquest.org/C005949/fun/blindspot.htm http://www.livescience.com/3919-human-eye-works.html http://www.ask.com/question/what-is-the-function-of-the-iris Bibliography The retina reflects the light rays. The light rays go through the pupil and pass into the interior part of the eye. HOW CAN YOU TEST FOR YOUR BLIND SPOT?
Transcript: Sclera - also known as the white of the eye, is the opaque, fibrous, protective, outer layer of the eye containing collagen and elastic fiber, the whole sclera is white, contrasting with the coloured iris. Central Retinal Artery - branches of the ophthalmic artery, running inferior to the optic nerve within its dural sheath to the eyeball. How to Apply Contact Lenses Ciliary Process - are formed by the inward folding of the various layers of the choroid, i.e., the choroid proper and the lamina basalis, and are received between corresponding foldings of the suspensory ligament of the lens. Lens Nucleus - The crystalline 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, thus allowing a sharp real image of the object of interest to be formed on the retina. Retina - is a light-sensitive layer of tissue, lining the inner surface of the eye. Cornea - is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Inside the Human eye Human Eye Vitreous Humor - is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates. It is often referred to as the vitreous body or simply "the vitreous". Ciliary Zonules - is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye. Choroid - also known as the choroidea or choroid coat, is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye (at 0.2 mm), while in the outlying areas it narrows to 0.1 mm. About the Human Eye Pupil - is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil. Iris - is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. The color of the iris is often referred to as "eye color." Lense Cortex - the tissue that surrounds the lens nucleus
Transcript: Most commonly experienced is the disorientation a person will feel when leaving a movie theater in the middle of the day.... When leaving a room that is extremely dimly lit then entering the outside world where the sun is blasting fucking rays at you at a rate that is not important... Your cones and rods must adjust to immediately give vision. They must switch to allow the cones to power over as to them being less light sensitive and more easily distinguish pigmentation... While the rods were extremely important inside the theater because in a dim lit room you must still be able to function so rods take forefront and act to give you ability to see in dark areas Basic Bitch Terminology Cones: active at higher light levels (photopic vision), are capable of color vision and are responsible for high spatial acuity Rods: responsible for vision at low light levels (scotopic vision). Do not mediate color vision; have a low spatial acuity together both the cones and rods allow images to be processed one transfers light differentiation (cones) the other delegates intensity of light (rods) Optic Nerve: nerve that transmits impulses to the brain from the retina at the back of the eye Retina: layer at the back eye containing cells that are sensitive to light and trigger nerve impulses that pass via optic nerve Cornea: transparent layer forming the front of the eye Lens: biconvex structure in the eye that helps refract light to be focused on the retina Iris: membrane behind the cornea of the eye with an adjustable circular opening in the center Photoreceptor: sensory cells that are found in the retina that respond to light Image Transition Overview movie theater effect Human Eye: Functions in Vision location of basic bitch terms Eye Arrangement grasping the knowledge at the basic bitch level of eye functioning in correspondence with the brain complete lie...way above basic bitch level.. comprehension of how images enter eye transition of how photoreceptors interpret light into electrical pulses completion of brain interpreting pulses to image Photoreceptors Cones vs. Rods When the eyes focus on an object, light will enter the eye through the pupil. The iris adjusts the size of the pupil based on light intensity. The light is then focused onto the back of the eye, the retina, by the lens. The retina's photoreceptors react changing the signals into electrical pulses to send through the optic nerve creating an image in our brain. light is received through the cornea, works as a focusing mechanism to target the optimal reception onto the retina light hits on the retina directly responding are the photoreceptors image in the eye is produced upside down all takes place before the brain even makes sense of what it is seeing, hence no one notices seeing the world upside down Conspectus Light to Retina
Transcript: When light reaches either the rods or the cones of the retina, it's converted into an electric signal that is sent to the brain through the optic nerve. The brain then recieves the electrical signals as the images we see. When the muscles relax, they pull on and flatten the lens, allowing the eye to see objects that are far away. To see closer objects clearly, the ciliary muscle must contract in order to thicken the lens. The cornea, a transparent structure in the very front of the eye, helps focus incoming light. Behind the cornea, the iris has an adjustable circular opening called the pupil, which can expand or contract depending on the amount of light entering the eye. Pupil- An opening in the center of the iris that controls how much light enters the eye. The iris functions like the iris of a camera, which opens and closes, to control the amount of light that enters through the pupil. The Human Eye Retina-The membrane that lines the back of the eye, containing photoreceptor cells. The photoreceptor nerve cells react to the presence and intensity of light by sending impulses to the brain through the optic nerve. In the brain, the nerve impulses that are received from the photoreceptor cells, are assimilated into images. The first thing light touches when entering the eye is a thin veil of tears that coats the front of the eye. Behind the moisture is the front window of the eye, called the cornea. This clear covering helps to focus the light. Lens- Immediately behind the iris, it performs delicate focusing of light rays to the retina. People under 40, the lens is soft and pliable, allowing for fine focusing from a variety of distances. People over 40, the lens begins to become less pliable, making focusing upon objects near to the eye more difficult, known as presbyopia. Cornea- Is the primary focusing element of the eye. The outer layer is the epithelium, which protects the eye and is made of transparent cells that have the ability to regenerate quickly. The inner layer is also made of transparent tissue, which allows light to pass. Anatomy How The Eye Works
Transcript: Human Eye Anatomy of the eye Vision Normal vision: One considered to have "normal vision" is one who has 20/20 vision. Essentially one has 20/20 vision if he/she can read the Snellen eye chart from twenty feet away. In normal vision the cornea bends or refracts the rays that pass through the pupil. Common vision problems: Myopia (nearsightedness): a type of refractive error in the eye - a condition of the eye where the light that comes in does not directly focus on the retina but in front of it Hyperopia (farsightedness): a type of refractive error in the eye - a condition in which light is focused behind the retina in the back of the eye From the Eye to the Brain When light first enters the eye it first passes through the cornea, the primary lens in the eye, then passes through two other lens, the aqueous humor, then the vitreous humor and then ultimately reaches the retina where it essentially gets processed through receptor cells known as rods and cones. The cones handle color vision and process details whereas the rods are processed in low light and can only detect neutral colors such as black and white. These cells in the retina convert the light into electrical impulses. The optic nerve sends these impulses to the brain where an image is produced. Works Cited http://www.afb.org/seniorsite.asp?SectionID=63&TopicID=286 Sclera: white, tough wall of the eye, it keeps the eyes shape and protects its delicate internal parts Cornea: clear, dome-shaped surface that covers the front of the eye, most powerful lens in the eye's optical system Iris:colored part of the eye, a ring of muscle fibers located behind the cornea and in front of the lens, contracts and expands, opening and closing the pupil, in response to the brightness of surrounding light, helps protect the sensitive retina Pupil: the hole in the center of the iris in which light passes through Retina: is the film of the eye which converts light rays into electrical signals and sends them to the brain through the optic nerve, the sides of the retina are responsible for our peripheral vision (the center area, called the macula, is used for our fine central vision and color vision, the retina is where most the problems leading to vision loss occur) Optic nerve: bundle of more than one million nerve fibers takes the signals gathered by the rods and cones of the retina and transmits them to the brain, where they are translated into the constant stream of images that make up human eyesight Created by: Ummehanie Raja http://science.howstuffworks.com/environmental/life/human-biology/eye2.htm http://www.aoa.org/x6024.xml
Transcript: Human Eye The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the mammalian eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors. In common with the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive the light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock. General Properties The eye is not shaped like a perfect sphere, rather it is a fused two-piece unit. The smaller frontal unit, more curved, called the cornea is linked to the larger unit called the sclera. The corneal segment is typically about 8 mm (0.3 in) in radius. The sclerotic chamber constitutes the remaining five-sixths; its radius is typically about 12 mm. The cornea and sclera are connected by a ring called the limbus. The iris – the color of the eye – and its black center, the pupil, are seen instead of the cornea due to the cornea's transparency. To see inside the eye, an ophthalmoscope is needed, since light is not reflected out. The fundus (area opposite the pupil) shows the characteristic pale optic disk (papilla), where vessels entering the eye pass across and optic nerve fibers depart the globe. Dimensions The dimensions differ among adults by only one or two millimeters. The vertical measure, generally less than the horizontal distance, is about 24 mm among adults, at birth about 16–17 millimeters (about 0.65 inch). The eyeball grows rapidly, increasing to 22.5–23 mm (approx. 0.89 in) by three years of age. By age 13, the eye attains its full size. The typical adult eye has an anterior to posterior diameter of 24 millimeters, a volume of six cubic millimeters (0.4 cu. in.), and a weight of 7.5 grams (0.25 oz.). Components The eye is made up of three coats, enclosing three transparent structures. The outermost layer is composed of the cornea and sclera. The middle layer consists of the choroid, ciliary body, and iris. The innermost is the retina, which gets its circulation from the vessels of the choroid as well as the retinal vessels, which can be seen in an ophthalmoscope. Within these coats are the aqueous humor, the vitreous body, and the flexible lens. The aqueous humor is a clear fluid that is contained in two areas: the anterior chamber between the cornea and the iris, and the posterior chamber between the iris and the lens. The lens is suspended to the ciliary body by the suspensory ligament (Zonule of Zinn), made up of fine transparent fibers. The vitreous body is a clear jelly that is much larger than the aqueous humor, present behind lens and the rest, and is bordered by the sclera, zonule, and lens. They are connected via the pupil. Dynamic range The retina has a static contrast ratio of around 100:1 (about 6.5 f-stops). As soon as the eye moves (saccades) it re-adjusts its exposure both chemically and geometrically by adjusting the iris which regulates the size of the pupil. Initial dark adaptation takes place in approximately four seconds of profound, uninterrupted darkness; full adaptation through adjustments in retinal chemistry (the Purkinje effect) is mostly complete in thirty minutes. Hence, a dynamic contrast ratio of about 1,000,000:1 (about 20 f-stops) is possible. The process is nonlinear and multifaceted, so an interruption by light merely starts the adaptation process over again. Full adaptation is dependent on good blood flow; thus dark adaptation may be hampered by poor circulation, and vasoconstrictors like tobacco. The eye includes a lens not dissimilar to lenses found in optical instruments such as cameras and the same principles can be applied. The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop. Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it can range from 2 mm (f/8.3) in a brightly lit place to 8 mm (f/2.1) in the dark. The latter value decreases slowly with age; older people's eyes sometimes dilate to not more than 5-6mm. Field of view The approximate field of view of an individual human eye is 95° away from the nose, 75° downward, 60° toward the nose, and 60° upward, allowing humans to have an almost 180-degree forward-facing horizontal field of view. About 12–15° temporal and 1.5° below the horizontal is the optic nerve or blind spot which is roughly 7.5° high and 5.5° wide. Eye irritation Eye irritation has been defined as “the magnitude of any stinging, scratching, burning, or other irritating sensation from the eye”. It is a common problem experienced by people of all ages. Related eye symptoms and signs of
Transcript: When you look up, some of this blue light reaches your eyes from all over the sky. Since you see blue light from everywhere overhead, the sky looks blue. The lens, like the lens of a camera, opens and shuts to allow light to reach the retina to focus an image. Rods translate light into monochromic values, everything inbetween black and white wheras cones convert them into color. The retina is the film of the eye. It converts light rays into electrical signals and sends them to the brain through the optic nerve The cornea helps shield the eye from germs and dust. It also focuses light that comes in Pupil- the opening of the eye. The size of the opening is regulated by the iris Iris- pigmented part of the eye (gives people their eye color)
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