structure of the eye

There are 6 sets of muscles attached to outer surface of eye ball which helps to rotate it in different direction. The colorful structure of the eye that changes the shape of the pupil to allow for different amounts of light to enter the inner eye. Structure of Human Eye. The eye works much the same as a camera. The high density of cones in the macula makes the visual image detailed, just as a high-resolution digital camera has more megapixels. The inside lining of the eye is covered by special light-sensing cells that are collectively called the retina. The human eye contains about 125 million rods, which are necessary for seeing in dim light. So, this is called the cornea. It consists of the following parts: Sclera: It is the outer covering, a protective tough white layer called the sclera (white part of the eye). Each orbit is a pear-shaped structure that is formed by several bones. The legacy of this great resource continues as the MSD Manual outside of North America. The retina contains the cells that sense light (photoreceptors) and the blood vessels that nourish them. Related conditions. In this article, we’ll go in depth exploring the structure of the human eye so that you can be better informed and know how to properly approach any eye issues you may be facing. The link you have selected will take you to a third-party website. Our eyes might be small, but they provide us with what many people consider to be the most important of our senses – vision. It is the clear, transparent front part of the eye that covers the iris, pupil and anterior chamber and provides most of an eye’s optical power (if too flat = hyperopia/farsightedness; if too steep = myopia/nearsightedness). We shall now look at these layers in further detail. It consists of the sclera and cornea, which are continuous with each other. Just like a lens in a camera sends a message to produce a film, the lens in the eye 'refracts' (bends) incoming light onto the retina. Drusen: Deposits of yellowish extra cellular waste products that accumulate within and beneath the retinal pigmented epithelium (RPE) layer. The choroid. The legacy of this great resource continues as the MSD Manual outside of North America. The front part is also called the anterior segment of the eye. Cornea - The cornea is the clear, dome-like structure on the front part of the eye.The cornea delivers 2/3 of the refracting power to the eye. Cones are responsible for sharp, detailed central vision and color vision and are clustered mainly in the macula. Behind the iris sits the lens. These layers have different structures and functions. Lens. Structure of the Human Eye The eye is a hollow, spherical structure about 2.5 centimeters in diameter. A human eye is roughly 2.3 cm in diameter and is almost a spherical ball filled with some fluid. Light enters the eye by passing through the transparent cornea and aqueous humor. Near the front of the eye, in the area protected by the eyelids, the sclera is covered by a thin, transparent membrane (conjunctiva), which runs to the edge of the cornea. With help from other important structures in the eye, like the iris and cornea, the appropriate amount of light is directed towards the lens. Rods are grouped mainly in the peripheral areas of the retina. Eye pain may be severe and sharp, aching, or throbbing. It is composed of light sensitive cells known as rods and cones. Each eye constantly adjusts the amount of light it lets in, focuses on objects near and far, and produces continuous images that are instantly transmitted to the brain. The size of the pupil is controlled by the action of the pupillary sphincter muscle and dilator muscle. The retina coats the entire back of the eyeball. The cornea and the lens help to focus the light rays onto the back of the eye (retina). Connected to the sclera are the extra-ocular or extrinsic muscles of the eye. The iris—the circular, colored area of the eye that surrounds the pupil—controls the amount of light that enters the eye. A thin layer called the conjunctiva sits on top of this. The orbit is the bony cavity that contains the eyeball, muscles, nerves, and blood vessels, as well as the structures that produce and drain tears. Location: it is situated on an orbit of skull and is supplied by optic nerve. By changing its shape, the lens focuses light onto the retina. The Eye - Science Quiz: Our eyes are highly specialized organs that take in the light reflected off our surroundings and transform it into electrical impulses to send to the brain. ; Sclera - The sclera is the white, tough, outer covering of globe of the eye. Last full review/revision Mar 2019| Content last modified Mar 2019, © 2020 Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA), © 2021 Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA, Cornea (clear layer in front of the iris and pupil). It is seen by both eyes (called binocular vision). We do not control or have responsibility for the content of any third-party site. A person may feel only mild irritation of the eye surface or the sensation of a foreign object in the eye. A. Sclera. The iris allows more light into the eye (enlarging or dilating the pupil) when the environment is dark and allows less light into the eye (shrinking or constricting the pupil) when the environment is bright. It is the white (and opaque) part of the eyeball. Eye structure is a fascinating area of medical inquiry which has expanded over the years in many ways. Cornea: The outer, transparent structure at the front of the eye that covers the iris, pupil and anterior chamber; it is the eye's primary light-focusing structure. The optic nerve is attached to the sclera at the back of the eye. Is the transparent, curved front of the eye which helps to converge the light rays which enter the eye Sclera Is an opaque, fibrous, protective outer structure. Size and shape: Human eye is spherical about 2.5 cm in diameter. B. Choroid. The sclera is the outermost layer of tissue, also called the white of the eye. It contains a jellylike fluid called the vitreous humor. The middle of these fields of vision overlaps. Rods are responsible for night and peripheral (side) vision. The most sensitive part of the retina is a small area called the macula, which has millions of tightly packed photoreceptors (the type called cones). Eye Anatomy Handout Author: National Eye Institute , National Eye Health Education Program Subject: Diabetes and Healthy Eyes Toolkit and Website Keywords: Eye anatomy, eye diagram, cornea, iris, lens, macula, optic nerve, pupil, retina, vitrous gel, diabetic eye disease. Created Date: 6/27/2012 11:57:40 AM An Inside Look at the Eye. Cornea: clear front window of the eye that transmits and focuses light into the eye. The inside of the eye contains the two refractive structures of the eye called the lens and vitreous body. Near the front of the eye, in the area protected by the eyelids, the sclera is covered by a thin, transparent membrane ( conjunctiva ), which runs to the edge of the cornea. It also has muscles that allow its accommodation within or on top of the head, depth perception, and true colour vision. The photoreceptors in the retina convert the image into electrical signals, which are carried to the brain by the optic nerve. The anterior segment is divided into two chambers. Anatomy of the Eye. The iris of the eye functions like the diaphragm of a camera, controlling the amount of light reaching the back of the eye by automatically adjusting the size of the pupil (aperture). This layer is a very stable fibrous membrane that continues to retain the shape of the eye and provides protection. It needs to be … The Manual was first published as the Merck Manual in 1899 as a service to the community. These adaptations are regarded as the first evolutionary improvements in… The optic nerve from each eye divides in the optic chiasm. It is soft connective tissue, and the spherical shape of the eye is maintained by the pressure of the liquid inside. Glaucoma. Each photoreceptor is linked to a nerve fiber. This process is the basis of stereo vision or depth perception. Vision occurs when light enters the eye through the pupil. External components include: Sclera; Conjunctiva; Cornea; Iris; Pupil; Internal components include: The eyeball is divided into two sections, each of which is filled with fluid. Structure Function; Cornea: Refracts light - bends it as it enters the eye: Iris: Controls how much light enters the pupil: Lens: Further refracts light to focus it onto the retina Other articles where Eye is discussed: amphibian: Common features: The eye of the modern amphibian (or lissamphibian) has a lid, associated glands, and ducts. Muscles responsible for moving the … The front (anterior) chamber extends from the cornea to the iris. The eyes sit in bony cavities called the orbits, in the skull. Retina: a light sensitive layer that lines the interior of the eye. The two optic nerves meet at the optic chiasm, which is an area behind the eyes immediately in front of the pituitary gland and just below the front portion of the brain (cerebrum). 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