EYE STRUCTUREThe eye often is compared to the workings of a camera. But eye structure is more complex and sophisticated than any camera that you can buy. The eye is a light sensitive organ. In combination with key areas of the brain, it forms the system responsible for our vision. It is not my intention to present a boring, detail-laden, and technical explanation of eye anatomy and eye function in this section. Instead, my goal is to provide you with a resource to understand the information on glaucoma-eye-info.com – to understand eye structure and how glaucoma affects its function. For those of you that are interested, I have included a detailed diagram of eye anatomy
here.
The orbit is the eye structure that protects the eyeball from physical injuries suffered throughout life, such as blows to the head and falls. The eye is suspended within the orbit. This means that it does not rest directly on any bone. Suspension of the eye is made possible by a system of tendons and connective tissue.
Suspension of the eye within the orbit allows it to move rapidly in different directions and without friction. This is made possible by a system of muscles. This might be surprising to some of you because we do not typically think about muscles when talking about eye structure. However, these muscles play a critical role in our vision. Without them, we would only be able to focus forward and we would have to move our heads in order to make even slight changes.
When the extraocular muscles are functioning properly, the eyes are aligned with each other. This means that the gaze of both eyes is brought to the same point in space, which is essential for human binocular vision. Defects in eye alignment, either due to a disorder of the brain in coordinating the eyes or a disorder in one or more of the extraocular muscles, collectively are known as strabismus.
 Can my eye pop out of its orbit?No. This is a common misconception. The eye is held in place by the architecture of the tendons and connective tissue, along with its attachment to the six extraocular muscles. THE EYEBALL The eyeball is what people typically think about when we talk about eye structure. It is almost spherical in shape and is suspended in its orbit. The sclera is covered by a transparent membrane known as the conjunctiva. Inflammation of this membrane is called conjunctivitis.
The front part of the sclera is known as the cornea. It is a transparent eye structure that is a powerful refracting surface, providing about 2/3 of the total focusing power of the eye. Similar to lenses that are used in cameras, the cornea is shaped like a dome of glass. This property is critical to its focusing function. A dome shape also gives the cornea properties of reflection. This is the reason why at certain angles you can see your reflection in the eyes of others.
The most obvious detail of our eyes is their color. Some people have blue eyes; others have brown; some have green eyes; others have gray. Eye color is determined by pigment granules deposited on the iris. It forms the rear boundary of the anterior chamber of the eye (the cornea forms the front boundary). The iris contains muscles that control the size of the pupil, which is the dark-colored area in the center of the iris. These should not be confused with the extraocular muscles that control gross movement of the eye. The muscles of the iris regulate how much light enters the interior of the eye. Depending on the amount of light, the pupil responds by getting bigger (dialating) or smaller (constricting). In this respect, the iris is an eye structure that functions much like the aperture of a camera.
Does the pigment inside the iris that is responsible for eye color have any actual function?Yes. Even though eyes can appear in different colors, the pigment in them is the same. It is called melanin. This pigment also is found in our skin and hair. It has a protective function. Melanin has the unique property of being able to absorb large quantities of ultraviolet (UV) light, which is dangerous to cells. In this way, melanin helps to protect both our eyes and our skin from UV damage. THE LENS The lens of the eye is located directly behind the iris. In technical terms it has an ellipsoid biconvex shape. As you can see from the image to the right, The lens is a flexible eye structure. This unique characteristic enables us to focus on things both up close and far away. Your camera requires multiple lenses to achieve a crude version of this goal. The lens changes its shape through a process called accommodation. This is a mechanism by which the lens changes its optical power in order to maintain focus on an object as its distance from us changes. To see things up close, muscles squeeze the lens, which causes its curvature to increase. To see things far away, accommodation is not necessary. Instead, the muscles relax, which has the effect of flattening, or reducing the curvature of, the lens.
When I squint my eyes to see better, am I trying to force the lens of my eye to curve and enhance accommodation?
It might seem that way, but the answer is no. Instead, you are trying to restrict the sources of light entering the eye to a smaller area in a manner similar to a pinhole camera. Try squinting right now. You'll notice that your peripheral vision is significantly reduced, both vertically and horizontally. Squinting reduces our visual field so that only the most important light sources enter the eye. It is important to remember that the lens does not operate like a simple switch in which with one accommodated position we see up close and another relaxed position we see far away. Instead, the lens constantly is changing shape through minute adjustments. The elegance of eye structure and function is that this can occur with just one lens and without us being aware of the thousands, if not millions, of accommodations and relaxations that take place each day. ANTERIOR CHAMBER
The anterior chamber is filled with a watery substance called the aqueous humor. This special fluid is filtered from blood, circulates through the anterior chamber, and is return to the bloodstream through the trabecular meshwork. The aqueous humor is responsible for the pressure that I measure inside your eye. This pressure is known as
intraocular pressure.
Light enters the eye through the cornea, passes through the lens, and is focused onto the retina. But before light strikes the retina, it first must pass through the entire inside of the eye known as the posterior chamber. It constitutes almost 70% of total volume in the eyeball and is filled with a transparent gelatinous material called the vitreous humor.
The retina is the innermost layer of the eye and serves a function much like film in a camera. This implies that there are other layers in addition to the retina. To assist us in understanding them, it's helpful to think about a coconut.
Surrounding the inner white layer of the coconut is another layer that is very hard. Similarly, around the retina there is another layer called the uvea, which is essentially a vascular layer. This means that it is filled with blood vessels and therefore abundantly supplied with blood. The iris, ciliary body and choroid form an eye structure known as the uveal tract. Although it is very thin, when we look at the retina through a microscope we can see that it consists of ten layers. Each one represents different types of special nerve cells. Because it is such a delicate eye structure, the retina sometimes can separate from the choroid. When this happens, it is called retinal detachment. It is a medical emergency that must be treated quickly to prevent loss of vision in the effected eye. The portion of the retina that is associated with central vision (line-of-sight) is called macula. It is located in the back of the eye, next to the optic nerve. At the center of the macula is the fovea. The fovea is responsible for any activity where visual detail is of primary importance, such as reading, watching television or movies, playing video games, and driving. Macular degeneration refers to a condition in which there is a loss of vision in the central portion of the visual field. Photoreceptors are specialized cells that receive light that reaches the retina, translate this energy into nerve impulses through a process called phototransduction, so that the optic nerve can transfer them to the brain. There are two types of photoreceptors, rods and cones. The cones detect color differences and work in bright conditions. Rods do not distinguish color are responsible for sight in low-light conditions. You have might have heard the terms ultrasound and infrasound. These are sounds that the human ear can not perceive. Similarly, there are certain wavelengths of light, such as X-rays or ultraviolet rays, that cannot be perceived by the human eye. Ultimately, all the different parts of the eye work together to produce signals which are sent to the brain to produce a visual image or picture.
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The eye is located within a cavity in the cranium called the orbit. The cranium consists of the structures and bones of the skull that together protect the brain. It also forms the framework to which all the other tissues of the head are attached. 
There are six extraocular muscles (outside of the eye). The muscles move the eye much like the strings of a puppet. In terms of eye structure, there are two muscles attached to the eyeball above, two below, and one on each side.
The outermost layer of eyeball is called the sclera. This is a thin, but very tough, protective shell that commonly is called the white of the eye. There are a number of disorders of the sclera, the most common of which are scleritis and episcleritis.
Refraction is a process by which light waves are bent when they pass from one medium into another – in this case, from the air through the cornea and the rest of the eye. Refraction is a key process in the vision system. Without it, we would be unable to see. 
this means that it is circular and curves outward on both sides. 
The area bounded by the cornea, iris, pupil, and lens is called the anterior chamber. The iris and cornea form an angle known as the irideocorneal angle. I assess this and other structures of the anterior chamber using a procedure called
Coconuts are hollow and filled with fluid. For this example, we can think of the vitreous humor in the eye as analogous to the fluid inside of the coconut. The innermost layer of the coconut is white. It is the part that we eat. In our example, the retina is the eye structure analogous to the white part of the coconut. 
