The Eye

Refractive errors occur when the curvature of the cornea, which mainly dertermines the refractive power, is not aligned with the eye’s length. As a result, the light rays are prevented from focusing directly on the retina.

Nearsightedness (myopia): When the eyeball is too long, the light rays are focused in front of the retina. Distant objects appear blurry, those up close are clear.

Farsightedness (hyperopia): When the eyeball is too short, the light rays are focused behind the retina. Nearby objects appear blurry, distant ones are clear.

Astigmatism: The cornea’s irregular shape causes light rays to focus on more than one point. Overall vision appears blurry or distorted.

The human eye is truly remarkable in its design. Each eye is unique. The vision quality we enjoy is largely determined by the size and shape of our eyes. With a healthy eye, light rays entering the eye are focused directly on the retina to form a sharp image, which is then sent to the brain via the optic nerve and results in a visual image. When the eye’s dimensions are not aligned, the light rays are not correctly focused. This results in a refractive error such as nearsightedness, farsightedness or astigmatism (an irregular curvature of the cornea). Refractive errors are very widespread and affect people of all ages.

The Auckland Eye doctors explain the workings of the eye

The conjunctiva is the thin, moist, clear membrane that covers the sclera, the white part of the eye. It is the skin that lines the eye socket and protects and lubricates the eyeball.

The crystalline lens is the transparent structure inside of the eye located directly behind your iris. The sole function of your lens is to focus light rays onto the retina.

The vitreous is a clear jelly-like substance that fills the center of the eye. It is composed mainly of water and comprises about 2/3 of the eye’s volume. The vitreous helps the eye maintain a round shape and is attached to the retina at various points including the macula and the optic nerve.

The zonules are a series of fine fibers that connect the crystalline lens to the ciliary body. The function of your zonules is to hold the lens in place in the eye.

This video describes the function and structure of tears, showing the location of the glands, describing the role of each of the three layers, as well as the purpose of the tear film, the eyelids, and the tear ducts.

The sclera is the white portion of your eye. Making up the back five-sixth’s of the eyes outer layer. The function of the sclera is to provide protection for your eye, and to serve as the attachment for the extra ocular muscles which move the eye.

The retina is the nerve layer that lines the back of your eye. The retina’s function is to sense light and create impulses that are sent through the optic nerve and to the brain.

The pupil is the dark center in the middle of the iris. The pupil’s function is to regulate how much light enters the eye. The pupil’s size is automatically varied to regulate the amount of light entering the eye.

Shows the structure of the optic nerve, and how light hitting the retina is transmitted to the brain.

Describes the location and role of the macula and fovea.

The iris is the colored portion of your eye. Located behind the cornea, and in front of the crystalline lens. This structure separates the anterior and posterior chambers of the eye. The function of the iris is to help regulate the amount of light that enters your eye.

The cornea is the clear front window representing one-sixth of the outer layer of your eye. The primary function of the cornea is to focus and transmit light onto the retina.

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The choroid is the spongy middle layer of your eye located between the sclera and the retina. Filled with blood vessels, the choroid’s function is to nourish the outer layers of the retina.

The ciliary body is located behind your iris, near the crystalline lens. This structure has two functions. The aqueous fluid that fills the front of your eye is made inside the ciliary body. Also, the ciliary body is made up of muscles that allow the eye to focus at different distances.

This video displays the Optic Nerve Cross Section – Light Focus

This video displays the visual pathway.