When surveyed about the five senses — sight, hearing, taste, smell and touch — people consistently report that their eyesight is the mode of perception they value (and fear losing) most.
Despite this, many people don't have a good understanding of the anatomy of the eye, how vision works, and health problems that can affect the eye.
Structure of eye:
Anterior chamber:
The region of the eye between the cornea and the lens that contains aqueous humor.
The region of the eye between the cornea and the lens that contains aqueous humor.
Aqueous humor:
The fluid produced in the eye.
Bruch's membrane:
Located in the retina between the choroid and the retinal pigmented epithelium (RPE) layer; provides support to the retina and functions as the 'basement' membrane of the RPE layer.
The fluid produced in the eye.
Bruch's membrane:
Located in the retina between the choroid and the retinal pigmented epithelium (RPE) layer; provides support to the retina and functions as the 'basement' membrane of the RPE layer.
Ciliary body:
Part of the eye, above the lens, that produces the aqueous humor.
Part of the eye, above the lens, that produces the aqueous humor.
Choroid:
Layer of the eye behind the retina, contains blood vessels that nourish the retina.
Layer of the eye behind the retina, contains blood vessels that nourish the retina.
Cones:
The photoreceptor nerve cells present in the macula and concentrated in the fovea (the very center of the macula); enable people to see fine detail and color.
The photoreceptor nerve cells present in the macula and concentrated in the fovea (the very center of the macula); enable people to see fine detail and color.
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 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.
Drusen:
Deposits of yellowish extra cellular waste products that accumulate within and beneath the retinal pigmented epithelium (RPE) layer.
Deposits of yellowish extra cellular waste products that accumulate within and beneath the retinal pigmented epithelium (RPE) layer.
Fovea:
The pit or depression at the center of the macula that provides the greatest visual acuity.
The pit or depression at the center of the macula that provides the greatest visual acuity.
Iris:
The colored ring of tissue behind the cornea that regulates the amount of light entering the eye by adjusting the size of the pupil.
The colored ring of tissue behind the cornea that regulates the amount of light entering the eye by adjusting the size of the pupil.
Lens:
The transparent structure suspended behind the iris that helps to focus light on the retina; it primarly provides a fine-tuning adjustment to the primary focusing structure of the eye, which is the cornea.
The transparent structure suspended behind the iris that helps to focus light on the retina; it primarly provides a fine-tuning adjustment to the primary focusing structure of the eye, which is the cornea.
Macula:
The portion of the eye at the center of the retina that processes sharp, clear straight-ahead vision.
The portion of the eye at the center of the retina that processes sharp, clear straight-ahead vision.
Optic nerve:
The bundle of nerve fibers at the back of the eye that carry visual messages from the retina to the brain.
The bundle of nerve fibers at the back of the eye that carry visual messages from the retina to the brain.
Photoreceptors:
The light sensing nerve cells (rods and cones) located in the retina.
The light sensing nerve cells (rods and cones) located in the retina.
Pupil:
The adjustable opening at the center of the iris through which light enters the eye.
The adjustable opening at the center of the iris through which light enters the eye.
Retina:
The light sensitive layer of tissue that lines the back of the eye.
The light sensitive layer of tissue that lines the back of the eye.
Retinal Pigmented Epithelium (RPE):
A layer of cells that protects and nourishes the retina, removes waste products, prevents new blood vessel growth into the retinal layer and absorbs light not absorbed by the photoreceptor cells; these actions prevent the scattering of the light and enhance clarity of vision.
A layer of cells that protects and nourishes the retina, removes waste products, prevents new blood vessel growth into the retinal layer and absorbs light not absorbed by the photoreceptor cells; these actions prevent the scattering of the light and enhance clarity of vision.
Rods:
Photoreceptor nerve cells in the eyes that are sensitive to low light levels and are present in the retina, but outside the macula.
Photoreceptor nerve cells in the eyes that are sensitive to low light levels and are present in the retina, but outside the macula.
Sclera:
The tough outer coat that protects the entire eyeball.
The tough outer coat that protects the entire eyeball.
Trabecular meshwork:
Spongy tissue located near the cornea through which aqueous humor flows out of the eye.
Spongy tissue located near the cornea through which aqueous humor flows out of the eye.
Vitreous:
Clear jelly-like substance that fills the eye from the lens to the back of the eye.
Clear jelly-like substance that fills the eye from the lens to the back of the eye.
How The Eye Works
- Light is focused primarily by the cornea — the clear front surface of the eye, which acts like a camera lens.
- 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).
- The eye's crystalline lens is located directly behind the pupil and further focuses light. Through a process called accommodation, this lens helps the eye automatically focus on near and approaching objects, like an autofocus camera lens.
- Light focused by the cornea and crystalline lens (and limited by the iris and pupil) then reaches the retina — the light-sensitive inner lining of the back of the eye. The retina acts like an electronic image sensor of a digital camera, converting optical images into electronic signals. The optic nerve then transmits these signals to the visual cortex — the part of the brain that controls our sense of sight.
- In a number of ways, the human eye works much like a digital camera:
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