eyeball![click to hear](/images/speaker.jpg)
Enclosed in a bony cavity (orbit) and moved by six muscles, this complex organ collects light signals and transmits them to the brain to form images.
sclera ![click to hear](/images/speaker.jpg)
Strong fibrous opaque membrane covered by the conjunctiva; it surrounds the eyeball and protects the inner structures.
superior rectus muscle ![click to hear](/images/speaker.jpg)
Muscle allowing the eyeball to move upward.
fovea ![click to hear](/images/speaker.jpg)
Central depression of the yellow spot composed entirely of cones; the place where visual acuity is at its maximum.
lens ![click to hear](/images/speaker.jpg)
Transparent elastic area of the eye; focuses images on the retina to obtain clear vision.
choroid ![click to hear](/images/speaker.jpg)
Richly veined membrane located between the sclera and the retina, to which it carries nutrients and oxygen.
retina ![click to hear](/images/speaker.jpg)
Inner membrane at the back of the eye covered in light-sensitive nerve cells (photoreceptors); these transform light into an electrical impulse that is carried to the optic nerve.
macula ![click to hear](/images/speaker.jpg)
Area of the retina where the cones are concentrated; it plays an essential role in day vision and the perception of colors.
optic nerve ![click to hear](/images/speaker.jpg)
Nerve formed by the juncture of the nerve fibers of the retina; it carries visual information to the brain, where it is interpreted.
papilla ![click to hear](/images/speaker.jpg)
Protuberance formed by the anterior terminal part of the optic nerve in the retina; it has no light-sensitive cells and thus no vision. It is also called the blind spot.
vitreous body ![click to hear](/images/speaker.jpg)
Transparent gelatinous mass (almost 90% of the eye); it maintains constant intraocular pressure so the eye keeps its shape.
inferior rectus muscle ![click to hear](/images/speaker.jpg)
Muscle allowing the eyeball to move downward.
ciliary body ![click to hear](/images/speaker.jpg)
Muscle tissue secreting the aqueous humor; its muscles enable the lens to change shape to adapt vision for near or far.
suspensory ligament ![click to hear](/images/speaker.jpg)
Fibrous tissue connecting the ciliary body to the lens, holding it in place inside the eyeball.
iris ![click to hear](/images/speaker.jpg)
Colored central portion of the eyeball composed of muscles whose dilation or contraction controls the opening of the pupil.
conjunctiva ![click to hear](/images/speaker.jpg)
Fine transparent mucous covering the sclera and inner surface of the eyelid; it facilitates sliding thus giving the eyeball its wide range of movement.
aqueous humor ![click to hear](/images/speaker.jpg)
Transparent liquid contained in the anterior and posterior chambers; it nourishes the iris and maintains the pressure and shape of the eye.
pupil ![click to hear](/images/speaker.jpg)
Central orifice of the eye whose opening varies to regulate the amount of light entering the eye; light causes the pupil to contract.
cornea ![click to hear](/images/speaker.jpg)
Transparent fibrous membrane extending the sclera and whose curved shape makes light rays converge toward the inside of the eye.
anterior chamber ![click to hear](/images/speaker.jpg)
Cavity of the eye between the cornea and the iris containing the aqueous humor.
posterior chamber ![click to hear](/images/speaker.jpg)
Cavity of the eye between the iris and the lens containing the aqueous humor.