Orbit seven bones that make up the cavity that the eye sits inside. The eye itself takes
up about 1/5 of the orbit. Rest is fat, connective tissue, muscles, nerves and blood
vessels
Lids play a vital role in protection of the eye. Protects the eye from light, dirt, and
bumps. Function via reflex. Secrets oil for lubrication and prevention of tear evaporation.
Opening and closing facilitates the flow of tears across the eye.
Conjunctiva – a mucous membrane that lines the eyelid and covers the front part of the
eye
Cornea - The clear front window of the eye which transmits and focuses (i.e., sharpness
or clarity) light into the eye. Corneas do about 90% of the light bending to focus images
on the retina of the eye. It is very tough and transparent and protects the eye from
puncture and germs. Corrective laser surgery reshapes the cornea, changing the focus.
Iris - The colored part of the eye which helps regulate the amount of light entering the
eye. When there is bright light, the iris closes the pupil to let in less light. And when there
is low light, the iris opens up the pupil to let in more light. It helps sharpen focus and
allows nourishment from the vitreous to nourish the cornea
Pupil - The dark center opening in the middle of the iris. The pupil changes size to adjust
for the amount of light available (smaller for bright light and larger for low light). This
opening and closing of light into the eye is much like the aperture in most 35 mm
cameras which lets in more or less light depending upon the conditions. It is really an
absence of structure rather than a structure.
Lens - Focuses light rays onto the retina. Does about 10% of the focusing of the eye at
distances beyond 10 feet. It alters shape to provide focus from distance at the tip of the
nose to about 10 feet (accommodation) The lens is transparent, and can be replaced if
necessary. Our lens deteriorates as we age, resulting in the need for reading glasses.
Intraocular lenses are used to replace lenses clouded by cataracts. The lens actually flips
the image upside-down. The brain later rights the image and aligns the image from each
eye.
Cilliary Body – Controls the shape of the lens and produces aqueous – a fluid that fills
the space behind the Cornea and bathes the lens. Controls eye pressure
Vitreous Humor – The mass of clear, gelatinous substance filling the central cavity. This
gives the eye its shape.
Retina - The nerve layer lining the back of the eye. It covers the back 2/3 of the eye.
This is what gives us our wide field of view. The retina senses light using rods and cones.
Cones are for color vision and sharpness (acuity). Rods do night vision and low light.
There are many more rods than cones. The retina perceives the light and changes it into
electrical impulses that are sent through the optic nerve to the brain.
Fovea - The center of the macula which provides the sharp vision. This is where the
cones are primarily located.
Macula - The area in the retina that contains special light-sensitive cells. In the macula
these light-sensitive cells allow us to see fine details clearly in the center of our visual
field. The deterioration of the macula is a common condition as we get older (age related
macular degeneration or ARMD).
Choroid - Layer of blood vessels between the retina and the sclera. This is a thin a
spongy layer where the retina gets it food and nourishment.
Optic Nerve - A bundle of more than a million nerve fibers carrying visual messages
from the retina to the brain. (In order to see, we must have light and our eyes must be
connected to the brain.) Your brain actually controls what you see, since it combines
images. The retina sees images upside down but the brain turns images right side up.
Glaucoma is one of the most common eye conditions related to optic nerve damage. The
area that the optic nerve and retinal blood vessels enters is called the optic disc. This is
an area where there is no vision (blindspot)
Sclera - The white outer coat of the eye, surrounding the iris. It is the tough outer wall
of the eye. This along with the cornea forms the external coat of the eye