Eye anatomy

eyelids

protect eyes anteriorly

medial and lateral canthus

corners of eyelids where they meet

eyelashes

project from eyelid border

tarsal glands

at eyelid edges; produces oily secretion (lubricates eye)

conjunctiva

delicate membrane lining eyelid; covers outer eyelid surface

lacrimal ducts

flush tears medially across eyeball

lacrimal glands

above lateral end of eye; releases tears to anterior eyeball via ducts

lacrimal sac and nasolacrimal duct

drain tears to nasal cavity

extrinsic eye muscles

attach to outer eye surface; perform gross eye movements

sclera

outer, protective, “white of eye”

cornea

central, anterior, clear portion; light enters eye here

vascular

middle

choroid

posterior, rich w/blood; contains pigment: prevents light from scattering in eye

ciliary body

lens attaches via ciliary zonule

iris

pigmented, round opening (pupil), regulates amount of light entering the eye

retina

innermost; contains photoreceptors (respond to light): rods and cones; send electrical signals to optic nerve and cortex for vision

optic disc

blind spot; site where optic nerve exits eyeball; no photoreceptors here

lens

flexible, biconcave, crystal-like structure; divides eye into segments

aqueous humor

anterior; clear, watery fluid: maintains eye pressure, provides nutrients to lens and cornea

vitreous humor

posterior; gel-like substance; reinforces eyeball internally

what dilates the pupil?

the iris

what do both humors do?

maintain pressure

what is the location of best vision?

macula

what changes how much light enters the eye?

iris

what changes the shape of the lens (focusing)?

the ciliary body

what contains vessels which supply blood?

the choroid

what contains cells that are sensitive to light (rods and cones)?

the retina

what focuses light to the back of the eye?

the lens

what is the white of the eye?

the sclera

what transmits visual information to the brain?

the optic nerve

what is the transparent layer at the front of the eye?

the cornea