Eye
About 4/5 of the eye is enclosed within the bony orbit
I. Basic Layers
A. Sclera – white of the eye
Outer fibrous protective layer; avascular; helps give shape to the eye; permits light to come in
1. Cornea (anterior portion of the sclera) – colored portion of the eye; most of the
focusing power; avascular
B. Choroid (middle layer) – highly vascular and supplies blood for the entire eye; opaque layer
(light cannot pass through) darkish brown in color
1. ciliary body – attaches by ligaments to the lens
2. lens – clear, flexible capsule behind the iris and pupil
3. Iris – pigmented muscle that surrounds the pupil; regulates the diameter of the pupil;
controls the amount of light coming into the eye
4. Pupil – circular opening in the center of the iris
C. Retina – nervous tissue of the eye that receives images; forms image
1. rods- reacts to light; black/white vision
2. cones – reacts to color and fine detail; color vision
II. Chambers of the eye
A. Aqueous (middle) – Tear layer
Contains the 3rd eyelid (nictitating membrane) for protection; helps maintain the shape of the
eye and supplies nutrients to the cornea and lens; waste removal
B. Vitreous chamber – soft, clean, jellylike mass
III. Vocabulary
1. Ophthalm , ocul,opt = eye
a. ophthalmoscope
b. ophthalmic
c. optic
d. intraocular
2. Lacrim, dacryl – tear
3. is – equal
a. aniso(unequal) coria – unequal pupil diameter
4. mi – small
a. miotic – pupil contraction
5. mydri – wide
a. mydriatic – pupil dilation
6. tropia – to turn
a. esotropia – crossed eye
b. Entropion – turning in of the eyelid
c. Ectropion – turning out of the eyelid
7. epiphora – excessive tearing
IV. Pathological Conditions
1. Glau coma – increased intraocular pressure; blue appearance to the eye
2. Cataract – opacity of the lens; caused by age, diabetes, scratch on the eye
3. Cherry eye – collapse of the 3rd eyelid; treatment usually is to tack the membrane under the
lid.
4. Enucleation – removal of the eye
5. Conjunctivitis - pinkeye
6. Distichiasis – 2 rows of eyelashes on one eyelid that rubs on the cornea
7. Progressive retinal atrophy –retina slowly degenerates and causes blindness
9. Keratoconjunctivitis (dry eye) – decrease production of the aqueous portion