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Chapter 17
Sense Organs (Eyes)
Question | Answer |
---|---|
accommodation | Normal adjustment of the eye to focus on objects from far to near. The ciliary body adjusts the lens (rounding it) and the pupil constricts. When the eye focuses from near to far, the ciliary body flattens the lens and the pupil dilates. |
anterior chamber | Area behind the cornea and in front of the lens and iris. It contains aqueous humor. |
aqueous humor | Fluid produced by the ciliary body and found in the anterior chamber. A humor (Latin humidus means moist) is any body fluid, including blood and lymph |
biconvex | Consisting of two surfaces that are rounded, elevated, and curved evenly, like part of a sphere. The lens of the eye is a biconvex body |
choroid | Middle, vascular layer of the eye, between the retina and the sclera |
ciliary body | Structure surrounding the lens that connects the choroid and iris. It contains ciliary muscles, which control the shape of the lens, and it secretes aqueous humor. |
cone | Photoreceptor cell in the retina that transforms light energy into a nerve impulse. Cones are responsible for color and central vision |
conjunctiva | Delicate membrane lining the undersurface of the eyelids and covering the anterior eyeball |
cornea | Fibrous transparent layer of clear tissue that extends over the anterior portion of the eyeball. Derived from Latin corneus, meaning horny, perhaps because as it protrudes outward, it was thought to resemble a horn. |
fovea centralis | Tiny pit or depression in the retina that is the region of clearest vision |
fundus of the eye | Posterior, inner part of the eye |
iris | Pigmented (colored) layer that opens and closes to allow more or less light into the eye. The central opening of the iris is the pupil |
lens | Transparent, biconvex body behind the pupil of the eye. It bends (refracts) light rays to bring them into focus on the retina. |
macula | Yellowish region on the retina lateral to and slightly below the optic disc; contains the fovea centralis, which is the area of clearest vision |
optic chiasm | Point at which optic nerve fibers cross in the brain (chiasm means crossing). |
optic disc | Region at the back of the eye where the optic nerve meets the retina. It is the blind spot of the eye because it contains only nerve fibers, no rods or cones, and is thus insensitive to light. |
optic nerve | Cranial nerve carrying impulses from the retina to the brain (cerebral cortex). |
pupil | Central opening of the eye, surrounded by the iris, through which light rays pass. It appears dark. |
refraction | Bending of light rays by the cornea, lens, and fluids of the eye to bring the rays into focus on the retina. Refract means to break (-fract) back (re-). |
retina | Light-sensitive nerve cell layer of the eye containing photoreceptor cells (rods and cones). |
rod | Photoreceptor cell of the retina essential for vision in dim light and for peripheral vision |
sclera | Tough, white outer coat of the eyeball. |
thalamus | Relay center of the brain. Optic nerve fibers pass through the thalamus on their way to the cerebral cortex. |
vitreous humor | Soft, jelly-like material behind the lens in the vitreous chamber; helps maintain the shape of the eyeball |
aque/o | water |
blephar/o | eyelid |
conjunctiv/o | conjunctiva |
cor/o | pupil |
corne/o | cornea |
cycl/o | ciliary body or muscle of the eye |
dacry/o | tears, tear duct |
ir/o, irid/o | iris (colored portion of the eye around the pupil) |
kerat/o | cornea |
lacrim/o | tears |
ocul/o | eye |
ophthalm/o | eye |
opt/o, optic/o | eye, vision |
palpebr/o | eyelid |
papill/o | optic disc; nipple-like |
phac/o, phak/o | lens of the eye |
pupill/o | pupil |
retin/o | retina |
scler/o | sclera (white of the eye); hard |
uve/o | uvea; vascular layer of the eye (iris, ciliary body, and choroid) |
vitre/o | glassy |
ambly/o | dull, dim |
dipl/o | double |
glauc/o | grey |
mi/o | smaller, less |
mydr/o | widen, enlarge |
nyct/o | night |
phot/o | light |
presby/o | old age |
scot/o | darkness |
xer/o | dry |
-opia | vision |
-opsia | vision |
-tropia | to turn |
astigmatism | Defective curvature of the cornea or lens of the eye |
hyperopia (hypermetropia) | Farsightedness. |
myopia | Nearsightedness. |
presbyopia | Impairment of vision as a result of old age. |
miotic | a drug that contracts the pupil of the eye. |
cataract | clouding of the lens, causing decreased vision |
chalazion | Small, hard, cystic mass (granuloma) on the eyelid. |
diabetic retinopathy | Retinal effects of diabetes mellitus include microaneurysms, hemorrhages, dilation of retinal veins, and neovascularization (new blood vessels form in the retina). |
glaucoma | Increased intraocular pressure results in damage to the retina and optic nerve with loss of vision. |
Blepharitis | Inflammation of eyelid, causing redness, crusting, and swelling along lid margins |
Ptosis | Drooping of upper lid margin as a result of neuromuscular problems or trauma |
macular degeneration | Progressive damage to the macula of the retina. |
nystagmus | Repetitive rhythmic movements of one or both eyes. |
retinal detachment | Two layers of the retina separate from each other. |
strabismus | Abnormal deviation of the eye. |
fluorescein angiography | Intravenous injection of fluorescein (a dye) followed by serial photographs of the retina through dilated pupils. |
ophthalmoscopy | Visual examination of the interior of the eye. |
slit lamp microscopy | Examination of anterior ocular structures under microscopic magnification. |
visual acuity test | Clarity of vision is assessed |
visual field test | Measurement of the area (peripheral and central) within which objects are seen when the eyes are fixed, looking straight ahead without movement of the head |
keratoplasty | Surgical repair of the cornea. |
LASIK | Use of an excimer laser to correct errors of refraction (myopia, hyperopia, and astigmatism). |
scleral buckle | Suture of a silicone band to the sclera over a detached portion of the retina. |
vitrectomy | Removal of the vitreous humor. |
VF | visual field |