Chapter 17 - sense organs; eye and ear

eye pathway

stimulus to receptors in ear/eye, excite nerve fibers, impulses to brain = translated into sound sensations/visual images

eye parts

• pupil

• conjunctiva

• cornea

• sclera

• choroid

• iris

• ciliary body

• lens

• fundus

• anterior chamber

• aqueous humor

• vitreous chamber

• vitreous humor

• retina

• optic nerve

• optic disc

• macula

• fovea centralis

visual pathway

visual field sends stimulus = concentrate in macula, optic chiasm: half cross to contralateral → nerve affected changes visual deficit

accommodation

normal adjustment of eye to focus on objects far to near

anterior chamber

area behind cornea, in front of lens and iris

aqueous humor

fluid produced by ciliary body and found in anterior chamber

biconvex

two surfaces rounded/elevated, curved evenly, lens = biconvex

choroid

middle, vascular layer of eye, between retina and sclera

ciliary body

structure surrounding lens, connects choroid and iris, controls shape of lens and secretes aqueous humor

cone

photoreceptor cell in retina that transforms light energy into nerve impulse, responsible for color and central vision

conjunctiva

delicate membrane that lines undersurface of eyelids and covers anterior eyeball

cornea

fibrous transparent layer of clear tissue extends over anterior eye

fovea centralus

tiny depression in retina, clearest vision

fundus of eye

posterior, inner part of eye

iris

pigmented layer, open/close allow more/less light into

lens

transparent, biconvex body behind pupil of eye

macula

yellowish region on retina lateral/slightly below optic disc

optic chiasm

optic nerve fibers cross in brain

optic disc

region in back of eye, optic nerves meet retina, blind spot

optic nerve

cranial nerve, carry impulse from retina to brain

pupil

central opening of the eye, surrounded by iris, light rays pass

refraction

bending light rays by cornea, lens, fluids in eye, focus rays on retina

rod

photoreceptor cell or retina, vision in dim light and peripheral vision

sclera

tough, white outer coat of eye

thalamus

relay center of brain

vitreous humor

soft, jelly material behind lens, in vitreous chamber

aque/o

water

blephar/o

eyelid

conjunctiv/o

conjunctiva

cor/o

pupil

corne/o

cornea

cycl/o

ciliary body

dacry/o

tears, tear duct

ir/o

iris

irid/o

iris

kerat/o

cornea

lacrim/o

tears

ocul/o

eye

opthalm/o

eye

opt/o

eye, vision

optic/o

eye, vision

palpebr/o

eyelid

papill/o

optic disc

phac/o

lens of eye

phak/o

lens of eye

pupill/o

pupil

retin/o

retina

scler/o

sclera

uve/o

uvea

vitre/o

glassy

ambly/o

dull, dim

dipl/o

double

glauc/o

gray

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

turn

astigmatism

inability of eye to produce focused image on fovea or central retina

• cornea is steeper in one meridian/globe not round = doesn’t focus in macula

hyperopia/hypermetropia

farsightedness

• eyeball short, refractive too weak

• light focuses behind retina

  • see far, close = blurry

myopia

nearsightedness

• eyeball long, refractive too strong

• light rays focused in front of retina

  • my = shut → squint

presbyopia

vision impairment with age

• focusing power depends on elasticity of lens, decreases with age

  • slow decrease in ability to focus on objects close

• 45 = hold readings further away

  • natural part of aging, affects everyone

blepharitis

inflammation of eyelid - crusting, flaking, erythema of lid margins

• treat = baby shampoo - doesn’t irritate

  • usually doesn’t need ABX

cataract

opacity of lens - bilateral

• most curable of blindness

• opaque central area of lens; nuclear cataract - lens cloudy = altered image

  • posterior part of lens = posterior subcapsular cataract

  • senile cataract: aging, most common

  • frequent change of eyeglasses, visual loss, painless, blurred visions, glare, myopia, lens opacity

chalazion

painless, slowly enlarging nodule on eyelid, inflammation of meibomian glands (deep chalazion), zeis sebaceous glands (superficial)

• not usually infection

diabetic retinopathy

pathological changes of retina from system disease: microvascular change - inability to receive stimuli → patchy vision loss

• diabetes = change retinal vessels → weak/leak, microaneurysms/neovascularization, hemorrhage, retinal deposits, edema

  • manage: control blood glucose, yearly eye exam, laser photocoagulation: zap neurovascular/leaky vessels to help vision

glaucoma

increased IO pressure → optic nerve damage = impaired vision to blindness

• diagnosed with tonometry: measure IO pressure

  • (acute) open-angle glaucoma: most common, progressive/slow increase of pressure, optic atrophy, loss of vision: peripheral→ complete, painless, early asymptomatic, treat with meds and trabeculoplasty (laser therapy)

hordeolum

stye

• localized infection/inflammation of eyelid margin from hair follicle or meibomian glands

• staph aureus

  • painful

ptsosis

drooping of upper lid, neuromuscular/trauma

retinal detachment

separation between pigmented and sensory of retina

• >50

• superior temporal area

• from trauma or spontaneous

• curtain over eye, blurred vision, flashes (photopsia) and floaters (entopsia) - black squiggles

• immedient ophthalmologic referral - emergency

macular degeneration

progressive damage to macula of retina

• dry: atrophy and degeneration, clumps of extracellular debris- drusen, most common

• wet: neovascularization and leaky blood vessels

• leading cause of irreversible, severe visual loss in >65

  • loss of central visions, slow progression - treat

nystagmus

repetitive rhythmic movements of one/both eyes

• vertical or horizontal

  • from brain tumor, inner ear problems, normal in newborns

strabismus

abnormal deviation of eye from muscle weakness

• inward: esotropia

• outward: exotropia

• upward: hypertropia

• downward: hypotropia - squint

  • manage: corrective lenses (force eye to central), occlusion of good eye to develop macular vision in affected eye, early surgery in 2-24 months for function cure

xanthelasma

raised yellowish plaque on eyelid, lipid disorder

opthalmoscopy

examination of back of eyeball (fundus) - retina, optic disc, choroid, blood vessels

• use ophthalmoscope

enucleation

surgical removal of eye from orbit

• treat tumors, if eye has become blind/painful from disease/trauma

LASIK

Laser-Assisted in Situ Keratomileusis (shaping of the cornea) - permanently changes shape of cornea using excimer laser

• microkeratome (knife) - cuts flap in cornea - leave hinge at one end, flap folded back to reveal stroma (middle of cornea) - pulses from computer-controlled laser vaporize portion of stroma and slap replaced

ear

• outer ear; receives sound waves

• sound waves travel to middle ear

  • vibrations reach inner ear - labyrinth

outer ear

pinna/auricle: projecting flap

external auditory meatus - auditory canal

middle ear

tympanic membrane (eardrum), malleus, incus, stapes, oval window, eustachian tube

inner ear

labyrinth - cochlea, auditory nerve fibers

balance and equillibrium

vestibule, semicircular canals

auditory canal

channel leads from pinna to eardrum

auditory meatus

auditory canal

auditory nerve fibers

carry impulses from inner ear to brain

auditory tube

channel between middle ear and nasopharynx: eustachian tube

auricle

flap of ear, protruding part of external ear - pinna

cerumen

waxy substance secreted by external ear - earwax

cochlea

snail-shaped, spirally wound tube in inner ear

endolymph

fluid in labyrinth of inner ear

eustachian tube

auditory tube

incus

second ossicle, middle ear

labyrinth

maze-like series of canals of inner ear

malleus

first ossicle, middle ear

organ of Corti

sensitive auditory receptor area in cochlea and inner ear