Eye Intro Flashcards
What is refraction?
the bending of light; images are brought to a focus on the retina by the structures of the eye
What structures refract light to form images?
#1 cornea #2 lens: fine tunes
What happens with refraction in old age?
cilliary m stops working, lens can’t accommodate
what measures refractive power?
diopters= inverse of the lens focal length in meters; positive magnify (convex) and negative minify (concave)
ex. 1 diopter is a lens with a 1 m focal length
3 diopters is a lens with a 1/3 m focal length
how to spectacles with a + diopter affect eye?
shorten the eyes focal length to account for a shorter eyeball (hyperopia)
how to spectacles with a - diopter affect the eye?
lengthen the focal length to account of a longer eyeball (myopia)
what is myopia? how do you treat it?
nearsightedness: objects up close seen clearly, objects far away are blurry. Treat with a concave lens: have - diopter to lengthen focal length to account for a longer eyeball
What is the problem with myopia?
eye ball is too long or too curved; light is refracted to make a image before it reaches the retina
What is problem with hyperoria?
Fat lens; increased focal length creates picture behind fovea
how do hyperopic and myopic lenses compare?
hyperopic: short and fat
myopic: long and skinny
how does a concave lens work?
diverges light to extend its focal length
List motor control of eye.
oculomotor, abducens, and trochlear nerves
what is included in autonomic motor control of the eye? how does it effect the eye?
ciliary ganglion; causes ciliary body to squeeze the lens (increasing diopters.. decreasing focal length) and constricts pupil
what is the near reaction?
pupillary constriction when you focus on a near object (ciliary ganglion)
when the eye is relaxed what distance is it best for viewing? near or far?
far; the muscles contract to accommodate for near vision
how do anticholinergics effect the eye?
inhibit pupillary constriction; inhibit lacrimation
how does clouding of the aqueous, vitreous, and lens affect light passage through the eye?
normally it is clear for accurate light passage; clouding results in poor vision, this cannot be corrected with lenses
why do you test with glasses for best corrected vision?
because eye is cloudy and lenses won’t help fix it
what happens with DM when sugar is high? will the pinhole test correct it?
???
How is the retina structured?
inside out; neural layers superficial to photoreceptors
Can people have visual field defects and not realize it?
yes, the brain interpolates data to compensate for blind spots
what is the pathway for circulation of aqueous humor?
- ciliary body
- posterior chamber
- anterior chamber
- trabecular meshwork
- canal of schlemn
what makes aqueous fluid?
ciliary body
what is the Vitreous?
Clear jelly-like substance that fills the eye from the lens to the back of the eye.
what is the difference between open and closed angle glaucoma?
Open: chronic, more common, canal of schlemm clogged
closed: acute, pressure forces angle/canal opening shut so no reabsorption is possible
what is EOM (extra ocular muscle) testing used for?
to reveal cranial nerve dysfunction or peripheral problems with musculature (ex. entrapment)
what is the normal cup to disk ratio?
1:2
where is the neuroretinal rim?
between cup and disk borders
what is the sclera ring?
border of optic disk
Congested optic nerve head, protruding anteriorly towards interior of eye, with blurred margins, and poorly seen vessels is signs of?
chronic papilledema; caused by increased IOP
what is AV nicking?
arteriovenous nicking is when a small artery crosse a vein putting pressure on it, causing it to swell on either side of crossing
layers of visual reception from ganglion cell later to migrant membrane?
- axons of rentinal ganglion cells
- ganglion cell layer
- bipolar cell layer
- layers of rods and cones
- pigment epithelium
- pigment membrane
what vision is lost with a optic nerve lesion in right eye?
right eye vision
what vision is lost in chiasmatic lesion?
temporal vision (bitemporal hemianopsia)
what vision is lost in left eye optic tract lesion?
nasal vision in left eye; temporal vision right eye
where would the deficit be for posterior chiasmatic lesion?
contralateral vision loss; (contralateral homonymous hemianopia)
where would the deficit be for anterior chiasmatic lesion?
entire vision loss in one eye
where would the deficit be for visual cortex lesion?
homonymous contralateral hemianopia
where would the deficit be for lateral geniculate lesion?
Two layers: parvocellular and magnocellular.
Lesions of parvocellular layers disrupt the processing of color and fine detail.
Lesions of the magnocellular layers disrupt the detection of fast moving stimuli.
where would the deficit be for chiasmatic lesion?
ipsilateral temporal vision loss
what does the lateral giniculate do?
relays info to primary visual cortex via optic radiation
where would the deficit be for optic radiation?
homonymous contralateral hemianopia
