refraction and accomodation Flashcards
what is refraction
the bending of light
what are the 2 main sturctres that are involved in refraction
lens and cornea
which of the lens or the cornea is more powerful
cornea
whihc of the lens or cornea can change diameter
lens
at waht disttance doe shtan object need to be far enough away for the light rays coming of it to be parrell
6m
how does the corena and lens make the light go to the retian
they bend it
what happens to the picutre as it lands on the retian compared to when it entered the eye
it is flipped 180 degrees due to refraction
how does the lens thickenss change as it you read something closer
it gests thicker, congering the light more
what is accomoation
change of foucos on diatnant obects
what are 3 ways the eyes accomodate light rays
lens changes shape
pupils constrict
eyes converge
how does the cilary body cuase the lens to relax and become thicker
it contracts, and the ligaens aroun it luose, tus making it thicker
is capillary body contracting sympatheic or parasympahtic
parasympathiec
what hapens to the pupil to look at an object uplcose
it consticits
msucle whihc cuase puoli to constrict
pupilary constior/ spictor pupillae
what type of innervation is consticitor pupillae
parasympethic
what mucles are used of eye converion
medial rectus
what type of inervvation for medial rectus
3 cn - parasympethic
what is myopia
short sitedness
what is hyperopia
long sitedness
what is astigmatism
where the eye is not perficly spherical
what is presbyopia
long sited ness with old age
what is emmetrope
perfected sitedness
what happens in myopia in regards to light ways
the rays land in front of the retina,
cuase of myopia
eyeball too long , beinging power of the corna and lens is too powerful
what are the common symptoms of myopia
heachaes, not being able to see disatn objects
in totlder, loss of interested in sports and more interest in books
may see diverergntes squint in one eye, where the lateral aspect of the syes is used
what type of lens is used to correct myopia
bi concave
what happens to the light rays in hyperopia
they converge past the retina
cuase of hyperopia
the eye ball is too flat/ eyeball to shrot
what type of lens for hyperorpia
biconvex
what are the sympotns of hyperopia
eyestrain after reading/ using computre
convergent squins in children
what is the cuase of astimagnatism
one side of the lens being different to the other lens causing different being of ligh
what type of glases are used to treat astigmatis
cylindrical glasses
what type of contanct lens are use for astigmattism
toric lensse
what happens to the image in astigmat as it hane siwth diace
it does not change - it is still blury
what is the cuase of presbyopia
age makes the eye less mobile and eyeastic
thus cilary musle not cable to pulling it as much
when does presbypia normally occur
5th decade of liife
what type of lens is used for presboypia
biconvex
what is bc
base curgvature of a glass
what is dia
diameter of glases
what is cyl
the amount of cylinger a glasses has, ie how much it fixes astigmatism
what is axis
shows where the astimagis lies, and at what degree
