Refraction

Question 1

anomaly of the refractive state of the eye in which, with accommodation relaxed, the image of objects at infinity is not formed on the retina and is therefore blurred

Answer 1

ametropia

Question 2

image focuses in front of the retina

Answer 2

myopia

Question 3

image focuses behind the retina (when accommodation is relaxed)

Answer 3

hyperopia

Question 4

the point is focused as 2 lines resulting in a blurred and distored image; line foci may be in front of, behind or on the retina in part

Answer 4

astigmatism

Question 5

normal decrease in amp of accommodation that occurs with age restulting in the need for plus over the distance RX to see clearly at near

Answer 5

presbyopia

Question 6

a difference in has and needs, the eye has….

Answer 6

ametropia

Question 7

the ___ eye has an axial length and refractive power that focuses parallel light onto the retina when the pt is NOT accommodating (and looking at dist)

Answer 7

emmetropic eye

Question 8

the axial length of the eye is too long or too short for the power of the eye resulting in a refractive error, known as….

Answer 8

ametropia or discrepancy

Question 9

if has > needs, the discrepancy is …… and the rx needed is …..
person is …..

Answer 9

person is myope

Question 10

if the has < needs, the discrepancy is ____ and the rx is _______
person is ….

Answer 10

-
+
person is hyperope

Question 11

how are the rx and discrepancy related

Answer 11

equal and opposite in power

Question 12

where is the focus in a myope

Answer 12

in front of the retina

Question 13

where is the focus in a hyperope

Answer 13

behind the retina

Question 14

ametropia is also called… (2 things)

Answer 14

refractive error

discrepancy

Question 15

the perfect eye model only takes into consideration the ________ and not the _____ and ______

Answer 15

difference or discrepancy

• axial lengh
• refractive power

Question 16

the discrepancy lens is ______ NOT _____ or _______

Answer 16

CONCEPTUAL

NOT BIOLOGICAL OR PHYSICAL!!!!!!!!!!!

Question 17

what is on the retina coming from a point source of light

Answer 17

blur circle

Question 18

the distance between the retina and the actual point of focus

Answer 18

dioptric blur

Question 19

quantitatively, the amount of diopters necessary to reduce to zero the dioptric distance btwn the retina and point of focus

Answer 19

dioptric blur

Question 20

reduces the size of the blur circle w/o changing the dioptric blur

Answer 20

pin-hole

Question 21

pinhole reduces the ______ of the blur circle w/o changing the ________

Answer 21

diameter

dioptric blur

Question 22

in a good refraction, you make the blur circle smaller by reducing the ______

Answer 22

dioptric blur

Question 23

in myopia, has _____ needs

• too much ___ power
• discrepency is _____ and corrected with a _____

Answer 23

greater
+
+, -

Question 24

what does a minus powered lens do to a ray of light

Answer 24

diverges rays of light

Question 25

what does a plus discrepency do to light on the myopic eye

Answer 25

converge light

Question 26

why can the myopic eye see near objects clearly

Answer 26

accommodation

Question 27

what are responsible for accommodation

Answer 27

ciliary body and crystalline lens

Question 28

accommodation only provides ______ never ____

Answer 28

plus | minus

Question 29

the maximum power of accommodation

Answer 29

amplitude of accommodation

Question 30

why does accommodation only provide plus?

Answer 30

because it allows the organism to neutralize rays coming from near objects which are always minus in sign, NEVER PLUS

Question 31

all real objects nearer than optical infinity have ______ rays and therefore a power of ______

Answer 31

diverging | minus

Question 32

ampliitude peaks at age ____ and declines _____ w/ age after that

Answer 32

14 | steadily

Question 33

what is hofstetter's formula for amplitude

Answer 33

amp = 15 - 1/4age

Question 34

insufficient amplitude of accommadation due to healthy aging

Answer 34

presbyopia

Question 35

summation principle blur: plus = _____ , minus = _______ retina lens/rx: minus for ____, plus for _____, plus for __ objects: real objects are ____, objects at infinity are _____, virtual objects are ______ accomodation: ALWAYS ___ or _____ discrepancy/refractive error: ___ for myope, ____ for hyperope

Answer 35

blur: plus = in front of retinal, minus = behind retina lens: minus for myope, plus for hyperope, plus for adds ojects: real objects are minus, objects at infinity are 0, virtual objects are plus accomodatoin: plus or 0 discrepancy: plus for myope, minus for hyperope

Question 36

what is the summation principle

Answer 36

B = L + O + A + D

Question 37

D = 100/ cm, D = 40/ in

Answer 37

cm= 100/D, inches = 40/D

Question 38

too much plus on purpose is...

Answer 38

fog

Question 39

why do we fog an eye?

Answer 39

to get the pt to relax his accommodation. pt can see best when accommodation is 0

Question 40

perfect eye with a minus discrepancy and needs an rx of plus power is...

Answer 40

hyperope

Question 41

parallel light focuses behind the retina when the pt doesnt accommodate is...

Answer 41

hyperope

Question 42

what is "myope's revenge"

Answer 42

1. discomfort during near activies (asthenopia) 2. earlier presbyopia 3. complete dependence on correction later in life

Question 43

what is discomfort during near activities

Answer 43

asthenopia

Question 44

the most distnat point the eye can see in focus. | -a point in space conjugate to the retina where accommodation is relaxed

Answer 44

the far point (punctum remotum)

Question 45

the area of defintion from the lower to the upper limits of a particular scale

Answer 45

range

Question 46

what is the range of clear vision. what can it be determined by..

Answer 46

``` from the (near point) punctum proximum to the punctum remotum (far point) cc, sc, or thorugh an add ```

Question 47

the closest point the eye can see clearly using maximum accommodation

Answer 47

near point

Question 48

what do you enter for accommodation if you are searching for the far point? what about the near point?

Answer 48

``` far = 0 near = amp ```

Question 49

if the meridians are of the maximum and minimum power, they are known as the

Answer 49

principal meridians

Question 50

what does axis of cylinder correspond to

Answer 50

principal meridian containing plano power

Question 51

what are the 2 lenses stuck together in a sphero cylindrical lens

Answer 51

simple sphere and plano cylinder

Question 52

the rx has a direct relationship to the _____ optical cross

Answer 52

component

Question 53

what does a plus sphere do to rays

Answer 53

focuses parallel rays to a point

Question 54

what does a minus sphere do to rays

Answer 54

diverges rays so they behave as if they came from the same point

Question 55

the lines and the blurry ellipses together form a solid "image" which is called....

Answer 55

conoid of sturm

Question 56

any lens containing cyl brings light from a point soure to a __________ rahter than to a _____

Answer 56

focal conoid of sturm | focal point

Question 57

if both arms of the optical cross have plus power and the incidnet rays are coming from infinity, the conoid will be a ....

Answer 57

real image in real space

Question 58

if both arms of the optical cross are minus in power and the incident rays are parallel, then all of the conoid will be a ....

Answer 58

virtual image

Question 59

the dioptric midpoint of the 2 line foci

Answer 59

circle of least confusion

Question 60

points that coincides with the circle of least confusion

Answer 60

sphero equivalent

Question 61

an eye with uncorrected ______ cant focus a point source of light to a point focus

Answer 61

astigmatism

Question 62

for an eye with astigmatism, its discrepancy lens is a ______ rather than a spherical lens

Answer 62

spero cyl lens

Question 63

a meridian forms an image of the line perpendicular to itself

Answer 63

rule of perpendiculars