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NCSORB Flashcards

1
Q

Rods number 125 million & are responsible for ____ vision.

A

Night vision, black & white, motion, peripheal

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2
Q

Cones number about 6 million & are responsible for ___ perception

A

Day vision, detail, visual acuity, color

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3
Q

When measuring a frame PD with a ruler you should measure from the inside temporal edge of one eyewire, across the bridge, to which part of the opposite eyewire?

A

inside nasal edge

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4
Q

Glacuoma is caused by an increase in ___ in the eye

A

pressure

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5
Q

What does OC stand for

A

optical center

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6
Q

The focal point for a minus lens occurs ___ of the lens

A

in front

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7
Q

A polarized lens cuts out vertical or horizontal light

A

horizontal

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8
Q

What is the thinnest an industrial safety lens should be

A

3 mm

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9
Q

a multifocal lens style that provides a slow increase of a plus power from the distance portion of the lens to the near zone is called

A

progressive

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10
Q

the crystalline lens has a focal power of approx _____ diopters

A

twenty

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11
Q

What are the six muscles which allow the eye to move in different directions?

A

Internal (medial) rectus- in to nose

External (lateral) rectus- out to ear

Inferior rectus- down and out

Superior rectus- up and in

Inferior oblique- up and out

Superior oblique- down and in

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12
Q

How do you calculate minimum blank size

A

double the decentration & add it to the ED of the frame, then add 2
MBS= ED + (2X Decentration) + 2

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13
Q

What size SV lens blank would be the smallest possible for the following frame
A=54 B=40 ED=56
distance decentration= 5mm
Rx -10.00 -1.00X180

A

68

10+56+2=68

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14
Q

What is the standard for measuring spectacle tolerances

A

ANSI Z80.1

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15
Q

What year was the Boxing System introduced and by whom?

A

1962

Optical Manufacturers Association

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16
Q 
which bifocal lens is not a once piece construction:
 A) plastic round 22
 B) flat top 28 glass
 C) progressive plastic
 D) glass executive
A

B

flat top 28 glass

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17
Q

what is the index of the cornea

A

1.37

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18
Q

-3.00 +2.00 x135

is called what

A

compound myopic astigmatism

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19
Q

where is the posterior chamber

A

directly behind the iris and in front of the crystalline lens

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20
Q

this lens is the least dense available
A) CR-39

B) glass

C) hi-index

D) poly

A

CR-39

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21
Q

a patient comments that his old glasses gave him much better visual acuity than the new pair. after examining the glasses you find that both pairs have the same Rx. What should you do?
A) send the patient back to the doctor

B) check base curve, face form and tilt

C) remake entire pair of glasses

D) place new lens in different frame

A

B

check base curve face form and tilt

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22
Q

What is the index of flint glass

A

1.65

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23
Q

How many layers are there in the retina

A

ten

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24
Q

-1.00 +3.00 x180

is called what

A

mixed astigmatism

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25
Q

A plus lens moved ___ creates base in prism

A

in

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26
Q

a lens clock can be used to check the:
A) center thickness of a lens

B) nominal surface power of a lens

C) refractive power of a lens

D) tempering of a lens

A

C

refractive power of the lens

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27
Q

if a +16.00 diopter lens is moved closer to the eye, what effect would this have on the effective power
A) less plus

B) more plus

C) prism is created

D) no change

A

a

less plus

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28
Q

a ___ lens moved in creates base out prism

A

minus

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29
Q

a patient is complaining of pressure on the nose and behind the ears with his frame, what two things do you need to adjust to correct the problem on a plastic frame?
A) temple bend

B) lens mounting chord

C) temple bend and bridge

D) temple bend, lens mounting chord & pantoscopic angle

A

C

temple bend and bridge

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30
Q

light rays passing through a plus lens actually ____

A

intersect/ converge

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31
Q

the limbus of the eye is adjacent to the

A

cornea

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32
Q

what does the “7” in “7X28” trifocal mean

A

height of the intermediate window

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33
Q

What do BU and BD stand for

A

base up & base down

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34
Q

What is the index of PMMA plastic (plexiglass)

A

1.49

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35
Q

a -475 spherical lens decentered 4mm produces

A

1.9 prism diopters

(prentice rule: -4.75 * .4= 1.9)

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36
Q

blockage of the canal of schlemm produces primarily what

A

glauoma

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37
Q

What is the Canal of Schlemm

A

the canal that drains the aqueous humor from the anterior chamber of the eye and drains into the venous system (blood)

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38
Q

what is the number of major (external) muscles that control eye movement

A

six

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39
Q

what is the index of poly

A

1.59

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40
Q

where is the sclera located

A

front portion, or “white” of the eye

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41
Q

what is the area between the iris/pupil and the cornea called

A

anterior chamber

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42
Q

what is the index of the crystalline lens

A

1.42

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43
Q

bifocal adds are correctly verified when the optican checks the add from which side of the lens against the lens stop

A

front

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44
Q

which lens material is the most impact resistant

A

poly

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45
Q

___ is the absence of the crystalline lens of the eye, if not replaced with an artificial intraocular lens

A

aphakia

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46
Q

when a cataract patient has had an intraocular lens (IOL) inserted they are

A

pseudophakic

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47
Q

the inability to accomodate is

A

presbyopia

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48
Q

when verifying a pair of glasses in the lensometer to determine if any vertical imbalance is present, it is accepted industry practice to start with

A

The lens with the strongest power in the vertical (90 degree) meridian

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49
Q

determine the binocular horizontal decentration for the following
Frame PD is 75mm

Patients binocular PD is 69mm

A

6mm

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50
Q

a condition of the cornea in which the cornea asssumes a cone shape is called what

A

kerataconus

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51
Q

what is the minimum height for a FT Trifocal

A

18mm

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52
Q

what are the five layers of the cornea

A

Epithelium
Bowmans Membrane

Stroma

Descemets Membrane

Endothelium

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53
Q

when light rays come to two separate points of focus, one on the retina & one in front of the retina it is called

A

simple myopic astigmatism

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54
Q

what is cellulose acetate

A

plastic/zyl frames

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55
Q

when a frame for a six year old child is selected, a saddle bridge is a better choice than a comparable frame with adjustable pads for which of the following reasons:
A) adjustable pads and their guard arms may be a hazard if the child falls

B) a saddle bridge distributes weight over a greater portion of the nose

C) a saddle bridge retains adjustment better than an adjustable pad

A

all of the above

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56
Q

what index is water

A

1.33

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57
Q

the area where the upper and lower eyelids meet, also containing tear ducts is called

A

canthus

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58
Q

the focal length for a plus lens is referred to as ___

A

postive

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59
Q

what does the lens clock do

A

measures base curve

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60
Q

concave surfaces curve what way

A

inward

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61
Q

when fitting a patient with trifocals, what is the usual point of reference for the fitting height

A

lower pupil margin

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62
Q

what metal, used for frames, is strong, resistant to corrosion, and stable under high temperatures

A

titanium

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63
Q

which coating/tint will increase the transmission of light through a lens

A

anti-reflective

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64
Q

what are the four basic uses of prism lenses

A

1) relieving prism: made for a weak muscle, the base is placed over the deficient muscle
2) stimulating prism: used to stimulate a lazy muscle. the apex is placed over the muscle

3) measuring prism: used to measure the strength of a muscle or a group of muscles
4) dissociating prism: used to effect a temporary destruction of fusion to determine the muscle problem

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65
Q

vertex distance is:

A

the distance from the back/posterior or ocular surface of the lens to the front/anterior surface of the cornea

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66
Q

when light rays come to two separate points of focus, one in front of and one behind the retina, it is called

A

mixed astigmatism

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67
Q

the vitreous chamber takes up approx ___ of the eye

A

2/3

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68
Q

when light rays come to two separate points of focus, one on the retina and one in front of or behind the retina is calld

A

simple astigmatism

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69
Q

when light rays come to two separate points of focus, one on the retina and one behind the retina it is called

A

simple hyperopic astigmatism

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70
Q

___ is a drooping of the upper eyelid

A

ptosis (blepharoptosis)

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71
Q

-.50 -0.25x180

is called what

A

compound myopic astigmatism

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72
Q

a polariscope is used to

A

measure lens stress (determine if lens has been heat treated)

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73
Q

a transparent, gel-like substance that fills the space between the crystalline lens and the retina is called

A

vitreous humor

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74
Q

what is a lens caliper used for

A

measuring lens thickness

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75
Q

the focal point for a plus lens occurs ___ the lens

A

behind

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76
Q

what is the reticle center of a lensometer used for

A

reading lens power

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77
Q

the line drawn directly across a lens shape at the 180 line is called

A

datum line

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78
Q

the tissue membrane lining the inside back of the eye, which contains the sensory receptor cells that collect light energy is called what

A

retina

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79
Q

determine the vertical decentration

B= 51

Patients OC 32 mm

A

6.5 mm up

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80
Q

a minus lens moved out creates ___ prism

A

base in

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81
Q

what muscles dialate in dim light

A

dialator

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82
Q

prism is

A

a wedge shaped piece of optical medium with a base and an apex. a prism has no focusing power, it deviates light

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83
Q

when light rays do not form a single point focused on the retina it is called

A

astigmatism

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84
Q

when light rays come to two separate points of focus, both on the same side of the retina it is called

A

compound astigmatism

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85
Q

Iseikonic Lenses

A
  • Lenses designed to increase or decrease the spectacle magnification of the lens without changing its back vertex dioptric power
  • Used to correct aniseikonia
  • aniseikonia is= an ocular condition where there is a significant difference in the perceived size of images
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86
Q

what is the minimum height for a flat top bifocal

A

11 mm excluding sports relating fitting

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87
Q

what is the bony socket that surrounds and protects the eye while providing a structure for attachment of the ocular muscles called

A

orbit

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88
Q

what muscles constrict the pupil in bright light

A

sphincter

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89
Q

phoria is a ____ for the eye to ___ ___ from its normal position

A

tendency, away from

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90
Q

strabismus is commonly known as

A

crossed eyes
or

squint

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91
Q

what is the major refracting body of the eye

A

cornea

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92
Q

what is the densest lens available

A

poly

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93
Q

+100 +200 x090

is called what

A

compound hyperoptic astigmatism

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94
Q

slab off is grinding away the ___ surface of the lens

A

back

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95
Q

bicentric grinding (slab off) is done on only on lens. the ___ minus or ___ plus. the prism that results is ___

A

most minus, least plus, base up

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96
Q

what does PD stand for

A

Pupillary distance

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97
Q

how many layers are there to the cornea

A

five

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98
Q

a network of nerve fibers that send impulses from the retina to the brain for interpretation as visual images is called what

A

optic nerve

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99
Q

a definite turn of the eye is called

A

tropia

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100
Q

how do you calculate proper base curves for minus lenses

A

1/2 the spherical equivalent and add +6.00

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101
Q

loss of elasticity of the lens leads to what

A

presbyopia

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102
Q

define A B ED and DBL

A 
A= temple to nose
B= top to bottom

ED= (effective diameter) corner to corner

DBL= (distance between lenses) bridge

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103
Q

clouding of the crystalline lens is

A

a cataract

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104
Q

what takes more material than glass to bend the light rays

A

cr-39

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105
Q

on the power drum of a lensometer, which power values are black and which are red

A

plus is black

minus is red

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106
Q

convex surface curves what way

A

outward

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107
Q

a plus lens moved ___ from the eye gains plus power

A

away

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108
Q

the muscle that controls the amount of incoming light, commonly referred to as ‘the colored part of the eye” is

A

the iris

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109
Q

antimetropia means one eye is ___ and the other eye is ____

A

myopic, hyperopic

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110
Q

located directly behind the iris, this lens is ____ in shape

A

biconvex

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111
Q

the three principal parts of the eyes optical system are

A

cornea, crystalline lens, & retina

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112
Q

what is the index of crown glass

A

1.523

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113
Q

the focal length for a minus lens is referred to as

A

virtual

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114
Q

what is the best way to measure for a flat top bifocal

A

from the lower eyelid

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115
Q

what are the three ways to measure pupilary distance with a PD ruler

A

from the center of each pupil

from the inner corner of one pupil to the outer corner of the other

from the inner corner of one iris to the outer corner of the other

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116
Q

what is the macula

A

the small area of retina that surrounds the fovea and that, with the fovea, compromises the area of the retina that gives distinct vision. contains most of the cones

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117
Q

what is the fovea

A

a small depression in the retina at the back of the eye, the part of the macula adapted for the most acute vision

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118
Q

what are the three nose pad angles

A

frontal angle, splay (spread) angle & verticle angle

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119
Q

a minus lens moved closer to the eye ___ minus power

A

gain/increases

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120
Q

a plus lens moved out creates ___ prism

A

base out

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121
Q

composed of skin and fleshy tissue, which provide a protective covering for the eye is called what

A

eyelid (palpebra)

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122
Q

plano -100 X045

is called what

A

simple myopic astigmatism

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123
Q

what is the usual product an optician provides when helping a patient who is being treated for amblyopia

A

an occulder

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124
Q

determine the monocular horizontal decentration for the following:
Frame PD 76

Patients monocular PD

OD 32/ OS 33.5

A

OD 6mm

OS 4.5 mm

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125
Q

when dropball testing a safety lens a ___ inch ball is dropped from ___ inches

A

1 inch

50inches

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126
Q

light rays passing through a minus lens have an ___ point of intersection

A

imaginary

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127
Q

what year was “Duty to Warn” implemented and what is it

A

1987

Duty of the offices to warn patients about the impact resistance of various lens materials

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128
Q

what contains all the sensory receptors for the transmission of light

A

retina

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129
Q

the word that means “double vision” is

A

diplopia

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130
Q

the anterior chamber contains a fluid called what

A

aqueous humor

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131
Q

when light rays come to two different points, both behind the retina it is called

A

compound hyperopic astigmatism

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132
Q

what is the minimum height for a blended bifocal

A

12mm

to compensate for the 1-2 mm band of blured vision around the seg

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133
Q

where is the retina located

A

the lining located at the inner backside of the eye

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134
Q

what index is air

A

1.00

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135
Q

when a light ray strikes a prism it is deviated toward the ___ but the ___ is displaced toward the ___

A

base, image, apex

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136
Q

when light rays come to two separate points of focus, both in front of the retina it is called

A

compound myopic astigmatism

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137
Q

where is the vitreous chamber located

A

between the posterior surface of the crystalline lens and the back of the eye

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138
Q

What does OU stand for

A

occli uterque

both eyes

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139
Q

What does OD stand for

A

occulus dexter

right eye

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140
Q

what does OS stand for

A

occulus sinister

left eye

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141
Q

the aqueous humor has an index of refraction of

A

1.33

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142
Q

scotoma: detachment of ___ and ___ caused by a sharp blow or injury to the head

A

rods, cones

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143
Q

the white tissue that covers the front surface of the eye which protects and shapes the eye is called

A

sclera

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144
Q

what has up to approx 40 diopters of power

A

the cornea

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145
Q

what do the letters DBL represent

A

distance between lenses (bridge size)

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146
Q 
which of the following are layers of the cornea:
 A) Bowmans Membrane
 B) Sclera
 C) Stroma
 D) Meibomian
A

a & c

Bowmans Membrane and Stroma

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147
Q

what is the index of a high index lens

A

1.60

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148
Q

this lens has more molecules than CR-39 but less than high-index

A

glass

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149
Q

what are the receptors called for the retina

A

rods and cones

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150
Q

a heat-treated or chemical hardened lens loses some of it’s impact resistance when it is

a) exposed to extreme cold

b) heated in a frame warmer
c) used for too many years
d) scratched or pitted

A

scratched or pitted

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151
Q

vertex distance is most important when fitting which of the folowing

a) multifocal
b) plastic lenses
c) glass lenses
d) Rx + or - 7 diopters

A

Rx + or - 7 diopters

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152
Q

plano +1.75 x45 is called what

A

simple hyperoptic astigmatism

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153
Q

which portion of the UV spectrum is considered harmful to the eyes

A

UVA and UVB

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154
Q

what type of bridge design makes a long nose appear shorter

A

low positioned saddle bridge

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155
Q

the opening in the iris through which incoming light rays pass is called

A

pupil

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156
Q

which instrument can be used to measure vertex distance

A

ruler and distometer

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157
Q

___ diopter of prism diverts a ray of light ___cm from its original path at ___ meter

A

1/1/1

1 prism diopter moves light 1 cm away from 1 meter distance

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158
Q

a lens whose power is four diopters has a focal length of

A

25 cm
focal length is 1/power so 1/4 =.25

.25=25cm

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159
Q

how many inches are in a meter

A

39.37

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160
Q

what is the speed of light

A

186,000 miles per second

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161
Q

a lens that has two curves on the front surface is

A

plus cylinder lens

from when lenses used to be ground on the front surface

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162
Q

hyperoptic lenses for presbyopic patients have what prismatic effect in the reading area

A

base up

plus lenses are up under the oc, minus lenses are down under the oc (patients look down to read)

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163
Q

what does MRP stand for

A

major reference point

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164
Q

the MRP is located at the OC when…

A

no prism is prescribed

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165
Q 
with a (Geneva) lens clock you find:
front curve= +8.25

back surface highest curve= -6.50

back surface lowest curve= -4.75

what is the power of the lens

A

+3.50 -1.75
D1 (front curve) + D2 (back curve)= Dt (power)

+8.25 + -6.50= +1.75

+8.25 + -4.75= +3.50

distance between the two powers in the major meridians is the cyl, being 1.75. sign of the cyl is determined by direction of travel from one power to the next

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166
Q

looking 5mm above the oc of a lens power of +1.50 -0.50 X180 you will experience what prismatic effect
a)0.75 diopters BU

b) 0.50 diopters BD
c) 1.00 diopters BD
d) 0.50 diopters BU

A

0.50 diopters BD
oc is below the pupil, vertical meridian (90) +1.00 is power at 90 (+1.50) + (-0.50)= +1.00

prentice rule= .5 cm * 1=.50

BD because oc is below the pupil: plus lenses move the same direction, minus lenses move opposite

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167
Q

the standard for sports glasses was developed by

A

ASTM

American Society for Testing Materials

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168
Q

what factors are considered in computing the power of a thick lens

A

front curve
back curve

thickness

index

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169
Q

which Rx is written incorrectly
a) +1.00 -1.00 X 180

b) PL +2.50 X 100
c) +2.75 -1.50 X 90
d) +3.00 -1.25 x 145

A

c +2.75 -1.50 X90
axis should be written as 090

all figures must be written with three digits

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170
Q

what is a kryptoc

A

a brand name of round seg bifocals

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171
Q

longest vertical dimension of the seg is called

A

seg depth

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172
Q

zylonite is also known as what

A

cellulose nitrate

this was banned by the FDA as a frame material due to its flammability

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173
Q

the geometric center of a frame is the same as

A

A + DBL

GCD is also called Frame PD

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174
Q

if a patient has a symmetrical face and a monocular PD of 63/60 what is the monocular near PD

A

30

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175
Q

a glassblowers lens is commonly known as

A

Didymium lens

a trade name for special lenses designed to block infrared light from molten glass

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176
Q

what are palpebra

A

eyelids

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177
Q

what are conjuctiva

A

mucus membrane that lines the underside of each eyelid

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178
Q

what is an incident ray

A

the original ray of light that hits a surface or material

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179
Q

what is supraversion

A

both eyes move up

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180
Q

what instrument measures the curvature of the center cornea

A

keratometer

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181
Q

how many nanometer is A band ultraviolet light (UVA)

A

330-400nm

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182
Q

what is inset

A

halfway between distance pd and near pd

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183
Q

which UV spectrum is completely absorbed by the atmosphere

A

UVC

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184
Q

what are the three types of plastic bridge types

A

keyhole, saddle, modified saddle

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185
Q

which of the following is not used for correcting vertical imbalance at the reading level
a) unequal add powers

b) compensated segments
c) bicentric grinding

d )dissimilar segments

A

unequal add powers

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186
Q

how many millimeters in an inch

A

25.4

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187
Q

a lens has a power of +1.00 at 90 and -1.00 at 180 what is the lens power

A

-1.00 +2.00 X180
the difference between +1.00 and -1.00 is 2 diopters, cyl is 2.00 if sphere is -1.00 then axis is 180 so -1.00 +2.00 X180

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188
Q

what are the three tunics of the eye

A

Fibrous tunic (outer) protective- contains cornea and sclera

Vascular tunic (AKA Uveal tract) (middle) nourishing- contains choroid, ciliary body & iris

Nervous tunic (AKA Sensory tunic) (inner) light sensitive- (retina)

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189
Q

what multifocal will reduce image jump the most
a) FT40

b) ST28
c) FT35
d) kryptok

A

FT40

the wider the seg, the higher the oc will be, higher oc = less image jump (further from the segment)

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190
Q

how many centimeters in a meter

A

100
1.0 meter = .01 centimeters

10 cm = 0.10 meter

15 cm = 0.15 meter

etc etc

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191
Q

the size of an image will always increase if you

A

increase base curve

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192
Q

what is the formula for finding the power at 90 or 180. what is it for 45 or 135

A

90 or 180 is sphere plus cyl power

45 or 135 is sphere plus half the cyl power

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193
Q

what percentage of the cyl power is in effect at:

30, 45, 60, & 90 degrees away from the prescribed axis

A 
30= 25%
 45= 50%
 60= 75%
 90= 100%
 ( 0% at prescribed axis)
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194
Q

conventional slab off is also referred to as what? what direction is the prism ground in?

A

bicentric grinding
base up
(reverse slab off is down)

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195
Q

what is abberation

A

the failure of a refracting surface to bring all rays from an object point to a desired image point

(it can result in image blur or the curvature in the image of a straight line. it may be inherent in the lens design or error in processing.)

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196
Q

at what age is the amplitude of accommodation the highest

a) 10
b) 20
c) 40
d) 50

A

10

amplitude (capacity) is highest in children and decreases with age

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197
Q

the law of refraction basically states what

A

light bends toward the normal when it enters a medium more dense than from which it came

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198
Q

what is the Major Reference Point

A

the point on a lens at which the specified distance prescription requirements shall apply
(commonly but imprecisely referred to as Optical Center)

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199
Q

what is the mechanical center of a lens

A

the point on the lens surface around which a lens is cut an edged

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200
Q

what is the limbus

A

where the cornea meets the sclera

(corneoscleral junction)

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201
Q

what is LTB

A

Length To Bend
a measurement for temple lengths

from the center of the hinge barrel to the center of the bend

202
Q

how many diopters is the “1X” power on a microscope

A

+4.00 diopters

203
Q

what is chromatism

A

an appearance of colored lights (abnormal coloration)

204
Q

what is the frontalis muscle

A

brow muscle

gives the face more expression (raises eyebrows and wrinkles forehead)

205
Q

what is optical infinity

A

20 ft (6 meters) or more

206
Q

what is asthenopia

A

eye strain

207
Q

what is the superior lens edge

A

the top edge of the lens

208
Q

what is isometropia

A

refractive condition is the same in both eyes

209
Q

what is the canthus

A

angles formed by the meeting of upper and lower eyelids

210
Q

what is the index of trivex

A

1.53

211
Q

what is the optic disc

A

area in the retina where blood vessels and optic nerve exit the eye

212
Q

what is Muller’s muscle

A

short muscle that lifts the eyelid while you are awake. controlled by sympathetic nerves. if you are tired it relaxes the eyelid and your eyes will droop

213
Q

what is a pantograph

A

a machine used to copy a plastic pattern onto a plastic sheet. pattern can be copied in a different scale if needed

214
Q

what is ptosis

A

a drooping of the eyelid caused either by nerve weakness or paralysis

215
Q

what is infraversion

A

both eyes move down

216
Q

prism cannot be put into a lens with

A

no power

217
Q

how many nanometers is B band ultraviolet light (UVB)

A

275-330 nm

218
Q

what is the levator muscle

A

goes from back of eyeball, over the top and into the eyelid. lifts the eyelid out of the field of vision

219
Q

what is levoversion

A

both eyes move left

220
Q

what is dextroversion

A

both eyes move right

221
Q

how many nanometers is C band ultraviolet light (UVC)

A

200-275 nm

222
Q

How many nerve fibers are in the optic nerve

A

1.2 million

223
Q

what is nystagmus

A

small repetitive involuntary rhythmic side to side or up and down movements of the eye
“shaking of the eyes”

224
Q

what is the inferior lens edge

A

the bottom edge of the lens

225
Q

what is the annulus of Zinn

A

ring-like structure at apex of orbit where the four rectal muscles meet

226
Q

what is the lacrimal gland

A

produces tears, which flow across the eye to lubricate it

227
Q

what is orthophoria

A

no deviation of the eyes

228
Q

what is a retinoscope

A

instrument used to examine the refractive error of the eye

229
Q

what is another name for nanometer

A

millimicron

230
Q

what is a CRP

A

Corneal Reflection Pupilometer

231
Q

what is a focimeter

A

an instrument used to determine vertex power, axis location, optical center, and MRP at a given point on an ophthalmic lens
also known as a vertometer or lensometer

232
Q

what is a corrected curve lens

A

a lens that has been designed to reduce peripheral power errors for the conditions of intended use over a specified portion of the field of view

233
Q

what is sagitta

A

vertex depth

the depth of the surface curve on a lens measured over a specific diameter

234
Q

if a +10.00 lens is moved 5mm nearer the eye, it will be about

A 
.50 weaker plus
 effective power formula EP= D/ (1-fD)
 10*-.005= -0.05
 1- -0.05=+1.05
 10/1.05= 9.52
 power is approx .50 diopters weaker plus (plus power moved closer is weaker plus)
235
Q

what is scotoma

A

a blind area of reduced vision in the visual field (detachment of rods and cones)

236
Q

what is anisometropia

A

a condition in which the refractive error of one eye significantly differs from the other, but both are myopic or hyperopic (same sign Rx) (greater than 2 diopters in difference)

237
Q

what is ametropia

A

a refractive error in which the eye, when in a state of rest, does not focus the image of an object upon the retina. the general term for having either hyperopia, myopia, or astigmatism

238
Q

what is amblyopia

A

loss of vision with out any apparent disease of the eye, usually because of “lazy eye”

239
Q

a Geneva lens measure (clock) measures what

A

base curve

can also be used to find lens power based on curvature of front and back surfaces

240
Q

a characteristic most CR39 lens series have in common is

A

minus cylinder form

241
Q

in a minus powered lens light rays ___ and come to a focal point ___ the lens

A

diverge, in front of

242
Q

fusion occurs in

A

the brain

243
Q

what is fusion

A

the power of coordination by which the images received by the two eyes become a single image

244
Q

what controls the amount of light entering the eye

A

iris

245
Q

ANSI Z80.1 (2010) prism tolerances are:

A

vertical-
0-3.37= .33 diopters
greater than 3.37 = 1mm

horizontal-
0-2.75= .67 diopters
greater than 2.75 = 2.5mm

246
Q

ANSI Z80.1 (2010) cylinder axis tolerances are:

A 
0-.25 =14 degrees
 .25-.50= 7 degrees
 .50-.75= 5 degrees
 .75-1.50= 3 degrees
 greater than 1.50= 2 degrees
247
Q

ANSI Z80.1 (2010) sphere power tolerances are

A

SV & MF
0-6.50= .13 diopters
greater than 6.50= 2% of power

Progressives
0-8.00= .16 diopters
greater than 8.00= 2% of power

248
Q

ANSI Z80.1 (2010) cylinder power tolerances are

A

SV & MF
0-2.00= .13 diopters
2.00-4.50= .15 diopters
greater than 4.50= 4%

Progressives
0-2.00= .16 diopters
2.00-3.50= .18 diopters
greater than 3.50= 5%

249
Q

ANSI Z80.1 (2010) add power tolerances are

A

0-4.00= .12 diopters

greater than 4.00= .18 diopters

250
Q

how do you determine which type of astigmatism a prescription is ? (simple/compound myopic, simple/compound hyperopic, mixed astigmatism)

A

transpose the Rx from the original form, compare the new sphere power to the original sphere power.
if one is plus and one is minus, it’s mixed astigmatism
if both are plus or minus it is compound
if it is plano in one and either plus or minus in the other it is simple

251
Q

how do you find the spherical equivalent of an astigmatic (toric) lens

A

add the sphere to one-half of the cylinder power, drop the axis

+1.00 +2.50 X 090= +2.25

252
Q

what is the formula to find focal length

A

Fm= 1/D

 Fm= focal length in meters
 D= power
 \+10.00 Rx:
 1/10= .10 (.10 meters=10 centimeter)
 focal length is 10cm
253
Q

a +12.00 lens is prescribed at a vertex distance of 13mm. the optican fits the glasses at 9mm. what is the power of the lens at that fitting position

a) +12.00
b) +11.50
c) +12.25
d) +10.50

A

+11.50

plus lenses moved closer to the face become weaker

254
Q

How many millimeters in a meter

A

1000
1mm= 0.001 meter
5mm= 0.005 meter
10mm= 0.01 meter

255
Q

how do you determine the effective power of a lens

A

EP= D/ (1-fD)
D= current power
f= difference in vertex difference measured in meters (1mm=0.001m)
f will be a positive number if it is moved further from Rx vertex distance, a negative number if moved closer to Rx vertex distance

256
Q

what is the formula to find lens power at a focal distance

A

power= 1/ focal distance
if focal distance is 50cm
1/.5=2
power is +2.00

257
Q

what type of lens is convergent

A

plus lens

258
Q

what type of lens is divergent

A

minus lens

259
Q

what is tempering

A

a process of heat treatment to make the lens more impact resistant

260
Q

what is chem-tempering

A

A process of using potassium nitrate bath to make the lens more impact resistant. the process is called ion exchange because the smaller ions in the glass get replaced by the larger ions in the bath.

261
Q

what are the four things that control magnification

A

the prescription, the front curve, center thickness and vertex distance

262
Q

what is heterophoria

A

one eye, or both eyes, wander away fro the direction in which they should be so that the eyes are not looking in the same direction

263
Q

what is reverse slab off

A

base down prism, done on the least minus or most plus lens

264
Q

what is a tonometer

A

instrument that measures internal pressure of the eye

265
Q

internal (lateral) rectus

A

moves the eye outwards

266
Q

external (medial) rectus

A

moves the inwards

267
Q

superior rectus

A

moves the eye upwards and slightly outward

268
Q

inferior rectus

A

moves the eye downward and slightly inward

269
Q

superior oblique

A

moves the eye outward and downward

270
Q

inferior oblique

A

moves the eye outward and upward

271
Q

If a bifocal has its segments on the _____ of the lens, then the lens must be made in minus cylinder form.

A

front

272
Q

Light rays that come from ____ feet or more away are considered parallel.

A

20

273
Q

how many millimeters should the OC be ___ per degree of pantoscopic tilt

A

.5 (1/2)mm per degree lower

274
Q

How can you tell if a frame was made with the boxing or datum system?

A

Boxing system will have the labels “eyesize” and “DBL measurement” and datum system will have markings for “eyesize” and “bridge”. The boxing system will have small box between measurements on the frame and the datum systems will have x,- or / between measurements

275
Q

What are symptoms of too much base down prism?

A
  1. Floors and other spaces that are flat and horizontal appear to be concave, so that the person has the illusion of being inside a bowl
  2. walls, buildings, and other vertical spaces appear to be taller than they actually are.
  3. surfaces seem to slope, so that a sidewalk or hallway seems to be going uphill.
276
Q

what are the symptoms of too much base up prism

A
  1. floors and other spaces that are flat and horizontal appear to be convex, so that the person has the illusion of being on a little hill
  2. walls, buildings, and other vertical spaces appear to be shorter than they actually are.
  3. surfaces see to slope, so that a sidewalk or hallway seems to be going downhill.
277
Q

what is the formula for finding prism

A

prentice rule

prism=power * decentration (in centimeters, 2mm= .2cm)

278
Q

what index is the geneva lens measure calibrated to

A

1.53

279
Q

an uncoated, normal plastic (CR-39) lens will reflect approx what percent of light

A

8%

92% transmitted

280
Q

when two light waves are “in phase” they will

A

compound one another

281
Q

what is Tenon’s capsule

A

a layer of tissue that lies between the surface of the eye and the conjunctiva

282
Q

what is the ciliary body

A

attached to the outer edge of the iris near the wall of the eye. The ciliary body produces the fluid (aqueous humor) that fills the eye and nourishes its structures. It also helps to change the shape of the lens when focusing occurs.

283
Q

When determining the bifocal add you should measure the difference between what

A

the back vertex measurement of distance and near

(the difference between the sphere power in the distance from the back of the lens and the sphere power in the near from the back of the lens)

284
Q

the point on a lens where the prisms attach either base to base or apex to apex is

A

the optical center

285
Q

what has the greatest effect on lens magnification

A

lens power

286
Q

which of the following glass lenses is not a fused bifocal

a) curve top
b) straight top 28
c) executive
d) flat top 35

A

executive (in glass this is a one piece construction)

287
Q

a prism seg is designed to provide which of the following at near only
a) BI prism

b) BO prism
c) BU prism
d) BD prism

A

a BI prism

prism segs are a seldom used method for correcting vertical imbalance

288
Q

what is the approx dioptric power of the refractive system of the eye

A

usually between 58 and 62 diopters

289
Q

a bifocal seg that is flat on top and bottom with a depth of 14mm is

A

ribbon seg

290
Q

using the “360 degree” method, what are the directions of prism for each eye

A

0 degrees= BI for right BO for left

90 degrees= BU OU

180 degrees= BO for right BI for left

270 degrees= BD OU

“180 degree” method is same but 90 & 270 are still BU & BD

291
Q

a ___ PD is given as one number

A

Binocular

binocular= both eyes together

292
Q

a ___ PD is given as two seperate numbers

A

monocular

mono= one

293
Q

the optical cross is a graphic representation used to show the ___ of a lens

A

meridian powers (total lens power)

294
Q

as pantoscopic angle is increased

A

the spherical equivalent is increased

295
Q

how do you calculate base curve for plus lenses

A

spherical equivalent plus +6.00

296
Q

What is the specific gravity of CR-39

A

1.32

297
Q

What is the ABBE value of CR-39

A

58

298
Q

What percent of light is reflected from CR-39

A

4

299
Q

What is the specific gravity of polycarbonate

A

1.21

300
Q

What is the ABBE value of polycarbonate

A

29

301
Q

What percent of light is reflected from polycarbonate

A

5.2

302
Q

What is the index of refraction of trivex

A

1.53

303
Q

What is the specific gravity of trivex

A

1.11

304
Q

What is the ABBE value of trivex

A

46

305
Q

What percent of light is reflected from trivex

A

4.4

306
Q

What is the specific gravity of crown glass

A

2.54

307
Q

What is the ABBE value of crown glass

A

59

308
Q

What percent of light is reflected from crown glass

A

4.3

309
Q

What is the specific gravity of flint glass

A

1.62

310
Q

What is the ABBE value of flint glass

A

50-55

311
Q

ANSI Z80.1 (2010) tolerance for specified base curve is

A

Plus or minus 0.75 diopters

312
Q

What is the result if fusion cannot occur

A

Diplopia

313
Q

What word in relation to tropia and phoria means out

A

Exo

314
Q

What word in relation to tropia and phoria means in

A

Eso

315
Q

What word in relation to tropia and phoria means up

A

Hyper

316
Q

What word in relation to tropia and phoria means down

A

Hypo

317
Q

What is emmetropia

A

No refractive condition

318
Q

What is anisometropia

A

Where the refractive error of one eye differs significantly from that of the other but both eyes are either hyperopic or myopic (by 2 diopters or more)

319
Q

What is antimetropia

A

When one eye is hyperopic and one eye is myopic

320
Q

What is aniseknonia

A

A form of double vision that may occur when the image seen by one eye differs so much in size or shape from the other that the two images cannot be fused together by the brain.

321
Q

Lazy eye is

A

Amblyopia (a loss of vision without any apparent disease of the eye)

322
Q

If light comes to focus directly on the retina

A

Emmetropia

323
Q

If light comes to focus at one point in front of the retina

A

Simple Myopia

324
Q

If light comes to focus on one point behind the retina

A

Simple hyperopia

325
Q

If light comes to focus at two points in front of the retina

A

Compound myopic astigmatism

326
Q

If light comes to focus on two points behind the retina

A

Compound hyperopic astigmatism

327
Q

If light comes to focus on two points, one in front of the retina and one behind the retina

A

Mixed astigmatism

328
Q

When light comes to a focus with one point on the retina and one point in front of the retina

A

Simple myopic astigmatism

329
Q

When light comes to two points of focus, one on the retina and one behind the retina

A

Simple hyperopic astigmatism

330
Q

A refractive error when light does not focus on the retina

A

Ametropia

General term for any refractive error

331
Q

What is the vascular intermediate coat of the eye that furnishes nourishment to the other parts of the eye

A

Choroid

332
Q

Irregular astigmatism

A

When the principal meridians in the eye are not 90° apart

333
Q

Regular Astigmatism

A

When the two principal meridians in the eye are 90° apart

334
Q

What is the order of structures of the eye that light passes through from front to back

A

Cornea, aqueous humor, pupil, crystalline lens, vitreous humor, retina

335
Q

Cilia

A

Eyelashes

336
Q

Madrosis

A

Loss of eyelashes

337
Q

Trichasis

A

Ingrown eyelashes

338
Q

Stye

A

Purulent inflammation of infected eyelash follicles

339
Q

How many times does the average person blink per minute

A

7-12 or 12-18 depending on study material

340
Q

How large is the palpebral fissure

A

15mm high by 30mm wide

341
Q

What is the palpebral fissure

A

The vertical space between the upper and lower lids

342
Q

What are canthi

A

The angles formed where the upper and lower lids meet

343
Q

Lateral canthus is where

A

Towards temples, outer angle of lids

344
Q

Medial canthus is where

A

Towards nose, inner angle of lids

345
Q

Caruncle

A

Pinkish part of the eye lid at the medial canthus that houses two accessory tear glands

346
Q

What muscles close the lids

A

Orbicularis occuli

347
Q

What muscles open the lids

A

Levator palbebrae superiorus

348
Q

Müller muscle

A

Gives lids shape

A weakened muscle causes ptosis

349
Q

Tarsal plates

A

Stiff tissue that goes over lids from canthus to canthus

350
Q

Palpebral conjunctiva

A

Transparent mucous membrane the codes the insides of the eyelids

351
Q

Bulbar conjunctiva

A

Mucous membrane that covers the sclera

352
Q

How far does the upper lid move down during a blink

A

10-12mm

353
Q

The bottom lid moves up and____during a blink

A

2-5mm nasally

354
Q

The eyeball it self moves_____ inward in a forced blink and also rotates _____

A

1-2mm

Upward

355
Q

What are the folds formed by the junction of the bulbar and palpebral conjunctiva called

A

Fornix

356
Q

Superior fornix

A

Folds of conjunctiva behind upper lid

357
Q

Inferior fornix

A

Folds formed by conjunctiva behind lower lid

358
Q

Limbus

A

Transition zone between cornea and sclera

359
Q

What is limbal engorgement

A

When the prominent blood vessels in the limbus are irritated and dilate (can be caused by allergens, infections, or foreign bodies including contacts)

360
Q

Neovascularization

A

Caused by long-term corneal edema, the blood vessels from the limbus grow new structures and invade the cornea

361
Q

Hypotonic cornea

A

More water flows into cornea than out. Occurs when normal evaporation isn’t allowed to happen. Cornea is thicker than normal (edema)

362
Q

Isotonic cornea

A

Equal amounts of water flow in and out of cornea. Cornea is at normal thickness

363
Q

Hypertonic cornea

A

More water flows out than into cornea. Can be caused by a higher salt concentration on the cornea. Cornea is thinner than normal

364
Q

Zonular fibers

A

Attached to crystalline lens and ciliary muscles for accommodation

365
Q

Ciliary muscles

A

Attached to zonular fibers for accommodation

366
Q

Accommodation for distance vision occurs when

A

The ciliary muscles relax and the zonules contract, thinning the crystalline lens (more minus power in lens)

367
Q

Accommodation for near vision occurs when

A

The ciliary muscles contract and the zonules relax, thickening the crystalline lens. (More plus power in lens)

368
Q

Retinal detatchment

A

When the retina tissue pulls away from the choroid tissue

369
Q

What is the total refractive power of the eye

A

60 diopters

370
Q

What is the approximate refractive power of the cornea

A

40 diopters

371
Q

What is the approximate refractive power of the crystalline lens

A

20 diopters

372
Q

VID

A

Visible Iris Diameter

Average is 10.6

373
Q

HVID

A

Horizontal Visible Iris Diameter

Average 11.7m

374
Q

SEAL

A

Superior Epithelial Arcuate Lesion

Thin arced lesion in the upper part of cornea between “10 & 2 O’clock”

375
Q

What is the radius of curvature of the front of the cornea

A

7.7mm

376
Q

What is the radius of curvature of the back of the cornea

A

6.8mm

377
Q

The______is aspheric and elliptical in shape

A

Cornea

378
Q

What is the central thickness of the cornea

A

0.5mm

379
Q

What is the edge thickness of the cornea

A

1.0 mm

380
Q

Epithelium

A

Outermost layer of the cornea. It is the layer exposed to the tear film. About 10% of total corneal thickness. Highly regenerative, mild corneal abrasion’s are often completely healed within 24 hours

381
Q

Bowman’s membrane

A

Second layer of the cornea. Essentially a modification of the underlying stroma. Unlike the epithelium it will not regenerate if scratched or damaged

382
Q

Stroma

A

Approximately 90% of the corneal thickness. 200 to 250 layers of cells which light parallel to the corneal surface. Does not regenerate.

383
Q

Decemet’s membrane

A

A strong structureless layer which is secreted by the endothelium. Elastic and resistant to trauma and pathology

384
Q

Endothelium

A

Innermost layer of the cornea consisting of a single layer of flattened cells. Very susceptible to trauma and pathology. Provides deturgecence to cornea

385
Q

Greek word for rainbow

A

Iris

386
Q

Deturgence

A

The normal state of partial dehydration in the cornea

387
Q

What is the pH of the human tear

A

7.4

388
Q

What is the purpose of the iris

A

To control light levels inside the eye by expanding and contracting the pupil.

389
Q

What muscles in the iris expand the pupil

A

dilator muscles

390
Q

What muscles in the iris contract the pupil

A

sphincter muscles

391
Q

Aniridia

A

absence of the iris from the eye

392
Q

Ocular Albinism

A

no pigment (melanin) in the iris

393
Q

Iridocyclitis

A

inflammation of iris and ciliary body

394
Q

Rubeosis

A

growth of abnormal blood vessels in iris

395
Q

Uveitis

A

blanket term for any inflammation of the iris, ciliary body or choroids

396
Q

Aniscoria

A

pupil sizes are different in each eye

397
Q

Miosis

A

when the pupil constricts

398
Q

Mydriasis

A

when the pupils dilate

399
Q

Miotic drops

A

cause the pupil to constrict

400
Q

Mydratic drops

A

cause the pupil to dilate

401
Q

The crystalline lens is ____ in shape

A

biconvex

402
Q

Cataract

A

a cloudy opacity in the crystalline lens

403
Q

The _____ _____ causes a blind spot in vision that most people do not notice because of the overlap of vision from both eyes

A

optic nerve

404
Q

A Snellen Chart

A

is used to determine visual acuity

405
Q

20/20 means

A

the patient can see an object at 20 feet that a normally sighted person can also see at 20 feet

406
Q

A larger number at the bottom of visual acuity means

A

worse vision (20/40, 20/70 etc)

407
Q

A smaller number at the bottom of visual acuity

A

Better than normal vision (20/15, 20/10)

408
Q

What are the layers of the tear film

A

Lipid, Aqueous (Lacrimal), and Mucoid layer

409
Q

Lipid Layer

A

fatter material produced by meibomian glands, top layer of tear film. Primary function to prevent rapid evaporation of tears

410
Q

Mucoid layer

A

Innermost layer of tear film, lays immediately against corneal and conjunctival epithelial cells. Converts the epithelium, which is naturally hydrophobic into a hydrophilic surface.

411
Q

Aqueous layer

A

Also called Lacrimal layer. mostly water, provides moisture, nutrients and oxygen to the cornea

412
Q

What is the index of refraction of tears

A

1.3375

413
Q

Puncta

A

drain tears from eye with each blink by the force of lids closing

414
Q

Schirmers Test

A

Tests quantity of tears produced in dry eye patients. Strips of paper are placed in eyes for 5 minutes then wetness is measured. Should be about 15mm of wetness

415
Q

Rose-Bengal

A

a purplish stain used to assess integrity of cornea. Colors any dead or regenerating cells on epithelium as brown spots when viewed under a green filter (slit lamp)

416
Q

BUT Test

A

Break Up Time
How long tears take to start evaporating between blinks. 10-12 seconds is normal. Less than 7-10 can cause problems for contact lens wearers

417
Q

What is the wavelength of the Visible Spectrum of Light

A

370-750 nanometers

418
Q

What is the wavelength of short ultraviolet light

A

200-295 nanometers

419
Q

What is the wavelength of long ultraviolet light

A

296-400

420
Q

What is the wavelength of short infrared light

A

750-1400 nanometers

421
Q

What is the wavelength of UV C

A

200-290 nm

422
Q

What is the wavelength of UV B

A

290-320nm

423
Q

What is the wavelength of UV A

A

320-400nm

424
Q

UV C is

A

Extremely dangerous, but is absorbed completely by the ozone layer. However is is also emitted by welders torches

425
Q

UV B causes

A

sunburn, corneal burns, retinal damage. Over time, causes cataracts. Mainly absorbed by cornea and partly by crystalline lens.

426
Q

Exposure to UV B increases by ___with every___

A

10%

1000 feet of elevation

427
Q

UV A causes

A

Suntans, skin aging and contributes to cataracts. Primarily absorbed by crystalline lens

428
Q

What is the visible spectrum of light from longest waves to shortest waves

A

Red, Orange, Yellow, Green, Blue, Indigo, Violet

429
Q

Index of refraction can be determined by what formula

A

Speed of light in air (186,000 miles per second) by speed of light in a given material

430
Q

Angle of Incidence

A

the angle at which incoming rays of light strike the surface of an object

431
Q

Angle of Reflection

A

predictable angle of light bouncing off a reflective surface

432
Q

Snells Law

A

formula used to calculate angle of refraction in a medium with a known index of refraction

433
Q

Angle of Refraction

A

angle of light bending inside a medium

434
Q

Spherical Abberation

A

when parallel light rays enter a large area of a spherical lens surface, the peripheral rays focus sooner than the central rays and cause blurring of the image.

435
Q

What “shape” of distortion do strong plus lenses have

A

pincushion (inward curvature)

436
Q

What “shape” of distortion do strong minus lenses have

A

Barrel (outward bulging)

437
Q

Vogel’s rule for Plus lenses

A

Best base curve is found by adding sphere power (or spherical equivalent) to +6.00

438
Q

Vogel’s rule for minus lenses

A

Best base curve is found by adding half the sphere (or spherical equivalent) to +6.00

439
Q

If a patient comes in complaining that the new glasses make everything smaller, but the rx and all parameters are the same as the old pair…

A

the base curve was made flatter than the original

440
Q

If a patient comes in complaining that the new glasses make everything larger but the rx and all parameters match the old pair…

A

the base curve was made steeper than the original

441
Q

Meniscus lens

A

a lens with a convex front surface and concave back surface. Nearly all lenses made today are this shape

442
Q

Hard Designed PALs

A

have a wider distance and near area. Most of the “edge blur” is to the sides of the intermediate area

443
Q

Soft Designed PAL’s

A

distribute the edge blur from the center towards the distance and near so the intermediate area is wider

444
Q

Equithinning

A

Prism thinning on PALs. Base down prism ground equally into a set of PALs to reduce thickness difference between top and bottom portions of the lens

445
Q

Lenticular Lens

A

for patients with high rx’s. a center “disc” with all the rx is mounted into a carrier lens with little to no power. Reduces weight and thickness and aids in mounting of lens in a frame for eyeglasses

446
Q

An object viewed through a prism from one meter a way is displaced one centimeter. What is the power of the prism

A

one diopter

447
Q

Prism power formula

A

centimeters(displaced)/meters(distance away)

Object displaced 1cm at 0.5meter: 1/0.5= 2 diopters of prism

448
Q

Formula for finding power from focal length

A

1/Focal length=diopters of power

449
Q

Formula for focal length

A

1/power in diopters= focal length

450
Q

The Stronger the power the ____ the focal length

A

shorter

451
Q

The weaker the power the ___ the focal length

A

longer

452
Q

Rule of thumb for effective power of a lens

A

a 10.00 diopter lens moved 5mm will change by 5 diopters.

453
Q

base out prism on a plus lens is moved

A

towards the temples

454
Q

base in prism on a plus lens is moved

A

towards the nose

455
Q

base up prism in a plus lens is moved

A

up

456
Q

base down prism in a plus lens is moved

A

down

457
Q

base out prism in a minus lens is moved

A

towards the nose (in)

458
Q

base in prism on a minus lens is moved

A

towards the temples (out)

459
Q

base up prism on a minus lens is moved

A

down

460
Q

base down prism on a minus lens is moved

A

up

461
Q

Cancelling prism directions

A

Both lenses have base up, both lenses have base down or one lens has base in and one has base out

462
Q

If a set of lenses has 2 diopters BI on the OD and 4 diopters BO on OS how much prism is there

A

2 diopters BO on OS

The 4D OS cancels out the 2D OD, leaving another 2D in the OS leftover

463
Q

Compounding prism directions

A

Both lenses have base in, both lenses have base out, or One has base up and one has base down.

464
Q

If a pair of lenses have 2D BO in OD and 4D BO in OS how much prism is there

A

6D BO OU

465
Q

How to find horizontal prism in a lens with astigmatism

A

find power in 180 meridian, then use prentice rule

466
Q

How to find vertical prism in a lens with astigmatism

A

find power in the 90 meridian then use prentice rule

467
Q

How many mms below the pupil should optical centers be measured for (how many) degrees of pantoscopic tilt

A

One mm below the pupil for every two degrees of tilt

468
Q

How to calculate slab off for anisemetropia

A

find power at 90 (issue is at reading/vertical level) use prentice rule using how many mm patient looks below OC to read as decentration, then grind the base up prism into the most minus/least plus powered lens (accounting for compounding/cancelling prism amounts)

469
Q

Image Jump

A

caused by patient looking under the segment line for reading, going from distance OC to reading OC, causing prism.

470
Q

Calculate Image Jump using prentice rule

A

Use add power and near OC
Rx is +2.00 OU and +2.00 add power. Near OC is 5mm below segment line

5X2=10/10= 1 diopter image jump

471
Q

Most commonly used metal for making frames

A

monel

472
Q

An oval face should wear

A

can wear just about any frame shape

473
Q

An oblong face should wear

A

deep frames with low temple attachments. wider oval shaped frames

474
Q

round faces should wear

A

narrow frames with high temple attachments. rectangular frames

475
Q

square frames should wear

A

narrow frames with high temple attachments, oval shapes with more width than depth

476
Q

triangular (wide jaw, narrow forehead) faces should wear

A

darker colors. frame width should equal widest part of lower face. cat eye shapes

477
Q

diamond shaped (narrow forehead, wide cheeks narrow jaw) faces should wear

A

lighter colors, use frames with distinctive browlines, rimless styles, ovals and cat eyes

478
Q

Triangular faces with wide forehead and narrow narrow jaw should wear

A

light colors, wide bottomed frames, rimless styles

479
Q

patients with narrow pds benefit cosmetically from

A

lighter colored bridges on frames

480
Q

patients with wide pds benefit cosmetically from

A

darker bridges on frames

481
Q

to shorten a long nose

A

use a low set or dark bridge

482
Q

to lengthen a short nose

A

use a clear or high set bridge

483
Q

Refractive Astigmatism

A

Sum of any corneal and lenticular (internal) astigmatism in the eye. Amount of astigmatism in the spectacle Rx. Found during the refraction.

484
Q

Corneal astigmatism

A

most common form of astigmatism. Any astigmatism found on cornea. Determined using the difference between K-readings

485
Q

Lenticular astigmatism

A

astigmatism found in the internal structures of the eye. It is the difference between the Refracted Astigmatism and any Corneal Astigmatism found in the K readings

486
Q

How much astigmatism is usually required to be corrected by a toric lens

A

more than 0.75 diopters

487
Q

What is “With the Rule” astigmatism

A

when the horizontal (180 or about) meridian is flatter than the vertical (90 or about) meridian

488
Q

What is “Against the Rule” astigmatism

A

when the horizontal (at 180 or about) meridian is steeper than the vertical(90 or about) meridian

489
Q

What is “Oblique” astigmatism

A

When the horizontal meridian is closer to 45 degrees and the vertical meridian is closer to 135 degrees

490
Q

What is Residual Astigmatism

A

Any leftover astigmatism found during an over refraction while wearing contact lenses

491
Q

True or False

Spherical GP lenses can compensate for both corneal and lenticular astigmatism

A

False. They’re great at neutralizing corneal astigmatism (using tear lens) but cannot compensate for any lenticular astigmatism. Toric soft lenses would be best

492
Q

Are GP or Soft lenses better for against the rule astigmatism

A

soft, due to the way the drape the cornea

493
Q

A spherical GP lens is best used to correct for how much _____ astigmatism

A

Less than 2.5-3D of corneal, with the rule astigmatism

494
Q

Toric GP lenses should be used when

A

there is more than 3D of corneal astigmatism, when there is against the rule astigmatism, or to correct for lenticular astigmatism

495
Q

What other names is the base curve of contacts known as

A

Base Curve Radius (BCR)

Back Optic Zone Radius (BOZR)

Back Central Optical Radius (BCOR)

496
Q

The base curve of a contact lens can be

A

spherical or aspheric

497
Q

Aspheric contact lenses are specified by

A

E-Value

larger E-Value indicates a greater rate of flattening or lengthening from lens center to edge

498
Q

An E-Value on a contact lens means

A

a spherical base curve

499
Q

An E-Value from 0-1 are ___ curves

A

elliptical

500
Q

An E-Value of 1 is a ____ curve

A

parabolic

NCSORB (1 decks)

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