prism peter

Question 1

What does a relieving prism do?

Answer 1

Displaces the image toward the direction the eye turns

Question 2

Prism Base

Answer 2

A prism is placed before the eye with reference to the base

Question 3

3 Effect of a prism on light

Answer 3

Displacement, Dispersion, Deviation

Question 4

Effects of prism on light

Answer 4

Prism will have no focal length and light will deviate toward the base

Question 5

The_____ the prism the ______ the light will _____ and the _____ the image will be ______

Answer 5

Stronger, more, Deviate, More, Displaced

Question 6

Strabismus (heterotropia)

Answer 6

When one eye is not aligned with the other eye to look in a different direction

Question 7

What is Adverse Prism?

Answer 7

Stimulate an eye muscle to work harder, designed to strengthen weak muscles

Question 8

Who came up with Fresnel Prism

Answer 8

French physicist, Augusti Jean Fresnel

Question 9

What is Dissociating Prism

Answer 9

Affect temporary interference with a fusion of both eyes, use of risley prisms in phoropter

Question 10

Base
Compounding Situations

Answer 10

Base up and Base down
Base in and Base in
Base out and Base out

Question 11

What is the Prismatic effect?

Answer 11

visual discomfort when optical centers are not situated over the pupils

Question 12

What is Excessive Base down?

Answer 12

Makes people and vertical objects seem taller than they are

Question 13

Excessive Base Up

Answer 13

Makes people and vertical objects seem shorter than they are

Question 14

4 different prism power units

Answer 14

Deviating Angle, Prism Diopter, Centrad, Apical

Question 15

What is the Rule of Thumb for 45° off axis?

Answer 15

50% of cylinder power

Question 16

What unit is used to measure prism power in optics?

Answer 16

Prism diopter (∆)

Question 17

What is the apex of a prism?

Answer 17

The edge where two prism surfaces meet

Question 18

What is the patient’s reaction to excessive prism?

Answer 18

Discomfort, dizziness, and spatial distortion

Question 19

What is one drawback of Fresnel prisms?

Answer 19

Reduced visual contrast

Question 20

What happens with excessive BD prism?

Answer 20

Objects appear concave; patient feels like standing in a bowl

Question 21

Base
Cancelling situations

Answer 21

Base up and base up
Base down and base down
Base in and base out

Question 22

What does a 1 prism diopter do to light?

Answer 22

Deviates light 1 cm at 1 meter distance

Question 23

What is the formula for decentration from prism power?

Answer 23

Dec = 10 × ∆ / D

Question 24

Why add 2mm in MBS calculation?

Answer 24

To compensate for edge chipping or defects

Question 25

How is total prism effect calculated in compound situations?

Answer 25

Add both prisms together

Question 26

What base direction is used for esotropia correction?

Answer 26

Base in (apex in)

Question 27

How can you detect vertical imbalance?

Answer 27

Using lensometer and patient reading complaints

Question 28

What happens with excessive BU prism?

Answer 28

Objects appear convex; patient feels like on a mound

Question 29

What happens if dotted PD does not match patient PD?

Answer 29

Visual lines do not pass through optical centers

Question 30

What are the four prism power units?

Answer 30

Apical angle, Deviating angle, Prism Diopter, Centrad

Question 31

What is exotropia?

Answer 31

Outward turning of the eye

Question 32

What is the optical center in a minus lens?

Answer 32

Located at the apex

Question 33

What is a centrad?

Answer 33

A unit measuring displacement on an arc 1 meter from the prism

Question 34

What is the ANSI Z80 standard unit for prism?

Answer 34

Prism Diopter

Question 35

What causes vertical prism imbalance?

Answer 35

Looking above or below the optical center of the lens

Question 36

What is Prentice's Formula?

Answer 36

∆ = D × decentration (in mm) / 10

Question 37

How is total prism effect calculated in canceling situations?

Answer 37

Subtract smaller prism from the larger

Question 38

How does a prism deviate light?

Answer 38

Toward the base

Question 39

What are Risley prisms used for?

Answer 39

Applying a dissociating prism in a phoropter

Question 40

What is the goal of prescribing prism?

Answer 40

To align visual axes and reduce strain

Question 41

What base direction is used for exotropia correction?

Answer 41

Base In (apex out)

Question 42

What is the effect of base out prism?

Answer 42

Objects shift toward the apex; horizontal tilt in view

Question 43

How is distance between lenses measured?

Answer 43

DBL – shortest distance between nasal edges

Question 44

What happens when lenses are decentered outward in minus lenses?

Answer 44

Base In prism is induced

Question 45

What causes horizontal prism imbalance?

Answer 45

Incorrect decentration

Question 46

What is the base direction for decentering plus lens outward?

Answer 46

Base Out

Question 47

What is prismatic deviation?

Answer 47

The angle the light ray is bent from its original path

Question 48

What is the standard distance for prism measurement?

Answer 48

1 meter

Question 49

What is a Fresnel prism?

Answer 49

A wafer-thin press-on prism used for temporary correction

Question 50

How does a stronger prism affect light?

Answer 50

It bends light more and increases image displacement