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Final exam Flashcards

1
Q

What is reverse Slab-off?

A

Base down prism

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2
Q

When applied to a lens, Slab-off will be on the top half or BOTTOM half of the lens?

A

Bottom

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3
Q

What are the 5 Seidel Aberrations? Are they Chromatic or monochromatic?

A

MONOchromatic!
-Spherical, Coma, Oblique, Curvature of field & Distortion.

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4
Q

Cr-39

A

1.498 &
58

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5
Q

Polycarbonate

A

1.586 &
30

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6
Q

Trivex

A

1.532 &
43-45

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7
Q

Crown Glass

A

1.523 &
57

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8
Q

Hi-Index 1.67

A

1.67 &
32

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9
Q

what type of aberrations occurs ONLY wavelength of light?

A

MONOchromatic

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10
Q

what type of aberration occurs with MORE THAN ONE wavelength of life?

A

Chromatic

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11
Q

What is anisometropia?

A

2.00D or more difference in the refractive error between the right and left eyes

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12
Q

What causes vertical imbalance?

A

unwanted prism

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13
Q

what will the wearer experience as of result of vertical imbalance?

A

prism

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14
Q

What is slab off?
Another term for Slab-off?

A

base up prism added to bottom half of a lens to correct vertical imbalance

bicentric grind

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15
Q

What is the definition of lens aberration?

A

light of different wavelengths to be refracted // chromatic aberration

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16
Q

Which of the lens aberrations is related the health of the eye?

A

Zernike Polynomials

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17
Q

What are the chromatic lens aberrations?

A

Longitude / Lateral

18
Q

What are the all monochromatic lens aberrations ?

A

Zernike polynomials, Seidel Abberations

19
Q

Which lens abberations can be caused by WRAP AROUND frames or TITLING the lens?

A

OBLIQUE astigmatism

20
Q

what are the 4 variables of LENS DESIGNS?

A

index of refraction
lens thickness
vertex distance
lens form

21
Q

what are the 3 reasons to choose ASPHERIC LENS DESIGN?

A

improved vision, better peripheral, thinner and lighter lenses

22
Q

what is the difference between a spherical lens design and aspheric ?

A

SPHERICAL: shifter focused aberration
ASPHERIC: one focal point NO abberation

23
Q

Which REDUCES the occurrence of the lens abberation; a HIGH abbe value or low?

A

High ABBE value

24
Q

Which lens abberation can cause a PIN CUSHION or BARREL effect?

A

SEIDEL abberation

25
Q

List lens material least (BEST abbe) to most likely (WORST abbe) to cause lens abbreviation

A

Polycarbonate
Hi-Index 1.67
Trivex
Cr-39
Crown Glass

26
Q

If lens of 0 power (PL) is moved 10mm, how much prism is created?

A

1.0 cm

27
Q

What is the minimum amount of calculated vertical prism need to order Slab-Off for a person with Anisometropia?

A

1.50 D or more

28
Q

plus Lenticular lens

A

CENTRAL area with higher power than the sides

29
Q

Minus lenticular lens

A

LOWER power in center and higher power on Sides

30
Q

types of segmented lens

A

Double, bifocal, trifocal, round trifocal, executive

31
Q

ADDition for presbiopics? (which near)

A

Near ADD

32
Q

add to the sphere power?

A

Near power

33
Q

distance between the segs in a Double D lens?

A

13-14mm

34
Q

Greatest amount of image jump?

A

Round Segments

35
Q

Least amount of image jump?

A

Flat top segments

36
Q

Change in power and increases in cyclinder is more EVIDENT

A

HARD design

37
Q

Change in power and increases in unwanted cylinder is GRADUAL

A

soft design

38
Q

a tehcnique to use to increase thickeness to the bottom of a progressive

A

prism thinning

39
Q

where is prism read in a progressive lens?

A

the dot below the fitting cross is the location of the prism ref point

40
Q

how far apart are the laser marking on a progressive lens?

A

34mm

41
Q

what are the point of wear measurements?

A

the fitting cross

42
Q

meridian of the highest power and where the greatest thickness on a rx lens

A

△ = D d

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