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Ophthalmic Optics > B14 Review > Flashcards

B14 Review Flashcards

(59 cards)

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1
Q

What can you use to measure the curvature of a lens?

A

Lens clock

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2
Q

What can you use to measure the thickness of a lens?

A

Lens caliper

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3
Q

Where is the thickest part of a plus lens?

A

Center

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4
Q

Where is the thickest part of a minus lens?

A

Edge

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5
Q

How do you measure monocular PD?

A

Optical center to the center of the bridge

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6
Q

What can you use to measure the vertex distance of glasses?

A

Distometer

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7
Q

How do you measure seg height for bifocals?

A
  • Deepest part of the lens to the lower limbus
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8
Q

How do you measure seg height for trifocals?

A
  • From the deepest part of the lens to 1 mm below the pupillary margin, so that they’re not looking through the intermediate
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9
Q

How do you measure seg height of PALs?

A
  • Center of pupil to the deepest part of the lens

- add +0.5mm for plastic

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10
Q

What is x-ing?

A

Vertical misalign, twisted frame

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11
Q

What is “splaying”?

A

Temple spread

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12
Q

What is a “skewed bridge”? How do you fix it?

A
  • One lens is higher than the other

- force one side up and one side down

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13
Q

What does “variant planes” mean? How do you fix it?

A
  • One lens is infront of the other

- Push-pull method

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14
Q

What does pantoscopic tilt mean? What is its relationship to optical center location?

A
  • when the lower rim of the eyewire is closer to the patient’s face than the top
  • for every 2 degrees of PT, you should drop the optical center 1 mm
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15
Q

Which lens materials are hypoallergenic?

A

Stainless steel, titanium, nylon, optyl, polyamide

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16
Q

Pros/cons of nickel frames

A

Pros: durable, easy to adjust, resists corrosion

Cons: can cause allergic reaction

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17
Q

Pros/cons of Titanium frames

A

Pros: lightweight, strong, hypoallergenic

Cons: expensive

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18
Q

Which materials are hard to adjust?

A

Stainless, memory metal, polycarbonate, carbon fiber, optyl (memory plastic)

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19
Q

What kind of temple is this?

A

Skull

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20
Q

What kind of temple is this?

A

Library

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21
Q

What kind of temple is this?

A

Cable

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22
Q

What do convertible temples look like?

A
  • they can be bent to look like either skulls or librarys
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23
Q

Best lens material for sports?

A

Polycarb

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24
Q

What is the relationship between Abbe values and spherical aberrations?

Study These Flashcards
A

Higher Abbe value = less aberrations

25
Which materials have the highest Abbe values?
Glass and CR-39
26
Which material has the lowest Abbe value?
Polycarb
27
What is the default lens material for adults?
CR-39
28
What is the default lens material for kids?
Polycarb
29
Which lens material is the heaviest?
Glass
30
Which lens material is the lightest?
Polycarb or trivex (about the same)
31
What is the cut-off for High index?
+/- 4.00, where it becomes lighter than poycarb of equal power (due to allowing for less lens thickness)
32
When is trivex used?
Good alternative to Polycarb since it has similar impact resistance and weight but a higher Abbe value (and therefore less abberations)
33
Which lens material is the cheapest?
CR-39
34
Which lens material is the most expensive?
Glass or hi-index
35
Which lens material is the thickest?
Glass
36
Which lens material is the thinnest?
Hi-index
37
Which lens materials can be used in rimless or semi-rimlesss frames?
Polycarb or trivex
38
What affect (as far as power goes) will pantoscopic tilt have on a plus lens?
- will add plus cyl axis 180 | - will add plus spherical power
39
What affect does adding retroscopic (or reducing pantoscopic) tilt have on a plus lens?
- adds minus cyl x 180 | - adds minus sphere
40
What affect does adding faceform have on a plus lens?
- adds plus cyl x 090 | - adds plus sphere
41
What affect does reducing Faceform have on a plus lens?
- adds minus cyl x 090 | - adds minus sphere
42
What affect does increasing pantoscopic tilt have on a minus lens?
- adds minus cyl x 180 | - adds minus sphere
43
What affect does retroscopic tilt (or reducing pantoscopic tit) have on a minus lens?
- adds plus cyl x 180 | - adds plus sphere
44
What affect does faceform have on minus lenses?
- adds minus cyl x 090 | - adds minus sphere
45
What affect does decreasing faceform have on minus lenses?
- adds plus cyl x 090 | - adds plus sphere
46
What are the two most important abberations for spectacles?
- field curvature and oblique astigmatism
47
How do we reduce oblique astigmatism in lenses?
- Tscherning’s Ellipse/Ostwalt Curves
48
Plus lenses usually cause what kind of distortion?
- Pincushion
49
Minus lenses usually cause what kind of distortion?
- barrel
50
Some things to know about aspheric lenses?
- cannot use a lens clock since their power changes throughout the lens - cannot induce prism, it must be ground in
51
Benefits of aspheric lenses?
- less aberations - thinner and lighter - reduces the effect of magnification
52
What is Aniseikonia? What usually causes it?
- when the eyes have different image sizes | - anisometropia, or a large difference in Rx between eyes
53
Relationship (approximation) between anisometropia and aniseikonia?
1% aniseikonia per 1D of anisometropia
54
At what point does aniseikonia become more of a problem?
- 3-4% size difference (aniseikonia) or 3-4D Rx difference (anisometropia)
55
What are the ANSI standards for sun glasses?
- Z80.3, no glasses should transmit less than 8% of light
56
Which color lenses reduce glare the most? What color of light is filtered by this tint that is thought to be responsible for most glare issues?
Brown, blue light
57
Which color lenses increase constrast?
Yellow
58
Which color lenses filter all light evenly?
Gray
59
Which color lenses significantly affect color vision?
Green

Ophthalmic Optics (1 decks)

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