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OPT 2500 ( FULL OVERVIEW ) > UNIT ONE - History And Nomenclature > Flashcards

UNIT ONE - History And Nomenclature Flashcards

1
Q

Identify 1

A

PPC - Peripheral Curve Radius

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2
Q

Identify 2

A

IPC- intermediate curve radius

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3
Q

Identify 3

A

CPC-Base curve radius

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4
Q

Identify 4

A

1st and 2nd Junctions

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5
Q

Identify 5

A

Posterior OZ (Optical Zone)

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6
Q

Identify 6

A

Total Diameter

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7
Q

Identify 7

A

PPC Width

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8
Q

Identify 8

A

IPC Width

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9
Q

Identify 9

A

Curve or front anterior central curve

could have anterior OZ if flange

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10
Q

Identify 10

A

CT - Central Thickness

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11
Q

Define a contact lens.

A

Thin plastic placed on eye for visual defects and bandage.

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12
Q

What are two basic purposes for contact lenses?

A

Correct vision and therapeutic

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13
Q

What type of edge design is often put on a high plus lens to help reduce weight and thickness?

A

Myoflange

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14
Q

What type of edge design is often put on a high minus lens that is riding too high?

A

Hyperflange

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15
Q

What is CPC?

A

Central posterior curve

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16
Q

What is IAC?

A

Intermediate anterior curve

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17
Q

What is PPC?

A

Peripheral posterior curve

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18
Q

What is CAC?

A

Central anterior curve

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19
Q

How many peripheral curves does a tri curve lens have?

A

3

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20
Q

Which surface of a contact lens do refer to as the base curve?

A

CPC

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21
Q

Which surface of a contact lens delivers the power?

A

BVP- Back vertex power (posterior)

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22
Q

What are three classifications of contact lenses according to size or the area they cover?

A

Corneal, scleral, or semi scleral

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23
Q

Give two reasons why we put peripheral curves on the posterior surface of most contact lenses used today.

A

Comfort And tear exchange

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24
Q

A contact lens that absorbs water would be called

A

Hydrophilic

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25
Q

A contact lens that does not absorb water would be called

A

Hydrophobic

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26
Q

Lens diameter formula

A

Optical zone diameter +2 (IPC (BW)+PPC(BW))

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27
Q

What is the overall diameter of a contact lens that has an optical zone of 7 mm and IPC and PPC band widths of 0.3 mm and 0.4 mm respectively?

A

D = 8.4 mm

USE DIAMETER FORMULA:
OZ+2(IPC(BW)+PPC(BW))

BREAKDOWN:
OZ+ 2(IPC + PPC)
7.0+2(0.3+0.4)
7.0+2 x 0.7

D= 8.4mm

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28
Q

What is the overall diameter of a contact lens if it has in IPC width of .4 mm, a PPC width of .5 mm and an optical zone diameter of 6.5 mm?

A

D=8.3mm

USE DIAMETER FORMULA:
OZ+2(IPC(BW)+PPC(BW))

BREAKDOWN:

OZ=6.5 mm
IPC=0.4mm
PPC=0.5mm

  1. 5 + 2 (0.4 + 0.5)
  2. 5 + 1.8
  3. 3 mm
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29
Q

What is the optical zone diameter of a contact lens with an overall diameter of 8.8 mm, if the IPC and PPC width are .2 mm and .3 mm respectively?

A

OZ=7.8mm

USE DIAMETER FORMULA:
OZ+2(IPC(BW)+PPC(BW))

BREAKDOWN:

D= 8.8mm
OZ= 7.8
IPC= 0.2mm
PPC= 0.3mm
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30
Q

What unit is the CPC( base curve) measured in?

A

Millimeters of radius of an arc or in diopters

Example:
7.71mm = 43.75 D

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31
Q

Does a shorter radius of curvature mean more power or less power?

A

More power

32
Q

Does a longer radius of curvature mean more power or less power?

A

Less power

33
Q

Convert 42 Dioptric powers to radius of curvature 

A

8.03

TAKE 337.5 and divide by Diopter
337.5/42= 8.03

34
Q

As a dioptric power increases the radius of curvature of the cornea or the base curve of the contact lens, does it become shorter and steeper or longer and flatter?

A

Shorter and steeper

35
Q

As a dioptric power decreases the radius of curvature of the cornea or the base curve of the contact lens, does it become shorter and steeper or longer and flatter?

A

Longer and flatter

36
Q

Arrange the list of radii  of curvature from the steepest to the flattest:

  1. 7.500
  2. 6.750
  3. 7.417
  4. 8.257
  5. 9.926
  6. 6.250
A
  1. 6.250
  2. 6.750
  3. 7.417
  4. 7.500
  5. 8.257
  6. 9.926
37
Q

Define sagittal vault

A

The greater the sagittal height, the greater the vaulting of the lens.

38
Q

Define sagittal depth or height

A

The distance between a flat surface and the back surface of the central portion of the lens.

39
Q

The greater the sagittal vault ,

A

The steeper the lens fits

40
Q

Sagittal vault increases if the diameter of a lens is increased while the radius of curvature _________

A

Remains constant

41
Q

Sagittal vault increases if the diameter of a lens remains constant but the radius of curvature __________

42
Q

To steepen a lens

A
  1. Decrease (shorter) the base curve radius
    (Example: 7.50mm to 7.45mm)
  2. Increase the lens diameter
    (Example: 8.8mm to 9.0mm)
43
Q

To Flatten a lens

A
  1. Increase (longer) the base curve radius
    (Example: 7.50mm to 7.55mm)
  2. Decrease the lens diameter
    (Example: 8.8mm to 8.6mm)
44
Q

To effect a small change

A

Change one parameter only

Either the B.C or the diameter

45
Q

To effect a larger change

A

Change both parameters at the same time

46
Q

When the radius of a curve changes by 0.05mm

A

The power of a curve changes by approximately 0.25D

Example:

Change base curve radius from 7.85mm to 7.90mm, when you convert, the dioptric power changes from 43.00 D to 42.75 D.

This is 0.25D flatter curve.

47
Q

If the base curve of a contact lens was fitted as 7.70 mm then changed measuring 7.60mm, it is:

A

0.50 D steeper than the original lens

48
Q

If the base curve of a contact lens was fitted as 7.55mm then changed measuring 7.65mm, it is:

A

0.50D flatter than the original lens

49
Q

Which of the following radii of curvatures of contact lenses indicates the flattest base curve?

  1. 60mm
  2. 80mm
  3. 90mm
  4. 00mm
50
Q

Which of the following radii of curvature of contact lenses indicates the steepest base curve?

  1. 75mm
  2. 85mm
  3. 95mm
  4. 05mm
51
Q

If the base curve of a contact lens is 45.00D, its radius of curvature is:

52
Q

Which of the following dioptric power indicates the steeper curve?

  1. 00D
  2. 50D
  3. 00D
  4. 00D
53
Q

A contact lens is showing too much movement (loose or flat). If it’s base curve is 7.40mm, what lens would you select to tighten(steepen) the fit?

  1. 35mm
  2. 45mm
  3. 50mm
  4. 60mm
54
Q

A contact lens is showing no movement at all (tight or steep). If it’s base curve is 7.50mm, which lens would you select to loosen (flatten) the fit?

  1. 40mm
  2. 45mm
  3. 55mm
  4. 35mm
55
Q

Which dioptric power represents the flattest radius of curvature?

  1. 75D
  2. 25D
  3. 00D
  4. 25D
56
Q

Which dioptric power represents the steepest radius of curvature?

  1. 00D
  2. 75D
  3. 50D
  4. 25D
57
Q

Define Optical Zone

A

Chord diameter over which the base curve extends on the posterior surface of the contact lenses.

58
Q

Define lenticular flange

A

An increase or decrease in anterior edge thickness

59
Q

Define truncation

A

The removal of the interior and or superior portion of the lens to control rotation.

60
Q

Define fenestration

A

A tiny hole in a contact lens to allow for exchange of tears and oxygen.

61
Q

Define back surface

A

Lens design with two principal curves at right angles to each other on the posterior side and a spherical curve on the anterior side. 

62
Q

Define front surface

A

A lenses on the two principal curves at right angles to each other on the anterior side and a spherical curve on the posterior side. 

63
Q

Define bitoric

A

Cylindrical curves on both the anterior side and the posterior side with principal meridians located 90° apart. 

64
Q

Define blends

A

Junctures between posterior curves after being smooth out by polishing.

65
Q

Define Sagittal depth

A

The distance between the posterior surface of a central area of the lens and a flat surface. 

66
Q

TIGHTER, LOOSER, OR THE SAME:

Increase in sagittal depth

67
Q

TIGHTER, LOOSER, OR THE SAME:

Decrease in sagittal depth

68
Q

TIGHTER, LOOSER, OR THE SAME:

Steeper base curve

69
Q

TIGHTER, LOOSER, OR THE SAME:

Flatter base curve

70
Q

TIGHTER, LOOSER, OR THE SAME:

Larger diameter

71
Q

TIGHTER, LOOSER, OR THE SAME:

Smaller diameter

72
Q

TIGHTER, LOOSER, OR THE SAME:

Smaller diameter, steeper base curve

73
Q

TIGHTER, LOOSER, OR THE SAME:

Smaller diameter, flatter base curve

74
Q

TIGHTER, LOOSER, OR THE SAME:

Larger diameter, flatter base curve

75
Q

TIGHTER, LOOSER, OR THE SAME:

Larger diameter, steeper base curve

OPT 2500 ( FULL OVERVIEW ) (7 decks)

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