UNIT ONE - History And Nomenclature Flashcards
1
Q
Identify 1
A
PPC - Peripheral Curve Radius
2
Q
Identify 2
A
IPC- intermediate curve radius
3
Q
Identify 3
A
CPC-Base curve radius
4
Q
Identify 4
A
1st and 2nd Junctions
5
Q
Identify 5
A
Posterior OZ (Optical Zone)
6
Q
Identify 6
A
Total Diameter
7
Q
Identify 7
A
PPC Width
8
Q
Identify 8
A
IPC Width
9
Q
Identify 9
A
Curve or front anterior central curve
could have anterior OZ if flange
10
Q
Identify 10
A
CT - Central Thickness
11
Q
Define a contact lens.
A
Thin plastic placed on eye for visual defects and bandage.
12
Q
What are two basic purposes for contact lenses?
A
Correct vision and therapeutic
13
Q
What type of edge design is often put on a high plus lens to help reduce weight and thickness?
A
Myoflange
14
Q
What type of edge design is often put on a high minus lens that is riding too high?
A
Hyperflange
15
Q
What is CPC?
A
Central posterior curve
16
Q
What is IAC?
A
Intermediate anterior curve
17
Q
What is PPC?
A
Peripheral posterior curve
18
Q
What is CAC?
A
Central anterior curve
19
Q
How many peripheral curves does a tri curve lens have?
A
3
20
Q
Which surface of a contact lens do refer to as the base curve?
A
CPC
21
Q
Which surface of a contact lens delivers the power?
A
BVP- Back vertex power (posterior)
22
Q
What are three classifications of contact lenses according to size or the area they cover?
A
Corneal, scleral, or semi scleral
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
24
Q
A contact lens that absorbs water would be called
A
Hydrophilic
25
A contact lens that does not absorb water would be called
Hydrophobic
26
Lens diameter formula
Optical zone diameter +2 (IPC (BW)+PPC(BW))
27
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?
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
28
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?
D=8.3mm
USE DIAMETER FORMULA:
OZ+2(IPC(BW)+PPC(BW))
BREAKDOWN:
OZ=6.5 mm
IPC=0.4mm
PPC=0.5mm
6. 5 + 2 (0.4 + 0.5)
6. 5 + 1.8
8. 3 mm
29
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?
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
```
30
What unit is the CPC( base curve) measured in?
Millimeters of radius of an arc or in diopters
Example:
7.71mm = 43.75 D
31
Does a shorter radius of curvature mean more power or less power?
More power
32
Does a longer radius of curvature mean more power or less power?
Less power
33
Convert 42 Dioptric powers to radius of curvature 
8.03
TAKE 337.5 and divide by Diopter
337.5/42= 8.03
34
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?
Shorter and steeper
35
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?
Longer and flatter
36
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
1. 6.250
2. 6.750
3. 7.417
4. 7.500
5. 8.257
6. 9.926
37
Define sagittal vault
The greater the sagittal height, the greater the vaulting of the lens.
38
Define sagittal depth or height
The distance between a flat surface and the back surface of the central portion of the lens.
39
The greater the sagittal vault ,
The steeper the lens fits
40
Sagittal vault increases if the diameter of a lens is increased while the radius of curvature _________
Remains constant
41
Sagittal vault increases if the diameter of a lens remains constant but the radius of curvature __________
Decreased
42
To steepen a lens
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
To Flatten a lens
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
To effect a small change
Change one parameter only
| Either the B.C or the diameter
45
To effect a larger change
Change both parameters at the same time
46
When the radius of a curve changes by 0.05mm
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
If the base curve of a contact lens was fitted as 7.70 mm then changed measuring 7.60mm, it is:
0.50 D steeper than the original lens
48
If the base curve of a contact lens was fitted as 7.55mm then changed measuring 7.65mm, it is:
0.50D flatter than the original lens
49
Which of the following radii of curvatures of contact lenses indicates the flattest base curve?
7. 60mm
7. 80mm
7. 90mm
8. 00mm
8.00mm
50
Which of the following radii of curvature of contact lenses indicates the steepest base curve?
6. 75mm
6. 85mm
6. 95mm
7. 05mm
6.75mm
51
If the base curve of a contact lens is 45.00D, its radius of curvature is:
7.50mm
52
Which of the following dioptric power indicates the steeper curve?
42. 00D
42. 50D
43. 00D
45. 00D
45.00D
53
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?
7. 35mm
7. 45mm
7. 50mm
7. 60mm
7.35mm
54
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?
7. 40mm
7. 45mm
7. 55mm
7. 35mm
7.55mm
55
Which dioptric power represents the flattest radius of curvature?
44. 75D
44. 25D
46. 00D
45. 25D
44.25D
56
Which dioptric power represents the steepest radius of curvature?
46. 00D
45. 75D
46. 50D
45. 25D
46.50D
57
Define Optical Zone
Chord diameter over which the base curve extends on the posterior surface of the contact lenses.
58
Define lenticular flange
An increase or decrease in anterior edge thickness
59
Define truncation
The removal of the interior and or superior portion of the lens to control rotation.
60
Define fenestration
A tiny hole in a contact lens to allow for exchange of tears and oxygen.
61
Define back surface
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
Define front surface
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
Define bitoric
Cylindrical curves on both the anterior side and the posterior side with principal meridians located 90° apart. 
64
Define blends
Junctures between posterior curves after being smooth out by polishing.
65
Define Sagittal depth
The distance between the posterior surface of a central area of the lens and a flat surface. 
66
TIGHTER, LOOSER, OR THE SAME:
| Increase in sagittal depth
Tighter
67
TIGHTER, LOOSER, OR THE SAME:
| Decrease in sagittal depth
Looser
68
TIGHTER, LOOSER, OR THE SAME:
| Steeper base curve
Tighter
69
TIGHTER, LOOSER, OR THE SAME:
| Flatter base curve
Looser
70
TIGHTER, LOOSER, OR THE SAME:
| Larger diameter
Tighter
71
TIGHTER, LOOSER, OR THE SAME:
| Smaller diameter
Looser
72
TIGHTER, LOOSER, OR THE SAME:
| Smaller diameter, steeper base curve
Same
73
TIGHTER, LOOSER, OR THE SAME:
| Smaller diameter, flatter base curve
Looser
74
TIGHTER, LOOSER, OR THE SAME:
| Larger diameter, flatter base curve
Same
75
TIGHTER, LOOSER, OR THE SAME:
| Larger diameter, steeper base curve
Tighter
