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Ophthalmic Optics Block 9 > Standards And Measurements > Flashcards

Standards And Measurements Flashcards

(58 cards)

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1
Q

50-18-140

A

Eye-bridge-temple

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2
Q

Range of eye size

A

40-62

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3
Q

Range of bridge size

A

14-24

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4
Q

Range of temple measurements

A

120-150mm

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5
Q

Why are eyesize, bridge and temple listed o na frame and not any other measurements?

A

These are important for frame fit and selection. These are set and you cannot change these

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6
Q

Boxing system

A

Worldwide standardization of measurements of frames to determine frame size

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7
Q

A measurement

A

Horizontal width of the lens
Between the two vertical lines of the box to the edges of the lenses
Use the edge furthest to the temple and furthest to the nasal

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8
Q

B measurement

A

Vertical height of the lens

Greatest depth of lens (furthest top and bottom of the lens)

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9
Q

Datum line

A

Line right across the middle, vertical center of the frame

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10
Q

Geometric center

A

Half of the B and half of the A

The center of the lens

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11
Q

DBC

A

Distance between centers
-frame Pd
Horizontal centers b/w right and left openings

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12
Q

DBL

A

Distance between lenses

Shortest distance between the nasal edges of each lens

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13
Q

ED

A

Effective diameter

  • 2x the longest radium from their geometric center of the lens to the furthest edge
  • longest distance across the lens (not official)
  • important for cutout
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14
Q

OTL

A

Length of temple

-distance between the middle of the screw barrel to the back edge of the temple, just the length of the temple

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15
Q

Optical center

A

Point on lens where the light ways pass undeviated. No unintentional prism induced into it

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16
Q

Optical center, pupil center, and MRP in ideal world

A

Should be the same, but never are

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17
Q

Pupil center

A

Same as the optical center when no pantoscopic tilt

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18
Q

For every 2 degrees of pantoscopic tilt, you should do what to the optical center

A

Lower it 1 degree

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19
Q

The positioning of the lens for edging, such that as lens optical center is positioned appropriately

A

Centration

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20
Q

MRP major reference point

A

Same thing as optical center when there is no Rxed prism

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21
Q

The displacement, usually horizaontl, of the optical center of a spectacle lens from the geometric center

A

Decentration

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22
Q

If frame PD > patient PD

A

Decentration In

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23
Q

If the patient PD > frame PD

A

Decentration out

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24
Q

Distance from pupil center to the other, set at infinity

Study These Flashcards
A

Pupillary distance

25
How can you measure PD
Monocular and binocular
26
Far PD
Set it at infinity
27
Near PD
Converging eyes PD
28
PTs PD is split 34/32, Rx +2.50OU If the frame size is 44-14-140, how much should each lens be decanters relative to the geometric center?
44+14=58 58/2=29 each side 34-29 is 5 on the right out 32-29 on the right out
29
Rule of thumb for near and far PD
Move in each 2mm, but not 100%
30
-5.00 Ds 1prismD in in OU | What is the amount of decentration necessary to have the prescribed prismatic effect?
Prentice rule Prism= (decentration(mm) x Power)/10 1= (D.C. X -5.00)/10 D.C.=-2mm in
31
When looking for decentration, what rule do you use
Prentice rule Prism power=(dc(mm)xPower)/10
32
Seg height
Ther vertical distance between the bottom edge of the lens and the top of the segment
33
The vertical distance between the datum line and the top of the bifocal or trifocals
Seg drop
34
The distance the center of the near segment is moved laterally from the OC
Seg inset
35
Typical segment heights
- bifocal - trifocals - progressive
36
Bifocal seg height
Top of lower lid
37
Trifocals seg heights
Lower lid margin
38
Progressive seg height
Pupil center
39
Progressive PD
Monocular PD
40
A formula used to determine the smallest possible lens black for a given frame and PD combination
Minimum blank size (MBS) MBS=(DBC-PD) + ED
41
``` A= 52mm DBL=18mm PD=63mm ED=58mm Find MBS ```
52+18=70 MBS=(70-63)+58 65
42
If you get the MBS too thin, what is the problem
No room for error. Can add 2-4mm to it
43
The final step in the manufacturing of eyewear
The inspection process
44
A system of standard and tolerances used to verify eyewear
Inspection process
45
What benefit is the inspection process
Accountability Standard system across optical dispensaries Protest the patient
46
ANSI Z87.1
OSHA and educational eye and face protection that some people will need for their occupation
47
What is ANSI for
Optical and cosmetic ophthalmic. Allow for tolerances
48
How to calculate power in oblique meridians
Sph power + (the cyl power)(sin2theta) Power=S+Csin2theta
49
The differential vertical prismatic effect between the two eyes
Vertical imbalance
50
Can be induced by the right or left lenses of unequal powers when the wearer lowers his or her eyes to view through the near addition
Vertical imbalance
51
Surfacing of a portion of a lens to as to add a second optical center
Slab off Used to alleviate vertical imlabance at near Used to creat vertical prism in the lower portion of the lens
52
Slab off creating vertical prism
Base up prism, so base down is removed
53
Vertical imbalance equation
Lens power@90 X distance from OC/10
54
Calculate the imbalance OD -2.00 +2.25 add OS +1.00 +2.25 add Near power 10mm below OC
2BD 1BU Vertical imbalance of 3D
55
The distance from the back surface of a spectacle lens to the apex of the cornea
Vertex distance
56
When the vertex distance changes
The back vertex needs changed, important for exams for Rxing for glasses and CL
57
Moving away from the eye, ______the effective plus power
Increases -10 to -8 as getting further away from face
58
Equation for vertex distance
New power= (old power)/(1 + change x old power) Change=change in vertex power Minus=reduction Plus=increase In meters

Ophthalmic Optics Block 9 (3 decks)

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