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Ophthalmic Optics Block 9 > Standards And Measurements > Flashcards

Flashcards in Standards And Measurements Deck (58):
1

50-18-140

Eye-bridge-temple

2

Range of eye size

40-62

3

Range of bridge size

14-24

4

Range of temple measurements

120-150mm

5

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

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

6

Boxing system

Worldwide standardization of measurements of frames to determine frame size

7

A measurement

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

8

B measurement

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

9

Datum line

Line right across the middle, vertical center of the frame

10

Geometric center

Half of the B and half of the A
The center of the lens

11

DBC

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

12

DBL

Distance between lenses
Shortest distance between the nasal edges of each lens

13

ED

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

14

OTL

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

15

Optical center

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

16

Optical center, pupil center, and MRP in ideal world

Should be the same, but never are

17

Pupil center

Same as the optical center when no pantoscopic tilt

18

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

Lower it 1 degree

19

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

Centration

20

MRP major reference point

Same thing as optical center when there is no Rxed prism

21

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

Decentration

22

If frame PD > patient PD

Decentration In

23

If the patient PD > frame PD

Decentration out

24

Distance from pupil center to the other, set at infinity

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