Lensometry Multifocal Flashcards Preview

Ophthalmic Optics Block 9 > Lensometry Multifocal > Flashcards

Flashcards in Lensometry Multifocal Deck (48):
1

What is the green and orange light on the lensometer for

Green for light lenses
Orange for sunglasses

2

Lenses that contain two or more loess power to let you see at different distances

Multifocal

3

Who wears multifocal

Over 40, children

4

Types of multifocal

Progressive
Bifocal
Trifocals

5

Must you set the axis on 180 before doing lensometry>

No

6

Line multifocal design

Front surface design

7

What is the distance between the optical center and the top of a bifocal

3-5mm

8

What is the distance between the optical power and the trifocal add power

1-3mm

9

How to read the add power on lensometer

Go from single to single or from cyl to cyl. Don't fluctuate between the two

10

What side of the lens is thicker on multifocal

Front

11

How do you read the add power on a multifocal in lensometry

Flip the glasses around and find it that way. Also check the distance power again flipped and subtract the difference between the two, to make sure you are using a uniform side to do this.

12

When should you do the proper front/back vertex reading for add power

When the Rx is: +/-5 with an add of +2.50 or greater

13

Corrective lenses used in eyewear to correct presbyopia or other accommodation issues

Progressive lenses

14

Types of progressives

Multifocal, no lines, PAL

15

Downside of progressive lenses

Distortion on the side

16

Designates the point on a lens that should be placed at the center of the pupil

Fitting point

17

Areas used to verify prescribed distance power

Distance reference circle

18

Optical center of a PAL, used to check prism

Prism reference point

19

Located on nasal side, under micro-circles/references lenses type/material

Alignment markings and manufacturing logo

20

Used to verify total near point

Near reference point

21

Located on temporal side/ used to verify add power

Add power

22

What side is is the add power always on

Temporal side

23

When reading progressives, it is important to mark these points on each lense before proceeding

Dot it up

24

Where is the reference point usually

4mm up from the 180 line

25

Where is the prism in a progressive lens

Right int he middle of the 180 line

26

Reading distance on progressive lenses

Distance reference point

27

Where do you read the add power on a progressive lens

Read add power from the near reference point (down to the nasal)

Some manufacturers tell you not to do this. Short frames will read inaccurate. Digitally surfaced lenses will not be in quarter increments. Can be a +1.56 or something to that effect

28

How do you read the prism on a progressive

Right in the middle of the 180 line

29

Triangulated pieces of glass that pass through it and change the direction of light

Prism

30

Thinner in the middle, thicker on the side

Minus

31

Thicker inthe middle

Plus

32

A unit that describes the power of a prism to produce a cone centimeter deviation in a ray of light at a distance of one meter from the lens

Prism diopter

33

Involves the grinding of the surface of a lens during a manufacturing

Ground in prism

34

Involves decentering the optical center to utilize the pristmatic effects of sphere-cylindrical lens. Prentice's rule

Induced prism

35

How do you know you have ground in prism

It will never lien up with the mires

36

How do you know you have induced prism

The mires can only be centered when the lens is decentered

37

What kind of lenses can you induce prisms into

Single vision lenses

38

What kind of prism has to be in progressives

Ground in

39

Minor powers and prism

Cannot induce prism

40

Unwanted prism

Calculate prentice rules
Can be vertical and horizontal imbalance

41

Too much BD prism

Vertical objects appear taller than they are. Looks like you are walking up a hill

42

Too much BU prism

Vertical objects will appear smaller

43

Too much BI or BO prism

Horizontal lines will have a curve to them

44

PAL and prism thinner

In PAL, surface power power increases as you go down, but it also increases thickness on the opposite side. Manufacturers want their lenses to look as good as possible, use prism thinning which induces prism, whether Rxed or not.

Most thinning is BD

45

Prism that is up in both eyes, or down in both eyes

Cancel each other out

46

Prism that is in in one eye, and out in the other eye will

Cancel each other out

47

How do you read prism on a progressive lens

Read from the prism reference point

48

3 ways you can get prism from a single vision

Exam history
Lab ticket
Getting optical center while patient wears them