Stand Magnifiers And Equivalent Power

Question 1

Plus lens or plus lens combination mounted in a housing that sits on the material being viewed

Answer 1

Stand magnifiers

Question 2

Stand height

Answer 2

Typically less than the focal length of the lens

Question 3

Image of the stand magnifier

Answer 3

Forms erect virtual image a finite distance behind the page

Question 4

Enlargement of the lens

Answer 4

• depends not he Fe of the lens and emerging vergence
• system consists of the magnifier F1 and the pateitns add or accommodation
• magnification is a result of RDM and lenargment by the lens itself M=RDM x E

Question 5

Magnification of stand mag

Answer 5

M=RDM x E

Where they hold the material
Properties of the stand

Question 6

Add for stand magnifier

Answer 6

1/(i+h)

Virtual imag distance=i
Dist between lens and eye=h

Question 7

A stand mag has an enlargement factor of 1.8X and its image is 18cm behind the lens. The patient uses a +3.00 add and has a VA of 0.33/4M with the glasses alone. How far away from these glasses must the patient hold the mag?

Answer 7

+3.00 add=33cm working distance
Working distance=i+h
33cm=18cm +h
H=15cm

Question 8

A stand magnifier has an enlargement factor of 1.8X and its image is 18cm behind the lens. The patient uses a +2.00 add and has a VA of 0.50/4M with the glasses alone. The patient desires to change to a +3.00 add for fill time wear. What mag is this pateint expectd to achieve

Answer 8

Mag=RDM x E

(.5/.33)x 1.8=2.72x

Question 9

A stand magnifier has an enlargement factor of 1.8X and its image is 18cm behind the lens. The patient uses a +2.00 add and has a VA of 0.50/4M with the glasses alone. The patient desires to change to a +3.00 add for fill time wear. What M size can be read?

Answer 9

Mag=(what you got)/(what you need)

2.72x=(4M)/(what you need)
4/2.72=(what you need)
What you need=1.47M

Question 10

A stand magnifier enlarges an object 5X and the image is 20cm behind the lens. The patient has a +2.50 add and reference VA of 0.4/5M. Using his glasses, how far away from the spectacle plane must he hold the magnifier

Answer 10

40cm=20cm + h

h=20cm

Question 11

A stand magnifier enlarges an object 5X and the image is 20cm behind the lens, the patient has a +2.50 add and reference VA of 0.4/5M. What size print should be be able to read using the magnifier and his glasses?

Answer 11

.4/.4=RDM
5=E
5x1=5

5/5=1M

Question 12

A stand magnifier enlarges 3X and has an image location 30cm behind the lens. The patient’s reference acuity is 0.25m/8M using a +4.00 add. She prefers to hold the magnifier 14.5cm from the spectacle plane. What add will this absolute presbyope need?

Answer 12

WD=h+i
30=i
14.5=h
WD=30+14.5=44.5cm
1/.445=2.25

Question 13

A stand magnifier enlargers 3X and has an image location 30cm behind the lens. The patient’s reference acuity is 0.25m/8M. She prefers to hold the magnifier 14.5cm from the spectacle plane. With the appropriate adds, what size print would you expect her to read?

Answer 13

WD=h+i=30+14.5=.445m
MStand=RDM x E. (.25/.445)x3=1.68

1.68=8/X
X=4.75M

Question 14

Enlargement factor

Answer 14

Is sometimes published, but can also be calculated using the following formula

E=(V-Fe)/V

Question 15

Equivalent power of stand magnifier

Answer 15

Fe=F2xE

Question 16

What is the equivalent power of a stand magnifier labeled 3X, E=2.3X, i=22cm

Answer 16

Insufficient information

Need the add

Question 17

Use of stand magnifiers

Answer 17

Really good for better contrast. All stand magnifiers should be touching the material they are using

Question 18

Equivlanet power

Answer 18

• Fe for a lens or lens system is the power of the thin lens that if positioned at the second principal plane of the system, its posterior focal point cosincides with the posterior focal point of the system
• can use this to compare the magnification between optical systems
• there is considerable disparity between vertex power and equivalent power

Question 19

Equivlanet power of lenses separated by air

Answer 19

• if a patient accommodates with an add, or uses an add or accomodation in conjunction with a magnifier, a new optical system is created compared of the 2 plus lenses
• Fe=F1-F2-(t)(F1)*(F2)

Question 20

Fe is > F1

Answer 20

When the magnifier is held less than one focal length from the add

Question 21

Fe < F1

Answer 21

When the magnifier is held more than one focal length from the add

Question 22

Equivalent power microscope

Answer 22

F=M/r

Question 23

Equivalent power of HHM

Answer 23

F=M/r

Question 24

Equivalent power of stand mag

Answer 24

Fe=F2xE

Question 25

Equivlanet power of telemicroscope

Answer 25

Fe=F2xMTS