Magnification Flashcards
1
Q
What is magnification
A
- needed when the prescription does not create enough improvement and if visual acuity is insufficient for identified tasks
2
Q
What is the ratio that defines magnification
A
- after retinal image size/before retinal image size
3
Q
Methods of producing magnification
A
- increase object size
- decrease viewing distance
- real image or traverse magnification
- telescopic magnification
4
Q
Formula to increasing size of object
A
- M = new object size/old object size
5
Q
Methods for increasing object size
A
- large print books
- e-books
- large tv controls
- large digital alarm clock
6
Q
Formula for decreasing viewing distance
A
- original viewing distance/new viewing distance
- M=F/4
7
Q
Formula for real image magnification, and advantage
A
- size of image/size of original object
- M=h2d1/h1d1
- not optical method
Advantage
- ability to adjust the magnification
- manipulate contrast
- change colour
8
Q
Telescopic magnification formula
A
- M= angle subtended by image/angle subtended by object = θ ‘/θ
- M=-Fe/Fo
