Midterm 2: Angular Magnification

Question 1

Perception of size in vision is not related solely to _____ image size. It is related to ______ image size.

Answer 1

Lateral; retinal

Question 2

Perception is the combination of the lateral image ______ and the ______ of the image

Answer 2

size; location

Question 3

Angular magnification is the relative difference between…..

Answer 3

angle of the image makes to the eye AND the angle the object makes to the eye.

Question 4

What is Aniseikonia?

Answer 4

A difference in brain image sizes. Makes it difficult to fuse images which could makes it hard to have binocularity.

Question 5

How could angular magnification be associated with astigmatisms?

Answer 5

If there is a large astigmatism with a large difference in powers in the principal meridians, it could create a monocular image shape, adaption problems, and asthenopia (fatigue)

Question 6

How could you help a patient with MD when relating to angular magnification?

Answer 6

Increase the retinal size of the image so more photoreceptors can interpret the image

Question 7

3 Types of Angular Mag

Answer 7

1) Relative distance mag
2) Relative size mag
3) Spectacle mag

Question 8

Relative distance mag explanation/ equation.

Answer 8

Change distance of object without changing its size.

RDM = old distance / new distance

“If i move an object closer, it ill look bigger”

Question 9

Relative size mag explanation/equation

Answer 9

Change the size of the object but keep the same distance.

RSM = New size/ old size

Question 10

Spectacle mag explanation/ equation

Answer 10

Compares retinal image size with and without lens correction for only one eye. Also used for contact lenses and one eye by itself.

“How large the world looks before versus after the lens is put in front
of eye”

Question 11

Spectacle mag for minus lenses

Answer 11

image will always appear smaller

Question 12

Spectacle mag for plus lenses

Answer 12

Always larger UNLESS plus lens is far from the eye (f’ between you and object)

Question 13

Spectacle mag is based on how far the lens is from the eye, specifically the _________.

Answer 13

entrance pupil (iris image)

Question 14

What do we do to find the correct distance an object is from the eye?

Answer 14

Take the object distance and add 3 mm to include the distance to the entrance pupil from the surface of the cornea.

Question 15

What is the reference distance for spectacle magnification? Value for CL and spectacle lenses.

Answer 15

Distance from the back of correcting lens to entrance pupil.

For contact lenses: 3mm

For glasses: 3mm + vertex distance for specs

Question 16

What does angular mag have to do with?

Answer 16

The perception of how big something is.

Question 17

How do we find angular magnification using tangent?

Answer 17

Ma= Tan (angle of image) / Tan (angle of object)

Question 18

How do we find percent magnification of angular mag?

Answer 18

100(Ma-1)

Question 19

How much increase is 14% increase?

Answer 19

1.14x original object.

Question 20

Size of retinal image is given by the _______ ray which is the ray aimed at the center of the entrance pupil.

Answer 20

Chief ray

Question 21

What can cause spectacle magnification?

Answer 21

Power of lens - back vertex power, reference distance

Shape of lens - base curve, center thickness, index of refraction

Question 22

How to find spectacle magnification?

Answer 22

Ma (spectacle) = Power factor x Shape factor

Question 23

Power factor equation for distance used for spectacle mag equation

Answer 23

Ma = 1 - reference distance (object vergence) / 1 - reference distance (image vergence)

Question 24

Power factor equation for near used for spectacle mag equation

Answer 24

Ma = 1 / 1 - reference distance (power)

Question 25

If you move a lens further away, does that increase or decrease power factor?

Answer 25

increase

Question 26

f you power of lens, does that increase or decrease power factor?

Answer 26

increase