Physiological Optics 1.4

Question 1

Spectacle Mag Equation using Image Size

Answer 1

Image size w/ glasses / Image size w/o glasses

Question 2

Spectacle Mag Long Equation

Answer 2

Shape Factor x Power Factor
Shape Factor = 1 / 1 - (t/n F1)
Power Factor = 1 / 1 - hFv
h = vertex distance + 3mm

Question 3

Spectacle Mag Trends for Plus Lens

h, t, n, BC

Answer 3

Spectacle Mag increases with increases in h (vertex distance), t, and BC
Spectacle Mag decreases as n increases

Question 4

Spectacle Mag Trends for Minus Lens

h, t, n, BC

Answer 4

Spectacle Mag increases with increases in t and BC

Spectacle Mag decreases as n and h(vertex distance) increases

Question 5

Increase in thickness causes what change to Spectacle Mag

Answer 5

Increases for both plus and minus lenses

Question 6

Increase in BC causes what change to Spectacle Mag

Answer 6

Increases for both plus and minus lenses

Question 7

Increase in n causes what change to Spectacle Mag

Answer 7

Decreases for both plus and minus lenses

Question 8

Increase in vertex distance causes what change to Spectacle Mag

Answer 8

Increases for plus lenses but decreases for minus lenses

Question 9

Relative Spectacle Magnification

Answer 9

Compares the Image size in a corrected pt to the image size in a standard eye
Corrected image size / Standard eye image size

Question 10

Knapp’s Law

Answer 10

RSM = 1 if a lens is places at the eyes primary focal point
Correct Axial Ametropes with glasses
Correct Refractive Ametropes with CLs

Question 11

Compare image sizes in Uncorrected Ametropes

Refractive vs. Axial

Answer 11

Uncorrected Refractive Ametropes have the SAME image size

Uncorrected Axial Myopes have a larger image size than Axial Hyperopes

Question 12

Compare image sizes in Corrected Ametropes

Refractive vs. Axial

Answer 12

Spec Corrected Refractive Hyperopes have a larger image size than Axial Myopes
Spec Corrected Axial Hyperopes have a larger image size than Axial Myopes and an RSM = 1

Question 13

Anisekonia and Types

Answer 13

Anisekonia is difference in image size b/t eyes

• Anatomical: Anatomical Asymmetry (PR density)
• Induced: Optics of correction (Spectacle Mag)
• Meridional: differences in cyl power b/t eyes (Tilts a vertical image)

Question 14

How much anisekoinia is present per 1.00D of power difference

Answer 14

1% anisekonia, 3% becomes a problem

Question 15

Rules of Thumb for prescribing with Anisekonia

Answer 15

Prescribe a thicker, steeper lens for the eye with lower RSM
> 4.00 of anisekonia is usually Axial so Rx glasses
< 4.00 is usually refractive so Rx CLs

Question 16

Adaptation to Anisometropia in Myopes

Answer 16

Pt will learn to use one eye for distance and one for near

Question 17

Adaptation to Anisometropia in Hyperopes

Answer 17

Pt uses the same eye for distance and near putting them at risk for amblyopia

Question 18

Equation for Reflection at an interface

Answer 18

Uses Fresnel’s Law

[ (n2 - n1) / (n2 + n1) ]^2

Question 19

Equation for Overall Transmittance

Answer 19

(Transmittance at Front) (Transmittance at Back) (1 - %Absorbed)