Optics

Question 1

ATR

Answer 1

S - C x 090
in minus form, axis at 090
Steeper meridian at 180

Question 2

WTR

Answer 2

S - C x180
in minus form, axis at 180
Steeper meridian at 090

Question 3

Spherical CL fit over WTR astigmatism

Answer 3

Horizontal dumbbell shape fluorescein pattern

Question 4

Spherical CL fit over ATR astigmatism

Answer 4

Vertical dumbbell shape fluorescein pattern

Question 5

Amp Equations

Answer 5

Avg: 18.5 - 0.3(age)
Min: 15 - 0.25(age)

Question 6

Sheard’s Rule

Answer 6

Exo
Demand should be at least 2x reserve
Prism needed: 2/3(phoria) - 1/3(blur/break pt)

Question 7

Percival’s Rule

Answer 7

Eso
Bigger break/blur should be at least 2x smaller
Prism needed: 1/3(bigger blur) - 2/3(smaller blur)

Question 8

Frame PD

Answer 8

FPD = A + DBL

Question 9

Lens Decentration

Answer 9

Dec = (FPD - PD)/2

Question 10

Minimum Blank Size

Answer 10

MBS = ED + 2(Dec) + 2mm

Question 11

Seg Inset

Answer 11

SI = (Dist PD - Near PD)/2

Question 12

Total Inset

Answer 12

TI = Dec + SI

Question 13

Frame Adjustments

Answer 13

Move temple toward the problem

Decrease seg height by:
Increasing panto tilt
Decreasing vertex distance

Question 14

Optimal Refractive Index of AR Coating

Answer 14

nₐᵣ = √nₗₙₛ

Question 15

Polarizing Lenses limit light from what direction

Answer 15

Limit light reflected horizontally
(Allow only vertical)

Question 16

Lens Clock

Answer 16

Fₜ = F꜀ [(nₜ-1)/n꜀-1)]

n꜀ usually 1.523

Question 17

Equivalent Power

Answer 17

Fₑ = F₁ + F₂ - (t/n)F₁F₂

Question 18

Front Vertex Power

Answer 18

Fₙ = F₁ + F₂/(1-(t/n)F₂)

Question 19

Back Vertex Power

Answer 19

Fᵥ = F₁/(1-(t/n)F₁) + F₂

Question 20

Lens Thickness

Answer 20

t꜀ - tₑ = (Fₐr²)/[2(n-1)]

Question 21

Microscope Magnification

Answer 21

Mag = (Lateral Mag)(Fₒ/4)

Question 22

Hand Held Magnifier

Answer 22

Mag = dF

Question 23

Spectacle Magnification

Answer 23

Question 24

What increases Spec Mag

Answer 24

Increased thickness
Increased BC
Increased F
Increased vertex distance on PLUS lens
Decreased vertex distance on MINUS lens
Decreased n

Question 25

Power of a Mirror

Answer 25

F = -2n/r

Question 26

Distance lensometer must be turned to focus lines

Answer 26

x = Pₗ (fₛₜ²)

Question 27

BC/Keratometry Conversion

Answer 27

K = 337.5/BC

Question 28

Deviation Angle

Answer 28

θ = θₐ (n-1)

1ᵒ is about 1.75PD

Question 29

Amount of light reflected at a surface

Answer 29

R = [(n₂ - n₁)/(n₂ + n₁)]²

(Light transmitted = 1 - R)

Question 30

Do myopes accommodate and converge more with CLs or specs

Answer 30

More with CLs than specs

Question 31

What does keratometer treat the cornea surface as

Answer 31

Convex mirror

Question 32

Knapp’s Law

Answer 32

Axial ametropes best corrected with specs
Refractive ametropes best corrected with CL

Question 33

Night myopia occurs due to

Answer 33

Increased pupil size causing:
Decreased depth of focus
Increased aberrations
Induced/Inaccurate accommodation

Question 34

BIO vs DO

Answer 34

BIO:
- Inverted
- Reduced magnification
- Bigger field of view
- Greater depth of focus
DO:
- Upright
- Increased magnification
- Smaller field of view
- Increased depth of focus

Question 35

VA

Answer 35

20/SD
(20/Snellen Denominator)

Measure of high spatial frequency cutoff on contrast sensitivity function

Question 36

VA to Cycles Per Degree

Answer 36

600/SD

20/20 VA = 30 CPD

Question 37

1M to VA

Answer 37

1M = 20/50

Question 38

MAR

Answer 38

MAR = 1/VA

Question 39

Log MAR Estimation

Answer 39

20/20 = 0 LogMAR
0.1 = 1 line
0.02 = 1 letter

Question 40

Axis of astigmatism by sharpest clock dial line

Answer 40

Minus cylinder axis = clock hour x 30