Ophthalmic Optics Formulas Flashcards

1
Q

Minimum blank size

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Total decentration

A

(A + DBL) - pt PD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Frame PD

A

A + DBL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

ED

A

Double the distance of the edge of the lens farthest away from geometric center

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Frame difference

A

A size - B size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Exact sag formula

A

H is half the chord length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Thickness equation for biconvex lens

A

CT = Sf + ET + Sb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Crown glass

A

n = 1.523
V = 58

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

plastic CR-39

A

n = 1.498
V = 58

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Polycarbonate

A

n = 1.586
V = 30

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Trivex

A

n = 1.53, V=44

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Lens clock correction formula

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Nominal power

A

Front surface power + back surface power
F1+F2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Spherical equivalent

A

SE = sph + cyl/2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Distance target moved on lenso

A

f is focal length of the standard lens in the lensometer, Fv is Fbvp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Back vertex power

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Front vertex power

18
Q

OC locations of flat-top segs

A

For 22, 25, 28mm -> OC is 5mm below top of seg
For 35mm -> OC is 4.5mm below top of seg
For 40, 45mm -> OC is on the line (0mm)

19
Q

OC locations for round segs and executives

A

Round segs -> OC half way through diameter of round seg
Executive seg -> OC is on the line (0mm)

20
Q

Inset

A

frame pd - pt pd (divide by 2 if monocular situation)

21
Q

Seg inset

A

distance pd - near pd (divide by 2 if monocular situation)

22
Q

total inset

A

frame pd - near pd (divide by 2 if monocular situation)

also is seg inset + inset

23
Q

Image jump

A

Prism = cF
(distance bw seg OC to dist OC)(add power)

24
Q

TCA

A

amount of prism looking through / V

25
LCA
Power of lens / V
26
power error
(tangential error + sagittal error) /2
27
Effective power
left to right direction is positive
28
prism diopters
= cm/m (image jump over distance)
29
Angle of deviation (approx)
D = A (n-1)
30
Prism based on thickness of base and apex
Prism = 100g(n-1) / d d is distance bw apex and base g is thickness difference bw apex and base (match units)
31
One degree of deviation angle for a prism is how many prism diopters?
1.75 pd
32
Prentice rule
33
Amount of BD necessary in progressive lens
Add power x 2/3
34
Spec mag
35
Reflection formula
I is intensity of the light incident on the surface
36
Index relationship with reflection/transmittance
Increased n = increased reflections = decreased transmittance lenses seem dimmer to look through
37
Ultimate transmission
T(ultimate) = (T1)(T2)(T3) …
38
Ideal AR coat index formula
39
Lens maker equation
P = (n2 - n1) / r
40
Correcting vertical imbalance
Clinical methods - Slab off (BUMM, base up more minus), multiple specs, CLs, Fresnel prisms Academic methods - dissimilar segs, compensated R segs
41
Prentice rule for image jump in ADDs
Prism = dP , where d is the distance from the top of seg to near OC, and P is the power of the ADD only