Ophthalmology - Abo/okap - Optics

Front 1

In the conoid of Sturn, where is the location of the circle of least confusion?

Back 1

halfway (dioptrically) from each of the two lines

Front 2

What is the equation that relates the lens power in air and in fluid?

Back 2

D(air) = N(iol) - N(air)
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D(fluid) N(iol) - N(fluid)

Front 3

A Rodenstock lens gives you what kind of image

Back 3

Inverted and reversed

Front 4

Use two lines to identify an image

Back 4

1. line parallel to the axis will exit lens and travel through the focal point.
2. line through the optical center will not deviate.
* The three line principal will use a third line that will pass through the focal point and leave the lens parallel to the axis.

Front 5

Describe the power cross

Back 5

The power cross represents a lens system using meridians, which indicate what location the light is acted on which is 90* from the axis of a lens that causes that change (which can be represented with an axis cross).

Front 6

Convert a power cross to negative cyl Rx

Back 6

(most positive #) - (difference) x (Axis of most positive meridian)

Front 7

in a concave/convex mirror system, what is the relation of the radius and focal point

Back 7

Radius = 2 x focal point

Front 8

Equation for transverse magnification

Back 8

M = U = image height = image distance
-- ------------------ --------------------
V object height obj distance

Front 9

Equation for angular magnification

Back 9

M = D/4 D = lens power

Front 10

Equation for magnification of a telescope

Back 10

M = D eyepiece/D objective

Front 11

IOL power calculation

Back 11

D = A -2.5(AL) - 0.9(avg K)

Front 12

Equation for the reflecting power of a spherical mirror

Back 12

D = 100/f =200/r
f & r in cm

Front 13

Gradient method for AC/A

Back 13

PDsc -PDcc
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| Dsc - Dcc |

Front 14

using a + cyl to correct for astigmatism of the cornea. Where would the axis be placed

Back 14

at the steeper meridian

Front 15

Define Kestenbaum's rule

Back 15

power of lens needed to read newsprint = reciprocal of VA
e.g. 160/20 = +8 magnifier

Front 16

When light enters a medium of higher index what happens to speed, wavelength and frequency

Back 16

Frequency remains the same, and speed and wavelength slow down.

Front 17

As wavelength increases what happens to
1. refraction
2. defraction

Back 17

1. decreases
2. increases

Front 18

To increase power applied per delivery do what to:
1. energy
2. time
3. other things that increase power

Back 18

1. increse
2. decrease
3. q switch and mode lock

Front 19

Position of prisms:
1. glass
2. plastic

Back 19

1. prentice position: one surface perpendicular to the light
2. angle of min deviation

Front 20

What is the equation for refracting power of a surface?

Back 20

D = (n' - n)/r
r is in meters
D is +/- based on rectangle, with high n being colored in

Front 21

Aspects of a thick lens

Back 21

two nodal points/planes. If n is different from one side to the other, nodal points move to the higher n

Front 22

Basic scematic of the eye

Back 22

+60D
nodal point 17mm from retina & 5.5 from cornea

Front 23

Describe relation between degrees, seconds, minutes and Snellen acuity

Back 23

1 sec of arc = 1/60 of a minute of arc
1 minute of arc = 1/60 of a degree
20/20 means that you can distinguish at 1 arc minute (with a 5 minute E - which has five 1' lines and gaps)

Front 24

When using free lenses and a retinoscope, describe the results in an axis cross.

Back 24

axis is the same as the light of the intercept. lens power would be the lens used minus the working distance (~1.5)

Front 25

Describe the different telescopes

Back 25

Astronomic: uses two + lenses, image is inverted, length of scope is the sum of the focal lengths
Galilean: uses one + and one - lens, upright image, Length = difference in focal lengths

Front 26

What is the amount of mag/min induced by glasses?

Back 26

2% per diopter
- lens minifies
+ lens magnifies
6% image difference is tolerable

Front 27

describe ray tracing with mirrors

Back 27

central ray goes through radius, not the focal point

Front 28

Describe how cromatic light is bent at a prism

Back 28

Blue base
red top

Front 29

When using free lenses and a retinoscope, describe the results in an axis cross.

Back 29

axis is the same as the light of the intercept. lens power would be the lens used minus the working distance (~1.5)

Front 30

Describe the different telescopes

Back 30

Astronomic: uses two + lenses, image is inverted, length of scope is the sum of the focal lengths
Galilean: uses one + and one - lens, upright image, Length = difference in focal lengths

Front 31

What is the amount of mag/min induced by glasses?

Back 31

2% per diopter
- lens minifies
+ lens magnifies
6% image difference is tolerable

Front 32

describe ray tracing with mirrors

Back 32

central ray goes through radius, not the focal point

Front 33

Describe how cromatic light is bent at a prism

Back 33

Blue base
red top

Front 34

Go through the steps involved with converting glasses to RGP contacts.

Back 34

1. set base curve +0.50 steeper than the flattest K
2. convert glasses to minus lens
3. drop the cylinder
4. correct vertex distance based on far point
5. subtract 0.50 (tear lens)

Front 35

RK does what to the focal power of the cornea?

Back 35

It makes it more minus (flattens the center)

Front 36

When measuring strabismus in glasses, what is the correction?

Back 36

minus measures more
2.5 x D = x%
subtract that percentage from the observed value in a minus lens

Front 37

What is the reflecting power of a mirror

Back 37

1/f (in meters)

Front 38

give the refractive indicies of:
1. Water
2. cornea
3. lens
4. PMMA
5. crown glass
6. polycarb

Back 38

1. 1.33
2. 1.37
3. 1.42
4. 1.49
5. 1.52
6. 1.59