Optics Lecture 3

Question 1

What happens to the PSF if aberrations are added

Answer 1

It increases

Question 2

Formula for strehl ratio

Answer 2

(Max aberrated)/(max diffraction)

Question 3

Which aberration decreases amplitude and has transverse shift

Answer 3

Coma

Question 4

The spatial frequency at which the MTF goes to zero is

Answer 4

Resolution limit

Question 5

Device that control focus of retinal image for the purpose of measuring power of eye

Answer 5

Optometers

Question 6

Consists of movable target and a fixed positive power lens placed at its focal distance away from the eye

Answer 6

Simple optometer

Question 7

Advantages of simple optometer

Answer 7

Allows both positive and negative vergence

Question 8

Disadvantages of simple optometer

Answer 8

Target vergence and angular size vary inversely with target distance

Question 9

Movable auxiliary lens deals with

Answer 9

Badal optometer

Question 10

What is badal principle

Answer 10

1. Auxiliary lens (minus) between target and badal lens
2. Eye at back focal point of badal lens (plus)
3. Target vergence and angular size remain independs of distance allowing for both positive and negative vergence

Question 11

4 advantages of badal optometer

Answer 11

Linear power scale
Uniform sensitivity
Irradiance of eye
Constant focus (accom)

Question 12

The size of the image is Constant regardless of optical distance in which otptometer

Answer 12

Badal

Question 13

Which optometer has a speckle pattern

Answer 13

Laser speckle optometer

Question 14

With the laser speckle optometer, the pattern moves in the same direction as screen in what kind of eye

Answer 14

Myopic

Question 15

With the laser speckle optometer, the pattern moves in opposite direction of screen in what eye

Answer 15

Hyperopic

Question 16

If the point source is conjugate with retinal plane, the pattern will not move, instead it will

Answer 16

Boil

Question 17

Distance at which eye focus when there is nothing to focus on

Answer 17

Retina point of accomm

Question 18

In the chromatic optometer, what does an emmetrope see

Answer 18

Purple disc

Question 19

In the chromatic optometer, what does a myope see

Answer 19

Red central spot surrounded by blue

Question 20

In the chromatic optometer, what does a hyperope see

Answer 20

A blue spot surrounded by red

Question 21

Assess refractive state by photographing the pattern of light returned from pupil

Answer 21

Photo-refraction

Question 22

Advantages of photorefraction

Answer 22

• refract both eyes at same time

- limited attention required

Question 23

How to calculate magnitude3 of refractive error (RRE)

Answer 23

RRE = (d)/(2xpxa)

D= diameter of double pass point spread image
P = pupil diameter
A = distance from camera to pupil

Question 24

In photorefraction, a hyperopic eye

Answer 24

Red in periphery, blue in center (far point behind camera lens)

Question 25

In photorefraction, a myopic eye

Answer 25

Blue in periphery with red in center (far point between camera and eye)

Question 26

Can we prescribe refractive corrections from objective or WF measurement

Answer 26

No

Question 27

What is the gold standard of refraction

Answer 27

Clinical phoroptor method