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Optics II block 5 > Visual Acuity And Emmetropia > Flashcards

Visual Acuity And Emmetropia Flashcards

1
Q

Clarity or sharpness of vision

A

Resolution ability

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2
Q

What does resolution ability rely on

A

How close two targets are and the target distance from the eye

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3
Q

What is the best unit to use to resolution ability

A

Angle units

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4
Q

What units do we usually use in physics

A

Radians

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5
Q

What units do we usually use in real world

A

Degrees

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6
Q

What units does optometry usually work with

A

Arcminutes

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7
Q

What field utilizes arcseconds

A

Astronomy

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8
Q

To convert from radians to degrees

A

Multiply 180/pi

To get arc seconds, take the answer and divide by 60

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9
Q

To convert from degrees to radians

A

Multiple by pi/180

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10
Q

Can we see to infinity?

A

Yes

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11
Q

What limits our vision?

A

We can see to infinity but limited by poor eyesight that inhibits detail

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12
Q

How can we best express the separation of two stars

A

Arcsec

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13
Q

When something appears larger or smaller depending on how close it is to us, what do we actually see

A

Angular size

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14
Q

Apparent viewing angle

A

= target size (h)/target distance (d)

You will get the answer in radians, make sure to convert to arc minutes

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15
Q

The smaller angular separation of two distinct resolvable points

A

Minimum angle of resolution (MAR)

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16
Q

What is being determined in VA?

A

Minimum angle of resolution (MAR)

Smallest is better

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17
Q

What is the resolving power ability?

A

The reciprocal of the minimum angle of resolution (MAR)

Bigger the better

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18
Q

The separation (expressed either angularly or spatially) between the closest distinguishable image points

A

Resolution limit

19
Q

The smaller the better

A

Resolution limit

20
Q

Expressed in angle (arcminute, arc second) or length units

A

The reciprocal of the separation between the closest distinguishable points imaged through an optical instrument

21
Q

Resolving power (ability)

A

The larger the better

22
Q

Resolving power (ability)

A

Is expressed in inverse angle (arcmin-1) or inverse length (lines/mm, closes/degree)

23
Q

How do you calculate VA?

A

1/MAR

Make sure MAR is in arcminutes

24
Q

What is VA

A

Not about how far two resolvable objects are

It’s about how small their angular separation is

25
Q

The smaller the MAR, the

A

Better the VA

26
Q

In a corrected eye, what causes blur

A

Diffraction and abberations

27
Q

Larger the pupil diameter

A

The finer the PSF

28
Q

A more confined PSF is achieved with

A

A larger pupil

29
Q

The optical system is only limited by diffraction. Only in very good systems such as out eyes

A

Diffraction-limited

30
Q

Which of the following is a diffraction-limited PSF?

A

A perfect cone looking thing

31
Q

Is a finer or broader PSF better?

A

Finer

32
Q

Better vision is achieved with

A

With a more confined PSF

33
Q

Parks separated by the angular radius

A

Angular separation

34
Q

Can we magnify the image to get better resolution?

A

When two image spots overlap, it does not help any further to magnify the formed image. They will still be overlapping! The spots are either resolved or not

35
Q

Which of the following can be parametrized?

A

Lambda=0.55 microns

D=2mm

36
Q

Human eye minimum angle of resolution (diffraction limit)

A

1 arcminute

37
Q

Which of the following can be parametrized?
A. Wavelength
B. RI
C. Pupil diameter

A

A and C

38
Q

The greater the MAR, the ____ the VA

A

Less

39
Q

The less the MAR, the _____ the VA

A

Greater

40
Q

Small diameter pupil= _______ MAR in diffraction limited scenario

A

Large

41
Q

Best VA in ____ pupil in diffraction limited scenario

A

Larger

42
Q

Under dim light, resolution is better in diffraction limited system?

A

True

43
Q

Diameter of telescope lenses

A

Larger because in diffraction limited system, larger pupil=smaller MAR (better VA)

44
Q

Dependence of MAR on pupil diameter. Combined effect of diffraction and abberations

A

Pinhole is based on this

Optics II block 5 (11 decks)

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