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Optics II block 5 > Pupillary Optics > Flashcards

Pupillary Optics Flashcards

1
Q

What is the optical system that has no power?

A

Iris

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2
Q

Iris forms the ______ of the eye to block undesirable light

A

Aperture stop

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3
Q

The opening of the aperture stop is known as the _____

A

Pupil

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4
Q

What are the two muscles that control the pupil

A
  • sphincter pupillae

- dilator pupillae

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5
Q

What muscle constricts the pupil

A

Sphincter pupillae

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6
Q

What muscle dilates the pupil

A

Dilator pupillae

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7
Q

What division of the nervous system controls the pupilillary muscles

A

ANS

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8
Q

What is the pupil designed to do

A
  • prevent undesirable light from getting to the lens/retina
  • absorb light
  • have melanin granules in stroma and epithelium (brown)
  • has a unique biometrics ID system
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9
Q

What is the most reliable biometric ID systme?

A

Iris

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10
Q

Where are the melanin granules in people with brown eyes

A

Stroma and epithelium

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11
Q

Where are the melanin granules in people with blue eyes?

A

Only in the epithelium

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12
Q

Job description of the iris

A
  1. Stops undesirable light (pigmented tissue)
  2. Regulates retinal illuminance (pupil size and retinal layers)
  3. Controls DoF (smaller pupil)
  4. Helps in controlling retinal blur (diffraction and aberrations)
  5. Help design optical instruments (entrance and exit pupil)
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13
Q

Image of the aperture stop formed in object space (image formed by the cornea)

A

Entrance pupil (E)

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14
Q

Image of the aperture stop formed in the image space (image formed by the lens)

A

Exit pupil (E’)

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15
Q

___________ is an erect, virtual Aimee formed 0.5mm in front of the real pupil

A

Entrance pupil

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16
Q

Calculate the entrance pupil location where F=43D, n=1.336; n’=1, I=-3.6mm (anterior chamber depth)

A

L=nl
1.336/-.0036=-371.11D

L’=L+F
-371.11D+43D=-328.11D

I’=1/L’
1/-328.11D=-0.00304

Mag
L/L’
-371.11D/-328.11D=1.13

Entrance pupil appears larger than it really is, and is 13% larger than real pupil

Entrance pupil is erect, virtual image that is located 0.5mm in front of the actual pupil

Exit pupil is 0.07mm behind the real pupil and 3.1% larger than th real aperture

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17
Q

What is the most important factor affecting pupil size?

A

The level of illumination

18
Q

What is the range of hte pupil diameters

A

2-8mm

19
Q

How does the pupil respond to increase in illumination?

A

Decrease in pupil size

20
Q

What is the latency of the pupil with low illumination

A

0.5 secs before dilation

21
Q

Latency of pupil with increase illumination

A

Decrease to 0.2 or 0.3secs for constriction

22
Q

Pupil centration

A

Decentered by 0.5mm nasally relative to the optical axis

23
Q

Pupillary response and field of view

A
  • more response, if light distribution in the cenrealt visual field
  • less response, if light distribution in the peripheral visual field
24
Q

Pupil response to changed in light level is mediated by what

A

Both rod and cone photoreceptors

-pupil doesn’t directly respond to light, the retina reacts and sends a signal

25
Q

The constriction of the pupil due to direct light stimulation

A

Direct light reflex

26
Q

Pupils of both eyes respond equally to stimulation of only one eye

A

Consensual light reflex

27
Q

The pupil decreases in diameter when the eyes converse or accommodate

A

Near reflex

28
Q

What happens at the same time and changes the pupil size

A

Accommodation and convergence

29
Q

Pupil size and age

A

Decreases with age (senile miosis)

30
Q

What drugs dilate pupils

A

Mydriatics (simulating sympathetic system)

31
Q

Drugs that constrict pupil

A

Miotics (stimulating parasympathetic system)

32
Q

Psychological factors and pupil size

A
  • emotional states effect the pupil
  • pleasant mental images increase pupil size
  • unpleasant mental images decrease pupil size
33
Q

A decrease in pupil size ________ the DoF

A

Increases

34
Q

The range of distanced over which the systems detector cannot detect ant change in focus is called the

A

Depth of field

35
Q

________ affects the retinal light level

A

Pupil diameter

36
Q

How much of the light entering the eye reaches the retina

A

50-90%

37
Q

Light entering the eye and reaching the fovea (retina) depends upon what

A

The entry point in the pupil

38
Q

For _____ pupil diameters, aberrations cause deterioration in retinal image quality

A

Large

39
Q

For _____ pupil diameters, diffraction limits image quality

A

Small

40
Q

There is an optimum pupil diameter range of ______ that gives the best balance between these two effects for the corrected eye

A

2-3mm

Optics II block 5 (11 decks)

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