pupil

Question 1

Does the iris have optical power?

Answer 1

no

Question 2

iris anatomy

Answer 2

• Thin, muscular piece of tissue
• Sits right in front of the lens, touching the first surface
• Bulges forward when the eye accommodates
• Opaque tissue due to the melanin granules in the epithelium and sometimes stroma.

Question 3

role of iris

Answer 3

controls light going into the eye

Question 4

Important optical roles of the iris

Answer 4

1.  Defines pupil of the eye by blocking undesirable light
(pigmented tissue)
2. Regulates retinal illuminance
3. Controls depth-of-field
4. Aides in controlling retinal blur
(blur circle, aberrations, diffraction)

Question 5

_______ iris contains melanin granules in stroma and epithelium.

Answer 5

brown

Question 6

_____________ iris contain granules only in epithelium.

Answer 6

blue and green

Question 7

Unique pattern makes

it ideal for ____________.

Answer 7

biometric identification

Question 8

What type of light is scattered more than other wavelengths?

Answer 8

blue

Question 9

Transparency of tissue is governed by the tissue’s ability to do what to light?

Answer 9

1. absorb

2. scatter

Question 10

What color iris scatter (Rayleight) light, which inhibits transparency?

Answer 10

blue

Question 11

What color iris absorbs light?

Answer 11

brown

Question 12

A condition in which the two irises of an individual have different colors

Answer 12

heterochromia

Question 13

cause of heterochromia

Answer 13

Most cases of heterochromia are hereditary, caused by a disease or syndrome, or due to an injury. Sometimes one eye may change color following certain diseases or injuries.

Question 14

How does the pupil size affect the brightness of the retinal image?

Answer 14

Image brightness is proportional to the pupil area, not pupil diameter.

Question 15

The human visual system operates over what amount of log range?

Answer 15

10-log

Question 16

How much does the changing pupil size contribute to this?

Answer 16

The 16x change in luminance (1.2-log) helps, but is relatively small compared to the 10,000,000,000x change (10-log) of the entire visual system.

Question 17

Pupil diameter as a function of age

Answer 17

As we age, our pupil decreases.

*inverse relationship

Question 18

Maximum size of acceptable blur at the retina determines what?

Answer 18

depth of filed and depth of focus

Question 19

Range of object or image plane over which the image appears to be in focus.
Depends on the idea that a small amount of blur is allowable.

Answer 19

Depth of field & depth of focus:

Question 20

Depth of field of the eye ultimately sets the:

Answer 20

(1) precision to which the refractive state of the eye may be measured,
(2) The precision required in focusing optical instruments, and
(3) The accuracy of the accommodation system of the eye

Question 21

range of object space

Answer 21

depth of field

Question 22

range of image space

Answer 22

depth of focus

Question 23

A decrease in pupil size increases what?

Answer 23

depth of field

Question 24

how does KAMRA inlay help presbyopic pts?

Answer 24

artificially decreases pupil size, so that pt has larger depth of field

Question 25

What is the typical depth of field for the eye?

Answer 25

0.5-1 D

Question 26

Depth of field can be increased by increasing what? And who is this beneficial for?

Answer 26

ambient light level | presbyopes

Question 27

What is the downside of small pupils?

Answer 27

vision is more sensitive to nuclear cataracts

Question 28

Accurate measurement of | accommodative amplitude and subjective refraction is compromised by what?

Answer 28

small pupils

Question 29

Pinholes are an efficient way to screen for ___________ without measuring for them.

Answer 29

refractive errors

Question 30

Does pinhole correct refractive error? T/F

Answer 30

false

Question 31

A decrease in pupil diameter leads to a decrease ______________ at the retina

Answer 31

geometric blur size

Question 32

If pupil size increases, what happens to blur?

Answer 32

increases too | *direct relationship

Question 33

What is the relationship for aberrations and diffraction in the eye?

Answer 33

B=PK defines a linear relationship b/w the retina blur and pupil diameter when in the presence of a refractive error

Question 34

an optical defect in a lens or mirror, causing image blur.

Answer 34

aberration

Question 35

Whats the relationship of pupil size to aberration?

Answer 35

increase pupil size, increase aberration | *direct relationship

Question 36

The deviation from rectilinear propagation that occurs when light advances beyond an obstruction

Answer 36

Phenomenon of diffraction

Question 37

Can we use Snell's law to predict diffraction?

Answer 37

No, Diffraction is accurately predicted by Wave Optics

Question 38

How does diffraction affect the retinal image?

Answer 38

- For practical reasons, imaging systems are unable to collect the entire wavefront emitted from an object. For the eye, only a section passes through the pupil with the iris representing an obstruction that deviates the light. - This deviation blurs the image. - The image blur size for a point object = 1.22 λ f / d

Question 39

large slit generates _____ deviation of waves

Answer 39

little | *inverse relationship

Question 40

small lit generates ______ deviation of waves

Answer 40

large

Question 41

pt is best corrected and under dark environment (big pupil), whats the final limit for VA?

Answer 41

anatomy of neural system imposes upper limit on supernormal vision

Question 42

defines the bundle of light rays that pass from object to retinal image. And as we have just discussed, this bundle of rays influences retinal illuminance, depth of focus, and retinal blur size.

Answer 42

real pupil

Question 43

is the real pupil what we see when we look into someone’s eye, as for example when measuring this patient’s pupil with a pupillometer?

Answer 43

no, we are looking at image of pt's pupil (entrance pupil)

Question 44

image of the real pupil formed by the cornea. All light rays that pass through the real pupil also pass through the entrance pupil. It is an erect, virtual image that resides 0.5 mm in front of the real pupil.

Answer 44

entrance pupil

Question 45

image of the real pupil formed by the crystalline lens. All light rays that pass through the real pupil also pass through the exit pupil. It is an erect, virtual image that resides 0.1 mm behind the real pupil.

Answer 45

exit pupil