Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Visual Optics > 4: Optical Components of the Eye > Flashcards

4: Optical Components of the Eye Flashcards

1
Q

the cornea and tear film provide about ____ of the total refracting power of the eye

A

2/3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the tear film’s thickness and refractive index?

A

thickness of about 3-4 microns and refractive index of 1.337

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

the cornea has a thickness of about:

A

540 microns

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is the average radius of curvature at the vertex of the cornea for anterior surface

A

+7.8mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the average radius of curvature at the vertex of the cornea for posterior surface

A

+6.3mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the location and importance of the aqueous humor?

A

it fills the anterior chamber and posterior chamber and maintains the intraocular pressure of the eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

the anterior chamber becomes ______ on increased accommodation due to forward motion of the anterior crystalline lens surface

A

shallower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

the iris forms the ____ _____ of the eye

A

aperture stop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what can the iris alter?

A

the retinal illuminance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

the clinical “pupil” is actually the

A

entrance pupil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

power of the lens is approximately

A

+19 D

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

the lens contains a gradient index, meaning its:

A

refractive index is greatest in the nucleus (about 1.43), dropping off quickly near the periphery of cortex (about 1.36)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

in a relaxed lens, the thickness is

A

3.7 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

the most widely accepted model for the mechanism of accommodation is attributed to

A

Helmholz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

contraction of the annular ciliary body relaxes tension on the zonular fibers, allowing the lens to adopt a more ______ shape

A

curved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

during positive accommodation, the equatorial diameter of the lens ______ (increases/decreases)

A

decreases

17
Q

during positive accommodation, the lens thickness _____ (increases/decreases)

A

increases

18
Q

during positive accommodation, the anterior chamber depth _____ (increases/decreases)

A

decreases

19
Q

in a young eye, the power of the lens increases from about + ___ D in far vision to about +___D for an object at 10cm

A

from +19D to +30D

20
Q

in positive accommodation, what contributes to the increased lens power?

A

changes in the gradient index

21
Q

define presbyopia

A

the universal age-related loss of accommodative amplitude

22
Q

define a cataract

A

when the transparency of the lens decreases with age and it becomes yellowed

23
Q

the vitreous humor is a gel like substance, ____% water, with a refractive index of ____

A

98-99% water

refractive index, n=1.336

24
Q

the vitreous normally contains small opacities from what

A

within Cloquet’s canal, which is a remnant of the former hyaloid artery

25
Q

the vitreous chamber depth (VCD) averages about ____ mm in adults

A

16 mm

26
Q

of all the ocular components, _____ is the best predictor of an individual’s refractive error

A

VCD

27
Q

cone density is maximal at the

A

fovea

28
Q

rod density is maximal about ___ degrees eccentricity

A

20 degrees eccentricity

29
Q

there are no rods in the central ___ degree of the retina

A

1 degree

30
Q

____ are important in bright (photopic) conditions

A

cones

31
Q

____ are important in dark (scotopic) conditions

A

rods

32
Q

the blind spot corresponds to the optic nerve head and it about ____ temporal to the fixation point in object space

A

15 degrees temporal

33
Q

the cone receptor mosaic has what packing arrangement?

A

quasi-hexagonal

34
Q

what defines ones upper limit on the resolution performance of the eye?

A

the mean inter-cone spacing

35
Q

the inter-cone spacing is smallest at the

A

fovea (then increases peripherally)

36
Q

the waveguide properties of cone and rod outer segments lead to the psychophysical phenomenon of the

A

Stiles-Crawford effect

37
Q

define the Stiles-Crawford effect

A

light entering the eye from the edge of the pupil is less effectively transducer than light from the center of the pupil

38
Q

what is the Stiles-Crawford effect hypothesized to reduce?

A
  • reduces glare from intraocular light scatter

- reduce deleterious effects of ocular aberrations

39
Q

Stiles-Crawford effect is hypothesized to result in slightly better ____ and ____

A

visual acuity and contrast sensitivity

Visual Optics (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions