Visual Field 1

Question 1

what are the absolute limits for the human eye?
fixation to temporal limit? 
Nasal limit?
inf limit?
sup limit?

Answer 1

temporal: 100 degrees
nasal: 60
inf: 70
sup: 55-60

Question 2

what is the definition of perimetry

Answer 2

the study of the visual field using targets of various sizes, luminances, colors, and someitmes movements

Question 3

what is kinetic perimetry
when is it visible?
what kind of things are easier to see?

Answer 3

a stimulus is chosen (of a given size and luminance, or size and color) and is moved from an area where it is not seen to an area where it is seen

• at threshold
• usually moving things are easier to see

Question 4

what is static perimetry?

when is it first detected?

Answer 4

a location is chosen and the luminance or shape of the stimulus is changed until it is seen
-first detected at threshold

Question 5

what is an isopter?

Answer 5

a “line” connecting all points of equal visual sensitivites, equal thresholds, and it divides the seeing area from the non-seeing area for a given stimulus

Question 6

what is the infrathreshold? what is the suprathreshold?

Answer 6

infra: stimulus that are dimmer or smaller than one’s threshold
supra: stimulus that are brighter or bigger than one’s threshold

Question 7

what is the hill of vision
what does the base represent
what does the tip represent

Answer 7

the 3D representation using the horizontal axis as the location in visual space and the altitude (vertical direction) as the visual sensitivity at that location.

• base rep absolute boundaries
• tip rep most sensitive region which is the fovea

Question 8

when horizontal cuts on the hill are made what do we obtain?
when vertical cuts are made what do we obtain?

Answer 8

horiz cuts on the hill are made we obtain an isopter for a given stimulus

vert cuts made we obtain a graph to relate sensitivity from fixation

Question 9

what is a scotoma

where is it relative to the isopter?

Answer 9

an area of reduced or absent visual sensitivity which is inside the isopter and is surrounded by an area which does not have reduced sensitivity

Question 10

where is the location of a physiological blind spot? what is the size?

Answer 10

location: its center is located 15.5 degrees temporal to fixation and 1.5 degrees below the horizontal meridian
size: 5.5 degreees wide by 7.5 degrees high

Question 11

where is the blindspot for the right eye

where is the blindspot of the left eye

Answer 11

located on the right side of the visual field
-bc optic nerve is nasal so it is in the temporal visual field

left side

Question 12

what does a central scotoma involve?

Answer 12

fixation

Question 13

what does a centrocecal scotoma involve?

Answer 13

the area from the physiological blindspot up to and including fixation

Question 14

where is the paracentral scotoma?

Answer 14

any scotomoa within 20 degrees from fixation but excluding fixation itself.
-some books say 30 degrees from fixation

Question 15

where is the arcuate scotoma?

Answer 15

extends from the blind pot and bows over fixation

-arches from the blindspot into the nasal field and follows the course of the retinal nerve fibers

Question 16

what does a cuneate scotoma involve and where does it extend to

Answer 16

involves the blindspot and extends into the temporal field

Question 17

what is a depression

Answer 17

an inward turning of an isopter

-it differs from a scotoma in that it is not surrounded by an area visible to the stimulus, it is at an edge

Question 18

what is a nasal step

Answer 18

nasal step breaks right at the raphe, with a difference in sensitivity on each side of the horizontal divide.

Question 19

what is a temporal wedge

Answer 19

comes up from the blind spot and extends over temporally

Question 20

what is an absolute depression called

Answer 20

contraction

Question 21

how are scotomas and depressions related

Answer 21

scotoma can get larger and break through and become a depression

-a scotoma in one isopter can press down on another isopter and cause this isopter to have a depression

Question 22

what does steep and sloping mean

Answer 22

steeps means its been there and probably isn’t progressing

-sloping means changing or developing

Question 23

what does an amsler grid subtend a 10 degree field? 7 degree feidl?

Answer 23

• a 10 degree field when held approx. 11.3 inches (28.7cm) from the eye
• a 7 degree field when held 16 in from eye

Question 24

when do we use a tangent screen?

Answer 24

• pts who are unable to sit behind a bowl secondary to a physical condition
  ex. arthritis
• pts w/ markedly reduced central vision who cannot hold fixation in a bowl
• pts who respond better in an open space

Question 25

in hysterical fields how much is vf constricted

-what is the most common

Answer 25

10 degrees bilaterally

• tubular field: remarkably constant in size, shape, and steepness of margins
• always bilateral

Question 26

what is a tubular field

Answer 26

the field is the same linear size regardless of the distance of the test object from the pts eye
-this also assumes that the visual stimuli subtends the same visual angle at the various testing distances used

Question 27

what are the advantages to goldmann perimetry

Answer 27

1. both kinetic and static targets may be used
2. both central and peripheral fields may be tested
3. both the target luminance and size may be changed
4. a specific area of the field may be quickly isolated and tested

Question 28

what are the disadvantages of goldmann perimetry

Answer 28

1. testing the full field is time consuming and tedious
2. bc the exposure time, speed of movement, and point location are not set by the machine, there is some amount of variability among perimetrists

Question 29

with a pt with a hysterical field, what size remains constant and what changes?

Answer 29

the linear size of the field remains constant, but the angular size changes