visual fields I

Question 1

what is the visual field ?

Answer 1

• all the space that an eye can see at any given time

Question 2

what is the normal level of visual field ?

Answer 2

• superiorly is approximately 60 degrees
• inferiorly is 70 degrees
• nasally 60 degrees
• temporally 100 degrees

Question 3

what is visual field limited by ?

Answer 3

• limited by facial anatomy
  . forehead
  . eyebrows
  . nose

Question 4

what does the full field measure to ?

Answer 4

• the full field measures to a 200 degrees across

Question 5

what is the binocular visual field ?

Answer 5

• 120 degrees

Question 6

what is the vertical extent of the visual field ?

Answer 6

• the vertical extent of the visual field is the same monocularly as it is binocularly
  example- if you put your finger up high, and close either one of your eyes , you will still be able to see

Question 7

how to do a central visual field ?

Answer 7

• you must do within the central 30 degrees

Question 8

how to do a peripheral visual field ?

Answer 8

• beyond central 30 degrees

Question 9

where does nasal retina project ?

Answer 9

• projects temporally

Question 10

where does superior retina project ?

Answer 10

• projects inferiorly

Question 11

what does every point in the retina correspond to ?

Answer 11

• every point in the retina corresponds to a certain direction in the visual field

Question 12

where do you see damage in the superior temporal retina in visual field ?

Answer 12

• inferior nasal retina

Question 13

where is the highest density of cones ?

Answer 13

• centre of the macula and fovea

Question 14

where is the blind spot largest ?

Answer 14

• blind spot is larger vertically than horizontally

Question 15

where is the the blind spot ?

Answer 15

• always approximately 15 degrees from fixation ( from the fovea )

Question 16

where is the blind spot in the right eye ?

Answer 16

• blind spot on the right

Question 17

where is the blind spot in the left eye ?

Answer 17

• blind spot on the left

Question 18

what is difference between visual field and fundus exam ?

Answer 18

• the visual field is what the patient sees
• so right is on right
• left is in the left
• the fundus exam is what the clinician sees
• right eye on left
• left eye on right

Question 19

what is the measurement of visual field ?

Answer 19

• perimetry is the measurement of the visual field

Question 20

what are two types of perimetry ?

Answer 20

1. kinetic perimetry - stimulus is moving

2. static perimetry - stimulus stays down

Question 21

what is hill of vision ?

Answer 21

• height of the hill is threshold sensitivity
• everything inside the hill you can see except the blind spot
• everything outside the hill you cant see

Question 22

what is kinetic perimetry ?

Answer 22

. stimulus of fixed/luminance is moved from non-seeing to seeing until it is detected by the patient

Question 23

how to carry out kinetic perimetry ?

Answer 23

• move the stimulus from where they can’t see it until where they can and mark on map
• move about 15 - 30 degrees
• keep doing until you go around 360 degrees
• join together ( called an isopter )

Question 24

how to record kinetic perimetry ?

Answer 24

• eccentricity that the stimulus is seen at is then recorded
• points of equal sensitivity form together to make an isopter
• different isopters are measured using different stimulus sizes or light intensities or colour can be shown

Question 25

how is kinetic perimetry repeated ?

Answer 25

• procedure is repeated with a smaller/lower luminance stimulus

Question 26

what is reliable kinetic perimerty ?

Answer 26

• a minimum of 3 isopters is required to obtain a good ‘ contour map’ of the visual field
• thew higher the Roman numeral the higher the number the brighter the stimulus

Question 27

what are the manual types of kinetic perimetry ?

Answer 27

• gross perimetry

- goldmann perimeter

Question 28

how to do gross perimetry ?

Answer 28

• patient faces practitioner
• occlude one eye
• patient told to constantly fixate examiners nose
• target held 35cm from the patient’s eye outside the field of view
• patient reports when they are first aware of the target
• carried out in uniform surrounding if possible
• target moved at constant velocity in an imaginary arc
• once patient notices target ( mental note made of it ) and the target continues to the centre
• repeated in eight directions ( superior, superior temporal, temporal)
• repeated with other eye
• only very gross defects detected

Question 29

what are the advantages of gross perimetry ?

Answer 29

• quick
• cheap
• only method possible with young children/ elderly with stoke
• will detect gross field defects

Question 30

what are the disadvantages of gross perimetry ?

Answer 30

• virtually useless for small areas of loss
• no control of stimulus luminance/contrast
• no control over background
• recognition of defect entirely dependent on judgment of practitioner

Question 31

what is in goldmann perimetry ?

Answer 31

• patient’s side
• projector - put the light on to screen
• head rest
• button response - to press every time they see light
• practitioner’s side
• pantoscopic arm
• target luminance and size control
• chart

Question 32

how to set up goldmann bowl perimeter ?

Answer 32

• occlude one eye
• adjust chin/head rest so patient’s eye is in the centre of the telescope’s field
• instruct patient to look at light in the centre and let you know when they see light
• put up correct refractive correction

Question 33

what are the rules for refractive correction ?

Answer 33

• inside 30 field degrees always give reading correction ( distance correction + reading addition which is appropriate machine)
• Reading correction= distance correction + reading addition.
• outside 30 degrees no correction unless >+/- 8DS

Question 34

what is goldmann’s table near addition to use when doing the calculation?

Answer 34

. 40-44 +1.50 DS
. 45-49 + 2.00 DS
. 50-54 +2.50 DS
. 55 and older or cyclopleded +3.00 DS

Question 35

what is the rule of thumb of refractive correction in goldamm perimeter ?

Answer 35

1- cylinder correction < or equal to 1 dioptre convert to mean sphere
mean sphere = sphere + 0.5 x CYLINDER (half the cyl)

2- cylinder correction > 1.00 insert actual cylinder

Question 36

how to carry out goldmann perimeter ?

Answer 36

• select stimulus
• move stimulus in from periphery ( non-seeing to seeing )
• recored where they can see it
• continue to move the stimulus to the centre asking the patient to report if it disappears
• repeat for at least 2 other stimulus size/luminance combinations
• repeat for other eye

Question 37

what is the goldmann perimetry with the octopus ?

Answer 37

• age matched normal values: for immediate judgment or normality
• repeatable tests: automatic repetition and follow up of kinetic examination
• quantification : measurement of isopters for the quantification of progression
• automatic repetition of kinetic examinations using follow up button
• manual or automated kinetic testing

Question 38

how to plot kinetic perimetry manually with the humphrey ?

Answer 38

- choose the following
. size of stimulus
. intensity of stimulus
. colour of stimulus 
. no of meridian tested
. no of isopters tested
. special mapping ( plot blind spot, plot scotoma ) 
. does not monitor fixation constantly

Question 39

what are the advantages of kinetic goldmann perimetry ?

Answer 39

. useful for detecting contraction of the visual fields
. useful for detecting neurological problems
. useful in young children when automated not possible

Question 40

what are the disadvantages of kinetic goldmann perimetry ?

Answer 40

. requires skilled operator with manual perimetry
. results are operator dependent with manual perimetry
. time consuming with manual perimetry
. difficult to quantify results with manual perimetry
. children/adults with stroke may find manual perimetry easier
. poor sensitivity for detecting small scotomas both manual and automated
-scotomas are easily missed.