Visual Fields

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 extent of VF?

Answer 2

60 derees towards nasal
100 degrees to periphery
60 degrees up to forehead
75 degrees down to nose

Question 3

how is visual field limited?

Answer 3

limited by facial anatomy
-forehead 
eyebrows 
nose
cheek bone

Question 4

how much is central Visual Field?

Answer 4

30 degrees

Question 5

how much is peripheral Visual Field?

Answer 5

more than 30 degrees

Question 6

how does the visual field work in the retina?

Answer 6

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

Question 7

what does the retinal image look like?

Answer 7

image will be upside down and back to front

Question 8

how does the retinal sensitivity work?

Answer 8

retina most sensitive at macula

retina least sensitive at the optic disc

Question 9

why is the retina most sensitive at the macula

Answer 9

high density of cones

Question 10

why is the retina least sensitive at the optic disc?

Answer 10

low density of cones

Question 11

why is the physiology of the blind spot?

Answer 11

Blind spot is the temporal projection of optic nerve 
5.5 degree wide 
7.5 degree high 
15 degree from fixation 
1.5 degree below horizontal midline

Question 12

where is the blind spot in the R eye ?

Answer 12

Blind spot on the R hand side

Question 13

Where is the blind spot in the L eye?

Answer 13

Blind spot on the L hand side

Question 14

What is the definition of Visual Field?

Answer 14

Perimetry is the measurement of the Visual Field

Question 15

what types of perimetry are there?

Answer 15

Kinetic perimetry

Static Perimetry

Question 16

what is Kinetic perimetry?

Answer 16

A stimulus of fixed size and luminance is moved from a non seeing area top the seeing area until it is detected by the patient

Question 17

How is Kinetic perimetry recorded?

Answer 17

Go all around the 360 degree and points are shown eccentricity that stimulus is seen is then recorded as an isopter

Question 18

what is an Isopter?

Answer 18

Points of equal sensitivity form together to make an isopter

Question 19

If you change size and light sensitivity what changes?

Answer 19

isopter changes

Question 20

what is the shape of the isopter for a large and bright stimuli?

Answer 20

big round isopter

Question 21

what is the shape of the isopter for a small and dim stimuli

Answer 21

small isopter

Question 22

what do you get if the isopter is repeated three times?

Answer 22

Contour map of visual field

Question 23

What manual Kinetic Perimeter are there?

Answer 23

Gross Perimetry

Goldmann Perimetry

Question 24

How do you do gross perimetry?

Answer 24

1) patient faces practitioner
2) occlude one eye
3) patient fixate at practitioner nose
4) target held at 35cm from patients non seeing field of view
5) patient reports when target first seen
6) carried out uniform surrounding in all 8 position of gaze
7) tell patient when they cannot see it

Question 25

what do you take care of when doing gross perimetry?

Answer 25

• -target is moved at constant velocity in an imaginary arc
• -take a mental note of when px see the target
• -repeat in all 8 directions
• -only very gross defects detected
• -repeat other eye

Question 26

what are the 8 position of gaze?

Answer 26

Superior, superior nasal, nasal

inferior nasal, inferior, inferior temporal, temporal, superior temporal

Question 27

what is the advantage of gross perimetry?

Answer 27

Quick
Cheap
Only method possible with young children and elderly with strokes
will detect grodd field defects

Question 28

what is the disadvantage of gross perimetry?

Answer 28

• Useless for small area defect
• no control on stimulus contacts/luminance
• no control on background
• recongintion of defect depends all on the practitioners judgment

Question 29

How does the goldmann Bowl perimetry work?

Answer 29

1) Occlude one eye
2) ajdust chin rest head rest so that px eye is in centre of telescope vies
3) instruct px
4) put up correct refractive correction
5) select stimulus and record what they see
6) continue to move to the centre and report when it dispears
7) repeat again for 2 other stimulus
8) repeat other eye

Question 30

when can you have refractive correction for Visual Field?

Answer 30

inside 30 field degrees always give reading correction or >+/- 8DS

Question 31

What is the reading correction?

Answer 31

distance correction + reading addition

Question 32

what are the goldmann reading additions?

Answer 32

age 40-44 = +1.50D
age 45-49= + 2.00D
age 50-54= +2.50D
age 55+ = +3.00 D

Question 33

when do you not give reading correction?

Answer 33

when outside 30 degrees of field of view

Question 34

When do you give cylinder correction?

Answer 34

if cylinder is less that 1D give mean sphere

if cylinder is 1D or more give actual cyl

Question 35

what is mean sphere?

Answer 35

mean sphere= sphere + half cyl

Question 36

What is good about octopus goldmann perimetry?

Answer 36

• aged matched normal values- for immediate judgment of normality
• repeatable tests: automatic repetition and follow up kinetic examinations
• quantification: measurement of isopter for the quantification of progression
• Automatic repition of kinetic examinations using follow up bottom
• manual or automated kinetic testing

Question 37

what can you do with manually humphrey ?

Answer 37

choose:
size of stimulus
intensity of stimulus 
speed of stimulus
colour of stimulus
no of meridian tested
no of isopters tested
special mapping ( blind spot plot and scotoma plott)

Question 38

what does the humphrey not do?

Answer 38

It does not monitor fixation constantly

Question 39

what is the overall advantage of kinetic perimetry?

Answer 39

useful for detecting contraction of visual field

useful for detecting neurological problems

useful in young children when automated not possible

children/ adults with stroke may find find it easy to use manual perimetry

Question 40

what is the overall disadvantage of Kinetic perimetry?

Answer 40

..required skilled operator with manual perimetry
..results are operator dependent with manual
..time consuming with manual perimetry
..difficult to quantify results with manual
.. poor sensitivity for detecting scotomos both manual and automated

Question 41

what is missed with kinetic perimetry?

Answer 41

Scotomas

Question 42

How is gross perimetry recorded?

Answer 42

PERL(A)

Question 43

What does perl(A) mean?

Answer 43

pupil equally responsive to light and accommodation