Visual Pathway

Question 1

what is the horizontal raphe?

Answer 1

the line that bisects the eye into anterior and inferior

Question 2

what is the vertical demarcation line?

Answer 2

the line the bisects the eye into nasal and temporal- centre is the retina

Question 3

why are the fibers at the optic disc vulnerable to pressure and vascular changes?

Answer 3

because the fibers at the optic disc are quite tightly packed

Question 4

do retinal fibers cross the horizontal raphe?

Answer 4

no

Question 5

where are the fibres in the optic disc most vulnerable?

Answer 5

in the inferior rim that supply the inferior temporal retina

Question 6

if the fibres in the inferior temporal retina are damaged, what defect would this give you? and what disease is this an indicator of?

Answer 6

superior nasal visual field defect, also known as a classic nasal step. this happens in glaucoma

Question 7

does a nasal step cross the horizontal line?

Answer 7

no

Question 8

what are the 3 rules of retinal lesions?

Answer 8

1. can be unilateral or bilateral
2. often asymmetrical between the eyes
3. do not respect the vertical midline, they will go over it

Question 9

what does damage to the optic nerve do to the visual field?

Answer 9

if the damage is in the LE the there will be a full visual defect in the left eye. RE will be fine

Question 10

what is the visual field defect if there is damage in the optic chiasm?

Answer 10

as nasal fibers cross but temporal ones do not, the nasal fibers from both eyes will be taken out, resulting in temporal visual field loss in both eyes. this is called bitemporal hemianopia (heteronymous)

Question 11

if there is damage in the left optic tract (after the fibres leave the chiasm), what visual field defect will result?

Answer 11

the LE temporal and RE nasal fibres will be taken out, resulting in LE nasal and RE temporal VF loss. this would result in homonymous hemianopia

Question 12

once you hit the chiasm, do defects respect the vertical midline?

Answer 12

yes

Question 13

if you have a lesion in the left visual cortex, what is the VF defect?

Answer 13

LE temporal and RE nasal fibres are knocked out, resulting in LE nasal and RE temporal visual field loss

Question 14

if you get a bump resulting in damage to the inion, what is the VF loss?

Answer 14

as the fibres of the superior retina run above this inion, the VF loss will be inferior

Question 15

if you have loss of macula, and a congruent defect. where is the damage likely to be?

Answer 15

very posterior tip of the occipital lobe

Question 16

from what point on is the vertical midline always respected?

Answer 16

optic chiasm

Question 17

if the VF loss is unilateral, is the damage neurological or retinal?

Answer 17

more likely retinal

Question 18

if the VF loss is bilateral, is the damage post chiasmal or retinal?

Answer 18

post chiasmal

Question 19

the defect is hetero. is the VF loss chiasmal or post-chiasmal?

Answer 19

chiasmal

Question 20

the defect is homo. is the VF loss chiasmal or post-chiasmal?

Answer 20

post chiasmal

Question 21

if px has a left homo field defect, what side of the brain is the lesion in?

Answer 21

right

Question 22

how much false positive makes the test unreliable?

Answer 22

more than 33%

Question 23

how much false negative makes the test unreliable?

Answer 23

more than 33%

Question 24

how many fixation losses make the test unreliable?

Answer 24

more than 20%

Question 25

if there is a higher number on the numeric printout of a fields test, what does it mean?

Answer 25

px has higher threshold so is able to detect dim lights

Question 26

if there is a ‘0dB’ on the numeric printout of a fields test, what does it mean?

Answer 26

px is JUST able to see the perimeters at the brightest light

Question 27

if there is a ‘<0dB’ on the numeric printout of a fields test, what does it mean?

Answer 27

px cant detect the perimeters even at the brightest lights

Question 28

as we get older, where does the sensitivity of our vf decrease first?

Answer 28

periphery

Question 29

if there is a lots of minus numbers on the numeric printout of a fields test, what does it mean?

Answer 29

the px has consistently seen less than they should have for their age. the minus numbers are the number of dBs less than what they should have seen for their age

Question 30

how do probability maps work?

Answer 30

created using confidence intervals, if px lies outside of the normal values created, they only have a 5% chance of being normal

Question 31

what is a mean deviation in VF?

Answer 31

the average of the total deviation values, the greater the number, the worse their VF defect

Question 32

what value in mean deviation indicates significant field loss

Answer 32

greater than -2.00 dB

Question 33

what is the pattern standard deviation, what value is considered abnormal

Answer 33

the standard deviation around the mean of the total deviations, anything greater than +2.00 is abnormal