visual field defects? where is the pathology? Flashcards
how do you instruct your patient ?
> This test will test all the area you can see with each eye
I want you to always look straight ahead at the fixation light in the centre ( show them)
other lights will now flash in different places. Every time you see a light press your button
You will not see all the lights
the most important thing to remember is to always keep watching the fixating light in the centre
How to improve accuracy with your patient?
: ensure they are comfortable
- neck/ head position
- coat on or off
: explain how long it will take
-xx no of minutes
: patient can cause pause the test on a humphrey
define visual field defect?
A visual field defect is defined as a departure from the topography of the hill of vision from normal limits
why is it important to accurately describe type of visual field defect?
helps to determine the type of pathology
Helps to monitor the condition
what is contraction of visual field?
defect starts from peripheral to inside
what is depression or diffuse visual field loss?
a generalised reduction in the height of the hill of vision
what is localised defect?
small area of defect
what are defects called in visual fields?
Scotoma
How can Scotoma be classified?
Area of vision loss margins shape of defect central visual field baring of the blind spot
what type of scotomas with area vision loss do you get?
A. Absolute
B. Relative
what does absolute defect mean?
can see
can see
cannot see anything
What does relative defect mean ?
Can see , can see little,
cant see much
cannot see at all
what type of scotoma margins do you get?
A. Steep
B. Sloping
what does steep margins of scotoma look like?
from normal to not seeing nothing
What does sloping margins of scotoma look like?
from normal to little bit less to nothing at all seen
what type of shape defect to you get?
Hemianopia Altitudinal Hemianopia Macula sparing Macula splitting quadrantanopia
what does hemianopia look like?
Half of visual field not seen
What does altitudinal hemianopia look like?
superior or inferior loss of visual field
What does macula sparing defect look like?
visual field defect but macula is spared
What does macula splitting defect look like?
Half of the macula has defect ( macula split in half)
what does quadrantanopia defect look like?
a quadrant of the visual field cannot be seen
what type of central visual field are there?
Central scotoma Pericentral Scotoma Paracentral Scotoma Centrocecal Scotoma Nasal step Arcuate scotoma Ring scotoma
What is central scotoma?
scotoma in the centre of visual field effecting the fixation point on the fovea
What is pericentral Scotoma?
ring of defect surrounds the fixation point fovea but does not effect the fovea
What is paracentral scotoma?
Adjacent to fixation point fovea not surrounding it
What is centrocecal scotoma?
Extends from fixation point to blind spot
what is baring of the blind spot?
defect leaves the blind spot out
what is nasal step scotoma?
classic glaucoma defect that 1st effects nasal side and will not cross the horizontal midline
what is arcuate scotoma?
defect that arcs around from the blind spot
What is ring scotoma?
Defect ring around the visual field
what does homonymous hemianopia mean?
Half of the same side of visual field loss
What does Bi temporal hemianopia mean?
Half of temporal side of each eye visual field loss
What types does Homonymous hemianopia are there?
> Partial
Complete
Macula sparing
What is partial hemianopia?
defect does not come to midline
what does complete hemianopia mean?
defect comes all the way up to midline
What does the macula sparing hemianopia mean?
half of visual field lost but macula is spared
What is bi nasal hemianopia?
Both nasal half of visual field has been lost
what is congruous defect?
same shape and size defect with symmetry in both eyes
what is incongruous defect?
Defect that is not same size, shape or symmetry in both eyes
Define localisation?
Knowledge of the arrangement of the nerve fibres in the visual pathway will enable you to localise the visual field defect
What are the superior Temporal Fibres projected by in visual field?
superior temporal fibres project in inferior nasal visual field
What are the superior Nasal Fibres projected by in visual field?
superior nasal fibres projected in the inferior temporal visual field
What are the inferior Temporal Fibres projected by in visual field?
inferior temporal fibres projected in the superior nasal visual field
What are the Inferior Nasal Fibres projected by in visual field?
Inferior nasal fibres projected in the superior temporal fibres
What is nasal step?
the Fibres at the rim are the most crowded at the disc providing less structural and vascular support and are the most likely to become damaged in glaucoma
fibres from inferior rim supply the inferior temporal retina damage to this area corresponds to superior nasal visual field defect.
The areas supplied by the fibres corresponds to the nasal step and do not cross the horizontal raphe
What are the rules for visual field assessment?
Retinal lesions can be :
unilateral or bilatera
often asymmetrical between eyes
do not respect the verticle midline
what do macular fibres do?
Macular fibres cross
What do nasal fibres do?
Nasal fibres cross
What do temporal fibres do?
Temporal fibres uncrossed
what does unilateral field defect involve?
involves damage to anterior to the chiasm
what does a field which respects the vertical meridian suggest?
chiasmal or posterior to chaism damage
what do you get if damage is at the chiasm?
you get heteronymous defect
what do you get if the damage is before chiasm?
You get anterior unilateral defect
What do you get if the damage is after the chaism?
You get field defect that starts to respect vertical midline
What type of defect do you get with post chiasm?
Homonymous defect
what do you get with chiasmal defect?
Heteronymous
If damage is above the inion?
You get scotoma in inferior Visual Field
If the damage is below the inion?
You get scotoma in the superior Visual Field
How much doe the V1 relate to the macula?
60%
If pathology is in the left cerebral hemisphere?
The scotoma was on the right
If the pathology is in the right cerebral hemisphere?
The scotoma was on the left
Where do you get incongruent ?
incongruent optic tract
Where do you get congruent?
Congruent towards occipital lobe
what happens to anterior lesion?
spares the macula
what does unilateral field loss suggest?
Unilateral field loss not likely to be neurological ( anterior to the chiasm )
What does bilateral defect suggest?
post chiasm and respects the midline
Does the field loss respect the vertical meridian?
Suggests chiasmal or retrochiasmal
what factors do you look at in glaucoma defects?
Paracentral scotomas
Enlargement of the blind spot
Nasal step
Arcuate scotomas
