LEC 2: TYPES OF FIELDS LOSS & REPRESENTATION OF SENSITIVITY Flashcards
Describe what happens to fibers as they move down the optic nerve?
As you move down the optic nerve the fibers re-arrange themselves.
Does abnormality only occur on retinal levels or even in the optic nerve?
Abnormality can occur anywhere from the optic nerve to even in the retina.
What is Relative afferent pupillary defect-
A condition in which pupils respond differently to light stimuli shone in one eye at a time due to unilateral or asymmetrical disease of the retina or optic nerve. – it is indicative of the fact that there is damage in 1 eye.
What is the defect called that does not cross over horizontally. It only crosses the vertical?
This is called superior/ inferior altitudinal loss.
Altitudinal loss refers to?
Refers to damage in either the superior or inferior hemi-field. Hence, it can be superior or inferior loss only.
Px with Altitudinal loss are said to suffer a min-stroke in the optic nerve called?
AION- Anterior ischemic optic neuropathy
Where does AION- Anterior ischemic optic neuropathy defect occur in the visual pathway?
This defect occurs anteriorly in the visual pathway. NOT RETINA. It occurs in one eye.
AION- Anterior ischemic optic neuropathy occurs in both or 1 eye?
1 eye
Whenever performing evolutions both eyes need to be checked, why?
Because contribution from each eye occurs simultaneously to each visual field.
Left temporal fibres correspond to what what visual feild
Left temporal fibres correspond temporally to the nasal field in the right eye.
Hemianopia (Hemianopsia) meaning?
Loss of half of the visual field (with respect to the VERTICAL midline).
Quadrantanopia (Quadrant anopsia) meaning?
Loss of one quadrant of the visual field (with respect to the VERTICAL midline). MUST INDICATE SUPERIOR OR INFERIOR.
Left Vertical field loss corresponds to damage to which side of the brain?
Right side of the brain
Homonymous meaning?
Loss on the “same side” (e.g. right or left homonymous hemianopia).
Congruous meaning?
Similar shaped defect in both eyes (e.g. congruous or in-congruous hemianopia).
Unilateral or bilateral eye problems at optic nerve and beyond chiasma?
Optic nerve problems are 1 eye defected problems. As soon as you get to the chiasma and beyond (because fibres cross)- the 2 eyes are involved in the defect.
What is Bi-temporal hemianopia?
VERY RARE:
Hemianopia is on the temporal side in the RE & LE on the temporal. Therefore, called bi- temporal hemianopia.
Occurs from pituitary trauma
Optic radiations move to which 2 lobes?
Temporal and parietal lobe.
Defect in Temporal Lobe causes?
Superior quadrantic defect (‘pie in the sky’).
Defect in Parietal Lobe causes?
Inferior quadrantic defect. (‘pie on the floor’)
Describe in scientific terms what- right side pie on the floor defect means?
Defect on the right sided optic radiations parietal lobe causing left sided inferior defect.
Role of Threshold perimetry
It records the depth and severity of a defect.
Why do you record the depth of visual field defect?
Human eyes are most sensitive at the fovea and the ability to see the smallest or dimmest light declines as you move to the periphery.
Equation for threshold perimetry and sensitivity
Threshold perimetry: ∆L/L
Sensitivity: L/∆L
