Clinical Examination of Vision Flashcards
Right visual field is seen in the ____ side of brain
Right visual field is seen in the LEFT side of brain
in occipital cortex
The inferior retina sees _____ portion of the visual field
The inferior retina sees UPPER portion of the visual field
The superior retina sees _____ portion of the visual field
The superior retina sees LOWER portion of the visual field
The temporal retina sees _____ portion of the visual field
The temporal retina sees NASAL portion of the visual field
The nasal retina sees _____ portion of the visual field
The nasal retina sees TEMPORAL portion of the visual field
Which pt of the retina allows for visual acuity?
Center of retina
Small objects are only seen closer or farther to center of visual field?
CLOSER
What is the implication of the optic nerve’s nasal location?
Creates a blind spot over temporal vision
There is an absence of ___________ where the optic nerve leaves the eye.
There is an absence of RODS/CONES where the optic nerve leaves the eye (area of optic nerve head).
The optic nerve head (cup) receives retinal ganglion cell axons as they arch from above/below the __________________
The optic nerve head (cup) receives retinal ganglion cell axons as they arch from above/below the HORIZONTAL MERIDIAN OF THE RETINA
Where do most visual field defects begin and why?
Most begin in CENTER of vision and move out towards periphery.
(bc 90% of fibers in optic n. carry info from central 30 degrees of the visual field and lose their arcuate distribution as they travel through the orbit towards the optic chiasm)
Relative afferent pupillary defect can occur with minimal damage to the _______
Relative afferent pupillary defect can occur with minimal damage to the OPTIC N.
(Rarely w/ retinal damage, would need “ancient and devastating” level of damage)
Relative afferent pupillary defect, explain positive test
If optic n. is damaged, when light is shined in that eye, both pupils will DILATE.
Which retinal axons cross at chiasm? What is the implication of this?
Axons from nasal retina.
Chiasmal visual field defects are typically bitemporal.
Each optic tract carries info from contralateral hemifield of both eyes to the lateral geniculate bodies. What does this imply for optic tract disease?
Optic tract disease causes hemianopic defects affecting the same (homonymous) contralateral visual field of each eye.
After leaving lateral geniculate body, visual radiations carry info from the lower retina (upper visual field) to where?
These fibers loop down into temporal lobe (Meyer’s loop).
After leaving lateral geniculate body, visual radiations carry info from the upper retina (lower visual field) to where?
These fibers pass up directly through the parietal lobe.
A temporal lobe lesion picking off Meyer’s loop will cause what type of defect?
An upper field defect in both eyes.
Most of the occipital lobe is concerned with the _____ field of vision and information from corresponding points from the visual fields of each eye is processed by neurons which are _______.
Most of the occipital lobe is concerned with CENTRAL field of vision and information from corresponding points from the visual fields of each eye is processed by neurons which are CLOSE TO EACHOTHER.
Occipital lobe disease causes which type of defects?
Occipital lobe disease causes central, homonymous visual field defects, which are identical (congruous).
Visual field testing methods
- Confrontation
- Grid
- Tangent screen
- Manual perimeter
- Automated visual field
- Multifocal visual evoked potential
Multifocal visual evoked potential
Visual field test where brain waves are recorded from occipital lobe in response to checks flashing in visual field. Problem with visual field will show noisy signal indicating poor transmission.
Which part of occipital lobe does peripheral info come into?
Anterior tip of occipital cortex
Which part of occipital lobe does central info come into?
Posterior portion of occipital cortex
If discreet area is missing in one eye and no afferent pupillary defect is present, suspect which type of damage?
Retinal damage
If a visual field deficit is superior and temporal, describe the retinal lesion.
The retinal lesion should be nasal and inferior.
You observe a visual field deficit that is inferior and respects the horizontal meridian (immediately after crossing horizontal meridian, can’t see). Describe the lesion.
Lesion must be superior, close to or at the OPTIC NERVE HEAD.
Lesion is preventing ganglion cell axons from entering the optic nerve.
Optic Nerve Damage findings
- Loss of central vision in visual field
- Relative afferent pupillary defect
- Retina appears normal
- Imaging shows optic nerve inflammation
bitemporal hemianopia
- bilateral temporal fields of vision missing
- info from temporal fields enters nasal retina but can’t cross in chiasm
- most common cause: pituitary adenoma putting pressure on chiasm
Observe small paracentral defects in both eyes, not quite identical
Nasal field defect on R, temporal on L.
Describe lesion.
“Optic tracitis”
- inflammatory, can be caused by demyelinating plaques.
Lesion in R tract causing homonymous (L side) hemianopic scotomas.
Visual loss to both R, upper fields.
Defects are similar (quadrantic shape) but not quite identical.
Describe lesion.
Damage to meyers loop in L temporal lobe
- Defects are similar but not quite identical, so fibers are affected after crossing but not yet where they come together (neurons in occipital lobe).
- Commonly causes: tumor, stroke.
- Lower fibers carry info from superior visual field.
- -> Causes homonymous “pie in the sky” defect (quadrantic shape).
Entire field of vision is lost on R side in both eyes (complete hemianopia).
L-sided lesion is likely in the radiations, affecting all fibers coming from the R visual field in both eyes.
- Common cause: infarct in MCA.
(Unlikely to be an occipital lobe lesion, which spares the area near center, doesn’t split down middle.)
Observe almost superimposable visual field defects. What does this suggest?
Neurons receiving info from visual fields on each side are situated near each other in OCCIPITAL lobe.
Lesion: possible arteriovenous (AVM) malformation in L occipital lobe causing R congruous, homonymous hemianopia.
Often lg area of occipital lobe that sees in center of vision is spared.
Observe arching pattern of vision loss that respects the horizontal meridian. Where is the lesion?
At or near optic n. head.
- glaucoma
- ischemic optic neuropathy
Observe blob shape visual defect on one eye.
Retina appears normal.
Where is lesion?
Lesion is behind eye, likely along optic n. (especially if relevant pupillary defect).
junctional scotoma
Temporal field of vision loss on one side, optic n. defects on other side.
Lesion where optic n. comes into chiasm as they cross.
