Visual Field Defects Flashcards
What is the definition of a visual field?
The area of space that a eye can perceive
What is the name of the process used to assess the visual field?
Perimetry
What is the normal temporal angle for a visual field? What is the normal nasal angle for the visual field? What are the angles to which we can see superiorly and inferiorly?
Temporal angle: 100 degrees
Nasal angle: 60 degrees
Superior/Inferior angles: 60 degrees
What is the blind spot in the eye due to? Why don’t we notice it?
Optic nerve; the brain fills in this blind spot
When you look at a fixation point in the center, what are you using to perceive this image?
Fovea- within the macula
What part of the visual field does the nasal retina perceive? What part of the visual field does the temporal retina perceive?
Nasal retina perceives the temporal visual field while the temporal retina perceives the nasal visual field
What anatomical feature divides the nasal and temporal retina?
Fovea
The area from 60 to 100 degrees that can only be perceived by one eye at a time is known as what?
The temporal monocular crescent
What area represents the binocular visual field? The nasal visual fields of both eyes, the temporal visual fields of both eyes, the nasal retina, or the temporal retina
The nasal visual field of both eyes, which would be perceived by the temporal retina of both eyes- this represents the overlapping visual field of both the right and left eye
In a diagram of Tranquir’s Island of vision, that represents a visual field with an x, y, and z axis, what does the z axis represent?
Sensitivity of the visual field
In a diagram of Tranquir’s Island of Vision, where can one find the best acuity of 20:20 vision?
The tip of the island
What is the most important factor that affects visual sensitivity (or the shape of Tranquir’s island of vision)?
Character of the stimulus- the size, intensity, shape, color, duration, and movement of the stimulus
When will you first see a bright, larger object moving in from the periphery- when it first hits your island of vision or close to the tip of the island? What about a dim, smaller object?
Bright, large object: see as soon as it hits the island
Dim, small object: won’t be seen until it hits the tip of the island, or is right in front of your fovea
Moving in object from the periphery into the center and noting when the patient can see it is known as what form of perimetry?
Kinetic perimetry
Using a stationary object and then making it brighter until the patient can see it is known as what form of perimetry?
Static perimetry
What are the advantages and disadvantages of using confrontation visual fields to assess a patient’s visual field?
Advantages: inexpensive, fast, practical
Disadvantages: dependent on both the examiner and the examinee
When performing a confrontation visual field what should the examiner do?
Have the patient cover one eye with their palm, with the examiner covering the contralateral eye, then ask if the patient sees the examiners face, followed by finger counting (ask how many fingers in each quadrant), then finger waving from periphery, and then bring in a red object which has requires a higher sensitivity
What is a hemianopia?
A nasal or temporal defect where you can only see one or the other- can only see the nasal visual field or the temporal visual field
How do you use an Amsler grid to test visual field defects?
Place the small grid at 33cm and ask if patient has an missing, blurred, or distorted lines on the grid
How do you use a Tangent screen to assess visual field?
Examiner stands 1m away from the examinee, facing them, and brings an image in from each side
Amsler grid testing and tangent screen testing use: static perimetry or kinetic perimetry?
Kinetic perimetry
What is the definition of scotoma?
A chunk of the visual field is missing
The mean deviation provided by the Humphrey visual field test, gives you what information?
The weighted average of all visual defects in one eye
What causes an arcuate visual field defect?
Arc like shaped defect caused by retinal nerve fiber damage
What is a altitudinal visual field defect?
Either a superior or inferior visual field defect- split at the horizontal
What is a quadranopia?
Visual field defect in one quadrant
Relative versus absolute visual field defects differ in what aspect?
Relative visual field defects are only abnormal for certain stimuli while absolute are abnormal regardless of which type of stimulus is used
A defect in the temporal field of the right eye and the nasal field of the left eye is considered to by homonymous or heteronymous?
Homonymous- both affect the same side of the eye
A defect in the temporal field of the right eye and the temporal field of the left eye is considered to be homonymous or heteronymous?
Heteronymous- affecting different sides of the eyes
What does congruous mean?
The visual defect is similar in both the right and left eye
What is the anatomical pathway from the retina to the occipital lobe?
Retina, optic nerve, optic chiasm, optic tract, LGN, optic radiations, calcarine fissure
What divides the retina into the superior and inferior aspects?
Horizontal raphe
What two visual field defects would you expect with a retinal defect?
Central scotoma from a foveal lesion or arcuate defect from glaucoma
What are three visual field defects that can be seen when there’s a defect in the optic nerve?
Altitudinal field defect, central depression, or central scotoma
What usually causes an altitudinal field defect?
Anterior ischemic optic neuropathy- (NAION)
What fibers cross in the bottom of the optic chiasm? What part of the visual field do these fibers contain?
Fibers from the inferior nasal retina
Carry the superior temporal visual field
What fibers cross at the top of the optic chiasm? What part of the visual field do these fibers contain?
Fibers from the superior nasal retina
Carry the inferior temporal visual field
A pituitary tumor is most like to push against the lower portion of the optic chiasm, producing what kind of visual field defect?
Bitemporal supratemporal field defect
The fibers from the inferior nasal retina do something different immediately after reaching the optic chiasm, what is this?
Loop around the opposite optic nerve forming Wilibrands knee and then return to the optic chiasm
What is significant about Wilibrands knee if the optic nerve is cut?
Lose the complete vision in one eye, but also part of the visual field in the opposite eye- pie in the sky
What happens to the axons from the fovea after they leave the retina?
Cross in the center of the optic chiasm; very hard to damage from physical force because so deep
What is the hallmark visual field defect when the lesion affects the body of the chiasm?
bitemporal visual field defects
A lesion beyond the optic chiasm produces what type of visual field defects?
Homonymous
The more posterior the lesion is, with regard to the retinochiasmal pathway, the visual field defect is said to be more congruous or incongruous
Congruous
What visual field defect is seen with a lesion at the optic tract? What other symptoms are seen?
Incongruous homonymous field defect Contralateral RAPD (pupillary reflex) Contralateral paresis from the proximity to posterior limb of internal capsule
Lesion in the LGN of thalamus causes what kind of visual field?
Homonymous sectoranopia
After synapsing in the LGN, axons then travel to via the parietal and temporal radiations to the calcarine sulcus. What visual field is contained in the parietal and temporal radiations?
Parietal radiation: carries the inferior field
Temporal radiation: carries the superior field
Which optic radiation goes directly to the calcarine sulcus? Where does the other radiation go before going to the calcarine sulcus?
Parietal goes directly to the calcarine sulcus
Temporal loops around forming Meyer’s loop in the rostral part of the temporal lobe before going to the calcarine sulcus
The cuneate receives which optic radiations; the lingual gyrus receives which optic radiations?
Cuneate receives parrietal optic radiations
Lingual receives temporal optic radiations
With which type of lesion do you see macular sparing?
Occipital lobe lesion
Where do the monocular temporal crescent axons go in the occipital lobe?
The most anterior part of the calcarine fissure
