Visual Fields Flashcards
How many degrees is the nasal visual field?
60 degrees
How many degrees is the superior visual field?
60 degrees
How many degrees is the inferior visual field?
75 degrees
How many degrees is the temporal visual field?
100 degrees
How many degrees of binocular overlap should there be?
120 degrees
Where to retinal nerve fibers of the retina converge?
At the optic nerve
Nasal fibers of the retinal nerve fiber layers represent which part of the visual field?
Temporal visual field
Inferior fibers of the retinal nerve fibers represent which part of the visual field?
Superior visual field
Which fibers are considered “pre-chiasmal”?
Nasal and superior fibers - fibers traveling from the eye to the chiasm
What percent of the post-chiasmal fibers travel to the lateral geniculate nucleus?
80%
Where do the other 20% of the post-chismal fibers go?
Pretectal nucleus in the midbrain - to control the pupils
If there is lesion in the optic chiasm, what do the visual fields look like?
Bitemporal hemianopia - R and L temporal fields impacted
If there is a post-chiasmal lesion, what do the visual fields look like?
Same side of both eyes affected
How many layers are there in the lateral geniculate nucleus?
6
What are the first 2 layers of the LGN? What do they do?
Magno cellular - for moving stimuli
What are layers 3-6 of the LGN? What are they for?
Parvocellular - for color and acuity
The inferior fibers of the LGN represent which part of the visual field?
The superior portion
The inferior fibers of the LGN travel via ___ to the temporal lobe.
Meyer’s loop
What does PI-TS stand for?
Parietal lobe - Inferior fibers
Temporal lobe - Superior fibers
What does the central visual field involve?
Fixation
What does the centrocecal visual field involve?
Fixation to blind spot
Where is the paracentral visual field?
Adjacent to fixation (central)
Where is the pericentral visual field?
Surrounding fixation (central)
What is a scotoma?
Absolute or relative area of poor visual function surrounded by a normal visual field
What does it mean to have a homonymous visual field defect?
Same side visual field loss (Ex. Right field of left eye, right field of right eye)
What does it mean to have a heteronymous visual field defect?
Opposite field loss (Ex. Left field in left eye, right field in right eye - bitemporal hemianopsia)
On whom should the amsler grid test be performed?
Patients over 50
Diabetics
People with a history of macular degeneration
People on toxic medicines
People with reduced acuities
At 30 cm, how many degrees does each block of the Amsler grid represent?
1 degree
