Visual Fields Intro Flashcards
What is hemianopia?
Loss in half of the VF
What is quadrantanopia?
Loss of a quarter of the VF
What does homonymous mean?
VF loss is on the same side in each eye
What does heteronymous mean?
VF loss is on different sides in each eye
If there is visual field loss in only one eye, where is the damage?
Before the optic chiasm
If the VF loss is in both eyes, where is the damage?
At or after the chiasm
If VF damage is heteronymous, where is the damage?
At the optic chiasm
If VF loss is homonymous, where is the damage?
After the optic chiasm
What is generalised VF loss? What might be a cause?
Diffuse, equal loss across the VF
Likely caused by a cataract, small pupil or poorly/uncorrected refractive error
What is localised VF loss? AKA?
VF damage at a spot location
AKA focal or scotoma
What is constriction VF loss?
Loss at the edges of the VF, causing ‘tunnel vision’ effect
If a defect crosses the midline (H or V), what is the cause?
Photoreceptor damage
If the defect respects the horizontal midline, what is the cause?
Defective RNFL cells
What is included in a central scotoma?
Fovea
What is included in a centrocecal scotoma?
Fovea and blind spot
Where is a paracentral defect located?
Central vision, not including the fovea
Where is an arcuate defect located?
Forms an arc shape from the blind spot, across either superior or inferior retina, doesn’t cross the horizontal midline
What is the max extent of the visual field?
Temporal: 100 degrees
Nasal: 60 degrees
Superior: 60 degrees
Inferior: 75 degrees
What is the purpose of VF testing?
Early detection of defects, assessment of baseline VF, and follow up of concerns
What is the detection threshold?
Minimum brightness seen (first time px detects a light)
What is static perimetry and what are the types?
Targets (lights) are shown to the px in a sequence
Types: Threshold and Suprathreshold
How does threshold static perimetry work?
It either increases the brightness of the stimulus until it is just seen, or decreases until it’s not seen, or a combination of the two.
How does suprathreshold static perimetry work?
Shows a stimulus at a known amount brighter than the threshold
State an advantage and a disadvantage of threshold static perimetry.
Adv: accurate mapping of the whole VF
Disadv: time consuming, px may tire and get bored leading to inaccurate results
State an advantage and disadvantage of suprathreshold static perimetry.
Adv: much quicker test than threshold
Disadv: less accurate mapping, may miss small focal defects or early VF loss due to estimated threshold
What is kinetic perimetry?
Moving a spot of light, px reports when just seen or not seen
When interpreting static threshold results, what distance is between each spot?
6 degrees between each spot
3 degrees between centre line and first spot
On a deviation map, what is it grading against and what do + and - mean?
Grades against the normal for that age range.
+ = better than normal
- = worse than normal
