w3 VSE Visual Illusions Flashcards
(16 cards)
what is a visual illusion??
a misperception of a visual stimulus where the perceived image differs from the physical reality
why do visual illusions matter in optometry?
they reveal how perception works and highlight potential patient misunderstandings showing how visual processing can be distorted
example of a cognitive illusion??
Ames Room - a distorted room that tricks the brain into misjudging size based on pre assumed room geometry
what is a cognitive illusion?
an illusion caused by assumptions, knowledge and prior experiences influencing perception (your brain filling in the gaps)
What is the Müller-Lyer illusion?
2 lines of equal length appear different lengths because of arrow like ends influenced by depth perception cues
what does the Ebbinghaus illusion demonstrate??
contextual size contrast a central circle appears larger of smaller depending on the size of its surrounding circles
what is the clinical relevance in understanding illusions??
helps differentiate visual processing issues from actual pathology and improves understanding of visual development and neurological function
what are mach bands?? what are mach bands the result of??
mach bands are a visual illusion that exaggerates the contrast bet adjacent regions of diff brightness (edges appear lighter or darker than they actually are)
what are mach bands the result of??
mach bands are the result of the way our visual system processes contrast information, the brain enhances edges and boundaries to help us distinguish objects in our environment more effectively
what causes physiological illusions?
overstimulation of the retina or visual cortex e.g. brightness, colour, movements, pattern
an example of a physiological illusion??
Hermann Grid - bigger black squares, grey small circles/squares inbetween, focus on one gap, see grey squares surrounding due to retinal ganglion cell receptive field inhibition
what causes the Hermann Grid illusion???
lateral inhibition from teh retina’s receptive fields exaggerates contrasts at intersections
lateral inhibition??
A neural mechanism where excited neurons reduce the activity of their neighbours, enhancing contrast and edge detection in visual processing.
How does lateral inhibition enhance visual perception?
It sharpens borders and edges, helping the visual system detect fine detail and contrast more efficiently.
lateral inhibition and mach bands??
the cause of mach bands can be due to lateral inhibition in the retina ganglion cells inhibit their neighbours, boosting edge contrast perception.
however lateral inhibition cannot be the entire explanation for mach bands as if it was mach bands would be perceived at a sharp border between light and dark not a gradient
What is the primary perceptual phenomenon associated with the visual illusion known
as Mach Bands?
Enhanced contrast at the border between adjacent areas of different
brightness.
