w8 vse Entoptic Phenomena Flashcards
(17 cards)
Why don’t we normally notice the dim patch caused by macular pigments?
our brain adapts and ignores it, but the absorption of blue light by macular pigments can be used clinically (maxwell’s spot) to asses macular function
what is Maxwell’s spot and how is it formed?
it’s a dim spot caused by absorption of blue light by macular pigments in the central retina
what is hte different bet polarised and unpolarised light??
polarised light: oscillations in a single direction
unpolarised light: oscillations in all directions
How do macular pigments interact with polarised light?
They absorb harmful blue light, with absorption varying based on the orientation (horizontal or vertical angle).
How do animals use polarised light?
Animals like bees use it for navigation, and cuttlefish use it for camouflage and communication.
What is Haidinger’s Brushes and how does it appear?
Faint yellow-blue brush patterns seen when viewing polarised light, appearing above, below, or beside a polarised line.
they result from the macular pigment’s interaction with linearly polarised light
Some examples of entoptic phemonena:
Haidinger’s Brushes
Maxwell’s Spot
Purkinje Tree
Floaters
Phosphenes
What is the function of macular pigment in the retina?
macular pigment protects the retina by absorbing high-energy visible ligh (blue light)
What entoptic phenomena are associated with the macular pigment?
Haidinger’s Brushes and Maxwell’s Spot are entoptic phenomena linked to macular pigment absorption.
How can Maxwell’s Spot be used to assess macular pigment density?
The visibility, size, and sensitivity of Maxwell’s Spot correlate with macular pigment distribution, making it useful for detecting macular disease.
What is the Purkinje Tree phenomenon?
The Purkinje Tree refers to the visualization of the retinal blood vessels, seen as branching patterns when light is shined into the eye from an acute angle, typically in darkened rooms.
What causes floaters in the field of vision?
Floaters are small clumps of material in the vitreous humor that cast shadows on the retina, appearing as semi-transparent specks or threads drifting across the visual field.
What are phosphenes?
Phosphenes are visual phenomena that occur without light entering the eye, often resulting from pressure applied to the closed eyes.
why can humans perceive Haidinger’s Brushes despite lacking specialised receptors for polarisation vision??
The ability to see Haidinger’s brushes is because the macular pigment in the eyes interact with polarised light turning it into a contrast that is visible
How does the distribution of macular pigment affect the perception of Haidinger’s Brushes?
Haidinger’s Brushes only appear in the macula (the central part of the retina) because that’s where the macular pigment is concentrated.
What is the biophysical basis for human polarization perception?
Humans can detect polarised light because the macular pigment absorbs and changes the light, allowing us to see it even without special receptors.
What are entoptic phenomena primarily associated with in visual perception?
The perception of visual phenomena originating from within the eye itself
