Lab 5: Vision Flashcards
What is the latency for catching the ruler, and why?
~200ms in the light
- about 100ms for info to get from retina to occipital lobe (phototransduction etc.)
- about 100ms more for brain processing -> muscle contraction
Why is latency longer in the dark
phototransduction in rods is slower = longer latency
why is reaction time slower in the dark? (3)
- longer reaction time due to rods having longer phototransduction time
- harder to discern colour (rods don’t do colour)
- reduced acuity since rods have with bigger dendritic trees projecting to ganglion cells = larger receptive field = reduced acuity
why does the fovea have best acuity?
highest concentration of cones, and cones have small receptive fields
what causes our blindspot, and why don’t we normally notice it?
optic disk- where the optic nerve exits, so no photoreceptors
normally ok bc binocular vision- brain fills in with info from the other eye
near point/near response
- convergence (cross eyed) -> so image stays on fovea
- pupil constriction -> so light stays on the trues part of the retina, focuses light on fovea, minimises refraction
- accomodation = lens rounds (ciliary muscles contract) so image focused on retina
accomodation with age
decreases as lose elasticity in lens -> need convex lens to focus close images
presbyopia condition and treatment
age related loss of accomodation -> need convex lens to focus close images
hyperopia condition and treatment
eyeball too short -> far away ok but accomodation maxed out, need convex lens to focus close images (converges light, brings image further forward)
myopia condition and treatment
eyeball too long -> close up ok but need convex lens to focus far away (diverges light, brings image further back)
night vision and red light
25-30 mins needed for maximum dark adaptation, for rhodopsin to switch from trans to cis isoform
red light ok bc doesn’t activate rods (still in cis form) so can see in the dark
