Vision Flashcards
3 chambers
anterior, posterior and vitreous chamber
Why are the chambers important
Filled with different fluids (ions)
ant = aqueous humor
post =
vit = vitreous humor (sticky gel mass)
Lens changes shapes
due to actions of ciliary muscle and zonule fibres
Optic disk is
where all the nerves that carry sensory information about the light to optic nerve (cranial nerve 2)
Fovea is
the high density of our cone receptors
Cone receptors are responsible for
colour vision and high acuity
What is normal vision
Emmetropia
Features of Myopia include
eyeball being too long, image focused in front of retina not for the distant; corneal surface too curved
Hyperopia features include
eyeball too short; refracting system too weak; image not focused on retinal surface
Accommodation is where
we look in the distance and then we look at something close up = the change of lens thickness => increase in refractive index
(changes in ciliary muscles and zonule fibres)
Increase shape of lens means
accommodation - we can see nearby objects clearer
Structures of retina
Outer layer = cone and rod
Rod photoreceptors
light intensity
Cone photoreceptors
high acuity vision and colour
Fovea has a high distribution of
Cones
How does Phototransduction work
cGMp levels are high - binds to Na channels - keeping them open - allows Na+ influx - photoreceptor depolarisation - neurotransmitter released from terminal
When photoreceptor interacts with light
cGMP levels drop - activation of rhodopsins - cGMP no longer bind Na+ channels - closing them - increased -ve charge causes hyperpolarisation and no neurotransmitter release
Rods have single
photopigment
Cones contain photopigments that respond to 3 different wavelengths
short, medium, long
Dichromacy
colour blindness
Protanopia
Blue and green only
Deuteranopia
blue and red only
Trichromacy is
normal colour vision
Why is the Retina important
The retina is a layer of photoreceptors cells and glial cells within the eye that captures incoming photons and transmits them along neuronal pathways as both electrical and chemical signals for the brain to perceive a visual picture.
