130 - Visual Disterbance Flashcards
What is hyphaema?
Bleeding between iris and cornea
What protects the eye from trauma/damage?
Orbit bones (they blow out rather than the eye)
Soft tissue - lids + orbital fat
Tears - physically removes debris and contains immunoglobulins - it is antimicrobial
What are the 7 parts of an eye examination?
Examine externally Visual acuity Visual fields fundoscopy Eye movements intraoccular pressure Pupils Red Reflex
Where in the eye has no pain receptors?
The retina
What can happen to the vitreous cavity?
Loss of clarity
Blood
Pus
Uvitus
How does the lens respond to injury?
It goes cloudy
What pathologies related to the optic nerve can cause sudden visual disterbance?
Optic neuritis Papillitis Ischaemic optic neuritis Giant cell arthritis Compression - tumour?
If someone has trouble seeing in the centre of their vision, what may they have?
Age related Macular degeneration.
Blood vessels can grow into the retina and bleeed - ‘wet’, or can be ‘dry’.
Most common cause of blindness and partial sightedness.
What state is the rod/cone cells in in the dark?
Depolarised.
cGMP is produced
The Na/Ca channel is open
What state are rod/cone cells in in the light/
The become hyperpolarised
Describe what occurs in the rod/cones when light is absorbed.
Light hits rhodoopsin, changes retinal from cis to trans form.
This causes the alpha unit to be cleaved from transducin
this converts GDP to GTP
Phosphodiesterase is activated
This changes the cGMP to GMP
This closes the na/Ca channel (but it is still leaky), but the Na/Ca/K exchanger is still open
Ca is removed from the cell
It becomes hypperpolarised
–> LESS glutamate produced
–> Stimulates bipolar cells (some depolarise, some hyperpolarise)
What neeurotransmitter do rod/cones produce?
Glutamate
Does glutamate levels go up or down in light in a rod/cone cell?
Down
What is convergence?
Multiple bipolar cells synapse with just one ganglion - so multiple rods/cons activity is pooled.
east convergence at the fovea, where there is 1:1 synapsing.
What is the 3rd photosensitive cell?
Photosensitive retinal ganglion cells.