Flashcards in Vision Deck (33)
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1
Presbyopia
- diminished ability to focus on near objects due to old age
- EVERYONE has this when they get old
2
Focusing the light on the retina
- mostly done by cornea
- lens does fine adjustment
3
Aqueous humor: synthesis & removal
- synthesized by ciliary epithelium
- removal through trabecular meshwork
4
Glaucoma
- decreased aqueous humor outflow leading to increased intraocular pressure, which injures the optic nerve
- second most common cause of blindness
5
Sympathetic nervous system effect on pupil
Dilation via radial dilator muscles
6
Parasympathetic nervous system effect on pupil
constriction via pupillary sphincter
7
Efferent nerve defects
- anisocoria: unequal pupils
8
Afferent nerve defects
- pupils are always EQUAL
9
Cataract effect on pupil response to light
- none
- media opacities do not affect pupil response to light
10
Result of injury to sympathetic fibers to eye
Horner syndrome
11
Horner Syndrome
- anisocoria: small pupil on affected side
- ptosis: droopy eyelid on affected side
- diminished sweating on affected side
12
Sodium channels during darkness
- open
- depolarized membrane
13
Sodium channels during light
- closed
- hyperpolarized membrane
14
Phototransduction
- cascade of reactions that happen in the photoreceptors
**light--rhodopsin--transducin--phosphodiesterase--less cGMP--sodium channels close--graded HYPERpolarization**
15
What type of protein is rhodopsin
G-protein-coupled receptor
16
In oder for rhodopsin to be sensitive to light it needs what
- vitamin A derivative (11-cis retinal)
17
Result of light hitting rhodopsin
- isomerization of 11-cis retinal to all trans retinal
18
Visual cycle
- conversion of trans retinal back to 11-cis retinal
- occurs outside photoreceptor cell in retinal pigment epithelium (RPE)
19
Photoreceptor surface turn over
- RPE allows turnover of entire photoreceptor surface every 10 days
20
Conversion of light to neurological impulse
- minimum of three neurons: photoreceptor, bipolar cell, ganglion cell
- light stimulus on retina turns into neurological impulse
21
Graded potential neurons
- photoreceptor and bipolar cell
22
Action potential neuron
ganglion cells
23
Retina blood supply
- derived from ophthalmic artery: retinal vessels, choroidal vessels
24
Age related macular degeneration
- accumulation of extracellular lipids (lipofuscin) and protein deposits (drusen) beneath RPE
- most common cause of blindness
25
Retinal vasculature injury causes
- diabetic retinopathy
- atherosclerotic disease
26
Choroidal circulation injury causes
- age related macular degeneration (neovascularization)
27
Area bounded by temporal vascular arcades
Macula
28
Fovea
point of fixation in the center of the macula
29
Altinudal defects
- suggest disease inside the eye
30
