Flashcards in Vision Deck (33)
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
Unilateral field defects
suggest disease anterior to the chiasm
31
Bitemporal field defects
suggest disease at the chiasm
32
Homonymous field defects
suggest disease behind the chiasm
33