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MODHIII - Unit 3 > Vision > Flashcards

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

Unilateral field defects

suggest disease anterior to the chiasm