Vision

Question 1

Light?

Answer 1

visible electromagnetic radiation

–> daylight <400nm (UV high energy) to >700nm (infrared low energy)

Question 2

What is in these ares?

• Tunica fibrosa
• Tunica vasculosa (vascular)
• Tunica interna (internal)

Answer 2

1= (collagen) Sclera(white), cornea (clear)
2 = choroid, ciliary body(muscle that secretes aqueous humour), Iris
3= Retina, optic nerve

Question 3

Key aspects of the eyes function

• cell replenishing
• fluid pressure

Answer 3

continual replacing of cells/ tissues

fluid pressure = v important, regulated by protective sheaths (collagen) to prevent pressure growing

Question 4

Choroid?

Answer 4

Choroid = nutritional support for retina (full of blood vessels)

Question 5

Canal of Schlemm?

Answer 5

Canal of schlemm = drains fluid (if it doens’t= increase in ocular pressure)

Question 6

Where do they lens and cornea obtain nutrients from?

Answer 6

lens, cornea etc obtain nutrients from fluid

Question 7

Where is neuronal output from?

Answer 7

papilla = neuronal output from here

Question 8

Lamina Cribrosa?

What happens if increased or decreased pressure in eye?

Answer 8

loosening of fibres
increased = glaucoma - stresses lamina cribrosa = damages blood supply to optic nerve. Can block Iridocrina angle and block blood supply to retina too
decreased water content = cataract - lens becomes opaque, not clear

Question 9

optical components - focus light on retina (dioptric apparatus)
refractive index of:
air
cornea
aqueous humour
lens
vitreous humour

Answer 9

air - 1
cornea - 1.38
AH - 1.34 - liquid secreted from ciliary body from PC to AC. Absorbed by canal of schlemm
Lens - 1.41 - held by suspensory ligament to CB. tensioned by intraocular pressure
VH - 1.34

Question 10

Most common causes of blindness?

Answer 10

1) cataract - cloudyness - age/ diabetes/ UV

2) glaucoma - increased eye pressure (slow uptake of AH) = pressure on blood supply = retinal degeneration

Question 11

Image formation
iris purpose
photopupillary reflex
distance

Answer 11

iris - regulates light levels,
pupillary constrictor (smooth circular muscles)
pupillaru dilator (smooth radial muscle)
Photopupillary reflex:
-consensual light reflex (change in intensity)
-occurs in both eyes even if only 1 stimulated
Distance
- related to total light level

Question 12

Circuit for eye contraction?

how is this info sent to spinal cord?

Answer 12

Optic nerve NII send info to pre-tectal region (para-sympathetic) in PONS, then edinger-westphal nucleus, then NIII-oculomotor, then ciliary ganglion, then ciliary nerves = Iris muscles
(info sent to upper thoracic spinal cord via the superior cervical sympathetic ganglion)

Question 13

Edinger-Westphal nucleus function?

damaged?

Answer 13

= pupil constriction, lens accommodation, convergernce

• damaged = pupil dilation

Question 14

Near response

Answer 14

Emmetropia = eye relaxed - focus > 6m
convergence = eyes focus on one thing =eyes move closer together
miosis = constriction of the iris = smaller pupils
accommodation of lens = lens has to accommodate to the way its being pulled by ligaments (intaocular pressure and ciliary muscles working against each other)
For accommodation = ciliary muscle relaxed(opposite for near)

Question 15

Retina and layer

Answer 15

light has to go through many layers before hitting rods and cones

Question 16

Function of pigment epithelium?

Answer 16

Rods and cones, pigment epithelium (like a mirror - tapetum - which prevents losing light that has become lost in the eye == reflected back), then choroid

Question 17

Layers of eye from back to the front:

Answer 17

sclera, choroid, pigment epithelium, rods and cones outer segments, rods and cones nuclei, bipolar cells, ganglion cells, nerve fibres, vitreous body