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year 2 - neuroscience > Structure & Function of The Eye > Flashcards

Structure & Function of The Eye Flashcards

1
Q

Anatomy of the Eye?

A

ONENOTE!!

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2
Q

Lacrimal System?

A

Contains structures for tear production & drainage

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3
Q

3 types of tear production?

A
  1. Basal tears
  2. Reflex tears - in response to irritation
    o afferent CN V1
    o efferent PNS
  3. Crying tears
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4
Q

Explain how the Lacrimal System works

A
  1. Tears produced in LACRIMAL GLANDS
  2. Drain through TWO PUNCTA
    o through superior & inferior Canaliculi
  3. Collect in tear sac
  4. Drain through tear sac –> nose
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5
Q

Properties of the Tear Film?

A

ONENOTE!

o Maintains smooth corneal-air surface
o Facilitates O2 supply to cornea
o Removes debris
o Bactericide

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6
Q

Composition of the Tear Film?

A

o Superficial oily layer

  • reduce tear film evaporation
  • produced by Meibomian glands

o Aqueous layer
- produced by tear gland

o Mucin layer
- maintains wet corneal surface

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7
Q

Conjunctiva?

A

Thin transparent tissue that covers the outside surface of the eye

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8
Q

Properties of the conjunctiva?

A

Begins at the outer edge of the cornea

  • covers the visible surface of the eye
  • also lines the eyelids

Nourished by near-invisible blood vessels

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9
Q

Muscles that move the eye and layers of the eye ball?

A

6 extraocular muscles!

Layers of the eye ball:

  1. Retina (inside)
  2. Choroid (middle)
  3. Sclera (outside)
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10
Q

Retina?

A

Thin layer of photo-sensitive tissue that captures light rays

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11
Q

Choroid?

A

Component of the uvea (iris, ciliary body & choroid)

Composes of layers of blood vessels

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12
Q

Sclera?

A

Tough, opaque WHITE tissue - covers outside of eye

CONTINUOUS with the cornea!

HIGH water content

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13
Q

Cornea?

A

LOW water content!

o continous w. scleral layer
o transparent
o provides 2/3 of the eye’s focussing power
o higher refractive index than air, convex
o physical barrier e.g. infection barrier

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14
Q

Layers of the cornea?

A

5 LAYERS!

  1. Epithelium
  2. Bowman’s membrane (basal membrane of epithelium)
  3. Stroma (thickest layer, contains nerve endings)
    - NO blood vessels in normal cornea
  4. Descernet’s membrane (basal membrane of endothelium)
  5. Edothelium
    - pumps fluid OUT of cornea, prevents corneal oedema
    - only ONE cell thick
    - NO capacity to regenerate
    - cell density decreases w. age SO can result in corenal oedema & cloudiness
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15
Q

Uvea?

A

The VASCULAR coat of the eye ball
- lies between the sclera & retina

Composed of 3 parts
o iris
o ciliary body
o choroid

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16
Q

What does the close connections of the uvea structures often mean?

A

Means disease of ONE often affects the other two as well!

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17
Q

Len Zonules?

A

Fibrous ring!

Suspends the lens and consists of passive connective tissue

e.g. ciliary muscle contract, PUSHES towars zonules which are more FREE so lens constrict!

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18
Q

Iris?

A

Coloured part of the eye - controls light levels inside the eye

Round opening in centre = pupil

Embedded w. tiny muscles that
o dilate & constrict the pupil size

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19
Q

Function of the lens?

A
  1. Transparency - regular structure
  2. Refractive power
    - provides 1/3 (cornea provides other 2/3)
    - higher index than aq fluid
  3. Accommodation - elasticity
20
Q

Optic nerve?

A

Transmits electrical impulsed from the RETINA —> BRAIN

Connects back of the eye near the MACULA
- visible portion of it is called the OPTIC DISC

21
Q

Macula?

A

Located
o temporal to the optic nerve
o centre of retina

It is small & highly sensitive part of retina
- responsible for detailed central vision

22
Q

Fovea?

A

Very CENTRE of the macula!

23
Q

Anterior and posterior segments of the eye?

A

Divided by the LENS!

Anterior
o between cornea & lens
o filled with clear fluid
o provides nutrients

Posterior
o filled with VIRTEOUS fluid

24
Q

Normal pressure in the ciliary bodies?

A

12-21mmHg

25
Q

Function of the ciliary bodies?

A

Production of AQUEOUS HUMOUR!

26
Q

How is aqueous humour produced?

A
  1. Intraocular Aq flows into the posterior chamber
  2. Then flows into the scleral angle (with trabecular meshwork)

ONENOTE!!

27
Q

How is aqueous humour absorbed?

A

It is then absorbed via 2 methods:

a) Uveal-scleral Outflow
o Aq leaks between the sclerous & choroid
o 20% of drainage
o Prostglandin analogues target this

b) Schlemm’s canal & TM
o Aq goes to the bloodstream
o 80% of drainage

28
Q

Define Glaucoma

A

Disease of sustained high intraocular pressure (risk-factor)

29
Q

Is IOP the cause of Glaucoma?

A

NO - it is a risk-factor that is modifiable!

30
Q

Characteristics of Glaucoma

A

o Retinal ganglionic cell death
AND
o Enlarged optic disc cupping
(optic disc enlarges due to absence of retinal ganglionic cells)

31
Q

What does Glaucoma result in?

A

Visual field loss AND blindness

32
Q

Types of Glaucoma?

A
  1. Primary open angle glaucoma (most common)

o Trabecular meshwork dysfunction

  1. Closed angle glaucoma (acute or chronic)

o Increased IOP = causes lens/iris to bulge out
o restricts access to TM and thus limit outflow
o risk factors inc. having a small eye & a naturally small angle
o treatment is peripheral laser iridotomy to create drainage holes

33
Q

Optic nerve blind spot?

A

Where the optic nerve meets the retina
o NO light sensitive cells
o SO if image falls within this part, will NOT see the image

34
Q

Difference between macula and fovea

A

Fovea
o HIGHEST [CONES]
o NO [RODS]

Macula is opposite:
o RODS are MORE SENSITIVE to LIGHT - so peripheral stars seems brighter only because its not in the fovea vision

35
Q

2 types of vision?

A
  1. CENTRAL vision - mascular degeneration affects ACUITY

o detailed day vision
o for reading & facial recognition
o assessed by the visual ACUITY assessment

  1. Peripheral vision

o for shape, movement & night vision
o assessed by the visual FIELD assessment

36
Q

Retinal structure?

A

ONENOTE””

Outer layer = 1st order neurons
o PHOTORECEPTORS
o detection of light

Middle layer = 2nd order neurons
o BIPOLAR cells
o regulate/improve sensitivity AND process ligh

Inner layer = 2rd order neurons
o RETINAL GANGLIONIC cells
o transmission of signal to brain

37
Q

Two main classes of photoreceptors in the retina?

A
  1. ROD photoreceptors (scotopic = rod vision)

o LONGER outer segment = 100x MORE SENSITIVE to light
o it has a SLOW RESPONSE to light
o responsible for peripheral, NIGHT vision AND recognises motion
o 120m rods

  1. CONES photoreceptor (photopic = cone vision)

o LESS SENSITIVE to light
o FASTER RESPONSE to light
o responsible for central colour, DAY vision AND detail

38
Q

What is NOT found in fovea?

A

RODS (at all!)

The further away you are, the more rods ae found in the retina

39
Q

What is NOT found in the blindspot?

A

NO photoreceptors

40
Q

Frequency spectrum and photoreceptors?

A

Different photoreceptors respong to different wavelengths of light!

Human eye can see 450mm - 680/700mm

41
Q

What is the most common from of colour vision deficiency?

A

Red-green confusion

i.e. Deuteranomaly (M-cone peak shifted to L-cone peak as both peaks VERY close to one another)

ONENOTE!

42
Q

Rods peak sensitivity vs Cones?

A

RODS = 500nm

CONES = varies depending on type of cone e.g. S-cone, M-cone, L-cone

43
Q

How would you investigate colour vision deficiency?

A

Ishihara test - tests for deuteranomaly (most common form)

It’s the colour on the circle test!

44
Q

Light-Dark Adaption - explain the dark adaption

A

There is an increase in light sensitivity in the dark!

Biphasic process:
o Cone adaptation = 7mins
o Rod adaptation = 30mins (to regenerate the rhodopsin)

45
Q

Light-Dark Adaption - explain the light adaption

A

Occurs over 5mins!

Occurs via:
o neuro-adaptation
o bleahcing of photo-pigments
o inhibition of rod/cone funtion

46
Q

Light-Dark Adaption - explain the other type of adaptation

A

Pupil adaptation - minor effect of pupil constriction

year 2 - neuroscience (18 decks)

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