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Neuro > The eye and the visual stream > Flashcards

The eye and the visual stream Flashcards

1
Q

Features of the orbit

A
  • conical
    opens into the midline of the face
  • points back into the head
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2
Q

Bones of the orbit

A
  1. ) Orbital margin:
    - frontal
    - zygomatic
    - maxilla
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3
Q

Walls of the orbit

A
  1. ) Lacrimal
  2. ) Ethmoid
  3. ) Sphenoid: body/lesser & greater wings
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4
Q

Holes of the orbit

A
  1. ) Optic canal
  2. ) Superior orbital fissure
  3. ) Inferior orbital fissure
  4. ) Nasolacrimal fossa
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5
Q

Clinical: what can occur to the orbit

A

A blowout fracture

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6
Q

Layers of the eyelid

A
  1. ) Anterior skin
  2. ) Orbicularis oculi
  3. ) Levator superioris (have levator aponeurosis here)
  4. ) Tarsal plate
  5. ) Meibomian gland (lipid tear film)
  6. ) Posterior conjunctiva (mucous membrane)
  7. ) Puncta and canaliculi
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7
Q

Clinical link: what happens in facial palsy?

A
  • Inability to close eyelid

- Drooping of mouth

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8
Q

What makes up the conjunctiva?

A
  1. ) Tarsal (back of eyelid)
  2. ) Forniceal (superior and inferior)
  3. ) Bulbar (covers globe)
  4. ) Limbus (stem cells)
  5. ) Lateral (canthus)
  6. ) Medial (canthus): has caruncle and pilca semilunaris
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9
Q

Histology of the tear film

A

Has:

  1. ) columnar epithelium
  2. ) goblet cells
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10
Q

What makes up the surface layer of the conjunctiva?

A

Lipid: Meibomian glands

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11
Q

What makes up the middle layer of the conjunctiva?

A
  1. ) Aqueous: lacrimal glands
  2. ) Lysozyme
  3. ) Lactoferrin
  4. ) Antibodies
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12
Q

What makes up the deep layer of the conjunctiva?

A

Mucin: goblet cells

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13
Q

Clinical link: Sjogren’s syndrome. What are the features of this?

A
  1. ) Xerostomia (dryness of mouth)

2. ) Deep red tongue

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14
Q

What makes up the globe?

A
  1. ) The cornea

2. ) The sclera

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15
Q

What epithelium does the cornea have?

A

Non-keratinising squamous epithelium

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16
Q

What is the stroma of the cornea made up of?

A

Regular lamellae

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17
Q

What is the function of the endothelium in the cornea

A

It pumps fluid out of stroma

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18
Q

Features of the sclera

A
  1. ) Strong
  2. ) It is where the insertion of eye muscles is
  3. ) Has holes
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19
Q

What does the sclera have holes for?

A
  1. ) Optic nerve

2. ) Neurovascular bundle

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20
Q

Clinical link: what is keratoconus

A
  • disorder of the eye which results in progressive thinning of the cornea.
  • May result in blurry vision, double vision, astigmatism, and light sensitivity.
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21
Q

What four features make up the middle layer of the globe

A
  1. ) The uveal tract
  2. ) Iris
  3. ) The ciliary body
  4. ) The choroid
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22
Q

What features does the iris have?

A
  1. ) Pupil
  2. ) Sphincter + dilator muscles
  3. ) Pupil reflexes
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23
Q

What features does the ciliary body have?

A
  1. ) Ciliary epithelium: aqueous
  2. ) Ciliary muscle: accommodation
  3. ) Pars plana
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24
Q

What features does the choroid have?

A
  1. ) Highly vascular

2. ) Highly pigmented

25
Q

Clinical link: what is coloboma?

A

A hole in one of the structures of the eye

26
Q

What is within the inner layer of the globe?

A
  1. ) Inner retina

2. ) Outer retina

27
Q

What makes up the inner retina?

A
  1. ) Internal limiting membrane
  2. ) Nerve fibre layer
  3. ) Ganglion cell layer
  4. ) Inner plexiform layer
  5. ) Inner nuclear layer
  6. ) Outer plexiform layer
  7. ) Outer nuclear layer
  8. ) Outer limiting membrane
28
Q

What makes up the outer retina?

A
  1. ) Photoreceptors

2. ) Retinal pigment epithelium

29
Q

What are the two parts of the retina?

A
  1. ) The central retina

2. ) Peripheral retina

30
Q

What structures make up the central retina?

A
  1. ) Macula lutea
  2. ) Foveal centralis
  3. ) Cone photoreceptors
  4. ) Fine visual resolution
  5. ) Colour vision
  6. ) Photopic vision
31
Q

What structures make up the peripheral retina

A
  1. ) Rod photoreceptors
  2. ) Peripheral visual field
  3. ) Motion detection
  4. ) Scotopic vision
32
Q

Clinical link: what is a central retina artery occlusion

A

where the flow of blood through the central retinal artery is blocked

33
Q

Key features of the lens

A
  1. ) Continually grows
  2. ) Contained within elastic capsule
  3. ) Natural shape: almost spherical
  4. ) Shape controlled by ciliary muscle in the ciliary body vis zonules
  5. ) Allows for accommodation
  6. ) Fades with age
34
Q

What are zonules

A

Suspensory ligaments

35
Q

Clinical link: what is cataract surgery

A

Removing the natural lens of the eye and replacing it with a plastic one

36
Q

What are the two segments of the globe?

A
  1. ) The anterior segment

2. ) The posterior segment

37
Q

What makes up the anterior segment of the globe?

A
  1. ) Anterior chamber
  2. ) Cornea
  3. ) Iris
  4. ) Pupil
  5. ) Lens
  6. ) Posterior chamber
  7. ) Aqueous humour circulated from ciliary body (via pupil) into AC. Leaves via the trabecular meshwork in the ‘angle’
38
Q

What makes up the posterior segment of the globe?

A

Has vitreous humour

39
Q

Clinical link: what is angle closure

A
  • When the flow of aqueous humour out of the eye is blocked - Pressure inside the eye becomes too high very quickly
40
Q

What are the two parts of the humours of the globe?

A
  1. ) Aqueous

2. ) Vitreous

41
Q

Features of the aqueous part of the humours

A
  • Produced by ciliary epithelium in ciliary body
  • Maintains intraocular pressure between 12 + 20 mmHg above atm pressure
  • Circulates around lens
  • Low protein ‘plasma’
  • High vitamin C
  • Nourishment for avascular structures
42
Q

What are the key features of the vitreous part of the humour?

A
  • Made up of a collagen matrix

- Has hyaluronic acid and water

43
Q

What are the extraocilar muscles?

A
  1. ) Rectus muscles: horizontal (lateral + medial)
  2. ) Rectus muscles: vertical (superior and inferior)
  3. ) Oblique muscles: superior and inferior
44
Q

Features of the extraocular muscles

A
  1. ) Muscles arise from the orbital APEX
  2. ) Muscles insert anteriorly into sclera
  3. ) Nerve supply
45
Q

What is the nerve supply to the extraocular muscles

A

3rd: MR/LR/SR/LO
4th: SO
5th: LR

46
Q

Actions of the horizontal recti muscles

A
  1. ) Abduction

2. ) Adduction

47
Q

Actions of the vertical recti

A
  1. ) Elevation

2. ) Depression

48
Q

Actions of the oblique muscles

A
  1. ) Intorsion

2. ) Extorsion

49
Q

How does the transmission of light take place in the visual system?

A

Reasons:

  1. ) Wavelength (UV absorbed)
  2. ) Eyelids separated (ptosis)
  3. ) Normal tear film (dry eye)
  4. ) Transparent cornea (scarring, swelling)
  5. ) Clear aqueous (inflammation, blood)
  6. ) Normal pupil (too large, too small, incorrect position, occluded)
  7. ) Clear lens (cataract)
  8. ) Clear vitreous (blood, inflammation)
  9. ) Normal inner retina (swelling, blood)
50
Q

How does the refraction of light take place in the cornea?

A
  1. ) Interfaces:
    - air/tear film
    - tear film/cornea
    - corneal/aqueous
    - aqueous/lens
    - lens/vitreous
    - vitreous/retina
  2. ) Cornea is most significant (45D)
  3. ) Lens allows for change in focus (15-20D
51
Q

Clinical link: refractive error

A
  • Emmetropia: normal
  • Myopia: near sighted
  • Hyperopia: far sighted
  • Astigmatism: irregular vision
52
Q

How is light detected in the visual system?

A
  • Process of light detection: transduction
    1.) Photoreceptor outer segments
    2.) Discs contain rhodopsins
    3.) Respond to different wavelengths
    4.) Change in structure of retinal
    5.) Opens Na/K channels
    6.) Hyperpolarisation of membrane
    7.) Closes Ca channels
    8.) Reduces glutamate release
    Bipolar cells respond
53
Q

Clinical link: what is dyschromatopsia?

A

Colour blindess

54
Q

Clinical link: what is dyschromatopsia?

A

Colour blindness

55
Q

Describe the afferent pathway

A
  • Images temporal to midline fall on nasal retina
  • Images nasal to midline fall on temporal retina
  • Optic nerves transmit from each eye but maintain orientation
  • Splits at chiasm:
  • Nasal fibres (temporal field) cross
  • Tracts now have information from opposite field but from each eye
56
Q

Describe the efferent pathway

A 
Pupillary reflexes to light:
- Light sensitive ganglion cells
- Optic nerve, chiasm, tract
- Synapse in midbrain (3rd n)
- 3rd n to ciliary ganglion (orbit)
- Fibres to sphincter muscle
- Light stimulus in one eye therefor causes both pupils to constrict
(direct and consensual response)
- Afferent pupil defect
- Efferent pupil defect
57
Q

Clinical link: what is horners sydrome

A
  • loss of sweating on face
    2. ) Partial drooping of upper eyelid
    3. ) Small pupil
58
Q

Clinical link: what is Horner’s syndrome

A
  • loss of sweating on face
    2. ) Partial drooping of upper eyelid
    3. ) Small pupil

Neuro (33 decks)

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