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BIOL21402 > L7 & L8 - Vision I and II > Flashcards

L7 & L8 - Vision I and II Flashcards

1
Q

The three layers of the eyeball

A

Outer tunic - contains cornea/sclera, is fibrous

Middle tunic - consists of choroid, ciliary body, and iris, and is vascular and pigmented, also called (uveal tract)

Inner tunic - consists of the retina, is neurosensory

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2
Q

Outer tunic: what amount do the cornea and sclera take up, and what are its key characteristics?

A

Cornea - anterior/superficial 1/6th
Sclera - posterior/deep 5/6ths

  • Transparent
  • Avascular
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3
Q

Cornea: what does it do, what features help it do these purposes, what key features does it have, and what can incorrect shaping lead to?

A

Refract light - curvature of the anterior corneal surface, tear film (moist), and corneal thickness
Transmit light - regularly arranged epithelium

Avascular (oxygen is supplied from the tear film by dissolving and the aqueous humor supplies it with nutrients)

Incorrect shaping - astigmatism

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4
Q

Sclera: what is it made from, what does it do, and what features help it do its function?

A

Tough collagen fibres

Provides rigidity - allows insertion of extraocular muscles which help maintain eyeball shape

It is also opaque - the whites of the eye

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5
Q

What is the name of the place where the cornea meets the sclera?

A

The limbus

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6
Q

Cornea histology anteriorly-posteriorly/superificial-deep

A

Epithelium - stratified squamous, cells always getting damaged so must be replaced quickly

Bowman’s layer - acellular, composed of collagen fibres, function is debatable (removal doesn’t lead to functional issues, maybe rigidity?)

Stroma - thickest layer, parallel collagen fibre layers allow transparency

Descemet’s membrane - acellular, composed of collagen fibres, function is debatable (removal doesn’t lead to functional issues, maybe rigidity?)

Endothelium - simple cuboidal epithelia, in contact with the aqueous humour

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7
Q

Sclera histology anteriorly to posteriorly

A

Fascial sheath - the hammock of the eyeball, connective tissue that the eyeball sits in

Episclera - tough connective tissue layer

Stroma - same as cornea except fibres are randomly arranged, meaning it’s opaque

Lamina fusca - thin pigmented tissue layer

Choroid - Large part of the middle tunic, not part of the sclera really

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8
Q

What is another word for stroma?

A

Connective tissue

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9
Q

Aqueous humor

A

Transparent liquid lying anteriorly to the pupil and posterior to the cornea

It gives nutrients to the cornea

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10
Q

Scleral perforations

A

Anterior - anterior ciliary vessels, recti muscles

Posterior - optic nerve, central retinal vessels, ciliary nerves and vessels

Central - vortex veins

Lamina Cribrosa - the weakest part of the sclera, surrounds the optic nerve (sieve type beat, allows things to leave the eye)

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11
Q

Recti muscles

A

extraocular muscles

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12
Q

Middle tunic

A

Choroid - ciliary body - iris

Choroid - vascular pigmented layer, allows the passage of blood vessels and nerves to the anterior part of the eye, and prevents unwanted reflection of light

Ciliary body - accommodation, produces and secretes aqueous humor, and suspends the lens

Iris - controls pupil diameter

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13
Q

Choroid histology anteriorly to posteriorly

A

Passes from the back of the eye to the ciliary body, a large part of the middle tunic and immediately deep to the sclera

Suprachoroid - transition zone

Stroma - contains blood vessels, connective tissue, and melanocytes

Choriocapillaris - the deepest layer of vessels, supply blood to the retina

Bruch’s membrane - multi-layered sheet with an elastic core

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14
Q

Accommodation: what is it, how does the lens differ in different scenarios, and what allows accommodation to happen?

A

Changing the lens to change the view target (close object vs far object)

When looking at close objects - the lens is globular
When looking at far objects - the lens is thin

Lens accommodation occurs by the ciliary body

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15
Q

Melanocytes: what are they and what do they do?

A

Melanin pigment that absorbs excess light, and prevents unwanted reflection

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16
Q

Ciliary body histology

A

Ciliary muscle - three sets of smooth muscle fibres (these allow accommodation to occur)

Ciliary stroma - vascular connective tissue, enters into finger-like processes - ciliary processes (this region where ciliary processes are called pars plicata)

Ciliary epithelium - double layer, the outer is pigmented, the inner is non-pigmented, and it produces and secretes aqueous humour (outer-faces retina, inner faces ciliary stroma)

In accommodation for a close object, the ciliary body moves forward (contracts towards the lens) - suspensory ligaments become slack, allowing the lens to go globular and focus on something closer to the face

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17
Q

Pars plicata

A

The part of the ciliary body where you have all the ciliary processes

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18
Q

Iris histology

A

Stroma - contains sphincter pupillae muscle (innervated by parasympathetic NS)

Double epithelium layer - anterior myoepithelial layer containing the dilator pupillae muscle (innervated by sympathetic NS)

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19
Q

Miosis

A

Constriction/narrowing if the eye pupil using the sphincter pupillae muscle

Occurs when the parasympathetic nervous system is activated

20
Q

Mydriasis

A

Dilation/enlargement of the eye pupil using the dilator pupillae muscle

Occurs when the sympathetic nervous system is activated

21
Q

Collarette

A

Thick part of the iris, thick collagen layer surrounding the pupil

Part of the ciliary zone

22
Q

Trabeculae

A

Columns of collagen that radiate from the pupil

Part of the ciliary zone

23
Q

Fushs’ crypts

A

The part between trabeculae

Ciliary zone

24
Q

Inner tunic

A

Retina - transforms light energy into a neural signal

25
Q

Retina histology superficial to deep

A

Ganglion cells - nerves that transmit visual information towards the optic nerve

Amacrine cells - found at the interface between ganglion cells and bipolar cells

Bipolar cells - two poles (the only other place bipolar cells are found is in the ears)

Horizontal cells - found at the interface of photoreceptors and bipolar cells, reach across several cells allowing for horizontal processing and allows for fine-tuning of receptive information for sharp images

Photoreceptors - rods/cones

Pigmented epithelial layer - take photoreceptors that have had their shape altered after being hit by light and repackaging them and putting them back in their layer

26
Q

Photoreceptors

A

Rods/cones

When light hits the photopigment discs, they get damaged and move towards the epithelium later where it is repackaged and moved back to the layer

27
Q

In what direction is light transmitted/received?

A

Light enters towards the epithelial layer, information is moved in the opposite direction towards the ganglion

28
Q

Retinal layers superficial to deep and the parts of the retina they are associated with

A

A layer of optic nerve fibres

Inner limiting membrane - muller cells, help with retinal structure

Ganglion cell layer

Inner plexiform layer - axons of horizontal, amacrine, and bipolar cells

Inner nuclear layer - horizontal, amacrine, and bipolar cells’ nuclei

Outer plexiform layer - processes of rods and cones

Outer nuclear layer - nuclei of rods and cones

Outer limiting membrane - muller cells, help with retinal structure

Layer of rods and cones

Retinal pigment epithelium

Choroid - not an actual part of the retina so retina has 10 different layers (remember that at the back of the eye, where light is focussed onto, the layers go inner-middle-outer)

29
Q

‘Processes’ what do they really mean?

A

Processes are essentially the axon of things that aren’t neurones

30
Q

Horizontal cells: what type of information do they transfer, what do they do, and how many types are there?

A

Horizontal transfer of information

Able to effect inhibitory response

Several different types

31
Q

Amacrine cells: what type of information do they transfer and what do they do?

A

Horizontal transfer of information

Modulates information reaching ganglion cells

32
Q

Bipolar cells: what type of cells are they, what do they do, and how many types are there?

A

1st-order neurones of the visual pathway

relay information from photoreceptors to ganglion cells

Many different types

33
Q

Ganglion cells: what type of cells are they, where do their axons form, how do they leave the eye, and how many types are there?

A

2nd order neurones of the visual pathway

Axons form the optic nerve

Exit the retina at the optic disc - optic nerve exists eyeball at lamina cribrodsas

Many different types

34
Q

Retinal pigmented epithelium: what is it, what are its functions, and what are its anatomical relations?

A

Pigmented epithelial layer that forms the last layer of the retina

  • Protection (forms part of blood-retina barrier)
  • Phagocytoses fragments from the photoreceptor outer layer
  • Metabolises and stores vitamin A
  • Produces growth factors
  • Pigment helps to decrease the excess scattering of light

Directly superficial to Brush’s membrane and directly deep to the outer segment of the photoreceptors

35
Q

Ophthalmoscope view of the eye

A

Yellow spot - optic disc

Lateral to yellow spot, dark red spot - macula lutea, fovea centralis centrally

36
Q

Fovea centralis: what does it have the body’s highest concentration of?

A

Cones, colour detection stuff

37
Q

Clivus

A

The parts that rise up out of the foveola, but is still part of the fovea

38
Q

Aqueous humour: what does it do and what does it contain?

A

Supplies metabolic needs of the eye’s avascular structures (lens/cornea)
Supports the wall of the eyeball and helps to maintain its shape

  • Water
  • Glucose
  • Proteins
  • Dissolves gasses
  • Other nutrients
39
Q

Vitrous humour: what does it do and what does it contain?

A

Helps maintain eyeball shape
Transmits light
Contributes to the dioptric power of the eye
Support lens
Supports retinal layers

  • Proteins
  • Salts
  • Acids
  • Hyalocytes
  • 98% water
40
Q

Hyalocytes

A

Cell types that clump together and give you floaters

41
Q

Eyeball segments/chambers: how is an anatomical position determined?

A

The lens determines the anteriority/posteriority of SEGMENTS

chambers are ONLY found in the anterior segment - the anterior chamber is between the iris and cornea and the posterior chamber is behind the pupil, in front of the lens

42
Q

Label the following:

  • Lens
  • Iris
  • Suspensory ligaments
  • Ciliary body
  • Cornea
  • Sclera
  • Choroid
  • Retina
  • Anterior segment
  • Posterior segment
  • Anterior chamber
  • Posterior chamber
  • Canal of Schlemn
A

Find image of eye? idk

43
Q

Canal of Schlemn: where is it located, what does it do, and what is the rate of drainage?

A

Located at the iridocorneal angle

Drains aqueous humour using 25-35 collector channels after it has travelled through the trabecular meshwork

1-2µL/min - rate of formation of aqueous humour

44
Q

Intraocular pressure: what is the normal pressure and what factors determine it?

A

Normal - 10-20mmHg

  • Rate of formation of aqueous humour
  • rate of drainage of the trabecular meshwork
  • Pressure in the episcleral veins
45
Q

Glaucoma: what are the two types, how are they formed, what do they cause, and what do they lead to?

A

Narrow-angle - Iris inflammation, making it closer to the cornea, and narrowing the angle, covering the canal of Schlemn and preventing aqueous humour drainage

Open-angle - channels draining the canal of Schlemn become blocked and aqueous humour is not properly drained

  • Both may lead to increased intraocular pressure and can lead to optic nerve atrophy and defects in the visual field
  • Peripheral fields are first lost in glaucoma, it then spreads and narrows as it worsens
46
Q

Extra reading

A

Read Toris et al (2023) The Science of Glaucoma Management. Translational Research to Next-Generation Clinical Practise. Chapter 22, pg 217-229

47
Q
A

BIOL21402 (12 decks)

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