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LCRS Y2: Neuroscience and mental health > Structure and function of the eye > Flashcards

Structure and function of the eye Flashcards

1
Q

What are the inner and outer corners of the eye referred to as?

A

Medial and lateral canthus

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2
Q

What name is given to the border between the cornea and the sclera?

A

Corneal limbus

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3
Q

What is the clinical significance of the corneal limbus?

A

Common site for corneal epithelial neoplasm

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4
Q

Describe the nervous innervation of the cornea

A

Highly sensitive

Ophthalmic branch of trigeminal nerve

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5
Q

Describe the nerve supply to the lacrimal gland

A

PNS-mediated

CNV

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6
Q

Recall the drainage of tear film

A

Tear film: lacrimal gland, movement accross eye = superolateral to inferomedial, drainage through puncta to superior/ inferior canaliculus –> lacrimal sac –> nasolacrimal duct

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7
Q

Recall 3 functions of tear film

A
  1. Bactericide
  2. O2 and nutrient supply to ant. seg
  3. Smooth surface mainenance
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8
Q

Recall the layers of tear film from deep to superficial

A

Mucous, thick aqueous, oily

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9
Q

Describe the fx of each layer of tear film

A

mucous: protect eye surface, adhere tear film to eye
Thick aqueous: lubricant, bactericide, nutrition
Oily: prevention of evaporation

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10
Q

Where is the mucous layer of tear film produced?

A

Goblet cells in conjunctiva

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11
Q

Where is the oily layer of tear film produced?

A

Meibomian glands within eyelids

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12
Q

What sign in the eyes is indicative of intermittent hypertension?

A

Rupture of tiny vessels in conjunctiva

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13
Q

What surrounds the retina?

A

Uvea

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14
Q

What is the uvea made up of?

A

Predominantly vascular

  1. Choroid
  2. Ciliary body
  3. Iris
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15
Q

What does the choroid lie between?

A

Retina and sclera

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16
Q

What is the choroid made up of?

A

Vasculature supplying posterior segment of eye

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17
Q

What is the main component of the sclera?

A

Collagen

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18
Q

Recall and describe the most significant osmotic gradient that is maintained in the eye

A

Sclera = high H2O, cornea = low H2O
Sclera has protective fx
Cornea must remain transparent

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19
Q

How is the transparency of the cornea maintained?

A

Corneal endothelium actively removes water

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20
Q

In emmetropia, what provides the refractive power of the eye?

A

Cornea = 2/3 of power, lens = 1/3

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21
Q

Recall one advantage and one disadvantage of the barrier function of the cornea?

A

Ad: prevents infection
Disad: prevents drug entry

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22
Q

What are the 5 structures that make up the cornea, working superficial to deep?

A 
Epithelium
Bowman's membrane
Stroma
Descemet's membrane
Endothelium
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23
Q

Which element of the cornea cannot regenerate?

A

Endothelium

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24
Q

What characteristic of the lens makes it transparent?

A

Regular structure

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25
Recall the pathophysiology of age-related cateracts
Hydration of lens --> loss of transparency
26
Describe the shape of the lens
Aspheric: anterior and posterior surfaces have differing curvature
27
Recall the attachments of the lens
Attached all around by zonules/ lens zonulae, anchored to ciliary body
28
Recall what happens when the ciliary muscles contract?
Pressure on zonules decreased, lens gets smaller and thicker
29
Recall what happens when the ciliary muscles relax?
Pressure on zonules increases, lens gets wider and thinner
30
How can the optic nerve be identified with an ophthalmoscope?
Optic nerve head appears as bright optic disc
31
Where is the macula?
Roughly in centre of retina
32
Where is the aqueous humour found?
Anterior segment of eye (in front of lens)
33
Where is the vitreous humour found?
Posterior segment of eye (behind lens)
34
What is the fx of aqueous humour?
Nutrient and oxygen delivery
35
Recall the flow of aqueous humour
Ciiary body --> anterior chamber --> trabecular meshowrk (lies in limbus) --> Schlemm's canal/ uveal-scleral flow
36
Describe the 2 methods of aqueous humour drainage
1. Schlemm's canal = modified vein | 2. Uveal-scleral flow = passive, PG analogues act here
37
Describe the composition of vitreous humour
99% water, collagen, GAGs
38
What is the fx of vitreous?
Mechanical support
39
What is a normal IOP?
12-21mmHg
40
Recall the names of the layers and sublayers of the retina
Layers: retinal pigment epithelium and neuroretina | Sublayers of neuroretina: outer/ middle/ inner
41
Recall the composition of each of the layers of neuroretina
Outer: photoreceptors Middle: bipolar cells Inner: ganglion cells
42
Recall 2 functions of the retinal pigment epithelium
1. Waste removal | 2. Transport nutrients from choroid to photoreceptor cells
43
Recall the differences between rod and cone photoreceptors
Cones: colour, central vision, detail, fast response to light; n = 6 mill Rods: B&W, peripheral vision, sense movement; N = 120 mill
44
What is the fx of bipolar cells?
Fine-tuning of afferent info
45
Where do retinal ganglion cells synapse with 4th order neurons?
Lateral genticulate nucleus
46
What are the 2 oritentations of retinal ganglion cell, and what is the relevance of this
1. On-centre: stimulated by light falling on centre of its receptove field and inhibited by light falling on edge 2. off-centre: opposite
47
What is the receptive field of a neuron?
Retinal space within which incoming light can alter the firing pattern of a neuron
48
Which type of photoreceptors have lower convergence, and what is the clinical relevance of this?
Cones = finer visual acuity as smaller receptive field
49
What is the main test for colour-blindness?
Ischiara test
50
What are the 2 possible causes for colour-blindness?
1. Shift in the peak of photo-pigment sensitivity | 2. Absence of 1 or more of the 3 cone photpigment subtypes
51
Describe the mediation of light dark adaptation
Photoreceptor bleaching --> inhibition of rods/ cones accordingly (deending on whether it is light --> dark or dark --> light)
52
Which type of photoreceptor adapts to changes in light level more quickly?
Cones
53
What name is given to perfect vision?
Emmetropia
54
What is the mechanical problem in visual impairment?
Parallel lens converges to a point anterior/ posterior to the retina, or to more than one point
55
What term is used to describe convergence of the parallel lens anterior to the retina?
Myopia (short-sightedness)
56
What term is used to describe convergence of the parallel lens posterior to the retina?
Hypermetropia (long-sightedness)
57
What sort of glasses are used to correct myopia?
Concave
58
What general term is given to eyes that have a refractive error?
Ametropia
59
What is astigmatism?
Parralel lens focuses on not one point but two
60
What causes astigmatism?
Elliptical cornea
61
What term is given to a naturally-occuring loss of accommodation?
Presbyopia
62
What causes presbyopia?
Stiffening of lens

LCRS Y2: Neuroscience and mental health (17 decks)

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