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I. Ocular Physiology > Accommodation (F) > Flashcards

Accommodation (F) Flashcards

1
Q

What innervates the ciliary muscles? 1. What are the receptors found (along with their actions)? 2

A
  1. parasympathetic and sympathetic systems
  2. Para = M3 receptors (contraction)
    Sym = β2-adrenergic receptors (relaxation)
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2
Q

Which ciliary muscle fibers may trigger slightly before the others?

A

longitudinal

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3
Q

Embryonically, what is smooth muscle derived from? 1. What are ciliary muscle fibers derived from? 2

A
  1. mesoderm

2. ectoderm

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4
Q

What do longitudinal fibers have fewer of than smooth muscle? 1. More of? 2. Do longitudinal fibers have a smaller or larger nucleus? 3

A
  1. mitochondria
  2. myofibrils
  3. larger
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5
Q

What is the action of anterior portion of ciliary muscle fibers? 1. Action of posterior portion? 2

A
  1. applies force to the scleral spur and opens trabecular meshwork
  2. applies force to pars plana moving it anteriorly
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6
Q

What is the action of anterior portion of ciliary muscle fibers? 1. Action of posterior portion? 2

A
  1. applies force to the scleral spur and opens trabecular meshwork
  2. applies force to pars plana moving it anteriorly
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7
Q

Do the circular ciliary muscle fibers increase or decrease thickness during contraction? 1. Longitudinal fibers? 2 Radial fibers? 3

A
  1. increase
  2. decrease
  3. decrease
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8
Q

During relaxation, what is the reason the ciliary is returned to its unaccommodated configuration?

A

elasticity of the choroid pulling it back into place and posterior ciliary zonules

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9
Q

What are the functions of the ciliary zonules?

A
  1. Hold lens in place
  2. Transmit tensile forces for accommodative shape change of the lens
  3. Form fibril structures that allow fluid to pass
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10
Q

Where do the anterior zonules originate? 1. Where do they attach? 2

A
  1. pars plana and valleys of Kuhnt

2. anterior capsule

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11
Q

Where do the posterior zonules originate? 1. Where do they attach? 2

A
  1. near ora serrata and valleys of Kuhnt

2. posterior capsule (at ligament of Weiger) and vitreous membrane

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12
Q

Where do the equatorial zonules originate? 1. Where do they attach? 2

A
  1. valleys of Kuhnt

2. equatorial capsule

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13
Q

Where do the equatorial zonules originate? 1. Where do they attach? 2

A
  1. valleys of Kuhnt

2. equatorial capsule

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14
Q

What is the function of interciliary zonules or tensor fibrils? 1. Where do these occur? 2

A
  1. anchor the ciliary zonules passing through the pars plicata
  2. zonular plexus (valley of Kuhnt)
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15
Q

What synthesizes zonules?

A

non-pigmented ciliary epithelium

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16
Q

What is the percentage of people Marfans that have dislocated lens?

A

60%

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17
Q

What are zonules made out of? 1. What are the subcategories of these? 2

A
  1. glycoproteins

2. Fibrillin (make beads and string) and MAGP-1 (Microfibril-associated glycoprotein 1) (make beads)

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18
Q

How much collagen are in zonules? 1. Elastin? 2

A
  1. none

2. none

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19
Q

What are large cysteine-rich multidomain glycoprotein that polymerize in the extracellular space in a head-to-tail manner to form microfibrils?

A

fibrillins

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20
Q

What is the thin transparent elastic membrane around the lens? 1. What is it secreted by? 2. Where is it the thickest and the thinnest? 3

A
  1. lens capsule
  2. lens epithelial and fiber cells
  3. Thickest just anterior and posterior to equatorial region, thinnest posteriorly
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21
Q

What is the lens capsule composed of?

A
  1. Collagen IV
  2. Laminin
  3. Heparin sulfate proteoglycans (Perlecan, Nidogen, Collagen XVIII)
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22
Q

What is the lens capsule composed of?

A
  1. Collagen IV
  2. Laminin
  3. Heparin sulfate proteoglycans (Perlecan, Nidogen, Collagen XVIII)
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23
Q

What is the function of the lens capsule?

A

serves as a force distributor, evenly applying stored elastic energy over the surface of the lens

24
Q

What is the rate of decline of accommodation?

A

2.5D/10 years

25
Q

What is the inability to accommodate with age mostly due to?

A

increase in stiffness of lens

26
Q

How thick is the capsule at birth? 1. At age 60? 2. How does the elasticity change? 3

A
  1. 11 microns
  2. 20 microns
  3. 50% decrease
27
Q

What increases the stiffness of the lens capsule?

A

Non-enzymatic glycation of collagen

28
Q

What increases the stiffness of the lens capsule?

A

Non-enzymatic glycation of collagen

29
Q

What is the covalent bonding of proteins (collagen) with a sugar molecule (glucose/fructose)?

A

glycation

30
Q

What is the change in elasticity of zonule fibers with age?

A

none

31
Q

How does the Equatorial zonule insertion shift with age?

A

anterior to equator

32
Q

How does the contractile force of ciliary fibers change with age?

A

doe not change

33
Q

How does the contractile force of ciliary fibers change with age?

A

does not change

34
Q

What residues of collagen in the capsule has non-enzymatic, random intra/inter-molecular and interfibrillar cross-linking occur with age?

A

lysine and arginine

35
Q

What is the accommodative triad?

A

1) Ciliary muscle contraction
2) Pupil Constriction
3) Convergence

36
Q

What are the major excitatory neurons of the sphincter muscle? 1. Minor inhibitory neurons? 2

A
  1. parasympathetic (Mediated by acetylcholine and muscarinic receptors)
  2. sympathetic
37
Q

What are the major excitatory neurons of the dilator muscle? 1. Minor inhibitory neurons? 2

A
  1. sympathetic (Mediated by norepinephrine and α1 receptors)

2. parasympathetic

38
Q

What is a neurological disorder characterized by a tonically dilated pupil that reacts slowly to light and accommodation? 1. What is the cause of the pupil affect? 2

A
  1. Holmes-Adie syndrome

2. viral or bacterial infection damaging neurons in ciliary ganglion or lesion there

39
Q

What provides sensory innervation to the iris?

A

ophthalmic division of the trigeminal nerve (CN V)

40
Q

What provides sensory innervation to the iris?

A

ophthalmic division of the trigeminal nerve (CN V)

41
Q

What are the major functions of the pupil?

A

1) Control of retinal illumination
2) Reduction of optical aberrations
3) Improve depth of focus/field

42
Q

What causes the pupillary response?

A
  1. Light induced

2. Near-response (accommodation)

43
Q

What is the efferent pathway to control the pupillary response for light induced? 1. For near-response? 2

A
  1. Parasympathetic control of iris sphincter

2. Parasympathetic control of iris sphincter

44
Q

What is the pupillary light response mediated by?

A

projections to LGN and OPN from Intrinsically photosensitive retinal ganglion cells (ipRGC ), rods and cones

45
Q

How do ipRGCs sense light?

A

photosensitive pigment (melanopsin)

46
Q

Where do interneurons from the OPN project to?

A

Edinger-Westphal nucleus

47
Q

Where do interneurons from the OPN project to?

A

Edinger-Westphal nucleus

48
Q

Where does input from accommodative pupillary response come from?

A

cortical areas surrounding the visual cortex and from cortical areas within the frontal eye fields

49
Q

What does supranuclear neuronal input from near visual tasks stimulate?

A

parasympathetic neurons in Edinger-Westphal nucleus and stimulates ciliary muscle neurons

50
Q

How does pupillary dilation occur neuronally?

A
  1. Supranuclear inhibition of the Edinger-Westphal nucleus (sympathetic innervation, inhibiting para)
  2. Stimulation of sympathetic nerves in dilator muscle (not required)
51
Q

How can dilation occur humorally?

A

Circulating catecholamines in blood may act directly on iris dilator muscle via bloodstream

52
Q

What is a condition characterized by an unequal size of the pupils? 1. What does this indicate? 2

A
  1. Anisocoria
  2. damage has occurred to either iris sphincter or dilator muscle, Innervation is interrupted, or External pharmacologic factors influencing pupils
53
Q

What is a condition characterized by an unequal size of the pupils? 1. What does this indicate? 2

A
  1. Anisocoria
  2. damage has occurred to either iris sphincter or dilator muscle, Innervation is interrupted, or External pharmacologic factors influencing pupils
54
Q

What is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision?

A

vergence

55
Q

Where is accommodative esotropia commonly found?

A

hyperopes

I. Ocular Physiology (20 decks)

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