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OV3017 Eye Disease > 10 - Pathogenesis of Glaucoma > Flashcards

10 - Pathogenesis of Glaucoma Flashcards

1
Q

most common features of glaucoma

A
  • loss of retinal ganglion cells
  • thinning of retinal nerve fibre layer
  • cupping of disc
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2
Q

when does secondary glaucoma occur

A

when there is an underlying condition

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3
Q

what is open angle glaucoma

A
  • extracellular material becomes depositied in trabecular meshwork
  • gives rise to increased resistance to outflow - raise IOP
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4
Q

risk factors of glaucoma

A
  • black
  • IOP > 26mmHg
  • myopia (>3D)
  • diabetes
  • FH
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5
Q

clinical features of glaucoma

A
  • extensive inferior visual field loss
  • subtle changes in NRR
  • disc cupping
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6
Q

primary angle closure glaucoma

A
  • pupil block
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7
Q

role of IOP

A

represnts primary risk factor for developing glaucoma
- both incidence + progression of glauc can be controlled by decreasing IOP

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8
Q

what is increased IOP due to in OPEN ANGLE glaucoma

A
  • increased resistance ot outflow
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9
Q

what is increased IOP due to in CLOSED ANGLE glaucoma

A

pupillary block

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10
Q

how is impact of IOP on pathogenesis of glaucoma explained

A

2 theories
- mechanical (direct)
- vascular (indirect)

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11
Q

what is aqeous produced by

A

ciliary epithelium

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12
Q

where does aqeous drainage occur

A

irido- corneal angle via conventinal + uveo scleral pathways

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13
Q

what is IOP determined by

A

the balance between aqueous production and drainage

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14
Q

mechanism of aqueous production

A
  • pigmented and non-pigmented cells of ciliary epithelium make aqeuous
  • ions move around in the aqeous and are transported from stroma to pigment cells, through gap junctions to NPE
  • active transport of ions from NPE to posterior chamber
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15
Q

what is the catalyser of this mechanism (aqueous production)

A
  • carbonic anhydrase
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16
Q

aquous outflow pathways

A
  1. majority drains through trabecular meshwork/canal of schlemm (conventional pathway)
  2. some drains through uveo-scleral pathway
17
Q

what are the 3 distinct layers of aqueous outflow pathway ( conventional)

A
  1. uveo trabeucli
  2. corneal-scleral trabeculi
  3. juxta canicular - adjacent to canal of schlemm
18
Q

glaucoma is associated with an increased?

A
  • resistance to outflow
19
Q

in open angle glaucoma, where is resistance higher than normal

A

-JCT (INNER WALL REGION)

20
Q

changes occur to the cells of the JCT - what does this do

A

slows the rate of aqueous production, so higher IOP

21
Q

how do you differentiate changes in outflow pathway (POAG) to normal ageing changes

A

plaque like deposits in the JCT

22
Q

how can secondary glaucomas arise

A
  • intertrabecular spaces being blocked by cellular or non-cellular material
23
Q

aqueous outflow pathway - uveo scleral

A
  • this area is good for drugs like prostoglandin analogs
  • aqueous enters ciliary body + leaves through vascular roots
24
Q

mechanism of optic nerve damage (direct)

A
  • loss of retinal ganglion cells, optic nerve head
  • high IOP = stress and strain to eye = changes to lamina cribosa
  • this remodelling leads to axonal damage + disruption of axonal transport
  • essential factors not delivered = shrinkage + atrophy of RGC axons
25
Q

why is axoplasmic flow important

A
  • delivers essential topic factors to neural cell body
  • interfering with pathway leads to death of retinal ganglion cells
26
Q

Mechanism of optic nerve damage (indirect)

A

IOP can stress the nerves
- this stress can have acute and chronic effects on delivery of nutrients in blood to axons in lamina cribosa

27
Q

when can ischaemia still occur

A

in predisposed indivudals with normal IOP

28
Q

pharmacological regulation of IOP

A

trabecular outflow
- muscarinic agonists

uveoscleral outflow
- prostaglandin agonists

aqueous humour inflow
- beta blockers
-carbonic anhydrase inhibtors
- alpha agonists

29
Q

surgery to improve drainage in glaucoma

A

-Selective laser trabeculoplasty
-Trabeculectomy- to open up pathway
-Minimally invasive glaucoma surgery (MIGS)

30
Q

how can IOP be lowered

A

pharmacologically using drugs that reduce aqueous production or enhance drainage

31
Q
A

OV3017 Eye Disease (19 decks)

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