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Glaucoma Flashcards

1
Q

What injury is common to ALL glaucomas?

A

Death of retinal ganglion cells and their axons

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2
Q

The low and normotensive glaucomas in people are theorized to be due to what?

A
  1. IOP spikes

2. secondary circulatory or excitotoxic effects on retina or optic nerve

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3
Q

What is the general trend of incidence of canine glaucoma?

A

Increasing

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4
Q

What are the 10 most common breeds with glaucoma?

A 
ACS (5.52%) [American Cocker]
Basset Hound (5.44%)
Chow Chow (4.70%)
Shar Pei (4.40%)
Boston Terrier (2.88%)
Wire Fox Terrier (2.28%)
Norwegian Elkhound (1.98%)
Siberian Husky (1.88%)
Cairn Terrier (1.82%)
Miniature Poodle (1.68%)
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5
Q

Some dog breeds have a sex predilection for glaucoma. What sex is more commonly affected?

A

Females

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6
Q

What was the most common cause of secondary glaucoma?

A

Lens induced uveitis

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7
Q

What percentage of secondary glaucomas are due to LIU?

A

81%

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8
Q

Other than LIU, what are the next most common causes of secondary glaucoma?

A 
lens luxation (12.0%)
postcataract surgery (5.1%)
uveitis of unknown cause (7.1%)
hyphema of unknown cause (7.3%)
intraocular neoplasms (3.5%)
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9
Q

What is the combined (primary and secondary) prevalence of glaucoma in the dog worldwide?

A

1.7%

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10
Q

3 possible causes of glaucoma?

A
  1. primary
  2. secondary
  3. congenital
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11
Q

What are the categories of filtration angle appearance? (2 big categories with 3 subcategories each)

A
  1. Open angle
  2. Closed angle
  3. Narrow angle
    AND
  4. Open ciliary cleft
  5. Closed ciliary cleft
  6. Collapsed ciliary cleft
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12
Q

What is the width of the iridocorneal angle measured?

A

opening of the most anterior portion of the ciliary cleft

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13
Q

In the dog, where is the majority of the angle located?

A

In the ciliary cleft

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14
Q

What are the 2 categories of primary glaucoma?

A

Open/normal angle/cleft (acute or chronic)

Narrow/closed angle/cleft (acute or chronic)

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15
Q

What are the 2 causes of congenital glaucoma?

A
  1. Pectinate ligament dysplasia

2. Goniodysgenesis

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16
Q

What age group do you usually first see congenital glaucoma?

A

< 6 months

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17
Q

What is the prevalence of congenital glaucoma?

A

RARE

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18
Q

What age group do you usually see breed-specific glaucoma develop?

A

6-10 years

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19
Q

What IOP is usually needed for endothelial dysfunction?

A

> 40 mmHg

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20
Q

What tends to give lower values at normal values: TonoVet or TonoPen?

A

TonoVet (yes, really)

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21
Q

What is thought to be more accurate tonometer at high IOPs?

A

TonoVet

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22
Q

When is IOP highest in dog? Lowest?

A

Highest in early AM, lowest in late evening

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23
Q

What is the IOP variation from early morning to late evening in: normal dogs? Those with POAG?

A

Normal: 2-4 mmHg
POAG: 6-10 mmHg+

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24
Q

Describe how blindness occurs secondary to elevated IOP.

A

Initial event prevents normal AH outflow –> physical changes involving AH outflow obstruction –> elevated IOP too high for normal AXOPLASMIC FLOW and BLOOD FLOW –> RGC dysfunction with ON degeneration and atrophy –> visual field loss/blondness

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25
Q

What type of disease are the canine glaucomas classified as?

A

a NEURODEGENERATIVE disease

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26
Q

What genetic mutation is seen in Beagles with POAG?

A

ADAMTS10

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27
Q

What is the ADAMTS10 mutation thought to do?

A

Alter fribrillin

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28
Q

What is thought to cause optic neuropathy (proposed mechanism)?

A

Collagen defect = altered pressure resistance

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29
Q

How does lens subluxation seem to contribute to glaucoma?

A

Loss of zonular tension = iridocorneal angle closure and ciliary cleft collapse

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30
Q

Buphthalmos: what species does it not occur in (and when)?

A

ADULT human

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31
Q

Haab’s stria (break in Descemet’s) only occurs if what happens to the cornea?

A

It gets stretched (either chronic glaucoma or acute spike)

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32
Q

How might you end up with pigmentary keratitis secondary to glaucoma?

A

Buphthalmos –> lagophthalmos with decr blink reflex and incr tear evaporation –> exposure keratitis –> pigmentary keratitis

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33
Q

What secondary abnormality can be seen with the sclera secondary to glaucoma?

A

Staphylomas

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34
Q

Where are scleral staphylomas most likely to occur in a buphthalmic globe?

A

where nerves and vessels penetrate (equator)

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35
Q

What cell is present in the trabecular meshwork to clean it up?

A

Macrophage

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36
Q

How much do pectinate ligaments contribute to resistance of AH outflow?

A

Almost none unless dysplastic

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37
Q

After the pectinate ligaments, what 3 trabecular meshworks does AH go through?

A

uveal –> corneoscleral –> juxtacanalicular

38
Q

What are the 2 outflow pathways?

A

1) Conventional

2) Uveoscleral

39
Q

Which outflow pathway is pressure INDEPENDENT?

A

uveoscleral

40
Q

What part of the trabecular meshwork causes the highest resistance?

A

Extracellular matrix

41
Q

What is the importance of MMPs in glaucoma?

A

Increase ECM turnover, reduce resistance to AH outflow through meshwork, and lower IOP

42
Q

What are 3 reasons the iris dilates with glaucoma?

A

1) lack of sensory input from RGCs
2) impaired neuronal and vascular supply to central iris
3) possibly mechanical opening of iris

43
Q

What happens to the iris (histologically) with glaucoma, and why is this bad?

A

Stroma thins and sphincter mm atrophies = pigment dispersion –> can further clog the outflow

44
Q

When the ciliary body gets so atrophied from glaucoma that IOP os <5 mmHg, what happens to the other structures in the eye?

A

Cataract, profound corneal edema, retinal detachments, intraocular hemorrhage

45
Q

Why are canine choroidal vessels especially affects by elevated IOP?

A

Pressure = decr blood flow thru these vessels, and they poorly autoregulate with decreased blood flow

46
Q

What IOP is needed to start affecting the choroidal vessels?

A

> 60 mmHg

47
Q

What is seen clinically if high IOPs cause choroidal vessel dysfunction?

A

Chorioretinal degeneration, in a pattern radiating from ONH

48
Q

What genetic defect is associated with primary lens laxations?

A

ADAMTS17

49
Q

How can PLL be differentiated from a secondary lens luxation? (just based on age)?

A

PLL: young = 1-4 yrs old! (not 6-10 like SLL)

50
Q

What part of the retina is most susceptible to damage, even from small increases in pressure?

A

INNER retina = RGCs and NFL; also ONH

51
Q

What pressure can affect axoplasmic flow?

A

25 mmHg!!

52
Q

Elevated glutamate found in animals with glaucoma supports what theory of RGC damage?

A

Ischemic

53
Q

Secondary glaucoma from lens luxation issue in what 7 breeds?

A

FTS CJ BW
Fox terrier, Tibetan terrier, Sealyham terrier
Cairn terrier, Jack Russel terrier

Border collie, Welsh Corgi

54
Q

What 2 breeds get POAG?

A

Beagle, Norwegian

55
Q

What breed has the highest prevalence of glaucoma?

A

American Cocker Spaniel

56
Q

What is special about ACS development of glaucoma in the contralateral eye?

A

Usually happens within a few months

57
Q

What is special about the disease in the Basset hound? How does this impact treatment?

A

Like to get concurrent anterior uveitis

Complicates medical and surgical treatment

58
Q

What breeds often retain vision into late into the disease? (4 breeds)

A

Chow Chow
Shar Pei
Samoyed
Norwegian Elkhound

59
Q

How old are most Great Danes that get glaucoma?

A

Avg 4 yrs

60
Q

What breed has a dominant mode of inheritance?

A

Welsh Springer Spaniel

61
Q

What is the most common cause of secondary glaucoma?

A

Cataract (another study said anterior uveitis)

62
Q

What percentage of cataracts dogs will develop glaucoma?

A

20%

63
Q

Order from most to least likely to cause glaucoma: anterior luxation, posterior luxation, subluxation

A

Anterior (73%), subluxation (43%), posterior (38%)

64
Q

Why is ICLE not jumped to with lens luxation?

A

High complication rate: glaucoma and RD

65
Q

3 ways intumescent lens can cause glaucoma

A

1) pupillary block
2) pushes iris forward = closes angle
2) synechiae from LIU

66
Q

What are the 2 most common causes of glaucoma in aphakic eyes?

A

1) Posterior synechiae and PIFMs

2) Anterior synechiae and PIFMs

67
Q

What clinical changes would make you suspect glaucoma secondary to cataract surgery?

A

IRIS BOMBE with SMALL PUPIL

68
Q

When is tPA useful (time range) for fibrin occlusion of pupil?

A

2 weeks duration

69
Q

If there is pupillary block in an aphakic eye, what can be done?

A

1) MEDICAL therapy: scopolamine with phenylephrine, anti-inflammatories (steroids and NSAIDs), systemic CAIs, mannitol
2) SURGICAL therapy: open with blade, hypodermic needle, laser iridotomy, iridectomy, iridencleisis

70
Q

Why is laser iridotomy usually not appropriate for pupillary block?

A

Closes in a few days

71
Q

What time point is the average onset of POH?

A

~5 hours

72
Q

Ocular melanosis is seen in what 3 breeds? Which of those 3 is it autosomal dominant?

A

Cairn terrier (auto dominant)
Boxer
Lab

73
Q

How does ocular melanosis lead to glaucoma?

A

uveal melanocytes and melanophages end up in the filtration angle

74
Q

Where is the clinical presentation of ocular melanosis?

A

First pigmentation/thickening of iris, then episcleral/scleral plaques, release of pigment into anterior chamber/AH, then deposition into outflow pathways (esp VENTRALLY), slow progression to pigmentation of tapetal fundus

75
Q

What is the rate of progression of ocular melanosis (to glaucoma)? What is the prognosis?

A

Rate of progression = SLOW

Prognosis = poor – will obstruct valves

76
Q

What 2 breeds get pigmentary/cystic glaucoma?

A

Golden retriever

Great Dane

77
Q

How old are most goldens that develop GRPG?

A

~8 yrs

78
Q

What are the first signs of GRPG?

A

1) pigment on anterior lens capsule
2) uveal cysts
3) iridal hyperpigementation
4) web-like strange of opaque material in the anterior chamber
5) cataracts

79
Q

Time from diagnosis of GRPG and glaucoma formation?

A

5 months (unlike Cairn terrier, where it is slow!)

80
Q

Prognosis of GRPG?

A

POOR (all will develop glaucoma and usually end up taking eye out)

81
Q

What are the 3 most common intraocular tumors of dogs?

A

1) melanoma
2) adenoma of iris/CB
3) adenocarcinoma of iris/CB

82
Q

Where do you usually see METASTATIC neoplasia in the eye (what structure)?

A

Ciliary body (makes sense…)

83
Q

What 2 neoplasms are the most common metastatic neoplasms of the eye?

A

1) LSA

2) Adenocarcinomas

84
Q

What is different in puppies with congenital glaucoma in regards to affect of buphthalmia? (2 things different than the buphthalmic adult)

A

1) globe may return to normal size if pressure controlled early enough
2) helps protect the ONH and retina, to some degree

85
Q

What is the post-op IOP for eyes with VALVED and UNVALVED gonioimplants?

A

Valved: 10-12 mmHg
Unvalued: <5 mmHg

86
Q

When will unvalved implants develop IOPs equal to that of valved implants? What does this coincide with?

A

3-6 wks post-op

Fibrosis around the implant

87
Q

Why are very low IOPs from unvalved implants bad?

A

Increase excessive fibrin formation, potentially hemorrhage and RD

88
Q

For endolaser to work in a glaucomatous eye, how much should be endolasered?

A

180 to ideally 270 degrees

89
Q

What is the average size of an intrascleral prosthesis?

A

20-22 cm

90
Q

How long should a temporary tarrsorhaphy be placed after intrascleral prosthesis? Why?

A

10-14 days

They usually don’t blink well

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