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Small Animal Optho/Neuro > Glaucoma > Flashcards

Glaucoma Flashcards

1
Q

In summary, glaucoma is characterized by _________________________ that is incompatible with ocular health.

A

elevated intraocular pressure

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2
Q

What are the 3 mechanisms by which glaucoma can cause irreversible vision loss?

A
  1. high intraocular pressure*
  2. optic nerve ischemia and death
  3. neurotoxic events
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3
Q

What is the NORMAL production and flow of aqueous humor?

A

AH is produced by the ciliary body, then travels through the posterior chamber through the pupil into the anterior chamber. Once there, it exits through the drainage angle.

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4
Q

What 2 things must be balanced in order to have NORMAL intraocular pressure?

A

AH production and AH outflow

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5
Q

What is the main physiological cause of glaucoma?
(Note: it has to do with the AH)

A

decreased OUTFLOW of AH, which increases IOP.

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6
Q

_________ is a heritable/breed-related abnormality of the aqueous drainage angle.

A

primary glaucoma

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7
Q

What are 8 possible causes of canine secondary glaucoma?

A
  1. lens luxation
  2. uveitis
  3. hyphema
  4. intraocular neoplasia
  5. melanocytic glaucoma
  6. pigmentary uveitis
  7. pseudophakia/aphakia
  8. trauma
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8
Q

T/F: primary glaucoma is rare in cats

A

true

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9
Q

what is the MOST common cause of glaucoma in cats?

A

uveitis

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10
Q

___________ is a condition that occurs in middle/older aged cats where fluid travels behind the lens, accumulates, and pushes the lens and iris forward which can lead to glaucoma formation.

A

aqueous humor misdirection

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11
Q

How you diagnose aqueous humor misdirection in cats?

A

look at the width/depth of their anterior chamber in both eyes.

If the AC is shallow, this could indicate that the lens and iris are being pushed forward by the misdirection of the fluid and subsequent accumulation.

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12
Q

What 5 clinical signs are typically seen in acute glaucoma?

A
  1. blepharospasm
  2. corneal edema (diffuse)
  3. episcleral injection
  4. dilated pupil (if pressure really high)
  5. variable vision (pressure- and chronicity- dependent)
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13
Q

What are 4 typical clinical signs of CHRONIC glaucoma in addition to all of the signs that occur with acute cases?

A
  1. buphthalmos
  2. Haab’s striae
  3. lens luxation
  4. optic nerve cupping
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14
Q

what is the physiologic mechanism for developing Haab’s striae?

A

when the globe enlarges (buphthalmos), the corneal endothelium and Desceme’s membrane stretches and breaks which creates striae.

This indicates chronicity because these take WEEKS to develop in most cases.

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15
Q

What can you see visually in lens subluxation caused by globe enlargement in cases of chronic glaucoma?

A

Aphakic crescent – lens zonules have broken

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16
Q

T/F: optic nerve cupping is reversible with acute management

A

false – irreversible!

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17
Q

In what 4 ways can we diagnose glaucoma?

A
  1. clinical signs
  2. history and signalment
  3. IOP measurement (tonometry)
  4. gonioscopy
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18
Q

What is a NORMAL IOP?

A

10-25 mmHg, but Dr. Herring says that if they go a little over that higher threshold, then it can still be considered normal in some cases.
what would be MORE concerning that actual numbers is if there is a disparity between the 2 eyes. Some patients can have glaucoma and have normal IOPs, but maybe one eye has a higher IOP than the normal eye and you’re catching it early or during a phase of the day where it is not being manifested.

19
Q

Why is relying on tonometry for early prediction of canine glaucoma unlikely to be successful?

A

tonometry can help us identify abnormal intraocular pressures and assess the efficacy of our treatments.
However, intraocular pressures vary greatly during the day, from day to day, and even more in patients with glaucoma.
Additionally, elevations in IOP is not progressive in cases of glaucoma, but rather an acute increase.

20
Q

What does gonioscopy measure/examine?

A

the drainage angle
helping to determine the likelihood of primary glaucoma based upon the angle morphology.
If the “normal” eye has a normal looking drainage angle (open angle with multiple “holes” for fluid drainage), then primary glaucoma is NOT the diagnosis and you should look for a secondary cause of glaucoma.

21
Q

What are the 3 goals of glaucoma management?

A
  1. maintain vision if possible
  2. patient comfort
  3. prophylaxis of “at-risk” eye
22
Q

What 4 things does your glaucoma management approach depend on?

A
  1. the etiology of glaucoma
  2. current IOP
  3. presence/absence of vision
  4. stage of disease
23
Q

What prostaglandin analogue is used in emergency management of glaucoma because it has a rapid onset of action?

A

topical latanoprost (Xalatan)

24
Q

What is the contraindication for topical latanoprost?

A

anterior lens luxation

25
Q

What therapy is used in emergent glaucoma cases that is quick acting, but short-lived. It is contraindicated in cases with cardiovascular insufficiency because the mechanism is to pull fluid into the vasculature which can lead to overload in these particular patients?
Also important to note that this treatment is inferior to topical prostaglandins.

A

Systemic hyperosmotic medications:
IV mannitol or oral glycerin

26
Q

what is a medication class used for maintenance therapy in glaucoma cases that shuts down fluid production from the source at which it is produced. This drug is safe in all species and with all types of glaucoma.

A

carbonic anhydrase inhibitors

dorzolamide, brinzolamide

27
Q

What medications are used for maintenance therapy of glaucoma and work by constricting the pupil to improve AH outflow. These medications are moderately effective and are a good choice for glaucoma prophylaxis?

A
  1. MIOTICS – demecarium bromide (never in cats) or pilocarpine

&

  1. PROSTAGLANDIN ANALOGUES – latanoprost, travoprost, bimatoprost (none effective in cats)
28
Q

T/F: pilocarpine is contraindicated in cats

A

false – demecarium bromide is

29
Q

T/F: prostaglandin analogues do not work in cats

A

true

30
Q

Which medication class is used in conjunction with other maintenance medications for glaucoma treatment. These medications work by decreasing fluid production and are useful for glaucoma prophylaxis. They work in all species.

A

B-blockers

ex. timolol maleate, betaxolol

these drugs will be contraindicated in cases of asthma or bradycardic animals.

31
Q

what are 2 side effects of using beta blockers in glaucoma cases?

A
  1. bradycardia
  2. exacerbation of asthma
32
Q

T/F: Dorzolamide-timolol is a commonly used, convenient, and effective combination drug for maintenance therapy of glaucoma.

A

true

33
Q

T/F: you should not be aggressive with glaucoma treatment because you could makes things worse and cause lens subluxations, iris atony, and rupture of zonule fibers.

A

false – you should treat aggressively to gain control of glaucoma.

34
Q

Why should you resist the temptation to taper medications in well-controlled glaucoma cases?

A

glaucoma is non-curable, therefore if the medications the patient is on are working, you should maintain this regimen.

35
Q

What does ‘follow-up’ entail for glaucoma cases?

A
  • at first, everyday / EOD
  • then, recheck q 3-4 wks
  • if eye is at-risk, rechecking IOP q 4-6 wks is helpful but its difficult to get clients to comply with this, so educating them on observing signs of glaucoma is important.
36
Q

T/F: when medically managing glaucoma patients, their IOP levels should be 23-24 mmHg.

A

false – high normal is undesirable.
Ideally, anything <15-20 is good for medical management of glaucoma.

37
Q

What can significantly delay the onset of primary glaucoma in the 2nd eye?

A

medical prophylaxis with medications like topical miotics, CAIs, or beta blockers.

38
Q

T/F: topical mydriatics are contraindicated in glaucoma cases

A

true
drug examples include atropine, tropicamide

39
Q

What 2 surgical options are available for decreasing aqueous humor production to treat glaucoma?

A
  1. cyclophotocoagulation (laser therapy) – burns ciliary epithelium to decrease prod of AH. this px can fail when ciliary epithelium regenerates
  2. cyclocryotherapy – freeze ciliary epithelium to decrease prod of AH.
40
Q

What surgical option is available for glaucoma patients that would increase aqueous humor outflow?

how can this surgical option FAIL?

A

placement of aqueous shunts/gonioimplants

these can fail when fibrous membranes develop over it and it obstructs fluid from getting out of the system.

41
Q

what is the prognosis for vision with glaucoma?

A

Poor
many cases go blind within several months and sx intervention only prolongs vision retention, it does NOT cure the disease.

42
Q

When are salvage procedures indicated for glaucoma patients?

A

when you have irreversibly blind eyes, meds are not working, pressures are really high, and the patient is in pain.

43
Q

what 3 salvage procedures are available for glaucoma patients?

A
  1. enucleation
  2. evisceration / intrascleral prosthesis
  3. chemical ciliary body ablation
44
Q

For chemical ciliary body ablation, what medication is injected into the eye?

A

gentamicin

note that this procedure is for BLIND EYES ONLY and you should avoid lens puncture.
this procedure is only effective 65% of the time and has potential complications. It allows the eye to stay in place.

Small Animal Optho/Neuro (12 decks)

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