Glaucoma

Question 1

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

Answer 1

elevated intraocular pressure

Question 2

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

Answer 2

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

Question 3

What is the NORMAL production and flow of aqueous humor?

Answer 3

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.

Question 4

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

Answer 4

AH production and AH outflow

Question 5

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

Answer 5

decreased OUTFLOW of AH, which increases IOP.

Question 6

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

Answer 6

primary glaucoma

Question 7

What are 8 possible causes of canine secondary glaucoma?

Answer 7

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

Question 8

T/F: primary glaucoma is rare in cats

Answer 8

true

Question 9

what is the MOST common cause of glaucoma in cats?

Answer 9

uveitis

Question 10

___________ 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.

Answer 10

aqueous humor misdirection

Question 11

How you diagnose aqueous humor misdirection in cats?

Answer 11

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.

Question 12

What 5 clinical signs are typically seen in acute glaucoma?

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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.

Question 15

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

Answer 15

Aphakic crescent – lens zonules have broken

Question 16

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

Answer 16

false – irreversible!

Question 17

In what 4 ways can we diagnose glaucoma?

Answer 17

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

Question 18

What is a NORMAL IOP?

Answer 18

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.

Question 19

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

Answer 19

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.

Question 20

What does gonioscopy measure/examine?

Answer 20

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.

Question 21

What are the 3 goals of glaucoma management?

Answer 21

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

Question 22

What 4 things does your glaucoma management approach depend on?

Answer 22

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

Question 23

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

Answer 23

topical latanoprost (Xalatan)

Question 24

What is the contraindication for topical latanoprost?

Answer 24

anterior lens luxation

Question 25

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.

Answer 25

Systemic hyperosmotic medications: IV mannitol or oral glycerin

Question 26

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.

Answer 26

carbonic anhydrase inhibitors dorzolamide, brinzolamide

Question 27

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?

Answer 27

1. MIOTICS -- demecarium bromide (never in cats) or pilocarpine & 2. PROSTAGLANDIN ANALOGUES -- latanoprost, travoprost, bimatoprost (none effective in cats)

Question 28

T/F: pilocarpine is contraindicated in cats

Answer 28

false -- demecarium bromide is

Question 29

T/F: prostaglandin analogues do not work in cats

Answer 29

true

Question 30

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.

Answer 30

B-blockers ex. timolol maleate, betaxolol these drugs will be contraindicated in cases of asthma or bradycardic animals.

Question 31

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

Answer 31

1. bradycardia 2. exacerbation of asthma

Question 32

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

Answer 32

true

Question 33

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.

Answer 33

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

Question 34

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

Answer 34

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

Question 35

What does 'follow-up' entail for glaucoma cases?

Answer 35

- 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.

Question 36

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

Answer 36

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

Question 37

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

Answer 37

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

Question 38

T/F: topical mydriatics are contraindicated in glaucoma cases

Answer 38

true drug examples include atropine, tropicamide

Question 39

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

Answer 39

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.

Question 40

What surgical option is available for glaucoma patients that would increase aqueous humor outflow? *how can this surgical option FAIL?*

Answer 40

placement of aqueous shunts/gonioimplants these can fail when fibrous membranes develop over it and it obstructs fluid from getting out of the system.

Question 41

what is the prognosis for vision with glaucoma?

Answer 41

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

Question 42

When are salvage procedures indicated for glaucoma patients?

Answer 42

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

Question 43

what 3 salvage procedures are available for glaucoma patients?

Answer 43

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

Question 44

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

Answer 44

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.