Glaucoma

Question 1

What is glaucoma? What is the goal of therapy?

Answer 1

group of diseases associated with an increase in intraocular pressure, resulting in retinal and optic nerve damage, pain, and eventual blindness

prolong vision and comfort for as long as possible

Question 2

What is the normal flow of aqueous humor?

Answer 2

• AH produced at ciliary body and secreted through ciliary processes
• AH moves though posterior chamber, past the iris, and into the anterior chamber
• AH is absorbed at the iridocorneal angle

Question 3

What are the 3 types of glaucoma? How do patients present?

Answer 3

1. primary - unilateral
2. secondary
3. congenital - severe

red, painful eye + blindness

Question 4

What are the 2 unique signs of glaucoma not seen in other causes of red eyes?

Answer 4

1. midrange pupil - pressure pushed pupil open slightly
2. sluggish PLR

Question 5

What are some other signs of glaucoma?

Answer 5

• ocular pain = blepharospasm
• hyperemia
• episcleral congestion = enlarged ocular blood vessels
• corneal edema
• decreased or absent vision in affected eye
• lens subluxation - increased pressure stretches and breaks zonules
• buphthalmos - increased pressure causes swelling of the eye

Question 6

What is Haab’s striae?

Answer 6

glaucoma causes a break in Descemet’s membrane, resulting in the accumulation of lines of fibrin

Question 7

What is indicative of retinal damage with glaucoma?

Answer 7

optic nerve cupping

increased pressure causes degeneration of the retina —> dark, atrophied optic nerve (vision will not return)

Question 8

How is glaucoma diagnosed?

Answer 8

IOP measurement - normal range is 15-25 mmHg (will be higher!)

• applanation (tonopen)
• rebound (tonovet)
• indentation (Schiotz) - not common

Question 9

What is the difference in presentation of primary vs secondary glaucoma? What are 2 diagnostics used to differentiate?

Answer 9

primary typically presents unilaterally, but is a bilateral disease initially

1. high-resolution ultrasound - visualizes iridocorneal angle and ciliary cleft where fluid drains
2. gonioscopy - special lens evaluated the iridocorneal drainage angle

Question 10

High-resolution ultrasound:

Answer 10

iridocorneal angle and ciliary cleft are stenoic = blocks drainage of AH!

Question 11

In what animals is primary glaucoma most common? What causes it?

Answer 11

dogs (breed-related) - rare in cats

NO underlying ophthalmic disease —> goniodysgenesis, pectinate ligament dysplasia = must treat both eyes!

Question 12

What is important to note about the development of primary glaucoma?

Answer 12

typically presents in one eye at first, but will eventually affect both eyes

• MUST prophylactically treat the good eye to delay development of glaucoma

Question 13

Primary glaucoma:

Answer 13

• pectinate ligament dysplasia
• not ligament present, causing tissue to block the angle

Question 14

What are the 3 most common breeds that develop primary glaucoma?

Answer 14

1. American Cocker Spaniel
2. Basset Hound
3. Chow Chow

Question 15

What is secondary glaucoma? What is the most common cause?

Answer 15

increased IOP as a result of other ophthalmic or systemic disease —> affects one or both eyes

uveitis - look for aqueous flare, hypopyon, and hyphema

Question 16

What are some common causes of secondary glaucoma? How do they cause this?

Answer 16

• uveitis**
• lens luxation
• intumescent cataract
• hyphema
• intraocular neoplasia
• pupillary block
• pigmentary glaucoma

block the flow of AH out of the eye

Question 17

What are the 3 aims of glaucoma therapy?

Answer 17

1. decreased AH production
2. improve AH outflow
3. rapidly decrease IOP

Question 18

What 2 carbonic anhydrases are used to treat glaucoma? What function do they have?

Answer 18

1. Dorzolamide
2. Brinzolamide

decrease AH production —> helps will both types of glaucoma

(can be used in any species for any type)

Question 19

What beta-blocker is commonly used to treatr glaucoma? What function does it have?

Answer 19

Timolol

decreases AH production - also used in other eye to prevent development of glaucoma (primary)

Question 20

What prostaglandin analog can be used to treat glaucoma? What function does it have?

Answer 20

Latanoprost

increases AH outflow

Question 21

What does Lantanoprost work best for? When is use contraindicated?

Answer 21

PRIMARY glaucoma + emergency/maintenance

cats

Question 22

What combination of glaucoma medication is most commonly used?

Answer 22

Dorzolamide + Timolol combo

Question 23

What supportive therapy is important for treating glaucoma?

Answer 23

glaucoma is painful - pain management (+ vision maintenance) can be life-long

Question 24

What are 2 possible surgical treatments of glaucoma?

Answer 24

1. cyclophotocoagulation (CPC) with diode laser
2. valve or shunt

can maintain vision, not recommended in patients that are already blind

Question 25

What are 3 salvage procedures used for patients with severe glaucoma?

Answer 25

1. evisceration nad prosthesis
2. enucleation
3. gentamicin intravitreal injection

Question 26

What is the goal of surgical treatment of glaucoma?

Answer 26

preserve vision for as long as possible, while maintaining a comfortable and visual eye

Question 27

How is cyclophotocoagulation and placement of a shunt used to treat glaucoma? How can it be performed?

Answer 27

diode laser is preferentially absorbed by pigment and can open up and drain at ciliary body or iridocorneal angle in the anterior chamber

• through sclera
• with endolaser

Question 28

Cyclophotocoagulation laser:

Answer 28

Question 29

When can the effect of cyclophotocoagulation be observed? What post-operative maintenance is necessary?

Answer 29

2-3 weeks —> unpredictable

medical therapy (Dorzolamide + Timolol) —> post-op pressure spike can cause blindness

Question 30

How can the post-op pressure spike following cyclophotocoagulation be avoided?

Answer 30

place a valve or shunt to allow movement of AH

Question 31

What is evisceration and prosthesis? When is it used?

Answer 31

placing a silicone prosthesis within the cornea and sclera after removing intraocular contents

rare - blind, painful eyes where owners want to maintain a better cosmetic appearance of an eye withing the orbit

Question 32

What complications are associated with evisceration and prothesis?

Answer 32

can still develop corneal ulcers and KCS

Question 33

Evisceration and prosthesis:

Answer 33

Question 34

How can sinking associated with an enucleation be avoided? Why is it preferred over evisceration and prosthesis?

Answer 34

placing an intraorbital prosthesis

heals faster (dogs don’t know the difference!)

Question 35

What medications are used for ciliary body ablation (intravitreal injection)? What are their purpose?

Answer 35

gentamicin or cidofovir

destroys the ciliary body responsible for producing AH in blind eyes

(need to know cause before using this procedure!)

Question 36

What complication is associated with ciliary body ablation? How does this procedure compare to other salvage procedures?

Answer 36

cataracts and phthisis bulbi - toxic to all parts of the eye (retina, optic nerve, lens)

• somewhat unpredictable
• not very expensive
• short procedure with sedation

Question 37

What is the prognosis of primary glaucoma like?

Answer 37

guarded

• early diagnosis and vigilant monitoring + medication/surgery can help maintain vision for years
• dogs typically lose vision in both eyes

Question 38

What is prognosis of secondary glaucoma like? What 3 things does it rely on?

Answer 38

guarded - can resolve completely or cause blindness, shrunken globe, enucleation, or evisceration and prothesis

1. cause
2. time to diagnose
3. response to therapy