Glaucoma Flashcards
What is glaucoma? What is the goal of therapy?
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
What is the normal flow of aqueous humor?
- 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
What are the 3 types of glaucoma? How do patients present?
- primary - unilateral
- secondary
- congenital - severe
red, painful eye + blindness
What are the 2 unique signs of glaucoma not seen in other causes of red eyes?
- midrange pupil - pressure pushed pupil open slightly
- sluggish PLR
What are some other signs of glaucoma?
- 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
What is Haab’s striae?
glaucoma causes a break in Descemet’s membrane, resulting in the accumulation of lines of fibrin
What is indicative of retinal damage with glaucoma?
optic nerve cupping
increased pressure causes degeneration of the retina —> dark, atrophied optic nerve (vision will not return)
How is glaucoma diagnosed?
IOP measurement - normal range is 15-25 mmHg (will be higher!)
- applanation (tonopen)
- rebound (tonovet)
- indentation (Schiotz) - not common
What is the difference in presentation of primary vs secondary glaucoma? What are 2 diagnostics used to differentiate?
primary typically presents unilaterally, but is a bilateral disease initially
- high-resolution ultrasound - visualizes iridocorneal angle and ciliary cleft where fluid drains
- gonioscopy - special lens evaluated the iridocorneal drainage angle
High-resolution ultrasound:
iridocorneal angle and ciliary cleft are stenoic = blocks drainage of AH!
In what animals is primary glaucoma most common? What causes it?
dogs (breed-related) - rare in cats
NO underlying ophthalmic disease —> goniodysgenesis, pectinate ligament dysplasia = must treat both eyes!
What is important to note about the development of primary glaucoma?
typically presents in one eye at first, but will eventually affect both eyes
- MUST prophylactically treat the good eye to delay development of glaucoma
Primary glaucoma:
- pectinate ligament dysplasia
- not ligament present, causing tissue to block the angle
What are the 3 most common breeds that develop primary glaucoma?
- American Cocker Spaniel
- Basset Hound
- Chow Chow
What is secondary glaucoma? What is the most common cause?
increased IOP as a result of other ophthalmic or systemic disease —> affects one or both eyes
uveitis - look for aqueous flare, hypopyon, and hyphema
What are some common causes of secondary glaucoma? How do they cause this?
- uveitis**
- lens luxation
- intumescent cataract
- hyphema
- intraocular neoplasia
- pupillary block
- pigmentary glaucoma
block the flow of AH out of the eye
What are the 3 aims of glaucoma therapy?
- decreased AH production
- improve AH outflow
- rapidly decrease IOP
What 2 carbonic anhydrases are used to treat glaucoma? What function do they have?
- Dorzolamide
- Brinzolamide
decrease AH production —> helps will both types of glaucoma
(can be used in any species for any type)
What beta-blocker is commonly used to treatr glaucoma? What function does it have?
Timolol
decreases AH production - also used in other eye to prevent development of glaucoma (primary)
What prostaglandin analog can be used to treat glaucoma? What function does it have?
Latanoprost
increases AH outflow
What does Lantanoprost work best for? When is use contraindicated?
PRIMARY glaucoma + emergency/maintenance
cats
What combination of glaucoma medication is most commonly used?
Dorzolamide + Timolol combo
What supportive therapy is important for treating glaucoma?
glaucoma is painful - pain management (+ vision maintenance) can be life-long
What are 2 possible surgical treatments of glaucoma?
- cyclophotocoagulation (CPC) with diode laser
- valve or shunt
can maintain vision, not recommended in patients that are already blind
What are 3 salvage procedures used for patients with severe glaucoma?
- evisceration nad prosthesis
- enucleation
- gentamicin intravitreal injection
What is the goal of surgical treatment of glaucoma?
preserve vision for as long as possible, while maintaining a comfortable and visual eye
How is cyclophotocoagulation and placement of a shunt used to treat glaucoma? How can it be performed?
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
Cyclophotocoagulation laser:
When can the effect of cyclophotocoagulation be observed? What post-operative maintenance is necessary?
2-3 weeks —> unpredictable
medical therapy (Dorzolamide + Timolol) —> post-op pressure spike can cause blindness
How can the post-op pressure spike following cyclophotocoagulation be avoided?
place a valve or shunt to allow movement of AH
What is evisceration and prosthesis? When is it used?
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
What complications are associated with evisceration and prothesis?
can still develop corneal ulcers and KCS
Evisceration and prosthesis:
How can sinking associated with an enucleation be avoided? Why is it preferred over evisceration and prosthesis?
placing an intraorbital prosthesis
heals faster (dogs don’t know the difference!)
What medications are used for ciliary body ablation (intravitreal injection)? What are their purpose?
gentamicin or cidofovir
destroys the ciliary body responsible for producing AH in blind eyes
(need to know cause before using this procedure!)
What complication is associated with ciliary body ablation? How does this procedure compare to other salvage procedures?
cataracts and phthisis bulbi - toxic to all parts of the eye (retina, optic nerve, lens)
- somewhat unpredictable
- not very expensive
- short procedure with sedation
What is the prognosis of primary glaucoma like?
guarded
- early diagnosis and vigilant monitoring + medication/surgery can help maintain vision for years
- dogs typically lose vision in both eyes
What is prognosis of secondary glaucoma like? What 3 things does it rely on?
guarded - can resolve completely or cause blindness, shrunken globe, enucleation, or evisceration and prothesis
- cause
- time to diagnose
- response to therapy
