Glaucoma Flashcards by jared Jensen

Normal IOP is

10-25mmHg (dogs + cats)
10-30mmHg (horses)

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IOP is a balance between

production (ultrafiltration, simple diffusion, active secretion) and aqueous drainage

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What is the flow of aqeuous humor

ciliary body
posterior chamber
pupil
anterior chamber
iridocorneal angle

IOP is needed to maintain eye shape

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What causes obstruction of aqueous humor outflow

Primary: closed/narrow iridocorneal angle (ICA)

secondary to: uveitis, intraocular tumor, lensluxation

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Increased IOP leads to

-optic nerve degeneration
-retinal degeneration (retinal atrophy)
-blindness

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What are the clinical signs of glaucoma

-Corneal edema (water in the cornea (blue hazy cornea)
-Episcleral injection
-Mydriasis
-Blepharospasm
-Epiphora

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With glaucoma is the pupil small or large

large (mydriasis)

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What clinical signs tell you that glaucoma is chronic

1) Buphthalmos (enlarged eye)
2) Corneal striae, Haab’s striae= lines/stretch marks in the cornea
3) Lens subluxation = dislocation of the lens
4) Mydriasis
5) Cupped optic nerve head (optic nerve degeneration)
6) Tapetal hyperreflectivity
7) Retinal vascular attenuation (thinning of blood vessels)

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line / stretch marks in the cornea seen with chronic glaucoma

Corneal striae, Haab’s striae

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Increased IOP causing blindness by

optic nerve becomes degenerated and cupped and causes blindness

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T/F: primary glaucoma is common in cats and horses

false

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What breeds commonly get primary glaucoma

Cockerspaniels**
Basset hounds
Beagles (open angle)
Chow Chows
many more

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How does glaucoma typically develop

sudden onset pressure spike
generally unilateral in the initial stage
-other good eye is affected ~9months after the first eye if no drugs
-31 months after the first eye if started on anti-glaucoma drugs

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OD IOP=62mmHg and blind
OS IOP= 12mmHg and visual
What would you do as an ER doctor who sees this dog Saturday morning- owner says the dog (6yo Basset FS named Rose was visual the night before)
What do you do

Decrease IOP ASAP

Latanoprost OD 1 drop
-Repeat q10-15min x3
-Repeat IOP (tonometry) after an hour

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What causes IOP spike in primary glaucoma

-Inherited narrow/collapsed ICA
-Sudden complete collapse of ICA

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narrow/closed iridocorneal angle
-sign of primary glaucoma

goniodysgenesis

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procedure to differentiate between primary and secondary glaucoma

gonioscopy

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what would goniodysgenesis look like when doing gonioscopy

pectinate ligament cant be seen- will be darker line and have a closed angle

What species does secondary glaucoma effect

any species

What is the most common cause of secondary glaucoma ***

anterior uveitis

What are the 4 causes secondary glaucoma

1) Anterior uveitis
2) Lens luxation
3) Intraocular tumor
4) Intumescent cataract (swollen lens - most often due to diabetic cataracts)

What are the clinical signs of secondary glaucoma

-Pain: epiphora and blepharospasm
-Decreased to absent vision
-Episcleral injection (red)
-Cloudy eye (corneal edema, anterior uveitis)

What are the clinical signs of glaucoma secondary to uveitis

-Episcleral injection
-Perilimbal corneal edema
-Diffuse corneal edema
-Miotic pupil
-Potential oris bombe
-Hyphema or hypopyon
-IOP will be high normal (because glaucoma has high IOP and uveitis has low IOP) -> very alarming

How do you diagnose glaucoma

Tonometry with a Tonometer
1) Applanation Tonometry (Tonopen)
2) Rebound Tonometry (TonoVet)

10-25mmHg (dog/cat)
10-30mmHg (horse)

How do you decide primary vs secondary glaucoma

-breed,signalment -underlying cause -gonioscopy (referral to ophthalmologist) *Treatment may differ greatly for primary glaucoma

How do you treat acute onset, primary glaucoma

Decrease IOP ASAP to save vision only a few hours of high IOP to save vision 1) Prostaglandin analogues: Latanoprost and Travoprost - strong effect 2) Carbonic anhydrase inhibitors (Dorzolamide)- medium effect 3) Beta-blockers (Timolol) mild effect

What are the prostaglandin analogues used as emergency treatment for primary glaucoma

Latanoprost and Travoprost

Cosopt

combined Dorzolamide (carbonic anhydrase inhibitor) with Timalol (beta blocker) for glaucoma treatment

you have a 3yo MN pointer was in northern part of US one week ago for hunting started to have a red eye a couple days ago Squinting OD seems a little tired too and did not eat his dinner yesterday or breakfast this morning OD: IOP 27mmHg corneal edema, perilimbal corneal vascularization, episcleral injection, miotic pupil, uveitis, OD still visual what do you do

Find underlying cause of secondary uveitis -Infection (CBC/Chem/UA/Titers/4DX) -Neoplasia (chest xray, abdominal ultraosund, spinal tap, skull MRI) Immune mediated Treatment: -Topical steroids (1% prednisone) -Dorzolamide BID-TID Maybe -Atropine (when IOP is normal) -Sysemic steroids or NSAIDs are diagnostics -Systemic antibioitcs (Doxy) -Systemic antifungal (Itraconazole or fluconazole) recheck IOP in one day and start on topical atropine SID-TID and recheck in 7-10 days

What is contraindicated in glaucoma eyes

Atropine

How do you treat secondary glaucoma due to anterior lens luxation

-Emergency SX 1) Decrease IOP- Mannitol to dehydrate vitreous 2) Remove lens or eye (enucleation) or trans-corneal lens reduction * surgery dependent on vision - consensual PLR

What surgeries can be done for primary glaucoma

1) Gonio shunt/valve 2) Trans-scleral laser (decreases production of cilirary body) 3) Endolaser - burning ciliary body from the inside

What should you do for end-stage blind eye due to glaucoma

1) Enucleation- 100% success rate or 2) Exenteration (removal of globe and surrounding tissue) in case of extra or intraocular infection or neoplasia 3) Evisceration: globe content removal keeps: sclera, cornea, third eyelid, eyelids, glands (primary only) 4) Ciliary body chemical ablation

What is the side effect of evisceration

corneal ulcers, dry eye, abnormal appearance globe content is removed but sclera, cornea, third eyelid, eyelids, and glands are kept (no tapetum reflection)

Ciliary body chemical ablation

tx for primary glaucoma Intravitreal injection of cidofovir or gentamycin which is toxic to the ciliary body and will stop the production of aqueous humor side effects: inflammation- continue topical anti-inflammatory phthisis bulbi (small globe) which could cause entropion

What are the side effects of ciliary body chemical ablation

1) inflammation- continue topical anti-inflammatory 2) phthisis bulbi (small globe) which could cause entropion

ciliary body chemical ablation is only for

primary glaucoma

For blind eye glaucoma, when do you consider evisceration

owner wants the appearance of dog having an eye

For blind eye glaucoma, when do you consider exenteration instead of enucleation

extra- or intraocular infection or neoplasia

removal of the globe

enucleation

removal of the globe and surrounding tissue used incase of extra or intraocular infection or neoplasia

Exenteration

globe content removal but sclera, cornea, third eyelid, eyelid, and glands are kept

Evisceration