Glaucoma

Question 1

Glaucoma - what is it?

Answer 1

– Syndrome where increased intraocular pressure is

incompatible with vision

Question 2

Glaucoma - Pathophysiology

Answer 2

– Impaired drainage of aqueous humour
– Ischemia and hypoxia due to compression
– Cell death from retinal ganglion cells and optic nerve

Question 3

Congenital glaucoma

Answer 3

– Early form of primary glaucoma or malformation of
irido-corneal angle
– Any breed or sex
– Buphthalmia
– Prognosis: grave

Question 4

Hot breeds for primary glaucoma

Answer 4

cocker, boston, basset, poodle, shar pei, husky, samoyed

Question 5

primary glaucoma

Answer 5

– Bilateral:
• Asynchronous appearance
– Irido-corneal angle
• closed, narrow or open
– Goniodysgenesis
• Angle is abnormal
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Glaucoma


Question 6

Secondary glaucoma

Answer 6

– Lens luxation: TERRIERS
– Uveitis: Iris bombe
– Neoplasia

Question 7

Clinical signs of acute glaucoma.

Answer 7

Clinical signs: Acute
– Diffuse corneal edema
– “Red” eye
– Dilated fixed pupil
– Unilateral
– Vision loss

Question 8

Clinical signs of chronic glaucoma.

Answer 8

Clinical signs: Chronic – Buphthalmia
– Exposure keratitis
– Corneal striae
– Diffuse corneal edema – Fixed dilated pupil
– +/- lens luxation
– Retinal atrophy
– Vision


Question 9

Glaucoma tests - 3 instruments

Answer 9

– PLR: indirect
– Fluorescein stain 
– IOP
     • Schiotz vs Tonopen vs TonoVet 
– Proper restraint
– Technical ability

Question 10

Glaucoma Medical therapy

Answer 10

– Osmotic diuretics
– Carbonic Anhydrase Inhibitors 
– Prostaglandin analogues
– Beta adrenergic antagonists
– Parasympathomimetics
– Sympathomimetics

Question 11

Primary glaucoma - lens in place. How do you treat?

Answer 11

• Triple cocktail: 
– Trusopt (carbonic anhydrase inhibitor)
– Timolol (beta blocker)
– Travatan (prostaglandin analog)
IOP in 30-45 mins!
(Plan B - mannitol, can do drops after)

Question 12

Mannitol - how to treat with this

Answer 12

– 1g/kg IV in 20-30 mins
– Withold water for 2-3 hrs
– Repeat 1g/kg if IOP >30mmHg 1 hr post- injection

Question 13

Secondary glaucoma. How do you treat?

Answer 13

– Trusopt (carbonic anhydrase inhibitor)
– Timolol (beta blocker)
- Coriticosteroids (topical/uveitis)

Question 14

Aqueocentesis

Answer 14

Very controversial
30 g needle at limbus
1-3 drops of aqueous
No syringe
avoid iris and lens

Question 15

Reperfusion Injury with Glaucoma

Answer 15

If the eye has been under pressure for at least 24 hours, then no matter whether you take seconds or minutes, you’ll injure the eye with reprerfusion due to oxidative stress from released radicals.. Amlodipine could possibly help stabilize things (calcium channel blockers) and coriticosteroids, but we don’t have anything really efficacious

Question 16

Medical management

Answer 16

CAI are great, topical is better than oral
Beta blockers don’t work well in dogs, but can be added.
Prostaglandin analogues are great (big guns) but there are side-effects. Can give too low a pressure.
If you have a primary glaucoma, then the other eye likely has a good risk of glaucoma as well, so you can start it on a bit of medication. You can use Topical CAI and possibly add a topical beta blocker.

Question 17

Monitoring medical management - how often should you monitor?

Answer 17

Check every hour until within normal range
4-6 hours for 24 hours
Once weekly

Question 18

When not to use medication (give specific medications and examples of when not to use)

Answer 18

– Mannitol: diabetic, cardiac, renal patients
– Timolol (Beta blocker): cardiac or asthmatic (feline) patients
– Travaprost (prostaglandin analog): uveitis, lens luxation present
– Pilocarpine (parasympathomimetic, old): uveitis, lens luxation present

Question 19

Surgical treatment

Answer 19

Enucleation
Evisceration with intraocular prosthesis
Chemical ablation
Laser photocoagulation of ciliary body
Anterior chamber shunt

Question 20

Surgical management: blind eye

– Chemical ablation

Answer 20

• Gentamicine (Aminoglycoside) and dexamethasone
• 1/3 respond well
• 1/3 do not respond
• 1/3 respond too well – Phthisis bulbos

Question 21

How/when would you use a laser to photo coagulate the ciliary body as a treatment for glaucoma?

Answer 21

– laser photocoagulation of ciliary body –> can try to preserve vision
• Diminish aqueous fluid production
• Temporary fix
• 50% visual at 1 year

Question 22

Surgical management: visual eye – Anterior chamber shunt

Answer 22

• Aqueous humour exiting either through frontal sinus or through conjunctiva
• Longterm uveitis with fibrin blocking the tubing

Question 23

Pilocarpine

Answer 23

a volatile alkaloid obtained from jaborandi leaves, used to contract the pupils and to relieve pressure in the eye in glaucoma patients. (agonist -> muscarinic acetylcholine receptor M3)