Glaucoma Flashcards
What is the aqueous humor flow?
Ciliary body > posterior chamber > pupil > anterior chamber > iridocorneal angle > venous drainage
What is glaucoma almost always due to?
Impaired outflow
Where do the majority of species outflow aqueous humor?
Iridocorneal angle
What are the acute clinical signs of glaucoma?
Episcleral injection
Blepharospasm
Corneal edema
Mydriasis
Impaired vision
What are the chronic clinical signs of glaucoma?
Optic disc cupping
Retinal degeneration
Irreversible blindness
Buphthalmos (larger stretched out globe - haab’s stria (stretch marks))
Phthisis bulbi (shrinking of the eye - super end stage)
Lens subluxation
What does a buphthalmic globe indicate? Execept in?
Blindness
Except in puppies and shar peis
What is the IOP difference between buphthalmia and exophthalmia?
Often markedly elevated with buphthalmia
Normal or mildly elevated with exophthalmia
What is the corneal diameter difference between buphthalmia and exophthalmia?
Larger with buphthalmia
Normal with exophthalmia
What is the lens luxation difference between buphthalmia and exophthalmia?
Secondary subluxation with buphthalmia
Normal with exophthalmia
What is the vision difference between buphthalmia and exophthalmia?
Blind with buphthalmia
Usually visual with exophthalmia
What is a normal IOP?
12-24 mmHg
When should you check the IOP?
With every red eye (episcleral injection) with an intact cornea
What is the most accurate IOP?
The lowest
What is a main issue with tonopens?
Reduced accuracy at higher IOP especially with cats
Significantly underestimates IOP
How does applanation tonometry work?
Correlates force to flatten cornea with IOP
Local anesthetic is recommended
How does rebound tonometry work?
Correlates speed of bounce off cornea to IOP
No topical anesthetic is needed
How does rebound tonometry work?
Correlates speed of bounce off cornea to IOP
No topical anesthetic is needed
More accurate
What is the most common primary glaucoma in dogs?
Primary angle closure glaucoma
What breeds are predisposed to primary angle closure glaucoma?
Cocker spaniels and basset hounds
What type of glaucoma are beagles predisposed to?
Primary open angle glaucoma
What is secondary glaucoma associated with?
Other ocular or systemic abnormalities
What are the three most common causes of secondary glaucoma?
Uveitis - most common
Neoplasia
Lens luxation
What is the pathogenesis of primary angle closure glaucoma?
Development of iridocorneal angle arrested
Aqueous production does not = aqueous outflow
Aqueous outflow decreases so IOP increases
Diagnosis of exclusion
What is gonioscopy used for?
Examine the iridocorneal angle
Referral procedure
Subjective
What is the common signalment of primary angle closure glaucoma?
Female
Middle-aged to older dog
Cocker spaniel or basset hound
Glaucoma develops in other eye ~ 8 months later
What should you prepare patients for with a glaucoma patient?
A blind dog
We almost always eventually fail to preserve vision and are often considering comfort
What is the most effective canine therapy for primary glaucoma?
Latanoprost 0.0005%
Topical prostaglandin derivative (mimics uveitis)
Increases uveoscleral outflow
Potent mitotic
When are prostaglandin derivatives contraindicated?
Secondary glaucoma due to severe uveitis
Anterior lens luxation
Not effective in most forms of feline glaucoma
What should you use for secondary glaucoma in dogs and glaucoma in cats and horses?
Dorzolamide 2% / Timolol
Decreases aqueous production
Does not affect pupil size
Carbonic anhydrase inhibitor
Given between drops of Latanoprost
What can be used for inflammation control topically?
Neo/poly/dex 0.1%
Prednisolone acetate 1%
What can be used if topical medication is ineffective?
IV mannitol 20%
Hyperosmotic
Dehydrates vitreous
What are the contraindications when using Mannitol?
Heart disease
DM
Renal failure
Uveitis
What is the prognosis for medical management of glaucoma?
Medical therapy will often fail within 6 months
Glaucoma is progressive and does not go away
What surgical therapy can be done to increase outflow?
Gonioimplants
Tube inside anterior chamber
Gives you about 6 months of control of IOP before failure due to fibrosis
What surgical therapy can be done to decrease production of aqueous humor?
Destruction of the ciliary body
Cyclophotocoagulation - diode laser
Laser is dependent on pigment so it is not consistent
What are the complications of using a diode laser?
Postoperative pressure spike
Cataract formation
Inflammation
What should be done for the other healthy eye?
Prophylactic therapy
Dorzolamide/Timolol
Demarcarium bromide
Latanoprost
Recheck every 1-3 months
What are the three treatment options for end stage glaucoma?
Enucleation
Intrascleral prosthesis (remove inner contents of globe and place silicone ball)
Chemical ciliary body ablation (intravitreal gentamicin or cidofovir)
What are the contraindications for intrascleral prosthesis and chemical ciliary body ablation?
Corneal disease
Uveitis
Tumor
What is feline glaucoma usually due to?
Uveitis
What is the most common complaint of feline glaucoma?
Mydriasis
What procedure is contraindicated in cats?
Chemical ciliary body ablation
Can lead to aggressive tumor formation
What is the only salvage procedure available for cats?
Enucleation
Do not put a prothesis - they like to reject them
