Glaucoma Flashcards
Normal aqueous humor flow
Produced buy the ciliary body, actively secreted
Drainage w conventional outflow, uuveoscleral outflow
Production rate = drainage rate
Normal intraocular pressure
Canine - 10-25mmHg
Feline - 15-25mmHg
Equine - 17-28mmHg
Glaucoma
Multi factorial disease
Characterized by elevation of intraocular pressure incompatible with ocular health
Pathogenesis of glaucoma
Reduced aqueous humor drainage capacity
in all cases - Multiple potential mechanisms
Results in progressive IOP elevation
Irreversible vision loss through optic nerve and retinal ganglion cell death
Primary classification of glaucoma
Heritable, breed related abnormality of aqueous drainage angle
Secondary classification of glaucoma
Numerous causes of secondary drainage angle obstructions
Clinical signs of acute disease
Blepharospasm
Corneal edema
Episcleral injection
Dilated pupil
Variable vision
Clinical signs with chronic disease
All acute signs are possible
Buphthalmos
Haabs striae - lines on cornea, breaking of descemetes membrane bc of stretching
Lens subluxation - related to stretching
Cupped optic nerve - damage from pressure
Canine primary glaucoma
Breed-related/hereditary condition
• drainage angle abnormality
• Bilateral disease potential - one eye typically affected first, second eye affected weeks to
months later
Canine secondary glaucoma
Lens luxation
Uveitis
Hyphema
Intraocular neoplasia
Melanocytic glaucoma- terriers
Pigmentary uveitis - Golden retrievers
Pseudophakia/Aphakia
Trauma
Feline glaucoma
Primary glaucoma is rare - Siamese, Persian, Burmese
Secondary glaucoma - similar causes as dogs, uveitis is most common cause**
aqueous humor misdirect - fluid goes backwards towards virtuous humor, unique to cats**
Equine glaucoma
Primary is rare - minis or Appaloosa
Most cases secondary to equine recurrent uveitis
Clinical signs of equine glaucoma
Usual insidious disease in EQ
Corneal edema - intermittent or persistent
Dilated pupil
Habb’s striae
Lens subluxation
Vision loss
DX for glaucoma
Signs
History
IOP measurement
Gonioscopy
Tonometry
Measurement of IOP
Acceptable methods - rebound, applanation, indentation
Abnormalities - absolute numbers, differences in eyes
Role of tonometry
Primary DX for assessing glaucoma therapy
IOP varies during the day and from day to day
Gonioscopy
Examination of drainage angle
Requires specialized lens
Helps determine likelihood of primary glaucoma based on angle morphology
Goals of therapy
Maintenance of vision where possible
Patient comfort
Prophylaxis in “at risk” eyes
Types of glaucoma treatment
Emergency management
Maintenance therapy
Salvage procedures
Emergency management
Systemic hyperosmotic meds - IV mannitol, oral glycerin - quick but short acting
** contradicted for cardiovascular cases**
Topical prostaglandin analogue - Latanoprost
Maintenance meds
CAI - carbonic anhydrase inhibitors
Very effective drug class - used in all species for all forms of glaucoma w topical or systemic
ADR - GI upset, panting, lethargy
Topical analogues
Mitotic and prostaglandin analogues - moderate, avoid if glaucoma is secondary to uveitis or anterior lens lux due to ocular side effects
B-blockers
Topical drug for maintenance
Mildly effective, not adequate alone, side effects
Medical prophylaxis
Significantly delays onset of disease in second eye of dogs w primary glaucoma
Meds : topical miotics, CAI or b blockers can help
Treatment principles
Treat aggressively early in disease
Target IOP <20mmHg
DO NOT taper meds in “well controlled” cases
Consider surgery if available in early stages
Manage underlying ocular disease or secondary cause
** do not use atropine except in horses
Surgical management
Decrease aqueous production
Cyclodestructive procedures - cyclophotocoagulation, cyclocryotherapy
Increase aqueous outflow - filter /shunts
Prognosis for glaucoma
Long term vision - poor
Blind within several months, surgery could prolong
Salvage surgical procedures - consider blind eyes
Salvage procedures
Enucleation
Evisceration/intrascleral prosthesis
Chemical ciliary body ablation
Chemical ciliary body ablation
Intravitreal gentamicin injection
- 20-30mg +/- steroids
Blind eyes only
DO NOT puncture lens
Potential complications/not 100%
Secondary glaucoma common in terriers
Melanocytic glaucoma
Secondary glaucoma common in golden retrievers
Pigmentary uveitis
