Pulse - March 2021 - 27

VETERINARY OPHTHALMIC CONSULTING

QUICK REFERENCE

Glaucoma Therapy, Part One
Sara Calvarese, DACVO
Douglas Esson, DACVO

T

he glaucomas can generally be defined as
a group of ophthalmic diseases associated
with increased intraocular pressure (IOP)
& degeneration of the optic nerve. 
Rarely, glaucomatous changes may be congenital
(present at birth), with the prognosis for affected eyes
unfortunately poor.  The primary canine glaucomas are
associated with a genetic predisposition resulting in a
series of initiating events (long & short term), impaired
aqueous outflow, increased IOP), retinal ganglion cell
death, vision loss & pain. The secondary glaucomas are
associated with chronic changes (typically uveitic), and
include pathologies associated with phacolytic uveitis (especially in rapidly forming/diabetic cataracts),
lens instability/luxation (especially affecting the terrier
breeds), pigmentary/cystic pathology (notably affecting
Cairn Terriers, Golden Retrievers and American Bulldogs), Feline Aqueous Misdirection and neoplastic diseases (commonly lymphoma, melanoma & carcinoma).
The diagnosis of glaucoma is typically made on the
basis of clinical findings as well as tonometric evaluation.
Prompt medical management to lower IOP, decrease
intraocular inflammation, improve patient comfort, and
provide neuroprotection when possible is essential in the
initial treatment of glaucoma. Rapid lowering of IOP
can be achieved via the intravenous administration of
mannitol. Mannitol is an osmotic diuretic, a large molecule that increases the osmotic pressure of plasma relative
to the aqueous and vitreous, resulting in dehydration &
contracture of the vitreous, allowing the iris and lens to
move posteriorly, opening the iridocorneal angle. Mannitol is generally considered safe to administer in diabetics
but is contraindicated in cases of renal failure, dehydration, and severe cardiovascular disease. 
Glycerin is an osmotic diuretic which can be administered orally. It is metabolized to glucose, however,
and should not be administered to diabetic patients.
Side effects associated with both mannitol and glycerin
administration may include vomiting, dehydration, and
electrolyte imbalances.
Following the initial stabilization of IOP, more
definitive control can be achieved by a combination
of medical and/or surgical management to decrease
aqueous production and maximize its outflow. Potentially beneficial agents when treating glaucoma include
the prostaglandin analogues (such as latanaprost), the
carbonic anhydrase inhibitors (such as dorzolamide/

PULSE

MARCH 2021

brinzolamide) and parasympathomimetic agents (such
as demacarium bromide).
Prostaglandin analogues are generally considered
ineffective in feline patients as they lack the appropriate receptors. Medications which may result in miosis
should generally be avoided if an anterior lens luxation
is suspected or cannot be ruled out.
Ongoing medical therapy is likely to be required to
maintain control over IOP & intraocular inflammation
as well as to combat subsequent degeneration of optic
nerve tissue. 
Next month's article will address additional supportive measures to consider when treating glaucoma. P
VOC is independently and family owned with compassionate,
qualified and experienced team members. Doctors Esson and
Calvarese are Board-Certified Veterinary Ophthalmologists.

27



Pulse - March 2021

Table of Contents for the Digital Edition of Pulse - March 2021

Pulse - March 2021
Chapter Meetings & Calendar
President’s Perspective
SCVMA Profile
SCVMA Profile
Pulsepoints
Practical Pathology
Veterinarians Key to Planet’s Future, UC Davis Global Health Expert Believes
Medical Leeway
UC Davis Update
Tools for Success
Angel Fund
Dear Tabby
The RVT
Industry Insights
Quick Reference
AVMA Diplomates
Digital Photography for Veterinarians
Resources
Disease Table
Classifieds
From the SCVMA Office
Pulse - March 2021 - Pulse - March 2021
Pulse - March 2021 - Cover2
Pulse - March 2021 - 1
Pulse - March 2021 - 2
Pulse - March 2021 - Chapter Meetings & Calendar
Pulse - March 2021 - President’s Perspective
Pulse - March 2021 - SCVMA Profile
Pulse - March 2021 - SCVMA Profile
Pulse - March 2021 - Pulsepoints
Pulse - March 2021 - 8
Pulse - March 2021 - 9
Pulse - March 2021 - 10
Pulse - March 2021 - Practical Pathology
Pulse - March 2021 - Veterinarians Key to Planet’s Future, UC Davis Global Health Expert Believes
Pulse - March 2021 - 13
Pulse - March 2021 - 14
Pulse - March 2021 - 15
Pulse - March 2021 - 16
Pulse - March 2021 - 17
Pulse - March 2021 - 18
Pulse - March 2021 - Medical Leeway
Pulse - March 2021 - UC Davis Update
Pulse - March 2021 - Tools for Success
Pulse - March 2021 - Angel Fund
Pulse - March 2021 - Dear Tabby
Pulse - March 2021 - 24
Pulse - March 2021 - The RVT
Pulse - March 2021 - Industry Insights
Pulse - March 2021 - Quick Reference
Pulse - March 2021 - AVMA Diplomates
Pulse - March 2021 - Digital Photography for Veterinarians
Pulse - March 2021 - Resources
Pulse - March 2021 - 31
Pulse - March 2021 - 32
Pulse - March 2021 - Disease Table
Pulse - March 2021 - 34
Pulse - March 2021 - 35
Pulse - March 2021 - 36
Pulse - March 2021 - 37
Pulse - March 2021 - 38
Pulse - March 2021 - 39
Pulse - March 2021 - 40
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Pulse - March 2021 - 45
Pulse - March 2021 - 46
Pulse - March 2021 - 47
Pulse - March 2021 - 48
Pulse - March 2021 - 49
Pulse - March 2021 - 50
Pulse - March 2021 - Classifieds
Pulse - March 2021 - From the SCVMA Office
Pulse - March 2021 - Cover3
Pulse - March 2021 - Cover4
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