Pulse - April 2021 - 24

QUICK REFERENCE

VETERINARY OPHTHALMIC CONSULTING

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

L

ast month's article discussed
approaches to lowering intraocular pressure (IOP), but
glaucoma is also a neurodegenerative disease. While medical and
surgical management may control
IOP, secondary axonal neurodegenerative effects lead to extensive
damage independent of IOP control. Adjunctive therapy to attempt
to provide some degree of neuroprotection should be considered
when managing glaucomatous
patients. Additionally, ocular inflammation and patient discomfort
should be addressed. 
Neuroprotective therapy may provide
retinal ganglion cells and their axons protection against the glutamate-mediated
toxicity found under the conditions at the
level of the optic nerve head when glaucoma occurs. Multiple medications have
been proposed to have potentially neuroprotective effects, the most studied of
which is the NMDA-receptor antagonist
memantine, which may reduce retinal ganglion cell death and functional loss under
conditions of elevated IOP. The topical
alpha-2 adrenergic agonist brimonidine
has demonstrated neuroprotective effects
experimentally but has not been clinically evaluated in veterinary patients. Additional therapies under further evaluation
for their potentially neuroprotective properties include calcium-channel-blockers,
tnfα-inhibitors, ET1-antagonists, complement-inhibitors,
cholesterol-statins,
NOS-inhibitors,
ROC-inhibitors
&
ROS-scavengers. 
Patients presenting with elevated IOP
typically also demonstrate some degree
of intraocular inflammation.  A normal
or high-normal intraocular pressure in
a patient with active uveitis may suggest
impaired aqueous drainage and impending
glaucoma. Anti-inflammatory treatment,

24

 An abbreviated summary of the pathways involved in the cellular signalling associated with glaucomatous pathology, illustrating the complex
nature of these processes and challenges associated with developing
effective neuro-proetcive strategies. 

both topically and systemically can significantly improve patient comfort and may
help to protect optic nerve cells.  Pain
associated with glaucoma will only fully
subside when the IOP is controlled, however, providing systemic analgesia is an
important part of glaucoma therapy. Topical NSAIDS have not been shown to
provide suitable analgesia and have been
demonstrated to elevate IOPs in some
cases.
Anti-inflammatory therapy may also be
beneficial when instituting prophylactic
therapy in goniodysgenic patients. Primary
(goniodysgenic) glaucoma is a bilateral
disease and prophylactic anti-inflammatory therapy for the normotensive eye (in
conjunction with a topical anti-glaucoma
medication) has been shown to prolong
the time to onset of symptoms in the contralateral eye.  
Ultimately glaucoma typically becomes
a surgical disease in veterinary medicine.  Medical therapy to address glaucoma may allow a client time to evaluate

surgical options, provide the patient with
increased comfort, may temporarily
restore vision in some cases and may successfully prolong the time to onset in the
fellow normotensive eye.  
Rational glaucoma therapy should
encompass consideration of anti-inflammatory and potentially neuroprotective
modalities.  P
VOC is independently and family owned with
compassionate, qualified and experienced team
members. Doctors Esson and Calvarese are
Board-Certified Veterinary Ophthalmologists.

APRIL 2021

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Pulse - April 2021

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