signalment hx clinical sxs tonometry gonioscopy-primary vs secondary

glaucoma Flashcards by Jessica Ernst

Aqueous humor dynamics

aqueous humor produce in ciliary body

passive and active process

active-most important, secretion against concentration gradient

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Circulation of aqueous humor

secretion into posterior chamber

enters anterior chamber through pupil

circulates within anterior chamber

exits anterior chamber via iridiocorneal angle

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aqueous humor conventional outflow

from ICA into intrascleral venous plexus the into vortex veins

accounts for majority of aqueous humor outflow

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aqueous humor unconventional outflow

uveoscleral outflow

through iris root into supraciliary and suprachoroidal space

accounts for less aqueous humor outflow

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intraocular pressure

normal 10-25 mmHg

should not vary between eyes by more than 20%

balance between aqueous humor production and outflow

diurnal and seasonal fluctuation

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glaucoma definition

IOP>30 mmHg

elevated IOP causes death of reintal ganglion cells and their axons–>visual field loss & blindness

always due to decreased outflow

primary or secondary

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acute glaucoma

episcleral venous congestion

corneal edema

mydriasis

blepharospasm

epiphora

optic nerve pallor

blindness

usually a dog

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chronic glaucoma

episcleral veous congestion

corneal edema

mydriasis

blepharospasm

epiphora

optic nerve pallor

blindness

buphthalmos

Haab’s stria

deep corneal vascularization

lens (sub)luxation

optic disc cupping

tapetal hyperreflectivity

reintal vascular attenuation

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dx of glaucoma

signalment

clinical sxs

tonometry

gonioscopy-primary vs secondary

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types of tonometry

indentation-Schiotz

applanation-Tono-penVet

Rebound-TonoVet

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Schiotz tonometer

measures force required to indent cornea

topical anesthesia req

positioning is challenging

not recommended for weak corneas

Reasonable estimation of IOP

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Applanation Tonometry

measures forse required to flatten cornea

+/- topical anesthesia

can be used on diseased corneas

easier to use than Schiotz

variable readings with inexperience

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rebound tonometry

measures return bounce of probe from cornea

can be used on diseased corneas

accurate and reproducible readings

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primary glaucoma

genetic dog disease

bilateral

primary open angle glaucoma<<primary angle-closure glaucoma>

<p>
Females>males</p>

</primary>

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primary open angle glaucoma

biochemical alterations within trabecular network

greater resistance to aqueous humor outflow

insidious bilateral IOP elevation

Clinical disease not apparent until 2-5 years of age

primary angle closure glaucoma

micromovements causing blockage at pupil

decline of meshwork facility

sudden unilateral IOP elevation

fellow eye follows in 8 months

clinical disease not apparent until 4-10 years of age

most common presentation of primary glaucoma

acute, unilateral, red, cloudy eye with a dilated, non-responsive pupil in a dog

secondary glaucoma

cats & horses

unilateral or bilateral

concurrent ocular disease-Uveitis, ocular neoplasia, lens luxation, intumescent lens, Aqueous humor misdirection syndrome

intumescent lens

swelling of lens due to increased fluid content

forward displacement of lens

narrowing or closure

aqueous humor misdirection syndrome

aka malignant glaucoma

ciliary body-vitreous-lens block

posterior flow of aqueous humor into vitreous cavity

build up of vitreous and aqueous humor pushes lens, iris and ciliary body anteriorly

pupil becomes obstructed

ICA narrows and closes

cats

secondary glauoma presentation

may be acute or chronic

affected eyes may be visual or blind

one or both eyes affected

cats, dogs and horses

goals of medical therapy

reduce and maintain IOP to level that is compatible with ocular heatlh

preservationo of vision

comfort

two main mechanisms for medical therapy

reduce aqueous humor production

increase aqueous humor outflow

main class of drugs used to tx glaucoma

osmotic diuretics beta blockers carbonic anhydrase inhibitors prostaglandin analogues

osmotic diuretics-Mannitol

osmotic gradient pulls fluid from eye-decreases ultrafiltration, shrinks vitreous volume lowers IOP within 1 hour emergency management of acute glaucoma caution: less effective in inflamed eye, avoid in CV dz, deh p, CKD can cause cerebral deh--\>nausea, vomiting and altered consciousness

Beta blockers-Timolol 0.25%, 0.5%

decreases aqueous humor production BID use for prophylactic tx of unaffected, fellow eye in primary glaucoma, maintenance therapy (with CAI) caution: CV dz, bronchial asthma, cats, small dogs

carbonic anhydrase inhibitors-

decrease aqueous humor production combine with beta blockers Dorzolamide-topical systemic-Methazolamide, Acetozolamide maintenance therapy caution: cats, diuresis, GI disturbance, Metabolic acidosis, hypokalemia

Prostaglandin analogues

increase uveoscleral outflow and decrease aqueous production latanoprost, travaprost, bimatoprost, unoprostone topical SID, BID rapid reduction in IOP DOGS ONLY! maintenance and emergency cases caution: extreme miosis occurs

surgical therapy goals

reduce and maintain IOP within normal limits preservation of vision comfort still need medical management

surgical therapy indications

glaucomatous eye for which medical management is no longer effective visual eye

surgical therapy main mechanisms

reduce aqueous humor production increase aqueous humor outflow

laser cyclophotocoagulation

destruction of ciliary body processes--\>decreased aqueous humor production fair to good for maintenance of IOP Adverse effects: post-op IOP spike (manage with meds), uveitis, cataract, staphyloma, retinal detachment, ciliary body process regrowth, phthisis bulbi

anterior chamber shunt

silicone tube in AC drains fluid outside of the eye primary glaucoma in dogs fair for control of IOP adverse effects: obstruction, implant migration

when is salvage procedures indicated?

glaucom a that presents chronically when medical and surgical management fail

enucleation

removal of globe, eyelid margins, conjunctiva and third eyelid potential complications: very uncommon, wound infection, woud dehiscence, blindness of fellow eye

evisceration and prosthesis

removal of ocular contents, leaving only cornea and sclera prosthesis put in complications: KCS, delayed/impaired health of corneal ulcers, dehiscence of surgical site extrusion of implant

intravitreous gentamicin

Gentamicin is toxic to ciliary body and retina combined with dexamethasone to decrease inflammation indicated only if general anesthesia can't be performed/finances 65% success rate caution-renal disease, ocular sarcoma