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Flashcards in glaucoma Deck (38):
1

Aqueous humor dynamics

aqueous humor produce in ciliary body

passive and active process

active-most important, secretion against concentration gradient

2

Circulation of aqueous humor

secretion into posterior chamber

enters anterior chamber through pupil

circulates within anterior chamber

exits anterior chamber via iridiocorneal angle

3

aqueous humor conventional outflow

from ICA into intrascleral venous plexus the into vortex veins

accounts for majority of aqueous humor outflow

4

aqueous humor unconventional outflow

uveoscleral outflow

through iris root into supraciliary and suprachoroidal space

accounts for less aqueous humor outflow

5

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

6

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

7

acute glaucoma

episcleral venous congestion

corneal edema

mydriasis

blepharospasm

epiphora

optic nerve pallor

blindness

usually a dog

8

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

9

dx of glaucoma

signalment

hx

clinical sxs

tonometry

gonioscopy-primary vs secondary

10

types of tonometry

indentation-Schiotz

applanation-Tono-penVet

Rebound-TonoVet

11

Schiotz tonometer

measures force required to indent cornea

topical anesthesia req

positioning is challenging

not recommended for weak corneas

Reasonable estimation of IOP

12

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

13

rebound tonometry

measures return bounce of probe from cornea

can be used on diseased corneas

accurate and reproducible readings

14

15

primary glaucoma

genetic dog disease

bilateral

primary open angle glaucoma<

Females>males

16

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

17

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

18

most common presentation of primary glaucoma

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

19

secondary glaucoma

cats & horses

unilateral or bilateral

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

20

intumescent lens

swelling of lens due to increased fluid content

forward displacement of lens

narrowing or closure

21

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

22

secondary glauoma presentation

may be acute or chronic

affected eyes may be visual or blind

one or both eyes affected

cats, dogs and horses

23

goals of medical therapy 

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

preservationo of vision

comfort

24

two main mechanisms for medical therapy

reduce aqueous humor production

increase aqueous humor outflow

25

main class of drugs used to tx glaucoma

osmotic diuretics

beta blockers

carbonic anhydrase inhibitors

prostaglandin analogues

26

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

27

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

28

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

29

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

30

surgical therapy goals

reduce and maintain IOP within normal limits

preservation of vision

comfort

still need medical management

31

surgical therapy indications

glaucomatous eye for which medical management is no longer effective

visual eye

32

surgical therapy main mechanisms

reduce aqueous humor production

increase aqueous humor outflow

33

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

34

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

35

when is salvage procedures indicated?

glaucom a that presents chronically

when medical and surgical management fail

36

enucleation

removal of globe, eyelid margins, conjunctiva and third eyelid

potential complications: very uncommon, wound infection, woud dehiscence, blindness of fellow eye

37

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

38

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