glaucoma Flashcards
what is gonioscopy ?
used to evaluate eye’s drainage angle
anterior chambre angle
what is the pathology behind glaucoma ?
chronic progressive optic neuropathy resulting in progressive irreversible vision loss
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increased intraocular pressure
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loss of retinal ganglion cells causing disc cupping
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associated visual field loss
what are the main subtypes of glaucoma ?
open angle glaucoma
angle closure glaucoma
secondary glaucoma
congenital glaucoma
what is normal tension glaucoma ?
a subtype of primary open angle glaucoma
where is the aqueous humor produced ?
ciliary bodies, specifically by pars plicata
what is the normal pathway of the aqueous humor ?
1.after being secreted by the ciliary bodies
2.passes from the posterior chamber to the anterior chamber
3. in front of the lens , via the pupil
4. drained at the trabecular meshwork at the angle of anterior chamber
5. passes through the canal of schelmn
what is the course of open angle glaucoma ?
chronic and slowly progressive
what is the presentation of open angle glaucoma ?
silent condition
usually asymptomatic
what are the risk factors associated with open angle glaucoma ?
increased intra-ocular pressure
aging
positive family history ( 1st degree relatives)
afro-caribbeans
central corneal thickness less than 555
high myopia, diabetes or hypeeertension
eye injury or surgery
what examinations are to be performed on a glaucoma patient ?
fundus examination
tonometry
gonioscopy
humphry visual field
what is the management stratergy for open angle glaucoma ?
halt optic nerve damage by reducing IOP
what are the treatment options regarding open angle gluacoma ?
medications
laser
filtration surgery
what are the different medications that can be usedd for open angle glaucoma ?
prostaglandin analogue
beta blocker
selective a2 receptor agonist
carbonic anhydrase inhibitor
why are prostaglandin analogues used ?
first line treatment
to increase uveoscleral outflow
which prostaglandins are used ?
latanoprost and bimatoprost
what are the side effects of using prostaglandin analogues ?
pigmentation
increase eyelash length
stinging sensation
what are the contraindications to using beta blockers ?
timolol
in asthmatics, COPD and heart block
what is the mechanism of action that occurs when using beta blockers in glaucoma ?
reduction on aqueous humor production
what selective a2 receptor agonist is used ?
brimonidine
what are the side effects associated with selective a2 receptor agonists ?
lethargy
dry eyes
dry mouth
allergy
what is the mechanims of action associated with carbonic anhydrase inhibiitors ?
reduced production of aqueous humor
dorzolamide
brinzolamide
why is high myopia associated with an increased chance of glaucoma ?
due to the increased axial length which lead to tilting of the optic disc and hence the optic nerve putting it at a higher risk of damage
what surgeries are performed for open angle glaucoma ?
- trabeculoplasty to provide an alternative pathway for the passage of the aqueous humor
- trabeculectomy to insert a shunt
what are the risk factors associated with angle closure gluacoma ?
hypermetropia
cataracts
mydriatics
abnormal iris configuration
asian ethnicity
elderly females
what are mydriatics ?
eye drops that dilate the pupil
how does an abnormal iris configuration cause a closed angle ?
1.plateau iris syndrome , on dilatation the iris folds into the angle and blocks the trabecular meshwork
2.. pupillary block - iris adhered to the lens blocking the flow of the aqueous humor ( posterior synechiae)
what are the symptoms of angle closure gluacoma ?
sudden onset of pain
blurred vision
colored halos around light
frontal headache
nausea and vomiting
what are the signs associated with closed angle glaucoma ?
IOP more than 40 mmgh
corneal oedema
limbal hyperemia
fixed mid-dilated pupil
shallow anterior chamber
closed angle on gonioscopy
what is the normal IOP ?
11-21 mmhg
what is the systemic treatment for angle closure glaucoma ?
refer to opthalmologist - medical emergency
1. IV Carbonic anhydrase inhibitor (CAI) Acetazolamide 500mgs.
2. PO Acetazolamide 500mgs
3. Anti-emetics
4. IV mannitol or Oral glycerol
what is the definitive treatment for angle closure glaucoma ?
peripheral laser iridotomy
lens extraction (to open the angle and deepen the AC)
surgical trabeculectomy or iridectomy
what are the three methods of drainage of aqueous humor in the eye ?
trabecular outflow ( 90% )
uvoscleral drainage
iris
what is the key modifiable factor in glaucoma ?
intra-ocular pressure
what is the normal cup:disc ratio ?
0.3
what is the cup: dic ration in glaucoma ?
more than 0.7 is usually indicative of glaucoma
what is the cup and what is the disc ?
cup : head of optic nerve
dic : neuro-retinal rim
