Glaucoma Flashcards
what is glaucoma?
Progressive optic neuropathy
Characterised by optic nerve head (disc) changes and corresponding visual field loss
Raised intraocular pressure
how does glaucoma occur?
poor aqueous production + drainage:
Anterior chamber angle – angle between cornea + iris, contains trabecular meshwork
Ciliary body – produces aqueous => post chamber (behind iris) => through pupil => anterior chamber
how does aqueous humor outflow?
- uveoscleral 25%
- trabecular 75%
where does trabecular aq. humor outflow?
drains into the episcleral circulation
where does uveoscleral aq. humor outflow?
drains into the choroidal circulation
describe the intraocular pressure (IOP)
balance between inflow and outflow of aqueous humor
what is the ideal IOP?
11-21 mmHg
what IOP indicated high risk glaucoma?
21 mmHg
what can cause IOP fluctuations
- time of day
- heartbeat
- blood pressure
- respiration
what are the different types of glaucoma?
- primary open angle glaucoma
- primary angle closure glaucoma
- secondary open angle glaucoma
- secondary angle closure glaucoma
describe primary open angle glaucoma
most common
abnormal resistance of aqueous outflow causing high pressure induced ischemia of optic nerve reducing axoplasmic flow
primary open angle glaucoma risk factors
smoking
diabetes
hypertension
high cholesterol
short-sighted
mechanism of action of primary open angle glaucoma
acute/chronic
sudden raise in IOP caused by …
1. narrow drainage angle between the cornea and iris
2. fluid cannot exit through trabecular meshwork/ schlemm’s canal
describe secondary open angle glaucoma
blockage of trabecular meshwork
e.g. cells/proteins, blood, tumour cells, corticosteroids
describe secondary closed angle glaucoma
narrowing /closure of angle
e.g. due to tumour pushing iris/lens forward, new blood vessels, forming fibrous tissue = restricting drainage
clinical features of glaucoma
enlarged cup with little neuroretinal ring
what is the treatment of glaucoma
- eye drops/topical
- systemic
- laser
- surgery
describe glaucoma eye drops/topical treatment
- prostaglandin analogues
- beta-blockers
- carbonic anhydrases inhibitors
- sympathomimetics
- miotics
describe glaucoma systemic treatment
- carbonic anhydrase inhibitors
- osmotics
what is the mechanism of action of prostaglandin analogues
increase uveoscleral outflow to increase drainage and decrease IOP
what are the side effects of prostaglandin analogues
- red eye
- pigmentation - iris/skin/lash thickening/lengthening
name examples of prostaglandin analogues
latanoprost
bimatoprost
travoprost
what is the prostaglandin analogues indication
ocular hypertension/glaucoma for the treatment of open angle glaucoma
what is the mechanism of action of beta blockers eye drops
reduce aqueous production in the ciliary body
what are the contraindications of beta blocker eye drops
asthma
COPD
heart block
bradycardia
heart failure
what are side effects of beta blocker eye drops
- allergic conjunctivitis
- bronchospasm
- CV: bradycardia/ heart block/ hypotension
- lethargy
- glucose intolerance
- impotence
what are examples of beta blocker eye drops
timolol
levobunolol
what is the mechanism of action of carbonic anhydrase inhibitor
decrease aqueous humour production in ciliary body
what are the contraindications of carbonic anhydrase inhibitors
- sulphonamide sensitivity
- liver failure (acetazolamide)
- renal failure (acetazolamide)
what are the side effects of carbonic anhydrase inhibitors
- topical burning/ watery eyes
- allergic conjunctivitis
- systemic:
- lethargy/depression
- metallic taste
- metabolic: hypokalaemia
- blood dyscrasia
what the examples of carbonic anhydrase inhibitors
topical:
- dorzolamide
- brinzolamide
systemic:
- acetazolamide (IV/PO)
name acetazolamide interactions
thiazide diuretics - profound hypokalaemia
name the mechanism of action of alpha-2 agonists
- decrease aqueous production
- increase uveoscleral outflow
name side effects of alpha-2 agonists
- allergic conjunctivitis
- systemic
- bradycardia/ hypotension
- insomnia/irritability
- GI disturbances
name which glaucoma drug at high risk of allergic conjunctivitis
alpha-2 agonists
name examples of alpha-2 agonists
brimonidine
apraclonidine
what are the MOA of apraclonidine
temporary lowering IOP causing increase side effects
e.g. allergic conjunctivitis and red eye
what is the mechanism of action of miotic
- contraction of ciliary muscle = opens trabecular meshwork = increasing trabecular outflow
- iris constriction may pull the iris away from angle
what are the side effects of miotics
- sweating/salivation
- nausea
- headache
- bradycardia
name examples of miotics
pilocarpine
what is the mechanism of action of osmotics
water drawn out of vitreous into blood by gradient = decreasing vitreous volume = lowering IOP
name side effects of osmotics
cardiovascular/ fluid overload
urinary retention
name contraindications of osmotics
cardiac disease/ heart failure
name examples of osmotics
IV mannitol
oral glycerol
