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