Glaucoma Flashcards
Define glaucoma
progressive optic neuropathy associated with characteristic structural damage to the optic nerve and associated visual dysfunction
Describe the route of signals from the retina to the brain
rods and cones
photoreceptors
bipolar cells
ganglion cell layer
optic nerve
brain
Pathology of glaucoma
death of retinal ganglion cells
What is it called when a patient has glaucoma despite normal intraocular pressure?
normal tension glaucoma
What is it called when a patient has high intraocular pressure but no glaucomatous damage is present?
ocular hypertension
How do you calculate ocular perfusion pressure?
2/3xMAP - IOP
(MAP = DBP + [1/3(SBP-DBP)])
Glaucoma risk factors
high intraocular pressure
age
genetics/family history
myopia (short-sightedness)
vascular/haematological
Normal intraocular pressure range
10-21 mmHg
Describe aqueous drainage
85% through conventional pathway - IOP dependent
15% through uveoscleral pathway - IOP independent
How is glaucoma classified?
congenital vs acquired
primary vs secondary
open vs closed/narrow
Symptoms of acute primary angle closure glaucoma
pain
red eye
headache
nausea
vomiting
reduced vision
haloes
Signs of acute primary angle closure glaucoma
injected eye
corneal oedema
mid-dilated pupil
shallow anterior chamber
closed angle
raised IOP
aqueous flare and cells
Acute primary angle closure glaucoma management
Acetazolamide 500mg IV
Pilocarpine 2% drops to both eyes
Dexamethasone drops
lie patient supine
laser peripheral iridotomy = definitive
What does acetazolamide do?
causes a reduction in aqueous humour
carbonic anhydrase inhibitor
What does pilocarpine do?
allows excess fluid to drain from the eye
cholinergic parasympathomimetic agent. It increase secretion by the exocrine glands, and produces contraction of the iris sphincter muscle and ciliary muscle (when given topically to the eyes) by mainly stimulating muscarinic receptors
What equipment is used to measure intraocular pressure?
goldmann tonometer
How is glaucoma diagnosed?
IOP
angle assessment
optic disc assessment
visual field assessment
How are prostaglandin analogues useful in glaucoma treatment?
increase uveoscleral outflow
Prostaglandin analogues examples
Latanaprost, Travaprost, Bimatoprost, Tafluprost
Prostaglandin analogues side effects
red eyes
lash growth
darkening of iris colour and skin
Name some beta blockers used in glaucoma
Timolol, Betaxolol, Carteolol, Levobunolol, Metipranolol
Why are beta blockers used in glaucoma?
reduce aqueous production
Name 2 alpha-2 agonists used in glaucoma
Brimonidine, Apraclonidine
How do alpha-2 agonists help in glaucoma?
reduce aqueous production
increase uveoscleral outflow
What is the vision requirement of the DVLA for group 1 (car) driving?
car number plate at 20m
visual acuity 6/12 or better with both eyes open
no significant defect in central 20 degrees
no significant defect 120 degrees horizontal
What is the vision requirement of the DVLA for group 2 (lorry) driving?
Va 6/7.5 in best eye and other eye no worse than 6/60
refraction no worse than +8 dioptres
no defect in central 30 degrees
no significant defect 160 degrees horizontal and 30 degrees either side of horizontal
