Glaucoma Flashcards
what produces aqueous fluid
ciliary bodies
where is aqueous fluid secreted + how
posterior chamber, 50% diffusion, 50% active secretion
how does aqueous fluid drain from the anterior chamber
via trabecular meshwork, into the canals of schlemm, then to the collecting channels into the venous system
what is aqueous used for
maintain IOP for eye shape, as well as providing nutrition to the cornea and removing waste
what is the average IOP
15.5
whats the normal range of IOP
10-21 mmHg
what is progressive open angle glaucoma
chronic increase in IOP leading to a loss of retina/nerve fibres + optic disc cupping, causing peripheral vision loss which may progress to total blindness
what is the most common type of glaucoma
progressive open angle glaucoma
what are risk factors of progressive open angle glaucoma
increased intraocular pressure FHx (most important) myopia afrocaribbean diabetes `
what % of people >40 and >75 have progressive open angle glaucoma
1% >40 ,5% >75
what is seen on fundoscopy when looking at an eye with progressive open angle glaucoma
optic disc atrophy (border blurring)
cupping (increased cup to disc ratio)
what is acute angle closure glaucoma
acute increased pressure causing pain, blurred vision , corneal odema, red eye and a fixed, mid-dilated pupil
what is the pathology of acute angle closure glaucoma
lens increases with age and pushes iris closer to the trabecular meshwork, at a critical point the iris blocks off the drainage causing a blockage and rapid rise in intraocular pressure
why may acute angle closure glaucoma be helped by going to bed
causes the pupil to constrict, causing iris to be pulled away from sides of eye, decreasing the blockage and allowing drainage - this means symptoms may be present for weeks before a full attack occurs
why may acute angle closure glaucoma be helped by going to bed
causes the pupil to constrict, causing iris to be pulled away from sides of eye, decreasing the blockage and allowing drainage - this means symptoms may be present for weeks before a full attack occurs
how do you treat acute angle closure glaucoma
pilocarpine/acetazolamide to shrink pupil
IV Diamox and mannitol
BILATERAL laser iridotomy or trabeculotomy allows drainage - bilateral = preventative
what is rubeotic glaucoma
complication of central retinal vein occlusion or diabetic retinopathy, where neovascularisation near the iris causes occlusion of the trabecular network causing rapid increase in IOP
what are the symptoms of rubeotic glaucoma
pain decreased VA red eye corneal odema rubeosis (neovascularisation of the iris - looks like a red ring) pupil distortion
how does each untreated IOP over the threshold relate to prognosis for vision
IOP >30 = blind in 3 years
IOP 25-30 = blind in 6 years
IOP 21-25 = blind in 15 years
how are visual fields mapped + which is more common now
Goldmann perimetry or automated perimetry (automated more common now)
how does goldmann perimetry work
hollow white bowl is placed in front of patient and lights of varying size and intensity are presented and the patient must say if they can see it
these are then mapped on a diagram
how does automated perimetry work
similar to goldmann perimetery i that they look at a blank screen with a light on it but the machine moves the lights automatically and the machine has a button to press when the light is seen, this then automatically maps the visual field
what eye drops are available for glaucoma treatment
prostaglandin analogues - latenoprost beta blockers carbonic anhydrase inhibitors - dozolamide alpha-agonists - brimonidine cholinergic - pilocarpine
which medical treatments for glaucoma cause decreased aqueous production
beta blockers
carbonic anhydrase inhibitors
alpha-agonists (partially)
what medical treatments for glaucoma cause increased aqueous outflow
cholinergics
prostaglandin analogues
alpha-agonists (partially)
what medical treatment for glaucoma can be given in tablet form
carbonic anhydrase inhibitors
what are the surgical options for glaucoma treatment
trabeculoplasty
trabeculotomy
iridotomy
what is a trabeculoplasty
50-100 shots delivered by a laser to trabecular meshwork to increase drainage
what type of glaucoma is trabeculoplasty limited to
open angle
what is a trabeculectomy
controlled fistula created where aqueous leaks out under conjunctiva
what is the success rate for trabeculectomy
50-90%
what are risk factors for failure for trabeculectomy
previous surgery Afro-Caribbean long term topical meds - especially pilocarpine co-existing uveitis diabetes
what are side effects of alpha blockers
dizziness
syncope
allergy
what are side effects of prostaglandin analogues
lash growth
pigmentation (usually of iris)
what are side effects of cholinergics
eye ache
headache
dim vision
what are side effects of carbonic anhydrase inhibitors
taste problem
acidosis
what kind of eye drops cause the least discomfort
preservative free
what are some new surgical techniques trialed for glaucoma
laser suture lysis
miucrotrabeculotomy
phacotrabeculotomy
what is the definition of ocular hypertension
increased IOP but no damage and full visual fields
how may people with ocular hypertension progress to glaucoma
1%
what is the normal value of the cup:disc ratio
< or equal to 0.4 (although this is contested)
if the inferior portion of the retina is damaged, what part of vision will be affected
the superior aspect
what treatment is 1st line for open angle glaucoma
prostaglandin inhibitors
what does IV mannitol do
shrinks vitreous, as it is an osmotic agent
why does an IOP >45 mean that eye drops are contraindicated
45 is the perfusion pressure of the retinal artery, so eye drops won’t be distributed if used with an IOP >45
what drugs are risk factors for causing acute glaucoma
nebulised ipratropium bromide
TCAs
anitmuscarinics
