glaucoma Flashcards
what is glaucoma?
damage to the optic nerve caused by a significant raise in IOP (intraoccqular pressure)
it’s caused by a blockade in the drainage of the aqueous humour
characteristic ‘cupping’ of nerve
loss of retinal nerve finer layer
advancing peripheral visual field loss
anatomy of the eye
vitreous chamber - filled with vitreous humor
anterior chamber- between the cornea and iris
posterior chamber- between the lens and iris *filled with aqueous humour
aqueous humor
produced by ciliary body
aqueous humour flows from ciliary body around the lens under the iris, through anterior chamber, through trabecular meshwork, into canal of Schlemm and into the general circulation
IOP
normally is 10-21 mmHg
this pressure is created by resistance to flow through the trabecular meshwork into canal of Schlemm
what is the pathophysiology of open angle glaucoma
gradual increase in resistance through the trabecular meshwork. this makes it more difficult for aqueous humour to flow through the meshwork and exit the eye so pressure slowly build in eye (chronic)
what is the pathophysiology of acute-angle closure glaucoma
the iris bulges forward and seals off the trabecular meshwork from the anterior chamber which prevents drainage and leads to a build up of pressure
*ophthalmology emergency
cupping of optic disc
increased pressure in the eye causes cupping of the optic disc. the optic cup is a small indent in the optic disc usually less than half the size the optic dic.
in raised IOP the indent becomes larger as the pressure in the eye puts pressure on the indent >0.5 size the optic disc
how does open-angle glaucoma present?
raised IOP over long period of time
routine screening idagnosis
affects peripheral vision first, then tunnel vision
fluctuating pain
headaches
blurred vision
halos around light (particularly at night time)
how to measure IOP
- non contact tanometry
shooting a ‘puff’ of air into the cornea and measuring the corneal response - goldmann applanation tonometry
special devise mounted on a slip lamp. makes contact with the cornea, applies different pressures get an accurate measurement
different ‘imaging’ of eyes
goldmann aplanation tonometry - to measure IOP
fundoscopy- to check for optic disc cupping and optic nerve health
visual field assessment- to check for peripheral vision loss
how is open angle glaucoma managed
treatment if IOP >24mmHg
- prostaglandin analogue eye drops (latanoprost) to increase uveoscleral outflow (side effect= eyelash growth, eyelid pigmentation, iris pigemtnaiton)
beta blockers (timolol) to reduce production of aqueous humor
carbonic anhydrase inhibitor (dorzalamide) (to reduce production of acquous humour)
sympathomimetics (brimonidine) to reduce production of aqueous fluid and increase uveoscleral outflow
surgery for IOP
trabeculectomy (if eye drops are ineffective)
creating new channel from anterior chamber, through the sclera under the conjunctiva
acute angle-closure glaucoma
iris bulges forward and this seals off the trabecular rmeshwork from the anterior chamber which prevents aqueous humour drainage. causes a continual build up of pressure particularly in the posterior chamber which puts more pressure on iris
- opthalmology emergency
- can lead to permanent vision loss
what are risk factors for acute angle glaucoma
Increasing age
Females are affected around 4 times more often than males
Family history
Chinese and East Asian ethnic origin. Unlike open-angle glaucoma, it is rare in people of black ethnic origin.
Shallow anterior chamber
meds that can ppt:
- Adrenergic medications such as noradrenalin
- Anticholinergic medications such as oxybutynin and solifenacin
- Tricyclic antidepressants such as amitriptyline, which have anticholinergic effects
how does acute angle glaucoma present?
Severely painful red eye
Blurred vision
Halos around lights
Associated headache, nausea and vomiting
red eye teary hazy cornea decreased visual acuity dilation of effected pupil fixed pupil size firm eyeball on palpation
