glaucoma Flashcards
what is glaucoma?
a group of disorders characterised by optic neuropathy due, in the majority of patients, to raised intraocular pressure (IOP)
what happens in acute angle-closure glaucoma?
there is a rise in IOP secondary to an impairment of aqueous outflow
what factors predispose to acute angle-closure glaucoma?
hypermetropia (long-sightedness)
pupillary dilatation
lens growth associated with age
what are features of acute angle closure glaucoma?
severe pain: may be ocular or headache
decreased visual acuity
symptoms worse with mydriasis (e.g. watching TV in a dark room)
hard, red-eye
haloes around lights
semi-dilated non-reacting pupil
corneal oedema results in dull or hazy cornea
systemic upset may be seen, such as nausea and vomiting and even abdominal pain
what ix are done for acute angle closure glaucoma?
tonometry to assess for elevated IOP
gonioscopy (literally looking, oscopy, at the angle, gonio): a special lens for the slit lamp that allows visualisation of the angle
what is the mx for acute angle closure glaucoma?
urgent referral to an ophthalmologist
combination of eye drops, for example:
- a direct parasympathomimetic (e.g. pilocarpine, causes contraction of the ciliary muscle → opening the trabecular meshwork → increased outflow of the aqueous humour)
- a beta-blocker (e.g. timolol, decreases aqueous humour production)
- an alpha-2 agonist (e.g. apraclonidine, dual mechanism, decreasing aqueous humour production and increasing uveoscleral outflow)
intravenous acetazolamide
- reduces aqueous secretions
what is the definitive mx of acute angle closure glaucoma?
laser peripheral iridotomy - creates a tiny hole in the peripheral iris → aqueous humour flowing to the angle
how are glaucomas classified?
based on whether the peripheral iris is covering the trabecular meshwork, which is important in the drainage of aqueous humour from the anterior chamber of the eye
what is affected in primary open angle glaucoma?
the iris is clear of the meshwork
what does the trabecular network do?
offers an increased resistance to aqueous outflow, causing increased IOP
what are Rf for primary open angle glaucoma?
increasing age
genetics
Afro Caribbean ethnicity
myopia
hypertension
diabetes mellitus
corticosteroids
what are features of primary open angle glaucoma?
peripheral visual field loss - nasal scotomas progressing to ‘tunnel vision’
decreased visual acuity
optic disc cupping
what are fundoscopy signs in primary open angle glaucoma?
- Optic disc cupping - cup-to-disc ratio >0.7 (normal = 0.4-0.7), occurs as loss of disc substance makes optic cup widen and deepen
- Optic disc pallor - indicating optic atrophy
- Bayonetting of vessels - vessels have breaks as they disappear into the deep cup and re-appear at the base
- Additional features - Cup notching (usually inferior where vessels enter disc), Disc haemorrhages
how do you dx Case finding and provisional diagnosis is done by an optometrist
Referral to the ophthalmologist is done via the GP
Final diagnosis is done by investigations as below
Case finding and provisional diagnosis is done by an optometrist
Referral to the ophthalmologist is done via the GP
Final diagnosis is done by investigations as below
what ix are done for primary open angle glaucoma?
automated perimetry to assess visual field
slit lamp examination with pupil dilatation to assess optic nerve and fundus for a baseline
applanation tonometry to measure IOP
central corneal thickness measurement
gonioscopy to assess peripheral anterior chamber configuration and depth
Assess risk of future visual impairment, using risk factors such as IOP, central corneal thickness (CCT), family history, life expectancy
