Glaucoma Flashcards
Define glaucoma
Optic neuropathy with field defect usually associated with ocular hypertension (intra-ocular pressure >21mmHg)
What is the difference between acute-closure and open-angle glaucoma
Acute-closure glaucoma (ACG) = reversible (appositional) or adhesional (synechial) closure of the anterior-chamber angle resulting in raised intra-ocular pressure (IOP)
Open-angle glaucoma = Open-angle glaucoma is characterised by an anatomically open angle but with an obstructed and slowed drainage system outflow
Aetiology of glaucoma
Primary causes:
=> Acute closed-angle glaucoma: thick cataractous lens | ectopic lens | DM | ocular ischaemia
=> Primary opened-angle glaucoma: neurodegenerative process where retinal ganglion cells degenerate | Associated with GLC1A and myocilin mutations
Secondary causes: Trauma Uveitis Steroids Rubeosis iridis (DM, central retinal vein occlusion)
Congenital
Buphthalmos
Inherited ocular disorders
Risk factors for glaucoma
Female Hyperopia Shallow peripheral anterior chamber Afro-Caribbean, myopia : open angle Asian, hyperopia: Close angle Older age Family history DM Medications that induce angle narrowing e.g. anticholinergics - atropine, sulphonamide, phenothiazines
Epidemiology of Glaucoma
Glaucoma is the second leading cause of blindness in the world, with open-angle glaucoma being the most common type.
Primary open-angle glaucoma is the most common type of glaucoma, accounting for around 70% of cases
1/3 of cases are from primary angle-closure glaucoma, and half of the cases that lead to blindness stem from this
F > M more acute closed angle glaucoma
Symptoms of acute closure Glaucoma
Severe pain (ocular/headache) REDUCED visual acuity , usually unilateral Eye redness Halos around lights Aching eye or brow pain Headache Nausea & vomiting Symptoms worse with mydriasis (e.g. watching tv in dark room)
Symptoms of open angle Glaucoma
Usually asymptomatic|
Peripheral visual field loss may be noted
Usually bilateral
Halo arounds lights
Signs of acute closure Glaucoma
Red eye Loss of red reflex Fixed and dilated pupil Moderately raised IOP Corneal oedema: hazy cornea Eye tender and hard on palpation Cupped optic disc Visual field defect (arcuate scotoma)
Signs of open angle glaucoma
Optic disc may be cupped Usually no signs Cup to disc ratio > 0.4 Notching of optic nerve cup Peripheral vision loss Increased IOP Scotoma - tunnel vision Loss of nerve fibre layer Retinal haemorrhages
Investigations for acute closure glaucoma
Gonioscopy, examination of anterior chamber: Trabecular meshwork is not visible in angle closure, because the peripheral iris is in contact with it (definitive)
Slit-lamp examination: Shallow anterior chamber | signs of glaucoma: large optic cup, narrowing of the neuroretinal rim, splinter haemorrhage, nerve fibre loss
Automatic static perimetry: ?Visual field defects
Investigations for open angle glaucoma
Tonometry: Intra-ocular pressure elevated if above normal range: 10 mmHg and 21 mmHg
Direct ophthalmoscopy: Cup-to-disc ratio over 0.6/asymmetry >0.2 may be suspicious of glaucoma | flame haemorrhages in late disease
Slit-lamp biomicroscopy: Cornea should be clear, anterior chamber should be deep, and drainage angle should be open
Visual Field testing: Scotomas indicating loss of the nerve fibre layer
