glaucoma Flashcards
Define glaucoma
Optic neuropathy with characteristic progression of field defects
usually associated with ocular hypertension (intra-ocular pressure >21mmHg)
What is acute closed angle (closure) glaucoma
reversible (appositional) or adhesional (synechial) closure of the anterior-chamber angle resulting in raised intra-ocular pressure (IOP)
Aetiology of Acute closed angle glaucoma
Blocked drainage due to approximation of iris to cornea from the anterior chamber via the canal of Schlemm/trabecular meshwork → increased IOP → compression of the retinal nerve fibres → scotoma and visual field loss
- thick cataractous lens
- Ectoptic lens
- DM
- Ocular ischaemia
- Trauma
- Uveitis
- Steroid use
- Rubeosis iridis (DM, central retinal vein occlusion)
Risk factors for acute closed angle glaucoma
Female
Hyperopia
Shallow peripheral anterior chamber
Afro-Caribbean
Older age
Family history
DM
Medications that induce angle narrowing e.g. anticholinergics - atropine, sulphonamide, phenothiazines
Symptoms of acute closed angle 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)
Signs of acute closed angle glaucoma on examination
Red eye
Fixed and dilated pupil
Loss of red reflex
Corneal oedema: hazy cornea
Eye tender and hard on palpation
Cupped optic disc
Visual field defect (arcuate scotoma)
Investigations for acute closed angle glaucoma
Fundoscopy: Cupped optic disc
Gonioscopy: Trabecular meshwork is not visible in angle closure, because the peripheral iris is in contact with it
Slit-lamp: shallow anterior chamber, large optic cup, narrowing of neuroretinal rim
Automatic static perimetry: visual field defects
Management for acute closed angle glaucoma
- Urgent referral to ophthalmology
- Medication: Combination of eye drops, for example:
- 4% topical pilocarpine (direct parasympathomimetic → causes contraction of the ciliary muscle → opening the trabecular meshwork → increased outflow of the aqueous humour)
- Dorzolamide (topical carbonic anhydrase inhibitor → reduces aqueous formation)
- Acetazolamide (IV/PO carbonic anhydrase inhibitor → reduces aqueous formation)
- Timolol (beta-blocker→ decreases aqueous humour production)
- Apraclonidine (alpha-2 agonist → dual mechanism, decreasing aqueous humour production and increasing uveoscleral outflow) - Definitive management: Laser peripheral iridotomy
- creates a tiny hole in the peripheral iris → aqueous humour flowing to the angle
- Both eyes - Lens extraction
Define open angle glaucoma
Characterised by an anatomically open angle but with an obstructed and slowed drainage system outflow
Aetiology for open angle glaucoma
Resistance to outflow through trabecular meshwork e.g. blood, inflammatory cells→ Increased intra-ocular pressure >21 → reduced blood flow → damage to the optic nerve → optic disc atrophy and cupping
- neurodegenerative process where retinal ganglion cells degenerate
- Associated with GLC1A and myocilin mutations
- Trauma
- Uveitis
- Steroids
- Rubeosis iridis (DM, central retinal vein occlusion)
- Buphthalmos
- Inherited ocular disorders
Risk factors for open angle glaucoma
Asian
Female
Myopia
Shallow peripheral anterior chamber
Older age
Family history
DM
Medications that induce angle narrowing e.g. anticholinergics - atropine, sulphonamide, phenothiazines
Symptoms of open angle glaucoma
Usually asymptomatic
Peripheral visual field loss may be noted
Usually bilateral
Halo arounds lights
Signs of open angle glaucoma on examination
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 open angle glaucoma
Field testing: scotoma (indicates loss of nerve fibre layer)
Fundoscopy: cupped optic disc
Tonometry: IOP >21mmHg, Goldmann prism semi-circle ends do NOT line up
Direct/indirect ophthalmoscopy: Cup-to-disc ratio over 0.6, flame haemorrhages in late disease
Slit-lamp biomicroscopy: drainage angle open, cornea clear, deep anterior chamber
Management for open angle glaucoma
Long term (topical hypotensives)
1st line (one → the other → a combination of both):
Beta-blocker → aqueous production: timolol, betaxolol
Prostaglandin analogue→uveoscleral outflow: latanoprost
2nd line:
Topical alpha-2 agonist → aqueous production: brimonidine tartrate
Carbonic anhydrase-I → aqueous production: acetazolamide
Topical miotic (M3 agonist) → uveoscleral outflow: pilocarpine
Surgical (can be used 1st line over medical if desired [NEW, 2019]) → laser trabeculoplasty
- Laser treatment: Laser trabeculoplasty for POAG | iridotomy for ACAG
- Conventional: Trabeculectomy | Canaloplasty | Iridectomy facilitates outflow of aqueous humour
- 5-fluorouracil or Mitomycin may be used to reduce scarring
