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Glaucoma (Pathophysiology (Anatomy
Anterior chamber is fluid filled space…
Glaucoma
Pathophysiology
Anatomy
Anterior chamber is fluid filled space between cornea and iris
Anterior chamber angle is angle betw iris and cornea, where they join the sclera
Posterior chamber is small fluid filled space between iris and lens
Aqueous physiology
Produced by ciliary body (CA has key role)
Secreted into posterior chamber, flows through pupil to anterior
Drains out of eye mostly via trabecular meshwork (canal of Schlemm) then episcleral circulation (90%)
10% drains via uveoscleral circulation (venous circulation of iris, ciliary body, sclera)
Aqeous secretion controlled by SNS activation of ciliary body; increased by B-2, decreased by A-2
IOP
Balance of production and outflow of aqueous homour
Maintains shape of globe
Normal 10-21 mmHg, diurnal variation
Glaucoma
Pressure >21 mmHg with signs/symptoms
Can get signs/symptoms with normal IOP in minority
Raised IOP can damage optic nerve or vessels supplying the nerve
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Diagnosis
Examination
CN examination
POAG: reduced acuity, visual field defects, normal pupil reflexes and movements
PACG: reduced acuity, hazy cornea, mid-dilated oval pupil
Fundoscopy
POAG: cupped disc, inc cup:disc ratio, disc pallor, asymmetrical disc, nasal shift of vessels, retinal haemorrhages
AACG: red eye, corneal oedema, mid-dilated oval pupil
External eye examination
POAG: nil
PACG: red eye, fixed semidilated pupil (vertically oval),
tender, hard eyeball
Investigations
Special tests
Goldman tonometry: high IOP
Goinoscopy: open/closed drainage angle
Goldman/Humphrey perimetry: reduced visual fields; initial step defect, then arcuate scotoma, temporal and central islands, complete loss
History
DH
Steroids, other meds, allergies
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PMH
Ocular (miopia/hypermetropia),
cataracts, CVD, eye trauma
SH
Occupation, living arrangements,
driving, smoking, alcohol
PC/HPC
POAG: asymptomatic, gradual reduced peripheral vision
AACG: sudden onset painful red eye, misty vision, N+V,
haloes around lights/glare, triggered in evening
(dilated eye, reduced angle)
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Prognosis
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POAG
Without treatment, progresses slowly with
irreversible loss of vision (peripheral then central)
Treatment delays progression
PACG
Without treatment, can progress to blindness
Outcome good with treatment (prevents further progression)
Definition
Glaucoma
Group of eye diseases characterised
by increased IOP leading to
progressive optic neuropathy
and visual field defects
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Classification
Open angle
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Secondary (SOAG)
Vascular: ischemic neovascularisation (DM, retinal vascular occlusion)
Infection/inflammation: uveitis
Trauma: trauma to drainage structures
Drugs: steriod induced
Congenital: rare
Closed angle
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Secondary (SACG)
Infection/inflammation: chronic anterior uveitis
Trauma: subluxated lens
Degenerative: cataract
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Management
PACG
Medical
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CA inhibitor
Indication: ASAP
E.g. acetazolamide PO/IV
MOA: reduces production of aqueous
SEs: allergic reactions, GIT upset, lethargy, parasthesia, hypokalemia, renal stones, loss of libido
Analgesia
Indication: pain
E.g. paracetamol, ibuprofen, codeine
Antiemetic
Indication: nausea
E.g. cyclizine, ondansetron
Surgical
Laser iridotomy
Indication: definitive tx
MOA: laser creates hole in iris to
allow drainage of aqueous into anterior chamber;
usually prophylactically treat other eye
Iridoplasty
Indication: iridotomy failure
MOA: aids iris shrinking away from trabecular
meshwork, increasing the drainage angle
Peripheral iridectomy
Indication: failure iridotomy
MOA: removal of small section of
iris to aid aqueous drainage
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POAG
Conservative
Information, advice, support
Refer to ophthalmology
Driving advice
Monitoring (IOP, optic disc, visual fields)
Medical
Topical prostaglandin analogue
Indication: 1L POAG (alone or plus B-blocker)
E.g. Latanoprost
MOA: increases aqueous drainage (uveoscleral)
SEs: conjunctival hyperemia, colour change iris blue-brown, hypertrichiasis (long thick eyelashes)
Topical B-blocker
Indication: 1L POAG (alone or plus a PG)
E.g. timolol
MOA: blocks B-adrenergic activation,
reducing production of aqueous
SEs: bronchospasm, bradycardia, hypotension, arrhythmia
CI: COPD, asthma, bradycardia
Topical A-agonist
Indication: add on treatment
E.g brimonidine
MOA: reduce aqueous production
and increase drainage
SE: allergic reactions (rare)
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Surgical
Trabeculectomy
Indication: medical tx fails/not tolerated
MOA: small hole (bleb) created in sclera to allow
drainage from anterior chamber into
blood supply of the conjunctiva
Drainage shunt
Indication: medical tx fails/not tolerated
MOA: small flexible tube inserted through sclera into
anterior chamber, allows aqueous drainage;
some have pressure valves to regulate drainage
Laser trabeculoplasty
Indication: medical tx fails/not tolerated
MOA: selective laser, argon laser, micropulse laser;
burn holes in trabecular network aiding drainage
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