Glaucoma Flashcards
what is the normal flow of aqueous humour?
produced by the ciliary processes in the posterior chamber. It then flows through the pupil and out through the trabecular meshwork and into the canal of Schlemm.
how does increased pressure damage the optic nerve?
o Raised intraocular pressure causes mechanical damage to axons
o Raised intraocular pressure causes ischaemia of the nerve axons by reducing blood flow at the nerve head
what is a glacuoma?
raised pressure in the eye
what are the different types of glaucoma?
Primary Glaucoma
Congenital Glaucoma
Secondary Glaucoma
what are the different types of primary glaucoma?
o Chronic open angle
o Acute and chronic closed angle
what are the different types of congenital glaucoma?
o Primary
o Secondary to maternal rubella infection
o Secondary to inherited ocular disorders
what are the different types of secondary glaucoma?
o Trauma o Ocular surgery o Associated with other ocular disease o Raised episcleral venous pressure o Steroid induced
what are the causes of chronic open angle glaucoma?
- High intraocular pressure
- Older age
- Afro Caribbean
- FH
- Myopia
- Thin cornea
- Migraine
- Systemic hypertension
- CVS disease
- Diabetes
what is the pathophysiology of chronic open angle glaucoma?
The trabecular meshwork appears normal but structurally and functionally offers an increased resistance to the outflow of aqueous.
This results in elevated ocular pressure
what is the cause of the obstruction in chronic open angle glaucoma?
o Thickening of the trabecular lamellae which reduces pore size
o Reduction in the number of lining trabecular cells
how does reduced blood flow in open angle glaucoma cause nerve loss to the optic head?
o Stretching
o Vascular compromise
o Alteration of glutamate transmitter pathways
what are the clinical features of the chronic open angle glaucoma?
- Elevated pressure
- Optic disc changes – increased cupping, vertical thinning and notching of neural rim, haemorrhage at disc , atrophy as damage progresses
- Visual loss – peripheral, central spared
what is the medical management of chronic open angle glaucoma?
o Topical B blockers
o Prostaglandin analogues
o Carbonic anhydrase inhibitors, alpha agonists
what is the surgical management of chronic open angle glaucoma?
o Trabeculectomy
o Plastic tube
o Laser procedure
acute angle glaucoma is a…
medical emergency
what are the risk factors of acute angle glaucoma?
shallow eyes, hypermetropia, a short eye, older age, presence of cataracts, small cornea, antidepressants, anticholinergics, thick glasses, steroids
what are the primary causes of acute angle glaucoma?
pupillary block, plateau iris configuration
what are the secondary causes of acute angle glaucoma?
phaemorphic, ciliochondrial expansion, lens subluxatoon, uveitis
what are the clinical features of acute angle glaucoma?
- Acute onset
- Painful
- Reduced visual acuity
- Coloured haloes around bright lights
- Headache, nausea, vomiting
- Red conjunctiva, cloudy cornea
- Pale optic disc
- Eye stony hard – blot
- Pupil mid dilated
- ICP>40
what is the management of acute angle glaucoma?
- Reduce pressure with medication then surgical iridotomy
- Medical – acetazolamide + timolol then brimodine
- Surgery – laser
what are the two mechanisms of acute angle glaucoma?
Pupillary block
Closure of outflow angle in
what is the pathophysiology of pupillary block in acute angle glaucoma?
o The lens pushes up against the back of iris blocking flow of aqueous humour through the pupil
o This resistance to aqueous flow produces a pressure-gradient across the iris
o Iris and lens are forced to move anteriorly
o Forward movement closes the irido-corneal angle and blocks the trabecular meshwork
o This causes build up of the aqueous fluid = RAPID RISE in eye pressure
what is the pathophysiology of closure of outflow angle in acute angle glaucoma?
o Hyperopic eyes which have naturally shallow anterior chambers
o When the pupil dilates the iris gets thicker and the irido-corneal angle becomes smaller and is more likely to close spontaneously
