Glaucoma Flashcards
What is the optic disc
where all the retinal nerve fibres converge to exit the eye in the optic nerve.
What field defect would you expect if a patient developed damage to the nerve fibres at 12 o’clock on the optic nerve?
An inferior arcuate loss. (superior retina corresponds to inferior part of visual field)
wHAT IS GLAUCOMA
Progresssive optic neuropathy causing specific optic nerve abnormailites - optic disc cupping - and field defects - arcuate field defects
Signs of glaucoma
Optic disc cupping
Field defects
Raised IOP
Why does the cup get bigger in glaucoma
Lose retinal nerve fibres - these axons degenerate, neuro-retinal rim shrinks (width around the disc) → cup gets bigger
Normal cup disc ratio
less than 0.5
What is most common field loss in glaucoma and why?
Arcuate - loss of inf (first to be dmaaged) or sup nerve fibres
How is IOP maintained
Ciliary body -> aqeous -> ant chamber eye
Trabecular meshwork in drainage angle -> schlemms canal -> venous system
Normal IOP
14-22 mmHg
Why is rais IOP ass w glaucoma?
Raised IOP casues damage to nerve fibre layer and optic disc → visual defects = glaucoma
Conditions when IOP and glaucoma unrelated
(If no damage -> ocular HPTN, damage w normal IOP - normal tension glaucoma)
What causes primary open angle glaucoma?
Blockage in trabecular meshawork or Schlemms canal causes IOP to rise
Which glaucomas are painful?
Acute angle closure glaucoma, uveitis, acute rubeotic glaucoma
Treatment for acute angle closure glaucoma
IV Diamox, pilocarpine drops, followed by laser treatment (prevents recurrence)
Drugs causing acute angle closure glaucoma
anti-depressants, anti-psychotics, anti-epileptics, benzodiazepines, asthma and GORD drugs, pupil dilators for fundoscopy
Symptoms of acute angle closure glaucoma
acute rise in pressure. This is acutely painful, is red, the patient often feels systemically unwell and their vision deteriorates.
Congenital glaucoma
“buphthalmos
Cloudy cornea
Intense photophobia
Blepharospasm
Watering eyes
Why review ocular HPTN?
10% chance of becoming primary angle glauocoma
Risk factors for normal tension glaucoma
Migraine, raynauds, women
Gold standard for glaucoma investiaggtion
Goldmann tonometer
Investigations ofr glaucoma
Goldmann tonometer
Gonioscopy
Optical cpherence tomography
What is gonioscopy?
View angle structure with mirrored lens
What does Optical coherence tomography (OCT) assess
Objective measurements of disc cupping
Assess nerve fibre layer
OCT highlights areas where the nerve fibre layer and optic disc rim are thinned in comparison to normal data, monitor progression of disc cupping
Benefits of OCT
It easy to perform taking a matter of seconds. It is totally safe and non-invasive, there is no harmful radiation.
Differntials causing optic disc cupping/sectoral pallor of optic nerve
- physiological disc cupping
- congenital abnormalities of the optic nerve
- retinal vascular occlusions
Other causes of peripheral field loss
- congenital abnormalities of the optic disc
- retinal vascular occlusions
- bitemporal hemianopia (optic chiasm compression)
- retinitis pigmentosa
What does glaucoma prognosis depend on?
- age at onset
- level of loss at diagnosis
- starting IOP ( the higher the more treatment that may be needed)
- type of glaucoma
- response to treatment
- ethnic origin
What topical treatments improve drainage in glaucoma?
Prostaglandin analogues - iatanoprost
Symphamomimetics - brimonidine
Miotics - pilocarpine
What topical treatments reduce aqeous production in glaucoma?
Beta blockers - timolol
Carbonic anhydras inhibitors - brinzolamide
Laser options for glaucoma
Selective laser trabeculoplasty (SLT)
Argon lasertrabeculoplasty (ALT)
What is optic disc cupping?
Thinning of the neuro-retinal rim
Acute angle glaucoma symptoms
Acute painful red eye
Pain often severe ass w headache, nausea, vomitting
Impaired visual acuity and lights surrounded by haloes
Semi dilated and fixed pupil
Tender, hard eye - palpate v gently - raised IOP
Precipitating factors acute angle glaucoma
Watch TV dark room
Semi-prone position
Use of adrenergic drug eg phenylephrine
Antimuscarinic drug eg tricyclic antidepressant
What causes haloes?
hazy oedematous cornea
Signs of chronic PAG
Increased IOP
Visual field defects
Cupped optic disc
Signs of angle closure on gonioscopy
What glaucoma is a medical emergency?
Acute angle glaucoma
1st line oral med for actue angle glaucoma
Acetazolamide 500mg
Antiemetic and anaglesia if required
What IOP requires starting preventative treatment?
24mmHg
SLT - selective laser trabeculoplasty
