Primary Open Angle Glaucoma Flashcards
What is glaucoma?
A group of eye conditions that lead to damage of the optic nerve and loss of retinal ganglion cells causing progressive loss of the visual fields usually due to raised intra-ocular pressure (IOP)
What can glaucoma be divided into?
- Primary vs Secondary
- Ope angle vs Closed angle
- Acute or Acute-on-chronic or Intermittent or Chronic
What is primary open angle glaucoma characterised by?
- Adult onset
- IOP at some point > 21mmHg
- Open iridocorneal angle
- Glaucomatous optic neuropathy
- Visual field loss compatible with nerve fibre damage
- Absence of underlying cause
- Usually bilateral
What is the primary problem in glaucoma?
Disease of the optic nerve
What is raised in most cases of glaucoma?
IOP
What causes raised IOP in open-angle glaucoma?
Reduced flow through the trabecular meshwork
What is the role of the trabecular meshwork?
To absorb the aqueous humour
How does the reduced flow through the trabecular meshwork in open-angle glaucoma progress?
As a chronic, painless, degenerative obstruction
What is the cause of primary open angle glaucoma?
There is no underlying cause (hence it’s called primary)😊
What are the risk factors for primary open angle glaucoma?
- Age
- Family history
- Afro-caribbean
- Ocular hypertension
- Myopia
- Retinal disease
- Diabetes
- Systemic hypertension
After what age does primary open angle glaucoma most commonly present?
65
What is myopia?
Short-sightedness
What retinal disease can increase the risk of primary open angle glaucoma?
- Central retinal vein occlusion
- Retinal detachment
- Retinitis pigmentosa
Are the majority of cases of primary open angle glaucoma symptomatic or asymptomatic?
Asymptomatic
Why are the majority of cases of primary open angle glaucoma asymptomatic ?
Because initial visual loss is in the peripheral vision which is covered by the other eye
When do patient begin to notice visual loss with primary open angle glaucoma?
When loss is severe and affects the central vision
How may primary open angle glaucoma be detected?
When checking IOP and visual fields of people with affected relatives or during a routine eye check
What abnormalities may raise suspicion of primary open angle glaucoma during a routine eye check?
- Abnormal disc
- Raised IOP
- Abnormal visual fields
How is primary open angle glaucoma clinically classified?
- Mild
- Moderate
- Severe
- End-stage
What is classified as mild primary open angle glaucoma?
Early visual field defects
What is classified as moderate primary open angle glaucoma?
Presence of arcuate scotoma (n-shaped visual field loss over central field) and thinning of the neuroretinal rim (cupping)
What is classified as severe primary open angle glaucoma?
Extensive visual field loss and marked thinning of the neuroretinal rim
What is classified as end-stage glaucoma?
Only small residual visual fields remaining with very little neuroretinal rim
What should assessment for primary open angle glaucoma involve?
- Goinoscopy
- Corneal thickness
- Tonometry
- Optic disc examination
- Visual field testing
What is goinoscopy?
Used to measure iridocorneal angle to assess whether open or closed angle glaucoma
Why should corneal thickness be assessed when investigating primary open angle glaucoma?
It can influence the IOP reading, thickened cornea can cause erroneously high reading
What is tonometry (in glaucoma assessment)?
Objective measure of the IOP based on resistance of the cornea to an indent
What is the normal range of IOP?
10-21mmHg
Why is examining the optic disc important in assessing primary open angle glaucoma?
It is a direct marker of disease progression
How is optic disc damage assess in primary open angle glaucoma?
By looking at the cup:disc ratio
What is the normal cup:disc ratio?
0.3 (can be up to 0.7)
What suggests glaucoma when looking at the optic disc?
Cupping with time rather than just cupping
What are the differentials for primary open angle glaucoma?
- Normal/low-tension glaucoma
- Closed-angle glaucoma
- High myopia
- Ocular hypertension
When should treatment for primary open angle glaucoma be started?
- After consistent readings of high IOP
- If the disease is obviously advanced
How is treatment for primary open angle glaucoma planned?
By setting a target IOP based upon the current degree of damage?
How is a target IOP set in treatment for primary open angle glaucoma?
At the pressure at which further damage is unlikely to occur (usually a 30% drop from current IOP)
What monitoring is regularly required in primary open angle glaucoma management?
- IOP measuring
- Visual field testing
- Optic dis examination
What is first line therapy type in primary open angle glaucoma?
Medical treatment
What is usually the first choice drug therapy for treating primary open angle glaucoma?
Topical beta blocker and prostaglandin analogue
What additional medications can be given in primary open angle glaucoma?
- Sympathomimetics
- Carbonic anhydrase inhibitors
- Miotics
How do prostaglandin analogues work to treat primary open angle glaucoma?
Increase aqueous outflow via the uveoscleral route
What are the contraindications for use of prostaglandin analogues ?
- Active uveitis
- Pregnancy and breast feeding
When should caution be take for prescribing prostaglandin analogues?
- Brittle or severe asthma
- Aphakia or pseudophakia
What is aphakia?
No lens
What are the potential side-effects of prostaglandin analogues ?
- Change in eye colour
- Brown pigmentation
- Thickening and lengthening of eye lashes
- Rarely; uveitis, ocular pruritus, photophobia and keratitis
How do beta-blockers work to treat primary open angle glaucoma?
Aqueous secretions are reduced by inhibition of the beta-receptors on the ciliary body
What are the contra-indications for the use of beta-blockers to treat primary open angle glaucoma?
- Bradycardia
- Heart block
- Uncontrolled heart failure
- Asthma
- COPD
When should caution be taken when prescribing beta-blockers for primary open angle glaucoma?
- Depression
- Myasthenia gravis
- Some other medication used e.g. verapamil
What are the potential side-effects of using beta-blockers to treat primary open angle glaucoma?
- Irritation
- Dry eyes
- Blepharo-conjunctivitis
- Bronchospasm
- Bradycardia
What is the action of carbonic anhydrase inhibitors to treat primary open angle glaucoma?
Reduce aqueous secretions by the ciliary body
What are the contraindications for the use of carbonic anhydrase inhibitors in primary open angle glaucoma?
- Renal impairment
- Metabolite imbalance
- Severe hepatic impairment
- Breast-feeding
When should caution be taken when using carbonic anhydrase inhibitors to treat primary open angle glaucoma?
- Elderly
- Hepatic impairment
- History of renal calculi
- History of intraocular surgery
- Pregnancy and breastfeeding
What are the potential side-effects of carbonic anhydrase inhibitors ?
- Localised discomfort
- Lacrimation
- Topical allergy
- Taste disturbance
- Nausea/vomiting
- Headache
- Dizziness
- Fatigue
What is the action of sympathomimetics in treating primary open angle glaucoma?
Reduces aqueous secretion and increase outflow through the trabecular meshwork
What are the contraindications for the use of sympathomimetics in primary open angle glaucoma?
- Angle-closure glaucoma
- Monoamine-oxidase
When should caution be taken when treating primary open angle glaucoma with sympathomimetics?
- Hypertension
- Heart disease
What are the potential side-effects of sympathomimetics?
- Mydriasis
- Dry eye
- Severe smarting and redness of the eye
- Lethargy
- Hypotension
What is the action of miotics in treating primary open angle glaucoma?
Open the drainage channels in the trabecular meshwork by ciliary muscle contraction
What are the contraindications for using miotics to treat primary open angle glaucoma?
- Uveitis
- Retinal holes
When should caution be taken when using miotics to treat primary open angle glaucoma?
- Retinal disease
- Cardiac disease
- Hypertension
- Asthma
- Peptic ulceration
- Urinary tract obstruction
- Parkinson’s disease
What are the potential side-effects of miotics in treating primary open angle glaucoma?
- Miosis
- Localised discomfort
- Sweating
- Bradycardia
- GI disturbance
What treatment options may be considered if medical management of primary open angle glaucoma is unsuccessful?
Laser or surgical treatment
What laser treatment options for primary open angle glaucoma are available?
- Argon laser trabeculoplasty
- Selective laser trabeculoplasty
- Cyclodide laser trabeculoplasty
What surgical treatment options are available for primary open angle glaucoma?
- Trabeculectomy
- Artificial shunts
When may primary open angle glaucoma affect ability to drive?
If it impacts visual fields
What are the potential complications fo primary open angle glaucoma?
- Visual loss