11.7.2 Glaucoma

Question 1

Define glaucoma

Answer 1

Chronic
- progressive, optic neuropathy with characteristic optic nerve changes and visual field loss, with intra-ocular pressure a key factor.
- But encompasses a diverse group of disorders…

Acute
- acute, marked increase in intraocular pressure

Question 2

Normal intra-ocular pressure

Answer 2

Balance between aqueous production and outflow maintains a normal intraocular pressure between 10 and 21 mmHg

Question 3

How is aqueous produced?

Answer 3

• By ciliary processes
• Mostly flow out via trabecular meshwork in angle

Question 4

Glaucoma classification

Answer 4

• Open angle
• Closed angle
• Primary
• Secondary
• Congenital glaucoma (Primary; Secondary)

So…..
• POAG (primary open angle glaucoma)
• PACG (primary angel close glaucoma)
• Secondary glaucoma’s

Question 5

Primary open angle glaucoma
Def
RF
Symptoms
Signs

Answer 5

Def
Glaucomatous optic nerve damage with with an elevated IOP, an open angle and an absence of a secondary cause.

RF
- IOP
- ⬆️ age
- race (african)
- family history
- DM
- myopia (nearsightedness)

Symptoms
- Often NONE!
- Elevated IOP, when it develops gradually, is usually
asymptomatic.
- Damage to the optic nerve therefore accumulates without the patient realizing.
- Roughly 50% of the optic nerve fibers can be lost before any visual filed loss can be detected
- peripheral visual field is affected first – thus damage is often advanced before it is noticed.
- Early detection is therefore key, but it is too rare for generalized screening programmes

Signs
- ⬇️ visual acuity when terminal
- loss of visual field
- disc changes (neuroretinal rim pallor; large & deep cup; nasal displacement of vessels; nerve fibre layer haemorrhage on disc margin)
- ⬆️ IOP

Question 6

Optic nerve damage pathophysiology

Answer 6

• Complex
• elevated IOP compresses nerve fibers as they exit eye, causing loss of nerve fibers.
• a sub group of patients get glaucomatous damage with a “normal” pressure.
• Thus effects from:
  • Blood flow – e.g. nocturnal hypotension, vasospasm (migraines and Raynauds phenomenon)
  • CSF pressure
  • Other factors also play a role

Question 7

Secondary open angle glaucoma
General
Pseudo-exfoliation syndrome

Answer 7

• Similar to POAG with elevated IOP and and open angle
• But with an identifiable cause e.g.
  • Pseudo - exfoliation syndrome
  • Angle damage from trauma (angle recession)
  • Chronic steroid use (especially steroid eye drops and peri-ocular steroid ointment) causes elevated pressure in those with a genetic susceptibility to this….
• Therefore, steroid eyedrops can only be prescribed by an ophthalmologist and the IOP must be monitored during their use !!!

Pseudo-exfoliation syndrome
- genetic form of open angle glaucoma
- Pseudo-exfoliation material may be visible on the lens
- Common in South Africa (and Scandinavia – but different genetics)
- More aggressive then POAG
- Has other effects on eye such as loose zonules and poor pupil dilation which can make cataract surgery more difficult

Question 8

Secondary closed angle glaucoma example: Neovascular glaucoma
Pathophysiology
Symptoms

Answer 8

Pathophysiology
- Retinal ischemia leads to anterior new vessel formation
- Ischaemia can be from:
• Retinal vein occlusion, especially central retinal vein, glaucoma often develops 2-3 months later “90 day glaucoma”
• Diabetes
• Poor ocular blood flow (ocular ischaemic syndrome)
• Uveitis, and other factors
- These grow on iris and in angle
- This cause elevated IOP and then permanent occlusion of the angle

Symptoms
- Presents with sudden pain and redness
- Vision may have already been poor due to previous vein
occlusion, or drop as cornea swells

Question 9

Angle closure
Pathophysiology / causes
Symptoms
Signs

Answer 9

Pathophysiology
- Primary angle closure occurs when there is apposition of the peripheral iris to the trabecular meshwork, usually due aqueous pushing the iris forward (pupil block)
- Usually occurs with age as the lens thickens
- Some medications are also associated (parasympathetic antagonists, sympathetic agonists)
- Can occur after medical dilation (rare)
- Can be:
• chronic (slow visual loss) or
• Acute
- Less common but more likely to cause blindness

Acute Symptoms
- Pain (may be severe)
- May have associated nausea and vomiting
- Redness
- Loss of vision
- May describe episodes of pain and blurring, often in evening, with halo’s around lights, relieved with sleep.

Acute signs
- Reduced vision
- Red eye
- Hazy cornea
- Shallow anterior chamber (may be best seen on other side)
- Mid-dilated, unreactive pupil
- Firm eye to digital palpation

Emergency referral needed to lower pressure and save vision

Question 10

Primary congenital glaucoma
General
Signs and symptoms

Answer 10

• Rare
• Usually sporadic
• Often bilateral, may be asymmetric
• Features depend on age of onset and level of IOP e.g.
  • True congenital: elevated IOP in-utero
  • Infantile: manifest before 3
  • Juvenile: between 3 and 16

Signs and symptoms

Corneal haze
- May be first sign noted by parents
- Due to oedema of the cornea
- Causes:
• Lacrimation
• photophobia
• blepharospasm

Buphthalmos
- Large eye due to elevated IOP prior to age three
- Thinned sclera may take on a blueish appearance
- Enlarged eye can be myopic (short sighted)

Other signs
- Breaks in corneal lining – Haab Striae
- Opticdisccupping