Introduction
PACG is a single glaucoma caused by a pupillary block mechanism.
- The formation of a posterior synechiae or pupillary block will cause aqueous humour to accumulate in the posterior chamber
- This pushes the iris forward against the TM
- Angle closure can either be appositional due to touch, or synechial due to adhesion
A plateau iris can occur, in which case there is an anterior non-pupillary block, but due to a narrow angle, can also cause glaucoma.
Uveitic Glaucoma (closure pathophysiology)
- Posterior synechiae causes pressure build up in the posterior chamber
- Peripheral anterior synechiae then occurs to close off the angle
- Inflammation and oedema of ciliary body causes forwards rotation, closing off the angle
Dead Giveaways
Angle Closure Spectrum
Primary Angle Closure Suspect (PACS) --> angle showed >180 degrees of ITC
Primary Angle Closure (PAC) --> angle showed >180 degrees of ITC, and evidence of elevated IOP or PAS
PACG --> As above, but with ON damage
Acute Angle Closure
Presents with more drastic symptoms due to sudden risk in IOP
Is an emergency, requiring immediate referral
Severe pain associated, such as eye pain, headache, nausea, vomiting, blurred vision and haloes of light
Signs:
IOP > 40mmHg and can be up to 80
Eye is very red and inflammed due to conjunctival and episcleral inflammation
Pupils can be unreactive due to ischaemia of the iris from the high pressure, causing it to be stuck and thus mid-dilated
Corneal oedema may be present, with shallow anterior chamber
Chronic Angle Closure
Typically asymptomatic, and is insidious until later stage disease where VF loss is already established
IOP is elevated, and usually this is bilateral, but with asymmetrical onset, leading one eye to be more affected
Gonioscopy reveals features of PACG
Secondary Angle Closure
Pulls Iris Towards TM
Neovascularisation (fibrovascular membrane contraction)
ICE syndrome
Uveitis due to PAS and posterior synechiae
Pushes Iris Towards from Behind
Iridociliary cyst or mass
Drug-induced
Aqueous misdirection into posterior chamber
diagnostic features
Risk:
Family Hx
Age
Female
East Asian, Inuit
Anatomical Risk:
Shallow anterior chamber
Shorter axial length (hyperopia)
Thicker lens (age)
Thicker iris
Acute Angle Closure
Progresses to glaucoma if not immediately treated
Sub-acute version exists, where the acute episodes resolves spontaneously, is more brief, and symptoms experienced is similar but less severe.
Sub-acute can be recurrent, and is much trickier to diagnose, depending more on history