This is a 'primary' disease, meaning there is no identifiable cause of the glaucomatous change.

Risk Factors

• MYOC and OPTN gene mutations.
• Steroids.
• Smoking.
• Myopia.
• Afro-Caribbean race.
• Increasing age.

People of Afro-Caribbean origin are more likely to be myopic (longer eyes) and are at risk of open-angle glaucoma, compared to east Asians who are more likely to be hyperopic (shorter eyes) and at risk of angle-closure glaucoma.

Presentation

• Asymptomatic at first but will develop visual field defects.
• Typical presentation is a 60-year-old black myope with a history of vascular risk factors.

Investigations

• Tonometry: IOP > 21mmHg.
• Slit-lamp examination: no signs of precipitating diseases.
• Gonioscopy: open angle.
• Fundoscopy: glaucomatous optic disc changes.
• Perimetry: visual field defects.

Treatment aims to control IOP.

Topical IOP lowering medications (1st line)

1. Topical prostaglandin or beta-blocker (other options are alpha-2 agonists, and carbonic anhydrase inhibitors).
2. No IOP reduction: try alternative first line.
3. Insufficient IOP reduction: combine topical medications.

Surgical IOP lowering procedures (2nd line)

• Issue with medical adherence but IOP is controllable: Selective laser trabeculoplasty (SLT).
• Uncontrolled IOP despite maximum meds: Trabeculectomy with anti-scarring mitomycin C (MMC) or 5-FU.

The failure rate of SLT is around 50% in 5 years.

Pupil block mechanism (Majority):

• Apposition of iris to lens → abnormal aqueous flow through the pupil → increase in the pressure difference between the posterior and anterior chambers → anterior bowing of the peripheral iris leading → peripheral anterior synechiae (PAS) → angle closure → obstructed aqueous outflow → elevated IOP → glaucomatous optic nerve damage

Plateau iris configuration (East Asian):

• Flat iris + anteriorly positioned ciliary processes → iris is pushed forward → angle closure.

Topiramate is associated with bilateral PACG.

APAC attack

• Sudden Pain + blurred vision + nausea + worse in the dark + red eye
  

  

• Highly elevated IOP + mid dilated fixed pupil + corneal oedema.

Resolved/Past APAC attacks

• Descemet's membrane folds.
• Glaukomflecken.

PACG

• Episodes of APAC or same as APAC but with glaucomatous changes.
• A more chronic state of disease.

Investigations

• Tonometry: IOP>21mmHg.
• Gonioscopy: closed-angle.

A closed-angle on gonioscopy is indicative of angle closure. To diagnose angle-closure glaucoma, you must see glaucomatous optic disc changes and visual field defects.

APAC

The aim is to stabilize IOP quickly to prevent blindness.

• First line: urgent admission + IV acetazolamide.
• Adjuncts: timolol + apraclonidine + steroids + pilocarpine + lie the patient supine.
• Monitor and consider systemic hyperosmotics (IV mannitol).
• Definitive treatment is bilateral peripheral iridotomy, with either ND:YAG laser or surgery.

PACG

The aim is to control IOP over time.

• Bilateral peripheral iridotomy.
• The same medication protocol as POAG.
• Cataract extraction is effective in acute and chronic stages.

Peripheral iridotomy is done bilaterally because angle closure in one eye drastically increases the risk of angle-closure in the fellow eye (other eye).

• Mostly sporadic but can be autosomal recessive.
• CYP1B1 gene mutation association.

Presentation

• Hx: infant boy + haab striae + buphthalmos + large corneal diameter + epiphora.

Investigation

• Elevated IOP (normal in infants is 10–12 mmHg).
• Widened corneal diameter.

• Angle surgery: Goniotomy if the cornea is clear. If the cornea is cloudy, then trabeculectomy can be attempted.

Glaucomatous changes with normal IOP.

Risk factors for progression

• Female sex.
• History of migraine.
• Disc haemorrhage at diagnosis.

Presentation

• Asymptomatic.
• More common in elderly east Asian females.
• Symptoms of vascular dysregulation such as migraine, Raynaud's, and low BP.

Investigations

• Tonometry: normal IOP.
• Gonioscopy: open angle.
• Fundoscopy: optic disc changes.
• Perimetry: visual field defects.
• Treatment follows the same protocol as POAG.

Tonometry can be falsely low in people with thinner corneas. This can be picked up with pachymetry.

• Some OHT patients convert to primary open-angle glaucoma within several years.
• Risk factors for conversion: older, higher IOP, larger cup/disc ratio, thinner cornea.
• Aim of treatment is to prevent conversion and control IOP. Achieved by topical IOP lowering medications following the same protocol as for POAG.