Primary Open Angle Glaucoma (POAG)

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Definition

  • Progressive, bilateral optic neuropathy with open anterior chamber angle, characterised by typical nerve fibre loss and elevated intraocular pressure (>21mmHg) not caused by other local or systemic pathology

Risk Factors

  • Higher IOP (per definition >21mmHg), older age, African descent (6x increased risk), first-degree relatives with POAG (6x increased risk), diabetes mellitus, myopia, arterial hypertension, migraine, thin central corneal thickness

Baseline Examination

  • Medical history
    • Medications, diseases (especially respiratory and cardiovascular), family history, ocular trauma, refractive surgery, allergies
  • Complete ophthalmologic examination including:
    • Exclusion of secondary causes (PEX, pigment dispersion, etc.)
    • Intraocular pressure (IOP): preferably using Goldmann applanation tonometry, possibly additional methods
    • Gonioscopy: Is the angle open?
    • Assessment of the optic disc (cup-disc-ratio, DDLS Stage, ISNT rule, disc hemorrhages, nerve fibre layer, peripapillary atrophy, disc size)
    • Pachymetry: Corneal thickness
    • OCT of retinal nerve fibre layer (RNFL) and ganglion cell layer (GCL)
    • Visual Field (usually Octopus G2)
    • Consider MRI head or lab tests if non-glaucomatous optic nerve damage is suspected

Follow-up

Initiation of Antihypertensive Therapy

  • see Topical Glaucoma Therapy
  • Initially monotherapy.
    • Often a prostaglandin analogue (e.g., Lumigan or Saflutan) or beta-blocker (e.g., Timoptic or Timisol).
  • Interval until follow-up check after starting therapy usually 4-8 weeks.
    • If satisfactory IOP: further check after 3-6 months.
    • If no IOP reduction: switch to another monotherapy, possibly SLT.
    • If inadequate IOP reduction: additional agent.
  • Maximum topical therapy: quadruple therapy e.g., Simbrinza 2x daily + Duotrav 1x daily
  • For children:
    • 1. Timo-Comod (Timolol, CI: Asthma) 0.5% once daily (not twice) or Azopt (Brinzolamide) twice daily.
    • 2. Cosopt S twice daily.
    • 3. DuoTrav once daily.
    • Note: Alphagan is contraindicated in children!
  • EGS Guidelines 5th Edition Therapeutical Algorithm in Glaucoma Topical Therapy

Treatment

  • Medical therapy: Usually initial therapy
    • see above
  • Laser Trabeculoplasty: Can also be initial therapy or secondary if there’s insufficient pressure reduction from medication
    • Laser application to the trabecular meshwork to improve aqueous humor outflow
    • Therapeutic effect varies greatly and is often temporary but can last months to years
    • SLT = Selective laser trabeculoplasty (Nd:YAG laser)
    • ALT = Argon laser trabeculoplasty (obsolete)
  • Surgical Therapy:
    • Trabeculectomy: Standard glaucoma surgery
    • Shunt techniques: Ahmed Tube, Baerveldt Tube
    • MIGS (Minimally Invasive Glaucoma Surgery)

Sources

  • EyeWiki Primary Open-Angle Glaucoma
  • European Glaucoma Society Terminology and Guidelines for Glaucoma, 5th Edition,
    • Licensed under a Creative Commons License Attribution-NonCommercial 4.0 International CC BY-NC 4.0 DEED
  • The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease; Kalla Gervasio MD, Travis Peck MD et al; Lippincott Williams&Wilkins; 8th Edition (2021)
  • Kanski‚Äôs Clinical Ophthalmology: A Systematic Approach; John E Salmon MD; Elsevier; 9th Edition (2019)