Gonioscopy

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Technique

  • Direct gonioscopy:
    • in a supine position, usually in the operating theatre
  • Indirect gonioscopy:
    • Can be performed at the slit lamp
    • Lenses:
      • Goldmann (1- or 3-mirror contact glass): use a gel (e.g. Lacrinorm), no indentation possible
      • Posner, Sussman, Zeiss: Indentation possible, no gel needed, may use lubrifying drops / topical anesthetic drops
    • Perform in a darkened room
    • Topical anaesthesia (e.g. Oxybuprocaine or Tetracaine gtt.)
    • Ask the patient to look straight ahead (may look upwards to insert the lens)
    • Use the smallest possible light slit, not too bright.
    • Assessment of the anterior chamber angle: usually easiest inferiorly, start there; then assess all four quadrants (rotate 360° with Goldmann lens)
    • consider indentation in case of a closed anterior chamber angle
      • To distinguish appositional closure and detect peripheral anterior synechiae (anterior chamber angle remains closed)
      • with Posner, Sussman or Zeiss lens; apply slight pressure to cornea
    • Always examine both eyes

Anterior chamber angle anatomy

from Wikipedia 1
  • 1 Schwalbe line = junction of the cornea and trabecular meshwork, to identify use a corneal light wedge: intersection of the reflection of the external corneal surface and the internal surface
  • 2 Trabecular meshwork: upper “non-functional” part and lower more pigmented “functional” part
    • Schlemm-Kanal: slightly darker line
  • 3 Scleral spur: prominent white line / ridge
  • 4 Ciliary body band: brown or gray band, can only be seen in deep angles
  • Iris processes: small pigmented strands of the iris surface that insert at the level of the scleral spur (found in 1/3 of normal eyes) ≠ peripheral anterior synechiae (wider)

Classification

  • Spaeth (most detailled)
    • Insertion level of the iris root:
      • A: anterior to Schwalbe’s line
      • B: posterior to Schwalbe’s line
      • C: on the scleral spur
      • D: behind the scleral spur
      • E: on the ciliary body band
    • Angular width of angle recess: 0-40°
    • Configuration of the peripheral iris: regular (r), steep (s, anteriorly convex), queer (q, anteriorly concave)
    • Pigmentation of the trabecular meshwork: 0 (not pigmented) – 4 (very pigmented)
  • Shaffer
    • 0: closed
    • 1: very narrow, ≤10°
    • 2: narrow, 10-20°
    • 3: open, 20-35°
    • 4: wide open, 35-45°
  • Scheie
    • 0: wide open, all structures visible
    • I: iris root visible
    • II: ciliary body obscured
    • III: posterior trabecular meshword not visible
    • IV: only Schwalbe’s line visible
    • Pigmentation of the trabecular meshwork: 0 (not pigmented) – 4 (very pigmented)
  • Peripheral anterior chamber depth (Slit lamp) – Van Herick method
    • how deep is the very peripheral anterior chamber, corneal thickness as unit measure, preferably on the temporal side
    • 0: iridocorneal contact, angle closure
    • 1: <1/4 corneal thickness, angle closure probable
    • 2: 1/4 corneal thickness, angle closure possible
    • 3: 1/2 corneal thickness, angle closure unlikely
    • 4: one corneal thicknesseine or more, angle closure very unlikely

Indications

  • Assessment of the anterior chamber angle in glaucoma patients (mandatory at initial diagnosis)
  • Open/closed angle in case of elevated IOP
  • Neovascularisation of the chamber angle
  • Angle recession , iris disinsertion or ciliary body cleft in case of trauma
  • Foreign body or lens particle in the chamber angle
  • Anomalies of the chamber angle
  • Tumour expansion

Sources