Assessment of Anterior Chamber Changes after Laser Peripheral Iridotomy using Anterior Segment OCT

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Assessment of Anterior Chamber Changes after
Laser Peripheral Iridotomy using Anterior Segment
OCT

• Joshua C. Teichman, MD
• Richard Lee, MD
• Andrea Butler, BSc
• Thomas B. Klein, MD FRCSC
• Iqbal Ike K. Ahmed, MD FRCSC
• Department of Ophthalmology
• University of Toronto

Financial Disclosure None of the authors have
any financial interest in the contents of this
poster.
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Background

• Gonioscopy is the gold standard for evaluating
  angle anatomy, and the results of laser
  peripheral iridotomy (LPI)
• Subjective, semi-quantitative, affected by
  pressure and lighting, and difficult to perform
• Anterior segment OCT (AS-OCT) may offer a
  precise, objective, non-contact alternative to
  gonioscopic evaluation

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Purpose

• To compare the anatomical changes that occur in
  the anterior chamber after laser peripheral
  iridotomy (LPI) using anterior segment optical
  coherence tomography (AS-OCT)

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Methods

• Using AS-OCT 74 patients with closed or
  occludable angles, as determined clinically, were
  imaged before and after LPI
• Low resolution scans of the horizontal and
  vertical meridians were obtained, as well as high
  resolution scans of all four quadrants
• Scans were conducted in the dark
• Patients who had previous surgery that would
  alter angle anatomy were excluded

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Data Measures
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Data Measures
Anterior chamber depth (ACD)
Lens rise (LRAC)
Iris convexity (IC)
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Results - Division into Groups

• Patients could be divided into two groups
• Angles opened significantly after LPI,
  defined as a change in TIA of gt 4
• Angles did not open significantly after LPI,
  defined as a change in TIA of lt 4
• There were 37 patients in each group

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Pre and Post LPI Images
Minimal change in angle after LPI
Significant change in angle after LPI
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Group with Improvement
Preoperatively Postoperatively
ACD (plt0.05) 2.213mm 2.253mm
AOD500 (plt0.0001) 79um 189um
TIA (plt0.0001) 7.8 19.3
IT1000 (p0.47) 418um 425um
IC (plt0.0001) 324um 132um
LRAC (p0.15) 0.253 0.243
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Group without Improvement
Preoperatively Postoperatively
ACD (p0.21) 2.209mm 2.242mm
AOD500 (p0.94) 89um 89um
TIA (p0.45) 10.4 10.7
IT1000 (p0.97) 392um 390um
IC (plt0.0001) 290um 167um
LRAC (p0.47) 0.267 0.264
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Conclusions

• In the group of patients whose angles opened
  significantly after LPI (change in TIA of gt 4)
• AOD500 increased significantly
• IC decreased significantly
• In the group of patients whose angles did not
  open significantly after LPI (change in TIA of lt
  4)
• No significant change in AOD500
• IC decreased significantly
• This may demonstrate that their narrow angles are
  likely due to a combined mechanism of pupil block
  and plateau iris

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Conclusions

• AS-OCT was useful in the objective measurement of
  iridocorneal angles before and after LPI
• AS-OCT appears to be helpful in differentiating
  mechanisms of narrow angles
• Pupil block
• Lens-related
• Plateau iris
• AS-OCT may be useful in predicting the effect of
  LPI preoperatively