1. 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.

2. 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

3. 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)

4. 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

5. Data Measures

6. Data Measures Anterior chamber depth (ACD) Lens rise (LR:AC)
Iris convexity (IC)

7. Results - Division into Groups
Patients could be divided into two groups
Angles opened significantly after LPI, defined as a change in TIA of > 4°
Angles did not open significantly after LPI, defined as a change in TIA of < 4°
There were 37 patients in each group

8. Pre and Post LPI Images Significant change in Minimal change in angle
angle after LPI
Minimal change in angle
after LPI

9. Group with Improvement
Preoperatively
Postoperatively
ACD* (p<0.05)
2.213mm
2.253mm
AOD500* (p<0.0001)
79um
189um
TIA* (p<0.0001)
7.8°
19.3°
IT (p=0.47)
418um
425um
IC* (p<0.0001)
324um
132um
LR:AC (p=0.15)
0.253
0.243

10. Group without Improvement
Preoperatively
Postoperatively
ACD (p=0.21)
2.209mm
2.242mm
AOD (p=0.94)
89um
TIA (p=0.45)
10.4°
10.7°
IT (p=0.97)
392um
390um
IC* (p<0.0001)
290um
167um
LR:AC (p=0.47)
0.267
0.264

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

12. 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