Comparison of Scheimpflug imaging and spectral domain anterior segment optical coherence tomography for detection of narrow anterior chamber angles

Abstract

Purpose: To compare the performance of anterior chamber volume (ACV) and anterior chamber depth (ACD) obtained using Scheimpflug imaging with angle opening distance (AOD500) and trabecular-iris space area (TISA500) obtained using spectral domain anterior segment optical coherence tomography (SD-ASOCT) in detecting narrow angles classified using gonioscopy.

Methods: In this prospective, cross-sectional observational study, 265 eyes of 265 consecutive patients underwent sequential Scheimpflug imaging, SD-ASOCT imaging, and gonioscopy. Correlations between gonioscopy grading, ACV, ACD, AOD500, and TISA500 were evaluated. Area under receiver operating characteristic curve (AUC), sensitivity, specificity, and likelihood ratios (LRs) were calculated to assess the performance of ACV, ACD, AOD500, and TISA500 in detecting narrow angles (defined as Shaffer grade ≤1 in all quadrants). SD-ASOCT images were obtained at the nasal and temporal quadrants only.

Results: Twenty-eight eyes (10.6%) were classified as narrow angles on gonioscopy. ACV correlated with gonioscopy grading (P<0.001) for temporal (r=0.204), superior (r=0.251), nasal (r=0.213), and inferior (r=0.236) quadrants. ACV correlated with TISA500 for nasal (r=0.135, P=0.029) and temporal (P=0.160, P=0.009) quadrants and also with AOD500 for nasal (r=0.498, P<0.001) and temporal (r=0.517, P<0.001) quadrants. For detection of narrow angles, ACV (AUC=0.935; 95% confidence interval (CI) =0.898-0.961) performed similar to ACD (AUC=0.88, P=0.06) and significantly better than AOD500 nasal (AUC=0.761, P=0.001), AOD500 temporal (AUC=0.808, P<0.001), TISA500 nasal (AUC=0.756, P<0.001), and TISA500 temporal (AUC=0.738, P<0.001). Using a cutoff of 113 mm(3), ACV had 90% sensitivity and 88% specificity for detecting narrow angles. Positive and negative LRs for ACV were 8.63 (95% CI=7.4-10.0) and 0.11 (95% CI=0.03-0.4), respectively.

Conclusions: ACV measurements using Scheimpflug imaging outperformed AOD500 and TISA500 using SD-ASOCT for detecting narrow angles.

Figure 1

Scatter plot demonstrating correlation of TISA500 (nasal and temporal) versus ACV. TISA, trabecular-iris space area at 500 μm from the scleral spur (mm²); ACV, anterior chamber volume using Scheimpflug (mm³); SD-ASOCT, spectral domain anterior segment optical coherence tomography.

Figure 2

Scatter plot demonstrating correlation of AOD500 (nasal and temporal) versus ACV. AOD, angle opening distance at 500 μm from the scleral spur (mm); ACV, anterior chamber volume using Scheimpflug (mm³); SD-ASOCT, spectral domain anterior segment optical coherence tomography.

Figure 3

Graph showing receiver operating characteristic curves of different parameters from Scheimpflug imaging (ACV and ACD) and SD-ASOCT (AOD500 and TISA500) of detecting narrow angles. Using a cutoff of 113 mm³, ACV had 88.29% sensitivity and 88.19% specificity in detecting narrow angles (Shaffer grade ≤1). AOD500, angle opening distance at 500 μm from the scleral spur; TISA500, trabecular-iris space area at 500 μm from the scleral spur; ACV, anterior chamber volume using Scheimpflug imaging; ACD, anterior chamber depth using Scheimpflug imaging.