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Editors Selection IGR 24-3

Examination methods: Laser scanning: Enhanced corneal compensation

Comment by Gadi Wollstein on:

18205 Scanning laser polarimetry with enhanced corneal compensation and optical coherence tomography in normal and glaucomatous eyes, Sehi M; Ume S; Greenfield DS, Investigative Ophthalmology and Visual Science, 2007; 48: 2099-2104

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Sehi et al. (572) tested a new iteration of scanning laser polarimetry (GDx) with enhanced corneal compensation (ECC). This version of the GDx was designed to eliminate artifacts that are associated with atypical birefringence patterns that were detected with earlier versions of GDx including the currently available iteration with the variable corneal compensation (VCC). The investigators assessed the association between GDx-ECC and VCC with optical coherence tomography (Stratus OCT) and compared their discrimination ability between healthy and glaucomatous eyes. Ninety-five healthy subjects and 63 early to moderate glaucoma subjects were enrolled from the multi-center Advanced Imaging in Glaucoma Study. Significantly higher correlation was reported for most retinal nerve fiber layer (RNFL) parameters between GDx-ECC and OCT compared with the correlation between GDx-VCC and OCT. Nevertheless, the discrimination ability of GDx-ECC and VCC was similar except for significant improvement with GDx-ECC in the inferior RNFL quadrant. The study is well designed and analyzed and supports the cumulative evidence that GDx-ECC results are less affected by optical aberration than previous iterations. The lack of substantial discriminative improvement with GDx-ECC might be due to the relatively low percentage of subjects with atypical birefringence in the study group (27%). Alternatively, better correlation might not be sufficient to improve the discriminatory ability of GDx since it might be affected by other confounders that were not accounted for in this study.

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