Scanning laser polarimetry with variable corneal compensation and optical coherence tomography in tilted disk

To determine whether scanning laser polarimetry with variable corneal compensation (GDx-VCC) or optical coherence tomography (OCT) is helpful for the analysis of the retinal nerve fiber layer (RNFL) thickness in glaucoma subjects with tilted disk.

Retrospective case-control study.

We included 21 glaucomatous eyes with tilted disk and 35 glaucomatous eyes without tilted disk. Peripapillary RNFL thickness measurement by GDx-VCC and OCT, and also visual field testing with a Humphrey Field Analyzer program 30-2 (HFA) were performed in all subjects.

In the group without tilted disk, the RNFL thickness values obtained with GDx-VCC and OCT analysis had a good correlation with mean deviation (MD), and clearly showed stage-dependent reduction. Conversely, in the group with tilted disk, a discrepancy in the RNFL measurement between GDx-VCC and OCT was observed. The correlation of RNFL measurement to the visual field was further examined at each hemifield (superior and inferior). In the group without tilted disk, the measurements of both instruments at each hemifield were in good correlation with the mean pattern deviation values. However, in the group with tilted disk, the GDx-VCC derived values did not correlate with the visual field defect in both hemifields, whereas OCT was in good association with both mean pattern deviation values. Infrared images acquired with a wavelength of nearly 780 nm revealed a high reflex from the sclera in the tilted disk.

Our study has suggested that RNFL analysis by OCT is more suitable for the glaucoma assessment in the tilted disk compared with GDx-VCC.