Difference between before and after Compensating for Cyclotorsion by Optical Coherence Tomography Guided Progression Analysis

Abstract

Purpose: This study evaluated the difference in parameters before and after the application of optical coherence tomography (OCT) Guided Progression Analysis (GPA) to compensate for cyclotorsion during image acquisition.Methods: Among glaucomatous eyes with ≥4 OCT tests, eyes with correction for cyclotorsion in GPA printouts defined as rotated OCT fundus images were included. The degree of cyclotorsion (i.e., the degree of fundus image rotation), direction of cyclotorsion (incyclotorsion or excyclotorsion), difference in optic nerve head (ONH) parameters, and retinal nerve fiber layer (RNFL) thickness before and after correction were analyzed.Results: Correction for cyclotorsion was seen in 33 of the 401 eyes (12.2%). Incyclotorsion was observed in 16 eyes (48.5%) and excyclotorsion in 17 (51.5%). The mean degree of cyclotorsion was 5.5 ± 2.3 degrees. The ONH parameters were unchanged after correcting for cyclotorsion. The mean overall, inferior, and superior quadrant RNFL thicknesses were 73.6 ± 14.8, 79.3 ± 26.3, and 90.1 ± 24.7 μm before correction and 73.6 ± 14.9, 79.6 ± 26.6, 89.7 ± 24.8 μm afterwards (p > 0.05). The difference in RNFL thickness after correction ranged from 0 to 6 μm.Conclusions: The difference in RNFL thickness before and after cyclotorsion correction by GPA was not large. GPA did not correct the ONH parameters induced by cyclotorsion. Regarding this, GPA algorithm improvements may be needed.