Effect of motion artifacts and scan circle displacements on Cirrus HD-OCT retinal nerve fiber layer thickness measurements.

Purpose: To evaluate the effect of scan circle displacements on retinal nerve fiber layer thickness (RNFLT) measurements in Cirrus HD-OCT scans with motion artifacts affecting the optic disc.

Methods: In this cross-sectional study, 70 scans from 18 healthy eyes and 100 scans from 26 glaucomatous eyes were divided into 85 pairs, each composed by a scan with one motion artifact affecting the optic disc, and a scan from the same eye without motion artifacts. En face images underwent automated realignment, and horizontal/vertical scan circle displacements were determined. Multiple regression analysis evaluated the relationship between scan circle displacements and RNFLT change.

Results: Scans with motion artifacts showed similar displacements in healthy and glaucomatous eyes (P values ≥ 0.08). Average RNFLT and quadrants were relatively unchanged, while clock-hours showed more changes (e.g., in glaucomatous eyes, clock-hour-7 RNFLT was lower in scans with motion artifacts, P = 0.05). Scan circle displacements produced average RNFLT changes above test-retest variability in 3/85 cases (3.53%). Retinal nerve fiber layer thickness tended to decrease in sectors moved away from the disc and to increase in sectors closer to the disc (R(2) ≤ 0.40 and R(2) ≤ 0.22 in healthy and glaucomatous eyes, respectively). In healthy eyes, horizontal displacements ≥ 423 and 325 μm were associated with average and quadrant RNFLT changes above test-retest variability, respectively.

Conclusions: Scan circle displacements occurred in all scans with motions artifacts affecting the optic disc. Average RNFLT and quadrants were more robust than clock-hours. Because motion artifacts may be difficult to detect, clinicians should carefully inspect en face OCT images for their presence and interpret clock-hour results cautiously.