The effect of head tilt on the measurements of retinal nerve fibre layer and macular thickness by spectral-domain optical coherence tomography

Background/aims: To evaluate the effect of head tilt on retinal nerve fibre layer (RNFL) and macular thickness measured by the Cirrus HD spectral-domain optical coherence tomography (Cirrus HD OCT). Methods: A total of 30 right eyes from 30 healthy young subjects underwent RNFL and macular thickness measurements with the Cirrus HD OCT. The measurements were performed at a baseline head position and at right and left head tilt positions. The differences in RNFL and macular thickness between the baseline head position and the positions with head tilt were analysed. Results: The right and left head tilt induced counter-clockwise (mean 8.27°) and clockwise (mean 8.47°) rotation of the optic disc. The right head tilt caused superior-temporal RNFL thickening, inferior-temporal RNFL thinning, superior outer macular thickening and inferior outer macular thinning (all p values <0.05). The left head tilt induced superior-temporal RNFL thinning, inferior-temporal RNFL thickening, superior outer macular thinning, nasal outer macular thickening and inferior outer macular thickening (all p values <0.05). Conclusions: RNFL and macular thickness measured with the Cirrus HD OCT was affected by head tilt. Artefacts caused by head tilt should be considered in the analysis of the Cirrus HD OCT measurements.