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Background To investigate the relationship between estimated mean ocular perfusion pressure (MOPP) and peripapillary perfusion density (PD) or vessel density (VD) as measured by spectral-domain optical coherence tomography angiography (OCTA) in young healthy eyes. Methods 132 healthy participants (264 eyes) under 45 years of age underwent optic disc OCTA scan sized 3×3 mm to acquire PD and VD in the superficial vascular complex (SVC). Optic nerve head (ONH) parameters including retinal nerve fibre layer (RNFL) thickness, rim area and disc area were measured. MOPP was estimated from systemic blood pressure and intraocular pressure (IOP). A linear mixed model was used to find the systemic and ocular factors associated with PD and VD. Results The average age of the subjects was 25.8 ±6.5 years. PD and VD showed a significant correlation with RNFL thickness (r=0.224, p<0.001 and r=0.214, p<0.001, respectively), but with MOPP, the correlation was only marginally significant (r=0.105, p=0.09 and r=0.112, p=0.07, respectively). After controlling for confounding factors, including age, sex, IOP, central corneal thickness, axial length and OCTA signal strength, PD and VD were significantly associated with ONH parameters (all p<0.05) but not with estimated MOPP (all p>0.05). Conclusion PD and VD in the SVC were significantly associated with ONH parameters while showing no association with estimated MOPP. OCTA-derived VD may not represent perfusion pressure, but is rather more dependent on peripapillary structure. [ABSTRACT FROM AUTHOR]

Aims To investigate the validity and reliability of Microsoft Kinect-based head tracker (KHT) for measuring head posture. Methods Considering the cervical range of motion (CROM) as a reference, one-dimensional and threedimensional (1D and 3D) head postures of 12 normal subjects (28–58 years of age; 6 women and 6 men) were obtained using the KHT. The KHT was validated by Pearson’s correlation coefficient and intraclass correlation (ICC) coefficient. Test–retest reliability of the KHT was determined by its 95% limit of agreement (LoA) with the Bland-Altman plot. Face recognition success rate was evaluated for each head posture. Results Measurements of 1D and 3D head posture performed using the KHT were very close to those of the CROM with correlation coefficients of 0.99 and 0.97 ( p<0.05), respectively, as well as with an ICC of >0.99 and 0.98, respectively. The reliability tests of the KHT in terms of 1D and 3D head postures had 95% LoA angles of approximately ±2.5° and ±6.5°, respectively. Conclusions The KHT showed good agreement with the CROM and relatively favourable test–retest reliability. Considering its high performance, convenience and low cost, KHT could be clinically used as a head posturemeasuring system. [ABSTRACT FROM AUTHOR]