Pulse-waveform analysis of normal population using laser speckle flowgraphy

Purpose: Laser speckle flowgraphy (LSFG), a new, non-invasive method of measuring the mean blur rate (MBR) of ocular blood flow, allows for the analysis of the pulse waveform of a heartbeat as it changes dynamically. Here, we investigated the relationship between the pulse waveform and clinical parameters, particularly age. Materials and methods: Sixty eyes of 60 healthy subjects without diabetes were enrolled from among patients undergoing annual health examinations. LSFG, and its analysis software, were used to determine pulse waveform parameters including MBR, skew, blowout score (BOS), blowout time (BOT), rising rate and falling rate in the optic nerve head (ONH), both specifically in the tissue area and in the ONH overall. Fifteen clinical parameters were also recorded, including age and blood pressure, as well as triglyceride and creatinine levels. Results: Skew, BOT and falling rate had a strong correlation (r>0.60) with age, but not with the other clinical parameters. This correlation with age was stronger in the tissue area (BOT: p<0.0001, r=-0.68; skew: p<0.0001, r=0.65; falling rate: p<0.0001, r=0.61) than in the ONH overall (BOT: p<0.0001, r=-0.67; skew: p<0.0001, r=0.60; falling rate: p<0.0001, r=0.59). Stepwise multiple regression analysis revealed that tissue area falling rate was an independent factor indicating age, and conversely that age was an independent factor indicating tissue area falling rate. Conclusions: The significant correlation of LSFG-measured tissue area falling rate with age suggests that it may be a new candidate biomarker for age-dependent microcirculation.