Research · Göttingen University Medical Center
How much doesa healthy face changefrom day to day?
Whether swelling after surgery is going down can only be judged if you know how much the tissue moves without any intervention at all. This study measures exactly that: in 19 healthy people, on five consecutive days, at the same time each day.
Scale
- 19participants
- 5consecutive days
- 3captures per day
- 456volume measurements
Background
After eyelid surgery it must be assessed whether the swelling is receding, which means measuring volume before and after. Tissue fluctuates without any intervention as well, driven by fluid balance, gravity, lymphatic flow and muscle tone. Until someone knows how large that natural noise is, real swelling cannot be told apart from it with any confidence.
The preceding study showed the device is precise enough for the job and recommended mode C as the clinically sensible outline. This study starts exactly there: it uses that mode and quantifies the intrinsic dynamics of the tissue in healthy volunteers.
Setup
Nineteen healthy participants aged 20 to 65, mean age 32. Measurements were taken on five consecutive days at the same time of day, in order to exclude time of day variation in the soft tissue. Jewellery off, hair tied back, relaxed jaw, closed lips, gaze on a fixed point.
Day one is the reference; every later day is compared against it. Three captures were taken per day and each comparison was evaluated three times, left and right eye separately. Together that makes 456 volume measurements.
Analysis
The analysis uses linear mixed effects models. A random intercept at participant level accounts for each person being measured repeatedly. Sex and age group enter as fixed effects.
Uncertainty in the model estimates is given as 95 per cent confidence intervals, and the expected spread of future individual measurements as prediction intervals from parametric bootstrapping. Measurement reliability is described through the intraclass correlation coefficient and the technical error of measurement, each in absolute and relative terms.
The significance level is five per cent, corrected with the Bonferroni-Holm method for multiple testing. Everything was computed in R using lme4 and ggeffects.
Status
Data collection is complete and so is the analysis. The manuscript is in preparation.
The results are deliberately withheld here. They will be added once the work is published.
People involved
The study was carried out at Göttingen University Medical Center. The manuscript contains no breakdown of individual contributions, so contributors are listed here in author order and by initials only.
Status
Manuscript in preparation. Ethics approval is in place.