Abstract
Purpose: :
To examine the temporal organization of spontaneous blinking series in normal subjects and patients with Graves upper eyelid retraction (UER).
Methods: :
Twenty subjects divided into two groups of 10 (controls and patients with UER) had their spontaneous blinking measured with magnetic search coil technique while watching a movie during 60 minutes. The control group (CG) was formed by 5M/5 F aged 27 to 61 (46.0 ± 13.6; mean ± SD) and the Graves group (CG) comprised of 3M/7F, aged 33 to 61 (46.7 ± 8.9; mean ± SD). Two time series were obtained for both groups: interblink time interval (IBI) and blink amplitude (AMP). Temporal analysis was performed using the software S+ 8.1 (FinMetrics). The parameter d of autoregressive fractionally integrated moving average model (ARFIMA), was estimated using Geweke-Porter-Hudak Test algorithm that is based on linear regression of the log periodogram.
Results: :
The median IBI and AMP values did not differ between groups (IBI - CG = 3.1 sec, GG = 4.4 sec, Mann-Whitney test, p = .472; AMP - CG = 23.1 degrees GG = 23.2 degrees, Mann-Whitney test, p = .969). Test for autocorrelation only two series (IBI-GG) did not show significance. Of the 40 time series analyzed 95% (38) showed positive autocorrelation (Ljung-Box test for autocorrelation). Significant long range dependence was verified in only 50% of the IBI series of CG and in 30% of the GG. For the AMP series the rate of significant long range dependence were higher: 70% for CG and 80% of the GG.
Conclusions: :
The positive autocorrelation of both IBI and AMP time series indicates that spontaneous blinking activity is not a white noise. The high rate of significant long range dependence observed for blinking amplitude suggests that there are patterns of orbicularis contraction which are repeated over time. Peripheral diseases such as UER does not interfere with this organization.
Keywords: eyelid • orbit • eye movements