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D. M. Garcia, L. O. Costa, A. A. Velasco e Cruz, A. Messias; Spontaneous Blinking in Graves' Upper Eyelid Retraction. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5054.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the rate and dynamics of spontaneous blinking in normal subjects and patients with Graves' upper eyelid retraction.
The magnetic search coil technique was used to register spontaneous blinks of 12 healthy subjects (age: 22 - 56 years - 12 eyelids) and 9 Graves patients (age: 22 - 62 years - 13 eyelids) during a 5 minute period of video observation. Overall, a total of 2092 blinks were recorded (1219 for the controls and 873 for the patients). Signals were digitized at a 200 Hz sampling rate (12 bits). Upper eyelid resting position (UERP) was measured relative to the pupil center with the Image J software.
The UERP was 3.7 ± 0.9 for the controls and 6.0 ±1.0 (SD) mm for the patients (t = 5.7; p < 0.0001). The blinking rate was significantly reduced for the patients (Controls: 21.4 ± 2.1 Graves: 13.2 ± 2.0 SE blinks/min; t=2.8; p=0.0057). Asymmetrical interblinking interval distributions were equally found in both groups. The mean absolute down phase amplitudes were similar in both groups (Controls 24.7 ± 3.4; Graves 21.5 ± 3.3 degrees (t=0.66; p=0.2575). However, when the amplitudes were normalized by the UERP (Amplitude/UERP), the patients showed significantly smaller ratios (Controls 1.38 ± 0.16; Graves 0.73 ± 0.16 (t= 2.84; p=0.0047). Moreover, 55% of the total blinks performed by the controls had amplitudes larger than their UERP, while in patients this figure dropped to 22% (Chi square= 254.6; p<0.0001). The mean slope of the linear relationship between amplitude and maximal velocity in Graves’ subjects was significantly smaller than in Controls (Controls: 19.6 ± 8.7 s-1; Graves: 14.9 ± 1.4 s-1; t=2.0; p=0.0249). Blink up-phase did not differ in either group.
Patients with Graves's orbitopathy showed reduced blink rates and abnormal blink dynamics. The amplitude of the down-phase of the blinks was insufficient to compensate for the upper eyelid retraction and the movements were slower than in controls. These results suggest that blinking dynamics might play an important role in the development of exposure keratitis in patients with Graves' eyelid retraction.
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