Lid Margin Sensitivity and Staining in Contact Lens Wear Versus No Lens Wear :

The present study measured the normal blink rate (BR) variations in relation to behavioral tasks in 150 healthy volunteers (70 males and 80 females; aged 35.9 +/- 17.9 years, range 5-87 years). The subjects were videotaped in a standard setting while performing three different tasks: resting quietly, reading a short passage, talking freely. The mean BR was computed during each task; the data were compared by means of analysis of variance and Student's t tests. Mean BR at rest was 17 blinks/min, during conversation it increased to 26, and it was as low as 4.5 while reading. As compared with rest, BR decreased by -55.08% while reading (p rest > reading, which occurred in 101 subjects (67.3%); 34 subjects (22.7%) had the pattern rest > conversation > reading; 12 (8.0%) had the pattern conversation > reading > rest. This study identified three normal behavioral BR patterns and showed that BR is more influenced by cognitive processes than by age, eye color, or local factors. The present findings provide a normal reference for the analysis of BR in movement disorders such as dystonia or tics.

We used a high-speed camera system to study in detail the eyelid motion dynamics of the human eyeblink. Films were made from a hidden location through a one-way mirror. In this manner, normal, unforced blinks were recorded. The descent of the upper eyelid reached its maximum speed at about the time that it crossed the visual axis, generally in the range of 17 to 20 cm/sec, but occasionally reaching a speed of over 40 cm/sec. The motion of the lower eyelid was mostly horizontal, in a nasally directed movement, with a total displacement in the range of 20 to 5 min. A distinction must be made between normal, unforced blinks, and voluntary, forced eyelid motion. In a normal blink, no appreciable upward rotation of the globe is observed. A forced blink or a restraint of motion of the upper eyelid results in a significant demonstration of Bell's movement. The globe moves posteriorly up to 1 to 6 mm as the upper eyelid descends, probably caused by eyelid pressure during the closing phase of the blink.