The experimental equipments consisted of a visual stimulus generator (VSG, version 1.03; Cambridge Research System [CRS], Cambridge, UK), display monitor, eye-tracker (250 Hz High Speed Video Eye Tracker [HS-VET]; CRS), response box, and host computer. Custom software (Delphi, ver. 7; Embarcadero, San Francisco, CA) was used both to measure the central visual field (full-threshold 24-2 automated perimetry, 0.5° stimulus, 200-ms presentation time, and 10-cd/m2 background luminance) at a testing distance of 330 mm and to record eye blink parameters. Eye blink parameters were recorded with an infrared-sensitive camera at a sampling rate of 60 Hz, which provided an objective, noninvasive, precise, and continuous measure of eye tracking in real time.