As natural brain process, mind-wandering happens spontaneously and is usually linked with outcomes that affect students\' performance in educational settings. In addition to capturing pupil and gaze coordinates in high resolution and with accuracy, wearable eye-trackers were used in this pilot study to infer student attention during an online lecture. While gaze is a good indicator for measuring visual attention, the need for more substantial proof of internal and covert attention is essential. This work uses an eye-tracker to measure the mind-wandering level. The data collection was carried out with 15 students in two different settings for self-caught and probe-caught conditions.