It is known that the use of glasses can hamper the quality and speed of user registration into eye-tracking devices. Studies have been done in which the performances of various eye-tracking devices were compared, typically under ideal viewing angles, with the user sitting behind a display under a fixed lighting condition. Here we investigated the influence of the use of glasses on the quality and time of user registration into a low-cost eye-tracking device under various lighting conditions. Furthermore, we compared the use of glasses on registration within the same group of participants. Participants with prescription glasses were asked to register into the eye-tracking device both with and without their glasses, if possible, and users without prescription glasses or with contact lenses were also asked to register without glasses or with replica, nonprescription glasses. The present results showed indeed that the use of glasses negatively influenced registration quality and time - significantly here, however, only when registration was performed under artificial lighting. Under natural lighting, the difference in registration quality and speed did not reach significance, but bordered on significance. A follow-up measurement confirmed these results, and suggested that calibration with glasses can improve when participants register under 'ideal' viewing angles for their particular viewing position.