A data collection device comprises at least two optical sensors configured to detect tick marks of a medicament dose indicator of the medicament delivery device in their respective detection areas, and a processing arrangement configured to determine a current medicament dosage programmed into said medicament delivery device based on a count of the tick marks that pass through the detection areas of the optical sensors during programming of said medicament dosage into said medicament delivery device. A direction of travel of the tick marks may be identified, to determine whether the programmed dosage is increasing or decreasing. The apparatus may be arranged to identify a baseline dosage amount using a camera image of the medicament dosage indicator, so that a starting point for the count of tick marks can be determined. The medicament delivery device may be an injector pen.
