Data Collection Apparatus for Attachment to an Injection Device

A system comprising:

• a medicament administration device comprising:
• a dose setting dial disposed at a proximal end of the medicament administration device;
• and
• an internal component that rotates around a longitudinal axis of the medicament administration device when a dose of medicament is delivered from the medicament administration device, wherein the internal component includes a plurality of reflective regions, and
• a data collection device comprising:
• an attachment assembly for attaching the data collection device to the dose setting dial;
• a light source configured to illuminate a portion of the internal component including the plurality of reflective regions;
• and
• an optical sensor configured to receive light reflected by the plurality of reflective regions,
• wherein the light source and optical sensor are located proximally of the dose setting dial when the data collection device is attached to the dose setting dial such that a light path between the light source, internal component, and optical sensor passes through a proximal end surface of the dose setting dial.