Purkinje reflections are reflections from eye surfaces, specifically, the cornea and crystalline lens. In AR glasses, these reflections can be used to for tracking the eyes and estimating vergence and accommodation. However, they can also be a significant source of stray light in these and other ocular devices.
The most powerful reflection is off the anterior cornea surface, due to the large difference in index of refraction between the cornea and air. The diverging reflection from this surface appears to come from within the crystalline lens. Since the cornea has a meniscus shape, the posterior reflection is similar, only weaker. Reflections from the crystalline lens also appear to come from within the eye.