Tear film stability assessment is one of the main tests in dry eye diagnosis. However, to date, no test methodology has been adopted as the gold standard due to several reasons, such as the methods being invasive, subjective, or unfeasible for the clinical environment. In this paper, a method that overcomes the above-mentioned limitations for tear film stability measurements is presented, and is based on the degradation of corneal reflex images caused by breakups. The experimental setup, which is based on recording the corneal reflex image or the first Purkinje image, is described, as well as the method used to determine tear film stability by means of the associated breakup time (BUT) using corneal reflex image degradation. Images obtained through simulations of the experimental setup are also shown. Moreover, BUT measurements performed using both the conventional fluorescein method and the proposed method in nine healthy adults are presented. Both the experimental and simulation images show corneal reflex image degradation due to the appearance of breakups in the tear film, highlighting the potential of the method to assess tear film stability. We have shown that the corneal reflex image degrades when the tear film breaks up and, thus, the proposed method can be used to assess tear film stability.