This study aimed to investigate pupillary involvement in patients with type 2 diabetes mellitus (DM) and to evaluate any relationship between severity of diabetic retinopathy (DR) and pupillary responses. Participants included 133 individuals in four groups: proliferative DR (n=21), non-proliferative DR (n=35), DM group without retinal involvement (n=31) and controls (n=46). Static pupillometry measurements including scotopic pupil diameter (PD), mesopic PD, low photopic PD, high latency, velocity, duration of pupil contraction and latency, duration and velocity of pupil dilation were taken using an automated quantitative pupillometry system. The authors conclude that patients with DR may also have diabetic autonomic neuropathy (DAN). DAN is known to be associated with high morbidity and mortality rates and all patients with DR should be referred for screening for cardiac autonomic neuropathy. The authors suggest that pupillometry has potential as a screening tool for detecting diabetic autonomic neuropathy.