Patients with diabetes type 1 and type 2 older than 21 years of age, in the specialized clinic of Kowsar Hospital (Semnan University of Medical Sciences) are examined. Eligible individuals enter the study and are randomly assigned to group 1 or group 2. In each group, visual acuity measurement, slit lamp biomicroscopy and fundus examination are performed. Intraocular pressure is measured with Goldmann applanation tonometer. pupil size, refraction and keratometry are measured with two different autorefractokeratometers. keratometry, pupil size and other anterior chamber parameters are also evaluated by Oculus Pentacam imaging. Then, the patients receive tropicamide 0.5% drops in group 1 and tropicamide 1% drops in group 2. 30 minutes later, all previous measurements are repeated. Patients and the ophthalmologist and the data analyzer are unaware of the drug type.