One hundred patients with diabetes from Srinagarind Hospital Eye Clinic were enrolled and randomized into two groups by block randomization. In group I (50 patients), 1% tropicamide combined with 2.5% phenylephrine were administered to dilate pupil whereas 1% tropicamide combined with 10% phenylephrine were used in Group II (50 patients). Pupil diameter, blood pressure and heart rate were measured before and after eye drop instillations.