Objective : To compare the mydriatic effect between eye drop combination of 0.5% tropicamide with 0.5% phenylephrine and two mydriatic drugs of 1% tropicamide and 10% phenylephrine in preoperative for cataract surgery.

Methods : Fifty-five cataract patients were prospective studied at Ramathibodi Hospital, under local anaesthesia. Patients were randomized into two groups, each group receiving a different preoperative mydriatic regimen. Regimen A consisted of two drugs 1% tropicamide and 10% phenylephrine, one drop instillation every 5 minutes 3 times alternately. Regimen B consisted of two drugs combination, 0.5% tropicamide with 0.5% phenylephrine, two deop 5 minutes separately. The main outcome measures were horizontal papillary diameter before local anaesthesia and successful in cataract surgery.

Results : The group who received regimen A attained a mean horizontal papillary diameter of 7.92 ? 1.10 mm. (before local anaesthesia). Seventeen eyes (70.83%) were dialated to > 8 mm. These pupils were not significant different from those receiving regimen B (8.40 ? 0.84 mm. P = 0.071). Twenty six eye (83.88%) were dilated to > 8 mm. before local anaesthesia. All cases were successful in cataract surgery and intraocular lens insertions.

Conclusion : The combination of 0.5% tropicamide and 0.5% phenylephrine is recommend as preoperative mydriatic for cataract surgery.