AIM:To investigate the influence to dilated pupil’s diameter of cataract patients with nonprohferative diabetic retinopathy (NPDR) by manual small incision cataract surgery (MSICS) and phacoemulsification(Phaco).METHODS:Pilot study.Sixty eyes of cataract patients with NPDR were divided into two groups,MSICS group of 30 eyes and Phaco group of 30 eyes.The pupil was dilated by Compound Tropicamide.The diameter of dilated pupil was compared before and after the cataract surgery.RESULTS:Before surgery,the dilated pupil’s diameter of MSICS group was 6.23±0.83mm,and Phaco group was 6.26±0.85mm.There was no significant difference between the two groups(P>0.05).Before and after the surgery,the difference of the dilated pupil’s diameter of MSICS group was 0.11±0.094mm,Phaco group was 0.17±0.119mm.The difference was significant(P<0.01).There was significant difference between the MSICS group and Phaco group in those above(P<0.05).CONCLUSION:Both MSICS and Phaco can reduce the diameter of dilated pupil of the cataract patients with NPDR.The phacoemulsification seems to reduce more.