Forty-two patients who received intensive therapy and 61 who received conventional therapy underwent cataract extraction ( adjusted risk reduction with intensive therapy , 48 % ; 95 % CI , 23 to 65 ; P = 0.002 ) ; 29 patients who received intensive therapy and 50 who received conventional therapy underwent vitrectomy , retinal-detachment surgery , or both ( adjusted risk reduction , 45 % ; 95 % CI , 12 to 66 ; P = 0.01 ) .