Diabetic retinopathy worsened by 2 stages or more in 35 ( 8.6 % ) of 409 participants ( 95 % CI , 5.8 % -11.2 % ) and improved by 2 stages or more in 5 ( 1.2 % ) of 409 participants ( 95 % CI , 0.1 % -2.3 % ) during the 4-year period .