The 197 patients in this dataset were a 50% random sample of the patients with "high-risk" diabetic retinopathy as defined by the Diabetic Retinopathy Study (DRS). Each patient had one eye randomized to laser treatment and the other eye received no treatment. For each eye, the event of interest was the time from initiation of treatment to the time when visual acuity dropped below 5/200 two visits in a row (call it "blindness"). Thus there is a built-in lag time of approximately 6 months (visits were every 3 months). Survival times in this dataset are therefore the actual time to blindness in months, minus the minimum possible time to event (6.5 months). Censoring was caused by death, dropout, or end of the study. The risk group variable was used to define the 'high risk' samples.
sample SAS code to read the data

Reference:Huster, Brookmeyer and Self, Biometrics, 1989.
A reference for the Diabetic Retinopathy Study (DRS) which describes the design and interim results is American Journal of Ophthalmology, 1976, 81:4, pp 383-396.