Partial results from a trial of laser coagulation for the treatment
of diabetic retinopathy.
Usage
diabetic
data(diabetic, package="survival")
Arguments
Format
A data frame with 394 observations on the following 8 variables.
id
subject id
laser
laser type: xenon or argon
age
age at diagnosis
eye
a factor with levels of leftright
trt
treatment: 0 = no treatment, 1= laser
risk
risk group of 6-12
time
time to event or last follow-up
status
status of 0= censored or 1 = visual loss
Details
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.
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.
References
Huster, Brookmeyer and Self, Biometrics, 1989.
American Journal of Ophthalmology, 1976, 81:4, pp 383-396
# juvenile diabetes is defined as and age less than 20juvenile <- 1*(diabetic$age < 20)
coxph(Surv(time, status) ~ trt + juvenile, cluster= id,
data= diabetic)