A trial of laser coagulation as a treatment to delay diabetic retinopathy.
data("retinopathy")A data frame with 394 observations on the following 9 variables.
idnumeric subject id
lasertype of laser used: xenon argon
eyewhich eye was treated: right left
ageage at diagnosis of diabetes
typetype of diabetes: juvenile adult,
(diagnosis before age 20)
trt0 = control eye, 1 = treated eye
futimetime to loss of vision or last follow-up
status0 = censored, 1 = loss of vision in this eye
riska risk score for the eye. This high risk subset is defined as a score of 6 or greater in at least one eye.
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, and has two observations in the data set. 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 the actual time to vision loss in months, minus the minimum possible time to event (6.5 months). Censoring was caused by death, dropout, or end of the study.
W. J. Huster, R. Brookmeyer and S. G. Self (1989). Modelling paired survival data with covariates, Biometrics 45:145-156.
A. L. Blair, D. R. Hadden, J. A. Weaver, D. B. Archer, P. B. Johnston and C. J. Maguire (1976). The 5-year prognosis for vision in diabetes, American Journal of Ophthalmology, 81:383-396.
# NOT RUN {
coxph(Surv(futime, status) ~ type + trt + cluster(id), retinopathy)
# }
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