Diabetic Retinopathy

Description

A trial of laser coagulation as a treatment to delay diabetic retinopathy.

Usage

retinopathy
data(retinopathy, package="survival")

Format

A data frame with 394 observations on the following 9 variables.

id

numeric subject id

laser

type of laser used: xenon argon

eye

which eye was treated: right left

age

age at diagnosis of diabetes

type

type of diabetes: juvenile adult, (diagnosis before age 20)

trt

0 = control eye, 1 = treated eye

futime

time to loss of vision or last follow-up

status

0 = censored, 1 = loss of vision in this eye

risk

a risk score for the eye. This high risk subset is defined as a score of 6 or greater in at least one eye.

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, 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.

References

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.

Examples

coxph(Surv(futime, status) ~ type + trt, cluster= id, retinopathy)