Interval between onset of mild nonproliferative and proliferative retinopathy in type I diabetes
S. Vitale, M. G. Maguire, R. P. Murphy, C. Hiner, L. Rourke, C. Sackett and A. Patz
Dana Center for Preventive Ophthalmology, Baltimore, Md., USA.
OBJECTIVE: To describe the interval between first appearance of mild
nonproliferative diabetic retinopathy (NPDR) and first appearance of
neovascularization (NV) in type I diabetes. SETTING: A longitudinal study
of 269 patients followed up annually. PARTICIPANTS: Participants had
insulin-dependent diabetes and were free of proliferative diabetic
retinopathy in both eyes at the baseline visit. MAIN OUTCOME MEASURE:
Stereoscopic color fundus photographs of each eye at each study visit,
graded for features of retinopathy. RESULTS: Among the 305 eyes for which
the duration of diabetes at the first appearance of mild NPDR could be
determined, NV developed in 28 by the end of the study. Survival analysis
showed that the later the onset of mild NPDR was, the shorter the time from
onset of mild NPDR to onset of NV (relative hazard for each additional year
to onset of mild NPDR, 1.22; 95% confidence interval, 1.10-1.35).
Adjustment for systolic and diastolic blood pressure, proteinuria, and
glycosylated hemoglobin (Hgb A10) levels did not change the relative hazard
estimate for onset of mild NPDR. Higher levels of Hgb A10 were associated
with a shorter time from onset of mild NPDR to onset of NV (relative
hazard, 1.26; 95% confidence interval, 1.05-1.51 [after adjusting for time
at onset of mild NPDR]), as were higher levels of diastolic blood pressure,
although not significantly (relative hazard for 10-mm Hg increase in
diastolic blood pressure, 1.52; 95% confidence interval, 0.82-2.83
[adjusting for onset of mild NPDR, Hgb A10 level, systolic blood pressure,
and proteinuria]). Neither proteinuria nor systolic blood pressure had an
effect on time from onset of mild NPDR to onset of NV, after adjustment for
time at onset of mild NPDR, Hgb A10 level, and diastolic blood pressure.
CONCLUSION: Later onset of mild NPDR is not necessarily associated with
delayed development of NV in patients with type I diabetes. Caution must
therefore be used in assessing the value of interventions that delay the
onset of mild NPDR without evidence of delayed onset of NV.
