Differences in pulsatile ocular blood flow among three classifications of diabetic retinopathy.

PURPOSE: Choroidal blood flow may be determined by pulsatile ocular blood flow (POBF) measurements. In the present study, the POBF of diabetic patients with increasingly severe retinopathy was compared with that in nondiabetic control subjects.
METHODS: The study was a masked cross-sectional analysis. Seventy-seven diabetic subjects, including 13 with mild or no retinopathy, 36 with moderate to severe retinopathy, and 28 with proliferative diabetic retinopathy (PDR), previously treated with panretinal photocoagulation (PRP). Fifty-six nondiabetic control subjects served as the comparison group. All subjects underwent masked measurement of POBF in the right eye by Langham pneumotonometry. Analysis of variance (ANOVA) determined whether differences existed between groups. Pair-wise comparisons between groups were conducted by Student's t-test.
RESULTS: The main outcome measures were ophthalmic pulse amplitudes, intraocular pressure (IOP), heart rate, and POBF. Patients with moderate to severe nonproliferative diabetic retinopathy (NPDR) had POBF 18% higher than the control (mean OBF, 943 microL/min). Among PRP-treated subjects with PDR, ocular blood flow was 22% below the control (mean OBF, 619 microL/min), and 34% less than moderate to severe nonproliferative diabetic retinopathy. Diabetic patients with no retinopathy or mild NPDR had OBF indistinguishable from the control (785 vs. 797 microL/min). Differences between the four groups were statistically significant by ANOVA (P < 0.0001).
CONCLUSIONS: POBF is unaffected early in diabetic retinopathy, but increases significantly in eyes with moderate to severe NPDR. POBF is decreased in eyes with laser-treated PDR. These experimental data represent the largest published assessment of POBF in NPDR. This is the first study to examine POBF in subjects with PRP-treated PDR.