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Hak Sung Chung, Alon Harris, Paul J. Halter, Larry Kagemann, Emma J. Roff, Hanna J. Garzozi, Sarah L. Hosking, Bruce J. Martin; Regional Differences in Retinal Vascular Reactivity. Invest. Ophthalmol. Vis. Sci. 1999;40(10):2448-2453.
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purpose. Although glaucomatous visual field defects are more common in the superior field
than in the inferior field, microaneurysms are more frequent in the
superior than in the inferior retina in diabetic retinopathy. The
authors hypothesized that differences in vascular hemodynamics in the
two areas might contribute to these phenomena.
methods. The blood flow response to hyperoxia and hypercapnia was evaluated in
peripapillary retinal tissue superior and inferior to the optic nerve
head using confocal scanning laser Doppler flowmetry. In 14 young,
healthy persons, blood flow was measured while breathing room air and
during isocapnic hyperoxia (100% O2 breathing) and isoxic
hypercapnia (Pco2 increased 15% above baseline).
Histograms were generated from pixel-by-pixel analysis of retinal
portions of superior and inferior temporal quadrants of the entire
results. Baseline blood flow in the inferior temporal quadrant was
significantly greater than in the superior temporal quadrant
(P < 0.05). However, the inferior region failed to
increase in perfusion during hypercapnia and experienced significant
mean blood flow reduction; flow reduction in the pixels at the 25th,
50th, 75th, and 90th percentile of flow; and an increased percentage of
pixels without measurable flow, during hyperoxia (each P < 0.05). In contrast, in the superior temporal
region, hyperoxia failed to reduce blood volume, velocity, or flow,
whereas hypercapnia significantly increased mean flow; increased flow
in the pixels at the 25th, 50th, 75th, and 90th percentile of flow; and
reduced the percentage of pixels without measurable flow (each P < 0.05).
conclusions. The inferior temporal quadrant of the peripapillary retina is, in
comparison with the superior temporal region, less responsive to
vasodilation and more responsive to vasoconstriction. These differences
could contribute to different susceptibility to visual field defect or
vascular dysfunction in the superior and inferior
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