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M. T. Nicolela, A. Belliveau, A. Mishra, M. L. Archibald, L. L. Terry, B. C. Chauhan; Increase of Plasma Endothelin-1 After Body Cooling: Relationship to Optic Disc Phenotypes, Disc Haemorrhages and Retinal Blood Flow. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5063.
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To compare retinal blood flow and changes of plasma endothelin-1 (ET-1) after body cooling in patients with different optic disc phenotypes and in patients with and without optic disc haemorrhages (ODH).
136 open-angle glaucoma patients with one of three optic disc phenotypes (focal, diffuse or sclerotic damage) being followed in a prospective study were submitted to a 30 minutes body cooling provocation test to measure changes in plasma levels of ET-1 at the 20th month visit. Additionally, these patients had their retinal peripapillary blood flow measured in the temporal area with the Heidelberg Retina Flowmeter. Patients identified as having at least one ODH in their annual optic disc photographs were compared to those without ODHs during follow-up.
48 patients with focal, 44 patients with diffuse and 44 patients with sclerotic optic disc phenotypes (mean age of 69 + 12, 63 + 11 and 72 + 9 years old respectively) are enrolled in the study. Baseline plasma ET-1 was similar between the three groups (mean of 0.94 + 0.47, 0.94 + 0.38 and 0.96 + 0.36 pg/ml respectively). After cooling, there was a significant increase in plasma ET-1 in patients with focal and sclerotic disc, but not in those with diffuse damage (p<0.05). The mean (95% CI) percentage increase of ET-1 was 26% (5 to 47%), 0.6% (-11 to 12%) and 16% (4 to 28%) in patients with focal, diffuse and sclerotic discs respectively. No differences in retinal blood flow were observed between the three groups. After reviewing their disc photographs (median of 3 photos per patient in the three groups, ranging from 1 to 4), 11 (30%) patients with focal. 7 (16%) patients with sclerotic and no patient with diffuse damage were identified as having at least one ODH in the study eye (p = 0.005). Patients with ODH had greater increase in plasma ET-1 than patients without ODH (average increase of 47% versus 10% respectively, p = 0.008). They also tended to have lower baseline retinal blood flow than those without ODHs (288 + 52 versus 314 + 79 AU, p=0.1).
This study showed that patients with focal and sclerotic optic disc phenotypes have significant increases in plasma ET-1 after body cooling, differently than patients with diffuse damage. Among these, patients with ODHs during follow-up had the highest changes in plasma ET-1, as well as a trend to lower baseline retinal blood flow. This study supports a role for abnormal vascular reactivity in patients with focal and sclerotic disc damage, particularly in cases with ODHs.
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