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G. T. Feke, J. Kolodjaschna, L. Pitler, J. W. McMeel, M. Lorenzi; Abnormal Retinal Vascular Reactivity in Response to Posture Change in Well-Controlled Type 1 Diabetic Patients With No Retinopathy. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3263.
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We recently reported that patients with well-controlled type 1 diabetes with no or minimal retinopathy do not show retinal circulatory abnormalities at steady state. We suggested that it may be necessary to apply a challenge to uncover subtle abnormalities. A change in posture from sitting to lying down produces an increased blood pressure at the entrance to the retinal circulation. We thus tested the retinal vascular response to posture change in a group of patients with the above characteristics.
We tested 13 patients with type 1 diabetes and no retinopathy (age 30.7± 9.1 years, mean ± SD, duration of diabetes 12.5 ± 5.9 years, and HbA1c 7.2 ± 0.5%) and 6 healthy control subjects (age 29.0 ± 10.1 years). Arterial diameter, blood speed, and blood flow rate in the superior temporal retinal artery of the left eye were measured first while sitting and then while reclining for approximately 30 minutes using a Canon retinal laser Doppler instrument. Brachial artery blood pressure and heart rate were measured periodically during the test. Nonparametric statistical tests were used in the analysis.
In the controls, arterial diameter decreased by 5.4 ± 2.2% (p=0.027) and blood speed increased by 16.2 ± 12.3% (p=0.028). The 4.7 ± 12.7% increase in blood flow rate was not significant (p=0.92). In contrast, only 7 of the 13 diabetic patients exhibited a decrease in arterial diameter (5.5 ± 1.6%, p=0.018) while reclining. The remaining 6 failed to show a decrease, instead showing a non-significant increase of 3.1 ± 3.5% (p=0.102). The arterial diameter response to posture change in this subgroup was significantly (p=0.003) different compared to the responses in the other diabetic subgroup and in the controls. This subgroup also failed to show a significant increase in blood speed while reclining (p=0.46). There were no significant differences in age, duration of diabetes, HbA1c, or arterial diameter while sitting between the two subgroups.
Our results show that the retinal vascular response to posture change is abnormal in a substantial portion of the well-controlled type 1 diabetic patients with no retinopathy that we tested. Studies are in progress to ascertain whether this abnormality in retinal vascular reactivity can be used as a marker for the development of clinical retinopathy and as a surrogate endpoint for preemptive treatments.
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