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R. M. Feldman, T. C. Prager, N. P. Bell, D. A. Lee, S. J. Muylaert; The Effect of Positional and Light/Dark Changes on Angle Opening Distance and Volume in Normals. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5095. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Ultrasound biomicroscopy (UBM) provides important information about the mechanisms of angle closure in glaucoma. The application of UBM has been limited by requiring supine measurements. The new bag/balloon technology has made positional measurements possible. To date there is a paucity of data when examining changes from positional and light variations on anterior chamber configuration. Anatomic changes in the anterior chamber between sitting and supine positions and in both light and dark conditions are compared.
A 35 MHz Sonomed VuMax II ultrasound biomicroscope using the ClearScanTM bag/balloon technology was utilized to visualize the anterior chamber angle. An automated program determined the angle opening distance (AOD) at 500 microns anterior to the scleral spur and the resultant angle volume with the mean of three measurements taken as datum in each test condition (light/dark X inferior/superior quadrant X sitting upright/supine X 5 subjects). Presentations of test conditions were randomized. Ambient light conditions were standardized with dim red light in the mesopic dark test phase.
Sitting vs. supine demonstrated a 19.4% greater AOD, dark condition, for the superior quadrant compared to 13.4% for the inferior quadrant. Sitting vs. supine showed an 11.4% greater AOD, light condition, for the superior quadrant compared to 8.3% for the inferior quadrant.
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