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L. M. Ventura, I. Golubev, O. Mansuri, F. Venzara, B. Lee, I. Nose, J.-M. Parel, V. Porciatti; Head-Down Posture Induces PERG Alterations in Glaucoma Suspects. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2876. doi: https://doi.org/.
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To characterize the changes in IOP, systemic blood pressure, and PERG in normal subjects and in glaucoma suspects after head-down posture (-10 deg body tilt).
In 28 normal subjects (mean age 37 ± 15 years) and 56 glaucoma suspects (mean age 56 ± 9 years), IOP, brachial blood pressure and PERG were measured in three positions (~10 minutes apart): (1) seated position (baseline), (2) head-down at -10 deg on a tilting bed (tilt), and (3) seated again (recovery). IOP was measured by means of a non-contact tonometer (Reichert PT-100); baseline values were: controls: 13.7 ± 2.1 mm Hg, patients: 16.5 ± 4.0 mm Hg. PERG was recorded simultaneously from both eyes by means of skin electrodes (PERGLA paradigm, Ophthalmology, 200,111:161-8).
Baseline PERG values were: amplitude controls, 1.16 ± 0.43 µV, patients: 0.8 ± 0.27 µV; phase controls: 1.87 ± 0.1 π rad, patients: 1.75 ± 0.12 π rad. Upon tilting, IOP increased (P<0.01) to a similar extent in controls and patients (controls: 17.0 ± 17%, patients: 18.2 ± 10.9% mm Hg). By contrast, PERG amplitude and phase decreased (P<0.01) more in patients than in controls (amplitude controls: minus 13.0 ± 23%, patients: minus 37.5 ± 28.8%; phase controls: minus 1.2 ± 3.7%, patients: minus 4.9 ± 7.8%). In patients, eyes with PERG changes exceeding the 95% tolerance intervals of changes occurring in controls were 26% for amplitude and 17% for phase. Correlations between IOP changes and PERG changes were not significant. The estimated Ocular Perfusion Pressure (OPP) during tilting, compared to baseline, did not change in controls and tended to a slight increase in patients. Changes in OPP were not correlated with PERG changes. IOP and PERG returned to baseline values in the recovery condition.
Head-down (-10 deg) body tilting induces measurable and reversible reductions of RGC function in a subpopulation of glaucoma suspects but not in normal controls. This non-invasive protocol may disclose impaired autoregulation and/or susceptibility to IOP insult in glaucoma suspects.
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