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Sylvana Ventzke, Eberhard Spoerl, Michael Haustein, Lutz E. Pillunat, Richard Stodtmeister; The Perfusion Pressure In The Prelaminar Layer Of The Optic Disc May Be Decreased By An Enhanced Pressure In The Central Retinal Vein. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3481.
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The prelaminar layer (PL) of the optic nerve head (ONH) is drained by the central retinal vein (CRV). In case this vessel doesn’t pulsate the pressure in it is higher than the intraocular pressure (IOP) and the perfusion pressure (PP) is lower than generally calculated. The CRV pressure has been measured until now by instruments calibrated in arbitrary units or in gram. In this study we used the contactlens dynamometer calibrated in mmHg. The values obtained may serve in calculating the perfusion pressure in the PL of the ONH.
Case control study. Subjects: Primary open angle glaucoma (POWG) n=27; age:69±9 years (arith.mean±std.dev.); m/f=7/20). Controls: n=27; age:68±10 years ; m/f=7/20. Measurement of the vein pulsation pressure (VPP) by contact lens dynamometry (Meditron, Voelklingen, Germany). IOP measurement: Goldmann applanation tonometry.
Spontaneous pulsation of the CRV (yes/no): POWG: OD: 10/17; OS: 9/18. Controls: OD: 26/1; OS: 25/2. Χ²-test OD and OS: p<0.05. Pulsation pressure of the central retinal vein (VPP) (pressures in mmHg): POWG: OD: 16.8±5.0; OS: 17.7±6.3. Controls: OD: 11.9±3.8; OS: 11.8±3.6. Difference statistically significant: t-test: p<0.01 in OD and OS. Normal distribution. IOP: POWG: OD: 15,4±2.9; OS: 14.9±2.8. Controls: OD: 14.4±2.7; OS:14.4±2.8. Normal distribution. CRV Pressure higher than IOP: POWG : OD n=18, OS n=19. Controls: OD n=6, OS n=4. In these cases the CRV pressure was higher than the IOP (distributions skewed to the right) : POWG: OD: 0.4;2.7;16.3 (Min;Med;Max), OS:0.3;4.0;23.0. Controls: OD: 1.0;2.0;6.0, OS: 1.0;1.5;3.0.
As expected according the observed frequencies of pulsations the average VPP was higher in glaucoma patients than in controls. In POWG patients the number of "no pulsation" was higher than the number of VPP values higher than the IOP. That may be explained by the coupling of the instrument to the eye. In 2/3 of our POWG patients the VPP values were higher than the IOP. In theses cases the PP in the CRV may be calculated: PP= (MAP of opththalmic artery) - VPP resulting in a lower PP than assumed until now.
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