Central retinal venous pulsation pressure in different stages of primary open-angle glaucoma.

BACKGROUND: To evaluate the central retinal venous pulsation pressure (CRVPP) in patients with intraocular pressure (IOP)-controlled early, moderate and advanced open-angle glaucoma and a healthy control group. METHODS: CRVPP was measured with a contact lens dynamometer calibrated in mm Hg (Meditron GmbH, Voelklingen, Germany) in 34 patients with IOP-controlled open-angle glaucoma who were selected consecutively and according to the stage of their visual fields and 27 age-matched healthy controls. If a spontaneous venous pulsation was seen, CRVPP was considered to be equal to IOP. Visual fields were tested with the Humphrey 30-2 SST programme. The ocular perfusion pressure was conventionally calculated as OPP1=2/3MAP - IOP (MAP=systemic mean arterial blood pressure) and, using the measured CRVPP in the formula, as OPP2=2/3MAP - CRVPP. Statistical analysis was performed using the Kruskal-Wallis and the Mann-Whitney U test. RESULTS: Median CRVPP was 14.0 mm Hg (IQR 12.0-16.0) in controls, 15.0 mm Hg (IQR 14.0-17.0) in early, 38.9 mm Hg (IQR 29.9-48.4) in moderate and 34.6 mm Hg (IQR 23.9-51.0) in advanced glaucoma cases. The conventionally calculated OPP1 was 49.8 mm Hg (IQR 42.7-57.6) for controls, 56.9 mm Hg (IQR 55.3-58.8) for early, 56.6 mm Hg (IQR 51.2-64.4) for moderate and 59.3 mm Hg (IQR 53.9-61.6) for advanced cases. OPP2 was equal to OPP1 in the control group, 56.1 mm Hg (IQR 54.5-57.9) in early, 25.1 mm Hg (IQR 15.7-38.6) and 34.2 mm Hg (IQR 20.4-47.5) in moderate and advanced cases. This difference was statistically significant for moderate (OPP2 lower; p=0.003) and advanced (OPP2 lower; p=0.002) cases. CONCLUSIONS: In more advanced cases of glaucoma, CRVPP seems to be much higher than previously thought. This might further compromise the perfusion pressure in the prelaminar region of the optic nerve head and be of clinical importance, especially in IOP-controlled more advanced cases. This should be considered as a possible risk factor for progression. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov ID: NCT01503996.

Enhanced pressure in the central retinal vein decreases the perfusion pressure in the prelaminar region of the optic nerve head.

PURPOSE: The pressure in the central retinal vein (CRVP) has been shown to be higher in glaucoma patients than in controls. Until now, these measurements have been performed in arbitrary units or in units of ophthalmodynamometric force. In our study, a contact lens dynamometer, calibrated in mm Hg, was used to calculate the retinal perfusion pressure. METHODS: A total of 27 patients with primary open angle glaucoma (POAG) and 27 healthy control subjects were included in the study. The IOP measurement included Goldmann applanation tonometry, whereas the pressure enhancement measurement consisted of contact lens dynamometry. results: the pressures are given in mm hg, and are expressed as the mean ± SD for the control subjects versus the POAG patients: IOP 14.4 ± 2.7 vs. 15.4 ± 2.9, systolic blood pressure 141 ± 20.1 vs. 153 ± 16.5 (P = 0.013), central retinal vein threshold pressure (CRVTP) 11.9 ± 3.8 vs. 16.8 ± 5.0, CRVP 15.0 ± 2.7 vs. 17.9 ± 4.2, and retinal perfusion pressure (PPret) standard 84 ± 12.2 vs. 94 ± 9.1 and new 83 ± 12.2 vs. 91 ± 9.6. The differences in PPret between using the new versus the standard method are 0.55 ± 1.33 vs. -2.5 ± 3.89 (P = 0.041 and P = 0.002, respectively). The PPret was at least 5.0 mm Hg lower in 5 of the 27 POAG patients when the new calculation method was used. CONCLUSIONS: The perfusion pressure in the retina and prelaminar region of the optic nerve head (ONH) may be lower than expected because the CRVP may be higher. The pressure measurement in the central retinal vein may be a step toward a better understanding of ONH pathophysiology.