ARE THERE REAL AND PSEUDO-NORMAL PRESSURE GLAUCOMAS - INFLUENCE OF THE INTRAOCULAR-PRESSURE IN THE SUPINE POSITION ON NORMAL-TENSION GLAUCOMA

Background Elevation of intraocular pressure in the supine position ha s been previously described in literature. Aim of this study is to inv estigate the elevation of intraocular pressure in normal tension glauc oma and its effect on the morphology of the optic disc, Visual field f unction and capillary blood flow of the retina and optic disc. Patient s and methods 56 eyes of 28 preperimetric and advanced normal tension glaucoma patients were prospectively evaluated. Ten eyes of ten normal patients served as a control group for the measurements of the intrao cular pressure. In the course of a 24-h pressure profile applanation t onometry was performed in the morning in a supine and three and ten mi nutes later in a sitting position with Draeger's and Goldmann's tonome ters. Arterial blood pressure was measured at the same time. The optic disc's morphology was evaluated by stereo photographs and Laser Scann ing Tomography. As a sensory test computer perimetry was used. Capilla ry blood flow was measured at defined areas of the retina and optic di sc. An intraocular pressure above 21 mm Hg in the supine position was used as a criterium to define two groups of normal tension glaucoma pa tients. Results In the supine position a statistically significant ele vation of intraocular pressure was observed in 24 normal tension glauc oma patients by 6.2+/-2.8 mm Hg up to 21.8+/-3 mm Hg. Diastolic blood pressure in the supine position (80+/-10.5 mm Hg) was significantly lo wer than in the sitting position (94+/-11 mm Hg, p=0.021). 12 of 28 no rmal tension glaucoma patients showed an intraocular pressure lower th an 22 mm Hg in the supine postion. In these patients a tendency toward s a higher incidence for the occurence of optic disc haemorrhages and significantly higher values for blood now (p<0.0005) and volume (p<0.0 05) in the retina and optic nerve head could be shown. In this group o f normal pressure glaucoma patients a higher incidence of migraene and vasospastic complaints was reported in the patients' history. Conclus ion In this study some normal tension glaucoma patients showed intraoc ular pressures in the supine position higher than 21 mm Hg and a lower diastolic arterial pressure. The higher incidence of haemorrhages and higher values for flow and volume parameters of the optic disc in nor mal tension glaucoma patients with an intraocular pressure lower than 22 mm Hg implicate the existence of two entities: real and pseudo norm al tension glaucomas.