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N. S. Kheradiya, A. Harris, I. BenZion, B. DeStefano, D. WuDunn, H. J. Garzozi, L. McCranor, C. W. Yung; Retrobulbar Hemodynamics and Intraocular Pressure in Primary Open Angle Glaucoma Patients. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4606.
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To investigate the relationship between retrobulbar blood flow velocities measured with color Doppler imaging (CDI) and intraocular pressure (IOP) in primary open angle glaucoma (POAG) patients
A retrospective analysis of 5 consecutive prospective POAG studies (69 POAG patients) carried out at the Indiana University School of Medicine was performed. Each patient was on timolol for one month prior to the study visit to minimize variations due to differing medications. For every patient, IOP was assessed as an average of three separate measurements using Goldman applanation tonometry. Retrobulbar blood flow velocities were assessed in the ophthalmic, central retinal, and short nasal and temporal posterior ciliary arteries using CDI (Siemens Quantum 2000). Peak systolic velocity, end diastolic velocity, and calculated resistive index were determined for each vessel and statistically compared to the IOP for each patient. The strength of the linear association among IOP and CDI parameters was assessed using Pearson Correlation Coefficients.
End diastolic velocity in the central retinal and ophthalmic arteries were significantly correlated with IOP (r=0.31, p=0.008, r=0.3, p=0.01, respectively) in glaucoma patients. The calculated vascular resistance in the ophthalmic artery was also significantly correlated (inversely) to IOP (r=-0.28, p=0.02). No significant correlations; however, were observed between IOP and any measure of short posterior ciliary artery blood flow in this cohort of glaucoma patients.
The lack of correlation between the short posterior ciliary arteries and IOP in glaucoma patients may indicate impaired hemodynamic autoregulation in the blood vessels supplying the optic nerve head. In this POAG cohort, the inability of blood vessels supplying the pre-laminar, laminar and retinal microcirculation to respond to fluctuations in IOP may contribute to optic nerve head damage seen in glaucomatous optic neuropathy.
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