FACTORS ASSOCIATED WITH RETROBULBAR HEMODYNAMIC MEASUREMENTS AT VARIABLE INTRAOCULAR-PRESSURE

Purpose: The authors determine those clinical variables that influence color Doppler measurements at spontaneous and artificially elevated i ntraocular pressure (IOP). Methods: Color Doppler peak systolic veloci ty (PSV), end diastolic velocity (EDV), and Pourcelot ratio (PR) were measured in the central retinal artery (CRA) and posterior ciliary art ery (PCA) at spontaneous IOP and artificially elevated IOP of 30 mmHg, 40 mmHg, and after release of suction-induced pressure elevation in 3 3 eyes of 33 patients. Those with varied ocular and systemic backgroun ds were enrolled to facilitate determination of relationships between these hemodynamic measures at elevated IOP and multiple patient charac teristics including the degree of glaucomatous damage. Results: Intrao cular pressure elevation reduced velocity and increased Pourcelot rati o in both vessels at 30 mmHg and at 40 mmHg. On release of suction-ind uced IOP elevation, velocity increased above the velocity measured at spontaneous IOP (hyperemic response). Blood pressure consistently corr elated with velocity and with PR in both vessels at all IOP levels tes ted, The change in velocity with IOP challenge decreased with age, and increased with vertical cup-to-disc ratio in the CRA, and decreased w ith ocular beta-blocker use in the PCA. Conclusion: Because blood pres sure and age relate to velocity, studies comparing cohorts with respec t to disease or drug effects should be matched for these variables. Wh ile it is clear that the presence of glaucoma and use of beta-blockers correlate with vascular parameters, from this study it is not possibl e to distinguish pathogenic factors from pathologic results of disease or drug effects.