Antiglaucomatous drugs effects on optic nerve head flow: design, baseline and preliminary report

Color Doppler imaging in ocular hypertension and open-angle glaucoma

“…On the other hand, there was a similarity in the blood-flow velocities between ocular hypertensive patients and normal subjects. The existence of intact autoregulation in ocular hypertension [8,26] and faulty autoregulation in glaucoma [8,23] may explain these findings, because autoregulation can maintain a constant blood flow despite changes in IOP. Based on these findings, we may speculate that blood flow and vascular autoregulation in ocular hypertension is maintained at least to a certain extent despite increased IOP; thus, our findings support the hypothesis that ocular hypertensive patients have more normal blood flow and autoregulation than those with glaucoma patients (glaucoma patients <ocular hypertensive patients <normal subjects).…”

Autoregulation of optic nerve head blood flow and its role in open-angle glaucoma

“…Retrobulbar (OA, CRA) 30 normals CDI Postural change No difference in velocity or RI in OA but significant difference between OA and CRA (p < 0.01 and p < 0.001) due to significant rises in pulse (p < 0.05) and DBP (p < 0.01) brought on by postural change; fall in RI in CRA with administration of timolol (p < 0.05) with effects independent of any simultaneous decrease in IOP in timolol eye (p < 0.01) [147] Evans et al In the CRA, all three groups had similar changes in EDV and RI, but that only the NTG group had a statistically significant change in PSV from sitting to supine [148] Joos et al indicating that the normal healthy eye is not able to regulate to maintain PCA blood flow velocities in response to these large induced increases in IOP [159] Garhofer et al MFVs lower in SPCA and CRA of OAG; nonlinear relationship between the pulsatility and resistive indices compared to the linear relationship that is seen in normal individuals [166] Shoshani et al [167] Pillunat et al IOP increase with scleral suction cup No significant decrease in blood flow until IOP elevations around 45-55 mmHg in all patients [157] Riva et al IOP increase with scleral suction cup Autoregulation failed at OPP of 10-15 mmHg [158] Weigert et al IOP increase with scleral suction cup In response to a moderate increase in IOP induced by scleral suction cup, there was no significant difference in ocular blood flow response between glaucomatous eyes and controls [160] Schmidl et al Isometric exercise (squatting) MAP, IOP and OPP significantly increased after squatting but no significant change to average blood flow [153] Schmidl et al Isometric exercise (hand gripping) Increase of flow (19%) resulting from an increase in velocity (17%) and volume (6%) was significantly less than predicted for a passive autoregulatory response; efficiency of autoregulation in normal subjects varies [155] Sampolesi et al Therapeutic IOP lowering In more advanced stages of glaucoma, autoregulation is not preserved, and antiglaucoma medications cannot restore normal ONH flow [161] Hafez et al Therapeutic IOP lowering Mean correlation between OPP and flowmetry prior to treatment was small (r = 0.32); it was even smaller after 6 months of IOP lowering (r = 0.15), suggesting that this population of both OAG and OHT patients had deficient autoregulation that was improved by lowering the IOP either with timolol or dorzolamide [162] Feke et al [149] Sehi et al velocity from sitting to supine. The most significant finding of Galambos' results were that the velocities in the SPCA seems tightly controlled in controls with no significant changes in any CDI parameters, where there were significant changes to these hemodynamic parameters in both NTG and POAG patients.…”

“…Notably, the patients in the study were on IOP-lowering medications during the evaluation, and there is evidence suggesting that pressure-lowering medications may improve ONH blood autoregulation [160]. In distinction to the aforementioned studies that raised IOP externally, other studies have evaluated the role of IOP lowering on autoregulation of blood flow in glaucoma [24,161,162]. Hafez et al studied 40 of their patients with either OAG or OHT who successfully had their IOP lowered by ‡20% within 1 month via any method as part of their routine treatment course in order to compare the ONH Heidelberg retinal flowmetry (HRF) before and after the IOP decrease.…”

“…One method by which this has been achieved is by artificially increasing IOP with scleral ring or scleral suction cup [99,[157][158][159][160]. Other studies have measured ocular blood flow in response to pressure lowering as part of routine glaucoma therapy [24,161,162].…”

Comparative Analysis of the Effects of Brimonidine and Dorzolamide on Ocular Blood Flow Velocity in Patients with Newly Diagnosed Primary Open-Angle Glaucoma

“…[28][29][30] However, Latina and colleagues 31 found that dorzolamide-not brimonidine-caused a statistically significant and sustained improvement in blood flow from baseline in the superotemporal and nasal peripapillary retinal regions using SLDF as examining tool. Scanning laser Doppler flowmeter is a noninvasive method, which allows blood flow measurement in specific retinal areas.…”