Retinal blood flow measurements and neuroretinal rim damage in glaucoma

Abstract

Aim: To assess retinal blood flow characteristics in subjects with normal tension glaucoma (NTG), primary open angle glaucoma (POAG), and a group of controls using the Heidelberg retina flowmeter (HRF). The vascular parameters were correlated against structural damage of the optic nerve head, assessed using the Heidelberg retina tomograph (HRT). Methods: HRF images were obtained in 76 subjects with NTG, 58 with POAG, and 38 controls. Optic nerve head images, acquired using the HRT, were analysed with Moorfields Regression Analysis software. The HRF variables, measured adjacent to a rim segment identified as ''abnormal,'' were compared with the vascular parameters of the ''normal'' rim segments. The HRF parameters of the segments identified as normal in glaucoma subjects were compared with matched control segments. Results: The glaucoma subjects had significantly lower retinal haemodynamics than the control subjects. There were no significant differences in the HRF parameters between the NTG and POAG subjects. The discs that had been identified as having abnormal segments had lower HRF values than those with a corresponding normal segment. The glaucoma subjects with normal rim segments had statistically significant lower velocity, flow, and volume measurements than the controls for each location sampled. Conclusion: This study shows a relation between structural damage of the optic nerve head and the level of retinal blood flow. The changes in the circulation could indicate that it may be an early marker of the pathological process.T he vascular aetiology of glaucoma hypothesises that a compromised blood supply to the optic nerve head contributes to optic nerve head damage. Localised damage may occur when the ocular perfusion pressure falls outside the normal range of autoregulation. This may be the result of a systemic dysfunction (low systemic blood pressure, large nocturnal dips in blood pressure, or peripheral vasospastic disorders), 1-5 or a local abnormality in the ocular blood supply. [6][7][8] The Heidelberg retina flowmeter (HRF, Heidelberg Engineering GmbH, Heidelberg, Germany) allows noninvasive quantification of the perfusion of the retina and optic nerve head. 9 The use of a confocal laser in this instrument has refined the technique of laser Doppler flowmetry by allowing discrete areas of the retina to be examined with an axial resolution of 300 mm.9 The incorporation of a scanning technique allows multiple sampling measurements over the area of interest. These measurements are utilised in the fast Fourier transformation algorithm. The validity and reproducibility of the technique have been well documented. 9-12The aim of this study was to compare the blood flow, volume and velocity as measured by the HRF between subjects with normal tension glaucoma (NTG), primary open angle glaucoma (POAG) and a group of controls. These vascular parameters were correlated against structural damage on the optic nerve head, as assessed using the Heidelberg retina tomograph (HRT, Heidelberg Engineering GmbH, Heidelbe...

Glaucoma and ocular blood flow: an anatomical perspective

“…Similar findings have been reported in exfoliative glaucoma in that decreased neuroretinal rim area was found to be correlated with decreased blood flow to the lamina cribrosa and rim, but not the peripapillary retina [120]. However, it has been shown that neuroretinal rim damage is associated with local blood flow reduction in OAG patients [121]. Abnormalities in ONH morphology were shown to be localized to quadrants that corresponded to lower blood flow.…”

Two-Year Randomized, Placebo-Controlled Study of Black Currant Anthocyanins on Visual Field in Glaucoma

“…Several clinical investigators [23,24,25] have revealed that both optic disk rim blood flow and peripapillary retinal blood flow are significantly lower in patients with OAG as compared with age-matched controls, and thus optic disk rim blood flow is significantly correlated with deterioration of existing visual field defects. Hafez et al [26] evaluated and compared optic disk rim blood flow in patients with OAG and those with ocular hypertension (OH) and found that OAG patients had significantly lower values than OH patients.…”

Glaucoma Risk Factors: Ocular Blood Flow

“…These losses have been related to larger cup-to-disc ratios, 166 and are spatially associated with optic nerve head structural damage and visual field defects. 167,168 Specifically, Logan et al 167 found decreased capillary flow in areas of the retina associated with abnormal optic disc segments. In contrast, normal optic disc segments from these same glaucoma patients were not associated with compromised retinal flow.…”

“…These losses have been related to larger cup-to-disc ratios, 166 and are spatially associated with optic nerve head structural damage and visual field defects. 167,168 Combined with the previous technologies' data on retinal blood flow, HRF measurements point to a reduction in retinal blood supply in ophthalmic disease such as glaucomatous optic neuropathy.…”