Correlation Between Finger Blood Flow and Changes in Optic Nerve Head Blood Flow Following Therapeutic Intraocular Pressure Reduction

The Association between the Pulsatile Choroidal Volume Change and Ocular Rigidity

Purpose

To assess the relationship between the pulsatile choroidal volume change (ΔV) and ocular rigidity (OR), an important biomechanical property of the eye.

Design

This is a prospective cross-sectional study.

Subjects

Two hundred seventeen participants (235 eyes) were included in this study. Of those, 18 eyes (18 participants) had exudative retinal disease, and 217 eyes (199 participants) had open-angle glaucoma (39.2%), suspect discs (12.4%), ocular hypertension (14.3%), or healthy eyes (34.1%).

Methods

Pulsatile choroidal volume change was measured using dynamic OCT, which detects the change in choroidal thickness during the cardiac cycle. Ocular rigidity was measured using an invasive procedure as well as using a validated optical method. Correlations between ΔV and OR were assessed in subjects with healthy eyes, eyes with glaucoma, or eyes with exudative retinal disease.

Main Outcome Measures

Ocular rigidity and pulsatile ocular volume change.

Results

In 18 eyes where OR was obtained invasively and ΔV was obtained noninvasively, a significant correlation was found between ΔV and OR (rs = -0.664, P = 0.003). Similarly, a strong inverse correlation was found between the noninvasive measurements of both ΔV and OR (rs = -0.748, P < 0.001) in a large cohort and maintained its significance across diagnostic groups (a more compliant eye is associated with greater ΔV). No correlation was found between ΔV and age, blood pressure, intraocular pressure, axial length, or diagnosis (P ≥ 0.05). Mean ΔV was 7.3 ± 3.4 μL for all groups combined with a range of 3.0 to 20.8 μL.

Conclusions

These results suggest an association between the biomechanics of the corneoscleral shell and pulsatile ocular blood flow, which may indicate that a more rigid eye exerts more resistance to pulsatile choroidal expansion. This highlights the dynamic nature of both blood flow and biomechanics in the eye, as well as how they may interact, leading to a greater understanding of the pathophysiology of ocular disease.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Ocular rigidity and neuroretinal damage in patients with vasospasticity: a pilot study

OBJECTIVE

Evidence suggests that ocular blood flow dysregulation in patients with vasospasticity could occur in response to biomechanical stimuli, contributing to optic nerve head susceptibility in glaucoma. We evaluate the role of vasospasticity in the association between ocular rigidity (OR) and neuroretinal damage, hypothesizing that low OR correlates with greater glaucoma damage in patients with vasospasticity.

DESIGN

Cross-sectional study.

PARTICIPANTS

Patients with open-angle glaucoma (OAG), suspect discs, or no glaucoma.

METHODS

OR was measured using a noninvasive, validated method developed by our group. Retinal nerve fibre layer (RNFL) and ganglion cell complex thicknesses were acquired using spectral domain optical coherence tomography. Vasospasticity was assessed by a standardized questionnaire that was based on existing validated questionnaires and adapted to our requirements. Atherosclerosis was evaluated based on Broadway and Drance's (1998) cardiovascular disease score. Correlations between OR and structural parameters were assessed in patients with vasospasticity and those with atherosclerosis.

RESULTS

Of 118 patients with either OAG (n = 67), suspect discs (n = 26), or no glaucoma (n = 25) who were recruited consecutively, 10 were classified as having vasospasticity, and 37 as having atherosclerosis. In the vasospastic group, significant correlations were found between OR and the minimum ganglion cell complex thickness (rs = 0.681, p = 0.030), the average RNFL thickness (rs = 0.745, p = 0.013), and the RNFL in the temporal quadrant (rs = 0.772, p = 0.009), indicating more damage with lower OR. Similar trends were maintained when applying multiple testing correction; however, only the eighth RNFL clock hour corresponding to the inferior-temporal peripapillary region remained significantly correlated with OR in the vasospastic group (p = 0.015). In contrast, no correlation was found in the atherosclerotic group (p > 0.05).

CONCLUSIONS

The findings of the current pilot study indicate a trend for more neuronal structural damage in less-rigid eyes of patients with vasospasticity, meaning that OR may play a greater role in glaucoma in vasospastic patients than in patients with atherosclerosis. Although these results provide interesting insight into the pathophysiology of OAG, further investigation is needed to confirm our observations.

Peripheral vascular disease - a new vascular disease associated with normal tension glaucoma: a case report

INTRODUCTION

Normal-tension glaucoma is known as a multifactorial optic neuropathy. A number of lines of evidence suggested that vascular factors played a significant role in the development of normal-tension glaucoma. The mechanisms underlying the abnormal ocular blood flow in normal-tension glaucoma are still not clear. Peripheral vascular disease seems to be associated with glaucoma populations independent of other cardiovascular risk factors. We found this presentation, for the first time, to our knowledge, as another probable vascular abnormality related to our patient with normal-tension glaucoma, although it is necessary to confirm its pathological effect in future studies.

CASE PRESENTATION

Our patient was a 48-year-old Spanish man without any personal and family history of interest except for circulatory problems of the lower limbs with repetitive ulcers at the frontal and lateral aspects of his legs. His chief complaint was vision loss when he came to consult us. In exploration, his best corrected visual acuity was 20/20 in both eyes; initial intraocular pressure in the right eye was 14-16 mmHg and in the left eye was 16-18 mmHg, with a mild sclerosis of the lens in slit-lamp examination. No inflammation or pigmented lesion was detected in the anterior chamber. Open angle confirmed by Goldman four quadrants gonioscopy. Funduscopic examination revealed a vertical cup disc ratio of 0.6 in the right eye and 0.8 in the left eye. The patient's neuroretinal rim was normal in the right eye, and superior thinning in the left eye was determined. Examination of the patient's visual field showed inferior mild probable nasal scotoma in the right eye and an inferior deep arcuate scotoma defect in the left eye. His optical coherence tomography examination revealed thinning of the peripapillary nerve fiber layer thickness in the left eye and superior loss of macular retinal ganglion cells in the left eye. Normal intraocular pressure values were measured on the intraocular pressure curve without treatment (maximum value, 18-20 mmHg), discarding higher intraocular pressures measured out of office. Ultrasonic pachymetry measured 515/520 μm, and normal intraocular pressure measured with a PASCAL tonometer ruled out probable corneal biomechanical underestimations. The patient's polysomnography study was normal and excluded sleep apnea syndrome. The patient's serial mean blood pressure was normal, especially in the lower limbs (mean value, 125/70 mmHg), ruling out the possibility of systemic hypotension. Thyroidal and coagulation abnormalities, autoimmune disease, and inflammatory disease were excluded. Normal immunologic study and normal vascular biopsy were observed, as well as normal brain magnetic resonance imaging and a normal carotid vascular study. The primary diagnosis was moderate medium peripheral arterial disease in the lower limbs, which was confirmed by echography after ruling out other probable vascular abnormalities related to normal-tension glaucoma.

CONCLUSION

After ruling out other systemic diseases and vascular abnormalities related to normal-tension glaucoma, we found peripheral arterial disease as a probable vascular abnormality related to normal-tension glaucoma in our patient. To our knowledge, this is the first time such a case has been reported. Thus, further research is needed to determine the relevance of these results to the general population.

Endothelial dysfunction in cardiovascular disease and Flammer syndrome-similarities and differences

The endothelium has increasingly been recognized as a smart barrier and a key regulator of blood flow in micro- and macrovascular beds. Endothelial dysfunction marks a stage of atherosclerosis and is an important prognostic marker for cardiovascular disease. Yet, some people who tend to be slim and physically active and with rather low blood pressure show a propensity to respond to certain stimuli such as emotional stress with endothelial-mediated vascular dysregulation (Flammer syndrome). This leads to characteristic vascular symptoms such as cold hands but also a risk for vascular-mediated diseases such as normal-tension glaucoma. It is the aim of this review to delineate the differences between Flammer syndrome and its "counterpart" endothelial dysfunction in the context of cardiovascular diseases.

Ocular Blood Flow and Normal Tension Glaucoma

Normal tension glaucoma (NTG) is known as a multifactorial optic neuropathy characterized by progressive retinal ganglion cell death and glaucomatous visual field loss, even though the intraocular pressure (IOP) does not exceed the normal range. The pathophysiology of NTG remains largely undetermined. It is hypothesized that the abnormal ocular blood flow is involved in the pathogenesis of this disease. A number of evidences suggested that the vascular factors played a significant role in the development of NTG. In recent years, the new imaging techniques, fluorescein angiography, color Doppler imaging (CDI), magnetic resonance imaging (MRI), and laser speckle flowgraphy (LSFG), have been used to evaluate the ocular blood flow and blood vessels, and the impaired vascular autoregulation was found in patients with NTG. Previous studies showed that NTG was associated with a variety of systemic diseases, including migraine, Alzheimer's disease, primary vascular dysregulation, and Flammer syndrome. The vascular factors were involved in these diseases. The mechanisms underlying the abnormal ocular blood flow in NTG are still not clear, but the risk factors for glaucomatous optic neuropathy likely included oxidative stress, vasospasm, and endothelial dysfunction.

Relationship between ocular surface temperature and peripheral vasoconstriction in healthy subjects: A thermographic study

An impairment of ocular blood flow regulation is commonly considered one of the main pathogenetic mechanisms involved in the development of several eye diseases, like glaucoma. The aim of this study was to investigate whether an alteration of ocular blood supply induced by peripheral vasoconstriction might be detected by measuring the ocular surface temperature. The ocular surface temperature was evaluated in a group of 38 healthy young subjects (28 males and 10 females; mean age: 25.4 ± 4.1 years) by infrared thermography. For each subject, the experimental procedure consisted of two thermographic acquisitions both lasting 10 s, recorded before and during the immersion of both hands in a mixture of ice and water (1.6 °C ± 0.4 °C). Specifically, the second acquisition began 20 s after the hand immersion. Analysis of variance was used to compare the ocular surface temperature of the two profiles. The analysis of infrared images was carried out every 2 s: at the eye opening (t0) until 10 s (t5), for both profiles. Data showed that ocular surface temperature increased significantly ( p-value < 0.05), especially near the sources of ocular blood supply, that is, temporal and nasal areas (mean increasing temperature at t0 for P1 = 0.12 °C ± 0.13 °C). Therefore, these results suggest a response of the ocular hemodynamic to the peripheral vasoconstriction. The ocular surface temperature may represent a cheap, non-invasive and non-time-consuming test to evaluate ocular vaso-regulation.

Initial central scotomas vs peripheral scotomas in normal-tension glaucoma: clinical characteristics and progression rates

PURPOSE

To investigate clinical characteristics and progression rates of the initial central scotomas (ICS) compared with the initial peripheral scotomas (IPS) in normal-tension glaucoma (NTG) patients.

METHODS

Among NTG patients showing a single hemifield defect and who performed more than five reliable standard visual field (VF) tests, medical records of ICS (involvement of ≥3 adjacent points with P<5% within the central 12° of fixation and one point with a P<0.01 within the central 6° of fixation) (n=32) or IPS (no VF abnormality within the central 6° of fixation) (n=34) were retrospectively analyzed. The changes of mean thresholds from 10 zones of the glaucoma hemifield test, central 6° and 12° zones, peripheral zones other than central 6° and 12°, and the entire hemifield were inspected. To calculate the progression rates, linear mixed-effect model was employed.

RESULTS

There were no significant differences between the two groups in age, gender, ocular factors including baseline/mean treated intraocular pressure, and systemic factors including systolic or diastolic blood pressure/perfusion pressure, mean ocular perfusion pressure (all P>0.05). There were no significant differences in baseline mean deviation and pattern standard deviation (P>0.05) between the two groups, but VF index was significantly lower in ICS group than in IPS group (P=0.001). The progression rates between the two groups were not significantly different in all zones we investigated (all P>0.05).

CONCLUSIONS

Newly diagnosed cases of NTG with ICS may not differ from those with IPS in clinical characteristics and progression rates under treatment.

Relationship between optic nerve head and finger blood flow

PURPOSE

To examine the relationship between optic nerve head (ONH) and finger blood flow in subjects with and without a primary vascular dysregulation (PVD).

METHODS

ONH blood flow and finger blood flow was measured in 15 subjects with PVD and in 24 subjects without PVD. PVD was defined as being present if it was detected in patient history as well as by nailfold capillaromicroscopy. PVD was defined as being absent if the patient history for PVD was negative and the results of nailfold capillaromicroscopy were negative. Scanning laser Doppler flowmetry (LDF) was used to measure ONH and finger blood flow. Finger temperature was measured in all subjects using a contact sensor.

RESULTS

ONH blood flow is significantly related to finger blood flow in subjects with PVD (p<0.01), but not in subjects without a PVD. Subjects with PVD had a significantly lower finger skin temperature in comparison to those without PVD (p<0.01)

CONCLUSIONS

The present study indicates a relationship between ONH and finger blood flow in subjects with PVD. This might be an indirect sign of a disturbed autoregulation of ocular blood flow in PVD subjects.

C-reactive protein and lipid profiles in Korean patients with normal tension glaucoma

Purpose

To compare high-sensitivity C-reactive protein (hsCRP) levels and lipid profiles between Korean normal tension glaucoma (NTG) patients and healthy controls.

Methods

This cross-sectional study included 38 Korean patients with NTG and 38 age- and sex-matched healthy control subjects. We excluded the patients with cardiovascular risk factors and other systemic diseases that might affect CRP levels and lipid profiles. Each patient underwent a Humphrey visual field examination and blood sampling for hsCRP and lipid profile analyses. Subsequently, the NTG patients were classified into two groups based on their untreated intraocular pressure (IOP) level: low NTG (LNTG) with IOP≤13 mmHg (13 subjects) and high NTG (HNTG) with relatively high IOP (>13 and ≤21 mmHg, 25 subjects). The hsCRP levels and lipid profiles were compared between NTG patients and healthy controls, and between LNTG, HNTG, and healthy controls.

Results

There were no significant differences in hsCRP and lipid profiles between either the NTG patients and healthy controls, or between the LNTG, HNTG, and controls (p>0.05) after exclusion of Korean patients with cardiovascular risk factors. There was no significant association between hsCRP and visual field indices (p>0.05).

Conclusions

High-sensitivity C-reactive protein-related vascular inflammatory conditions may not be directly associated with the development of NTG, regardless of the untreated IOP level.

Twenty-four hour blood pressure pattern in patients with normal tension glaucoma in the habitual position

PURPOSE

To investigate the relationship between blood pressure (BP) parameters in the habitual position and glaucomatous damage at initial presentation in patients with untreated normal tension glaucoma (NTG).

METHODS

Fifty-four eyes from 54 subjects diagnosed with NTG were consecutively enrolled. BP was measured with an automated ambulatory monitoring device in the habitual position during 24-hour in-hospitalization. Patients were classified into three groups: non-dippers, dippers, and over-dippers. corresponded to the degree of reduction in their nocturnal mean arterial pressure (MAP) compared with their diurnal MAP. Regression models were used to evaluate potential risk factors, including: age, pre-admission office intraocular pressure (IOP), central corneal thickness (CCT), and BP parameters. Functional outcome variables for glaucomatous damage included mean deviation (MD) and pattern standard deviation (PSD) on a Humphrey field analyzer (HFA). Anatomic outcome variables were TSNIT score (temporal, superior, nasal, inferior, and temporal) average, superior average, inferior average, and nerve fiber indicator (NFI) score on scanning laser polarimetry with variable corneal compensation (SLP-VCC; GDx-VCC).

RESULTS

Marked systolic blood pressure (SBP), diastolic blood pressure (DBP), and MAP fluctuation were noted in the over-dipper group (p<0.05). A linear regression analysis model revealed that nocturnal trough DBP and MAP, average nocturnal SBP, and MAP were all significantly associated with a decreased average TSNIT score and an increased NFI score.

CONCLUSIONS

Nocturnal BP reduction estimated in the habitual position was associated with structural damage in eyes with NTG. This finding may suggest systemic vascular etiology of NTG development associated with nocturnal BP reduction.

What is the present pathogenetic concept of glaucomatous optic neuropathy?

Glaucomatous optic neuropathy implies loss of neural tissue, activation of glial cells, tissue remodeling, and change of blood flow. The blood flow reduction is not only secondary but has a primary component. Activation of astrocytes leads to an altered microenvironment. An unstable ocular perfusion, either due to IOP fluctuation or a disturbed autoregulation (due to primary vascular dysregulation syndrome) leads to a mild reperfusion injury. The superoxide (O(2)(-)) anion produced in the mitochondria of the axons, fuses with the nitric oxide (NO) diffusing from the astrocytes, leading to the damaging peroxynitrite (ONOO(-)). It is possible that the diffusion of endothelin and metalloproteinases to the surrounding of the optic nerve head leads to a local vasoconstriction and thereby increases the risk for venous occlusion and weakens the blood-brain barrier, which in extreme situations results in splinter hemorrhages. Activated retinal astrocytes can be visualized clinically. The involvement of primary vascular dysregulation in the pathogenesis of glaucomatous optic neuropathy may explain why women, as well as Japanese, suffer more often from normal-tension glaucoma.

What is the link between vascular dysregulation and glaucoma?

The need of blood flow to different organs varies rapidly over time which is why there is sophisticated local regulation of blood flow. The term dysregulation simply means that blood flow is not properly adapted to this need. Dysregulative mechanisms can lead to an over- or underperfusion. A steady overperfusion may be less critical for long-term damage. A constant underperfusion, however, can lead to some tissue atrophy or in extreme situations to infarction. Unstable perfusion (underperfusion followed by reperfusion) leads to oxidative stress. There are a number of causes that lead to local or systemic vascular dysregulation. Systemic dysregulation can be primary or secondary of nature. A secondary dysregulation is due to other autoimmune diseases such as rheumatoid arthritis, giant cell arteritis, systemic lupus erythematodes, multiple sclerosis, colitis ulcerosa, or Crohns disease. Patients with a secondary vascular dysregulation normally have a high level of circulating endothelin-1 (ET-1). This increased level of ET-1 leads to a reduction of blood flow both in the choroid and the optic nerve head but has little influence on autoregulation. In contrast, primary vascular dysregulation has little influence on baseline ocular blood flow but interferes with autoregulation. This, in turn, leads to unstable oxygen supply, which seems to be a relevant component in the pathogenesis of glaucomatous optic neuropathy.