Pulsatile ocular blood flow: relationship with flow velocities in vessels supplying the retina and choroid

Evidence of vascular involvement in myopia: a review

The benign public perception of myopia (nearsightedness) as a visual inconvenience masks the severity of its sight-threatening consequences. Myopia is a significant risk factor for posterior pole conditions such as maculopathy, choroidal neovascularization and glaucoma, all of which have a vascular component. These associations strongly suggest that myopic eyes might experience vascular alterations prior to the development of complications. Myopic eyes are out of focus because they are larger in size, which in turn affects their overall structure and function, including those of the vascular beds. By reviewing the vascular changes that characterize myopia, this review aims to provide an understanding of the gross, cellular and molecular alterations identified at the structural and functional levels with the goal to provide an understanding of the latest evidence in the field of experimental and clinical myopia vascular research. From the evidence presented, we hypothesize that the interaction between excessive myopic eye growth and vascular alterations are tipping-points for the development of sight-threatening changes.

Choroidal vascularity index changes during the Valsalva manoeuvre in healthy volunteers

PURPOSE

To evaluate the effects of the Valsalva manoeuvre (VM) on the choroidal vascularity index (CVI) in healthy volunteers.

METHODS

This prospective, cross-sectional study included 60 eyes of 30 healthy volunteers. Enhanced depth imaging-optical coherence tomography scans of both eyes involving the fovea were taken, and a 1500 μm subfoveal choroidal area was selected for image binarization with open-access Fiji software. The binarized image was segmented into the stromal area (SA) and luminal area (LA), and CVI was calculated as the ratio (%) of LA to the total choroidal area (TCA). CVI, subfoveal choroidal thickness (SFCT), IOP, systolic and diastolic blood pressure were evaluated at rest and during the VM.

RESULTS

During the VM, a mean ± standard deviation increase in LA (0.02 ± 0.05 mm² , p < 0.001) and CVI (1.72 ± 2.83%, p < 0.001) was observed, whereas SA (-0.02 ± 0.05 mm² , p < 0.001) decreased. There was no significant change in TCA (0.00 ± 0.03 mm² , p = 0.55) or SFCT (1.05 ± 10.92 μm, p = 0.46). There was a moderate positive correlation between the spherical equivalent refractive error (SE) and SFCT both at rest and during VM (r₅₈  = 0.49, p < 0.0005 and r₅₈  = 0.49, p < 0.0005, respectively). However, there was no significant correlation between SE and CVI either at rest or during VM (p = 0.11 and 0.06, respectively). In a multiple linear regression analysis, CVI was only associated with SFCT; however, SFCT was also associated with SE, both at rest and during VM (p < 0.001).

CONCLUSION

Valsalva manoeuvre increases CVI by choroidal vascular dilation as demonstrated by an increase in LA and a decrease in SA. Researchers should be careful about unintentional VM during examinations.

Effect of ECG-gating Retinal Photographs on Retinal Vessel Caliber Measurements in Subjects with and without Type 2 Diabetes

Purpose/Aim of this study: Retinal vessel caliber is an independent risk marker of cardiovascular disease risk. However, variable mechanical delays in capturing retinal photographs and cardiac cycle-induced retinal vascular changes have been shown to reduce the accuracy of retinal vessel caliber measurements, but this has only ever been investigated in healthy subjects. This cross-sectional study is the first study to investigate this issue in type 2 diabetes. The aim of this study was to determine whether ECG-gating retinal photographs reduce the variability in retinal arteriolar and venular caliber measurements in controls and type 2 diabetes.Materials and Methods: Fifteen controls and 15 patients with type 2 diabetes were arbitrarily recruited from Westmead Hospital, Sydney, Australia. A mydriatic fundoscope connected to our novel ECG synchronization unit captured 10 ECG-gated (at the QRS) and 10 ungated digital retinal photographs of the left eye in a randomized fashion, blinded to study participants. Two independent reviewers used an in-house semi-automated software to grade single cross-sectional vessel diameters across photographs, between 900 and 1800 microns from the optic disc edge. The coefficient of variation compared caliber variability between retinal arterioles and venules.Results: Our ECG synchronization unit reported the smallest time delay (33.1 ± 48.4 ms) in image capture known in the literature. All 30 participants demonstrated a higher reduction in retinal arteriolar (ungated: 1.02, 95%CI 0.88-1.17% vs ECG-gated: 0.39, 95%CI 0.29-0.49%, p < .0001) than venular (ungated 0.62, 95%CI 0.53-0.73% vs ECG-gated: 0.26, 95%CI 0.19-0.35%, p < .0001) coefficient of variation by ECG-gating photographs. Intra-observer repeatability and inter-observer reproducibility analysis reported high interclass correlation coefficients ranging from 0.80 to 0.86 and 0.80 to 0.93 respectively.Conclusion: ECG-gating photographs at the QRS are recommended for retinal vessel caliber analysis in controls and patients with type 2 diabetes as they refine measurements.

Stimulation of Baroresponsive Parts of the Nucleus of the Solitary Tract Produces Nitric Oxide-mediated Choroidal Vasodilation in Rat Eye

Preganglionic parasympathetic neurons of the ventromedial part of the superior salivatory nucleus (SSN) mediate vasodilation of orbital and choroidal blood vessels, via their projection to the nitrergic pterygopalatine ganglion (PPG) neurons that innervate these vessels. We recently showed that the baroresponsive part of the nucleus of the solitary tract (NTS) innervates choroidal control parasympathetic preganglionic neurons of SSN in rats. As this projection provides a means by which blood pressure (BP) signals may modulate choroidal blood flow (ChBF), we investigated if activation of baroresponsive NTS evokes ChBF increases in rat eye, using Laser Doppler Flowmetry (LDF) to measure ChBF transclerally. We found that electrical activation of ipsilateral baroresponsive NTS and its efferent fiber pathway to choroidal SSN increased mean ChBF by about 40-80% above baseline, depending on current level. The ChBF responses obtained with stimulation of baroresponsive NTS were driven by increases in both choroidal blood volume (ChBVol; i.e., vasodilation) and choroidal blood velocity (ChBVel; possibly due to orbital vessel dilation). Stimulation of baroresponsive NTS, by contrast, yielded no significant mean increases in systemic arterial blood pressure (ABP). We further found that the increases in ChBF with NTS stimulation were significantly reduced by administration of the neuronal nitric oxide (NO) synthase inhibitor Nω-propyl-l-arginine (NPA), thus implicating nitrergic PPG terminals in the NTS-elicited ChBF increases. Our results show that the NTS neurons projecting to choroidal SSN do mediate increase in ChBF, and thus suggest a role of baroresponsive NTS in the BP-dependent regulation of ChBF.

Retinal Vessel Caliber, Choroidal Thickness and Ocular Pulse Amplitude Measurements in Essential Thrombocythemia

PURPOSE

The choroid and retina receive most of the blood that enter to the eye, and this uptake may be affected by essential thrombocythemia (ET) in which thrombosis and hemorrhage is common. This study compares choroidal thickness, retinal vascular caliber, and ocular pulse amplitude (OPA) measurements between patients with ET and healthy adults.

MATERIALS AND METHODS

Thirty-seven patients with ET and 37 age-sex-matched healthy adults were recruited in this cross-sectional and comparative study. Spectral-domain optical coherence tomography was used to measure the subfoveal choroidal thickness (SFCT) and retinal vascular caliber measurements. The Pascal dynamic contour tonometer was used for OPA and intraocular pressure (IOP) measurements. The independent samples t-test was used for comparison of measurements between the groups. Pearson's correlation coefficient analysis was used to detect correlations between the variables. A P < 0.05 was statistically significant.

RESULTS

SFCT, OPA, and IOP measurements were not statistically significant differences between the study group and the control group (P > 0.05, all comparisons). Blood platelet counts were not associated with choroidal thickness, OPA, and IOP (P > 0.05). Retinal arteriolar and venular calibers were statistically, significantly thicker in healthy controls when compared to the study group (P < 0.05).

CONCLUSIONS

Our results indicate that choroidal thickness and pulsatile blood flow are not significantly affected in ET and under high blood platelet counts. Retinal arteriolar and venular calibers are thinner in ET when compared to age-sex matched healthy controls.

Age-Related Changes in Ocular Blood Velocity in Suspects with Glaucomatous Optic Disc Appearance. Comparison with Healthy Subjects and Glaucoma Patients

Purpose

To evaluate retrobulbar blood flow characteristics of glaucoma suspects with glaucomatous optic disc appearance (GODA) in comparison to healthy control group (CG) and primary open angle glaucoma patients (POAG) and assess the effect of age.

Methods

145 patients from a single glaucoma clinic were enrolled and classified into two diagnostic groups (GODA and POAG). Third group of subjects consisted of 67 age matched individuals (CG). Retrobulbar blood velocity measurement in central retinal artery was performed using color Doppler imaging (CDI). CDI images were processed in custom software leading a range of parameter estimates from a continuous waveform signal. The effect of age on the estimated parameters was evaluated with the stepwise forward regression and ANCOVA in which age was used as a continuous factor. One-way ANOVA was used to test for the differences in the CDI parameters between the three considered groups. Correlation between restive index (RI) and pulsatility index (PI) was assessed with a bilinear fitting guaranteeing no discontinuities in RI intercept estimate. Fisher test was used to assess the applicability of a bilinear PI/RI relationship, while the statistics of the RI intercept estimate were evaluated using the bootstrap.

Results

ANCOVA showed significant interaction between age and group (p<0.05) for five out of nine considered CDI parameters. The RI intercept for CG and GODA groups was 0.602±0.047, and 0.574±0.044 respectively, while the RI intercept of 0.934±0.066 was found for the POAG.

Conclusions

The observed similarity of CG and GODA group and dissimilarity between GODA and POAG groups in terms of PI/RI relationship is remarkable. Age may play some role in the different mechanisms occurring in blood velocity dynamics in GODA and POAG subjects but it is not a strongly determining factor.

[Effects of blood flow properties on ocular hemodynamics]

AIM

to study the effects of blood rheology on ocular blood flow (OBF) parameters and estimated individual normal range of intraocular pressure (IOP).

MATERIAL AND METHODS

A total of 15 patients (15 eyes) taking warfarin were enrolled. Volumetric parameters and linear velocity of OBF under warfarin treatment and after its cessation were obtained by means of flowmetry (Paradigm's Blood Flow Analyzer) and color Doppler flow mapping (Voluson 730), respectively. On the basis of flowmetry results an individual normal range of IOP was calculated in all patients.

RESULTS

Pulsatile OBF does not appear to correlate with warfarin-induced changes in blood rheology (p = 0.09), however, depends on IOP fluctuations (p = 0.02). Resistance index of retinal vessels is found to rise significantly with increasing blood viscosity (p < 0.05).

CONCLUSION

The use of warfarin, an indirect thrombin inhibitor, has no effect on estimated individual normal range of IOP, which is crucial for glaucoma diagnosis and monitoring.

Choroidal changes after cardiopulmonary bypass

AIM

Choroid, which is the vascular tissue responsible for blood supply to the outer parts of the retina, might be affected by hemodynamic events. We aimed to reveal choroidal thickness and ocular pulse amplitude changes after cardiopulmonary bypass in which gross hemodynamic alterations occur.

METHODS

Forty-two eyes of 42 patients who underwent heart surgery with cardiopulmonary bypass were examined in this prospective, cross-sectional case series. The spectral domain optical coherence tomography (Spectralis, Heidelberg, Germany) was used to analyze sub-foveal choroidal thickness. The ocular pulse amplitude, the surrogate of gross choroidal blood flow, was measured with the Pascal dynamic contour tonometer (Pascal DCT, Swiss Microtechnology AG, Port, Switzerland).. The intraocular pressure was also measured with this tonometer. The examinations were performed pre-operatively and post-operatively at the first week and first month.

RESULTS

The mean age of the patients was 58.8 ± 12.4 years. The mean sub-foveal choroidal thickness and ocular pulse amplitude values did not change statistically significantly after the operations at the follow-up visits (p>0.05). Also, there were no important correlations between cardiopulmonary bypass time and mean sub-foveal choroidal thickness and ocular pulse amplitude changes at the post-operative first week (p>0.05). The intraocular pressure values were decreased markedly at the control visits (p<0.05).

CONCLUSIONS

Sub-foveal choroidal thickness and ocular pulse amplitude are unchanged, while intraocular pressure decreases one week and one month after cardiopulmonary bypass.

Clinical utility of spectral analysis of intraocular pressure pulse wave

Background

To evaluate the clinical utility of spectral analysis of intraocular pressure pulse wave in healthy eyes of a control group (CG), patients having glaucomatous optic disc appearance or ocular hypertension, and patients with primary open angle glaucoma or primary angle closure glaucoma.

Methods

This is a prospective study that enrolled 296 patients from a single glaucoma clinic. Age matched CG consisted of 62 individuals. Subjects underwent comprehensive clinical diagnostic procedures including intraocular pressure (IOP) measurement with dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT). DCT time series were analyzed with custom written software that included signal preprocessing, filtering and spectral analysis. An amplitude and energy content analysis, which takes into account non-stationarity of signals but also provides methodology that is independent of IOP and ocular pulse amplitude (OPA) levels, was applied. Spectral content up to the 6th harmonic of the pressure pulse wave was considered. Statistical analyses included descriptive statistics, normality test, and a multicomparison of medians for independent groups using Kruskal-Wallis test.

Results

GAT IOP showed statistical significance (Kruskal-Willis test p < 0.05) for three out of 10 considered multiple comparisons, DCT IOP and OPA showed statistically significant results in five and seven cases, respectively. Changes in heart rate and central corneal thickness between the groups were statistically significant in two cases. None of the above parameters showed statistically significant differences between CG and the suspects with glaucomatous optic disc appearance (GODA). On the other hand, spectral analysis showed statistically significant differences for that case.

Conclusions

Spectral analysis of the DCT signals was the only method showing statistically significant differences between healthy eyes and those of GODA suspects.

Long-term outcomes of rheohaemapheresis in the treatment of dry form of age-related macular degeneration

Purpose. Determining long-term effects of rheohaemapheresis on the dry form of age-related macular degeneration. Methods. This study evaluates 19 patients, average age of 67.6 years, treated with rheohaemapheresis and 18 patients, average age of 72.8 years, comprising the control group. Minimum follow up period was 3.5 years. Each treated patient received a series of 8 sessions of rheohaemapheresis of 1.5 plasma volumes within 10 weeks. We measured the drusenoid pigment epithelium detachment (DPED), best-corrected visual acuity (BCVA), electroretinography (ERG), and rheological parameters. Results. In the treatment group, the baseline BCVA was 0.74 (0.36-1.0) 95% CI and BCVA after 3.5 years was 0.79 (0.41-1.0) 95% CI (P = 0.726). In the control group, the baseline BCVA was 0.71 (0.15-1.0) 95% CI and BCVA after 3.5 years decreased to 0.7 (0.32-0.87) 95% CI (P = 0.031). Baseline DPED was 6.78 ± 3.79 mm(2); after 3.5 years, it decreased to 4.13 ± 3.84 mm(2) (P < 0.001). In the control group, the baseline DPED was 4.09 ± 3.48 mm(2); after 3.5 years, it increased to 6.69 ± 4.2 mm(2) (P = 0.001). We noted increasing levels of positive wave peaking at 50 milliseconds (P50) after treatment (P = 0.022) and a stable amplitude of photopic responses of treated patients. Conclusion. Over the long term, rheohaemapheresis reduced the DPED, improved the function of photoreceptors, and prevented the decline of BCVA.

Ocular blood flow velocity in primary open angle glaucoma--a tropical African population study

PURPOSE

To assess blood flow velocity in newly diagnosed indigenous black-skinned Africans with primary open angle glaucoma (POAG).

MATERIALS AND METHODS

Prospective case-control study at Obafemi Awolowo University Teaching Hospital, Ile-Ife, Nigeria on 50 newly diagnosed POAG patients (POAG group) and 50 control patients (control group). Ocular Doppler Color Imaging was performed on subjects in the supine position using 9 MHz linear array transducer of a Fukuda Denshi Ultrasound. The Peak Systolic Velocity (PSV) and End Diastolic Velocity (EDV) values were obtained by finding the average of two readings each for the ophthalmic artery (OA) and central retinal artery (CRA). Resistive Index (RI) was calculated as (PSV - EDV)/PSV. Data were analyzed and statistical significance was defined at P < 0.05.

RESULTS

The mean intraocular pressure (IOP) for the POAG group and control group was 28.1 ± 7.4 mmHg and 16.6 ± 2.0 mmHg, respectively (P < 0.001). The mean PSV for OA was 31.35 cm/s in POAG group and 37.61 cm/s for the control group (P < 0.001). The EDV for both OA and CRA were significantly lower in glaucoma patients as compared with the corresponding values in the control group (P < 0.001, both comparisons). The mean RI in the OA was 0.71 ± 0.05 and 0.63 ± 0.03 for the POAG and control group groups, respectively (P < 0.001). The increase in IOP in the POAG group was statistically significantly negatively correlated with PSV and EDV and positively correlated with RI for both OA and CRA.

CONCLUSION

The outcomes of this study indicate that ocular blood flow alterations including reductions in PSV and EDV and increase in RI of the OA and CRA are present in black-skinned Africans with POAG.

Doppler velocimetry of the orbital vessels in pregnancies complicated by preeclampsia

Hypertension is one of the most common clinical complications during pregnancy. Preeclampsia, in particular, still accounts for high maternal and fetal morbidity and mortality. Hemodynamic studies have shown that general arteriolar vasoconstriction, which leads to hypoperfusion of target organs, including the eye area, remains the most significant pathological change in preeclampsia. Color Doppler imaging is the most appropriate and the commonly used method for the study of ocular circulation, especially during pregnancy. It enables the visualization and flow measurement of retrobulbar blood vessels. The aim of this review is to evaluate studies that investigated the role of Doppler velocimetry of the maternal orbital vessels, especially the ophthalmic artery, as a tool for the differential diagnosis of hypertensive disorders of pregnancy, for the assessment of the degree and severity of preeclampsia, and for the prediction of these disturbances. The analysis of these studies indicates that the Doppler variables are accurate in the differential diagnosis of hypertensive disorders and in assessing the severity and progression of the preeclampsia and may also be useful markers in the treatment and management of pregnancy-induced hypertension. We found no study evaluating the role of orbital vessels Doppler variables in predicting preeclampsia or in the prognosis of maternal-fetal adverse events.

Factors affecting ocular pulse amplitude in eyes with open angle glaucoma and glaucoma-suspect eyes

PURPOSE

To investigate the associations between ocular pulse amplitude (OPA) as measured by dynamic contour tonometry (DCT) and ocular and systemic factors in patients with open angle glaucoma (OAG) and in glaucoma suspects.

METHODS

One hundred and seventy-three glaucoma-suspect patients were consecutively enrolled. All subjects underwent intraocular pressure (IOP) measurement by DCT and Goldmann applanation tonometry (GAT), OPA measurement by DCT, Humphrey visual field (HVF) examination and central corneal thickness measurements. Arterial pulse amplitude (APA) and ocular perfusion pressure (OPP) were defined as the difference between systolic and diastolic BP and the difference between mean arterial pressure and IOP, respectively. All subjects also completed a systemized questionnaire on systemic vascular morbidities.

RESULTS

Seventy-four eyes were diagnosed with OAG, based on HVF results. The overall mean CCT was 538.2±37.6 μm. In all 173 eyes, OPA was associated with spherical equivalent (SE, p<0.001) and with IOP by GAT (p=0.013) by multivariate analysis. Multivariate analysis of the 77 subgroup eyes of patients for whom BP parameters were available also revealed that OPA was associated with SE (p=0.007) and with IOP by GAT (p<0.001). When the subjects were classified into the groups with low, intermediate and high cardiovascular risk based on the questionnaire, there was no difference in OPA among these groups (p>0.05).

CONCLUSIONS

Ocular pulse amplitude was associated with IOP measured by GAT and SE in patients with OAG and in glaucoma suspects. There was neither significant correlation between systemic hemodynamic parameters and OPA, nor difference of OPA in patients with different cardiovascular risk. OPA is primarily a measure of pressure, and there are certain limitations towards its use as a hemodynamic index.

Contrast sensitivity, ocular blood flow and their potential role in assessing ischaemic retinal disease

PURPOSE

To examine the definition, evaluation methodology, association to ocular blood flow and potential clinical value of contrast sensitivity (CS) testing in clinical and research settings, focusing in patients with ischemic retinal disease.

METHODS

A review of the medical literature focusing on CS and ocular blood flow in ischemic retinal disease.

RESULTS

CS may be more sensitive than other methods at detecting subtle defects or improvements in primarily central retinal ganglion cell function early on in a disease process. CS testing attempts to provide spatial detection differences which are not directly assessed with standard visual acuity chart testing. Analyzing all studies that have assessed both CS change and ocular blood flow, it is apparent that both choroidal circulation and retinal circulation may have an important role in influencing CS.

CONCLUSION

The concept that CS is directly influenced by ocular blood flow is supported by reviewing the studies involving both. Although the studies in the literature have not established a direct cause and effect relationship per se, the literature review makes it logical to assume that changes in retinal and choroidal blood flow influence CS. This raises the possibility that a subjective visual characteristic, specifically CS, may be able to be evaluated more objectively by studying blood flow. It appears appropriate to study the relationship between blood flow and CS more extensively to develop improved ways of measuring various aspects of blood flow to the eye and to best quantify early changes in visual function.

Haemorheopheresis could block the progression of the dry form of age-related macular degeneration with soft drusen to the neovascular form

PURPOSE

To evaluate the influence of haemorheopheresis on anatomical and functional findings in patients with soft-drusen maculopathy.

METHODS

We investigated 29 eyes (16 patients) and randomized 25 eyes (16 controls) with soft-drusen maculopathy [soft, confluent and reticular drusen, drusenoid retinal pigment epithelium detachment (RPED)]. Each patient received a series of eight haemorheophereses (cascade filtration of 1.5 plasma volume) within 10 weeks. The patients were followed up using Early Treatment Diabetic Retinopathy Study (ETDRS) charts, optical coherence tomography, fluorescein angiography, electroretinography and measurements of pulsed ocular blood flow.

RESULTS

After the procedures, there was a substantial reduction in rheologically active substances [lipoproteins, α2-macroglobulin, immunoglobulin M (IgM), fibrinogen], plasma and blood viscosity. At the 1.5-year follow-up, we noticed soft drusen absorption; reattachment of drusenoid RPED and stabilization or improvement of visual acuity occurred in 72% of patients in comparison to only 39% of patients in the control group. Full-field electroretinograms showed significantly higher scotopic activity of treated patients in comparison with the control group, and mainly insignificant differences in photopic activity between both groups. Despite the significant increase of activity in the paramacular retina in treated patients, the differences in amplitudes of multifocal electroretinography (mfERG) average responses were insignificant between groups.

CONCLUSION

Haemorheopheresis seems to be capable of changing the activity of promoters of the natural course of soft-drusen maculopathy, its development and progression. Visual acuity and electrical activity of the retina can be stabilized or even improved. The therapy has been shown to be effective and safe.

Color Doppler imaging and ocular pulse amplitude in glaucomatous and healthy eyes

PURPOSE

To determine factors influencing color Doppler imaging (CDI) measurements, to compare retrobulbar flow velocities between patients with glaucoma and healthy controls, and to describe the correlation between CDI and ocular pulse amplitude (OPA).

METHODS

Patients with normal tension (n=28) or primary open angle glaucoma (n=19) and healthy controls (n=22) underwent CDI and OPA measurements. Intraocular pressure, corneal thickness, blood pressure, and heart rate were also measured. Spearman correlations were used to explore relations among these variables. A regression model for repeated measures was applied to compare between diagnostic groups the flow velocity indices in the retrobulbar vessels.

RESULTS

Retrobulbar diastolic blood flow velocities correlated with diastolic blood pressure and perfusion pressure (range of Spearman rho [rho] coefficients=0.25-0.28; p=0.044-0.013 for the different vessels). Corneal thickness showed a positive correlation with systolic and diastolic flow velocities in the central retinal artery (rho=0.29 and 0.31; p=0.017 and 0.011 for peak systolic and end diastolic velocity, respectively). Systolic and diastolic blood flow velocities were reduced in the retrobulbar vessels of patients with normal tension glaucoma (P=0.0004) as well as primary open angle glaucoma (P=0.003) compared to healthy controls. A correlation was found between OPA and the resistive index in the retrobulbar vessels of the healthy controls (range rho=0.42-0.53; p=0.059-0.014).

CONCLUSIONS

Retrobulbar blood flow velocities are reduced in patients with primary open angle glaucoma and normal tension glaucoma. Blood pressure and corneal thickness may influence CDI measurements. OPA correlates with the resistive index in CDI.

Acetazolamide influences ocular pulse amplitude

PURPOSE

To investigate the effect of systemic acetazolamide on ocular pulse amplitude (OPA) and on intraocular pressure (IOP).

METHODS

We determined OPA, IOP, mean arterial blood pressure and heart rate (HR) in 17 patients suffering from hypertensive primary open-angle glaucoma (htPOAG) and 22 healthy controls. Measurements were taken before and 2 h after oral intake of 500 mg of acetazolamide.

RESULTS

Mean OPA decreased 20.24% (SEM 2.95%) from 2.76 mmHg (SEM 0.16 mmHg) to 2.14 mmHg (SEM 0.13 mmHg) 2 h after oral administration of 500-mg acetazolamide. IOP dropped by 2.98 mmHg (SEM 0.28 mmHg), corresponding to a 17.19% (SEM 1.56%) reduction. The decrease in IOP correlated with the decrease of OPA (r(2) = 0.4, P < 0.0001).

CONCLUSIONS

Ocular pulse amplitude measurements are influenced by oral administration of acetazolamide. There was a decrease in the pulsatile component of choroidal blood flow and in IOP in both htPOAG and healthy controls. This needs to be taken into account for measurement of OPA with dynamic contour tonometry.

Correlation among choroidal, parapapillary, and retrobulbar vascular parameters in glaucoma

PURPOSE

To study and compare the correlation among choroidal, parapapillary, and retrobulbar vascular parameters in healthy subjects, glaucoma suspects, and open-angle glaucoma (OAG) patients.

DESIGN

Prospective observational clinical study.

METHODS

The study included one randomly selected eye from 21 normal subjects, 30 glaucoma suspects based on optic disc appearance, and 22 OAG patients. The pulsatile ocular blood flow (POBF), a measure of choroidal blood flow, was assessed using ocular blood flow analyzer whereas parapapillary blood flow and blood velocity of retrobulbar blood vessels were measured using scanning laser Doppler flowmetry and color Doppler imaging, respectively. All vascular parameters along with blood pressure and intraocular pressure measurements were obtained within a 2-hour period. Univariate regression analyses were used to evaluate the correlation of POBF values with parapapillary blood flow values, retrobulbar blood flow velocities, and resistive index, which represents vascular resistance, in each group. Two multiple linear regression models were created based on results of univariate analyses and included POBF, mean parapapillary blood flow, age, and mean ocular perfusion pressure; and POBF, temporal short posterior ciliary artery resistive index, age, and mean ocular perfusion pressure.

RESULTS

POBF was significantly associated with parapapillary blood flow (r2 = 0.54; P < .001, positive correlation) and temporal short posterior ciliary artery resistive index (r2 = 0.39; P < .001, negative correlation) in normal subjects. Results were consistent when corrected for age, intraocular pressure, and blood pressure parameters. POBF values did not correlate with parapapillary blood flow values or temporal short posterior ciliary artery resistive index in glaucoma suspects or OAG patients.

CONCLUSION

The relationships of POBF with parapapillary blood flow and calculated retrobulbar vascular resistance differs among normal subjects, glaucoma suspects, and OAG patients. This provides further evidence of vascular dysregulation in OAG.