Yukihiro Shiga

Waveform Analysis of Ocular Blood Flow and the Early Detection of Normal Tension Glaucoma

PURPOSE To investigate waveform changes in blood flow (BF) in the optic nerve head (ONH) and to evaluate their usefulness in identifying normal tension glaucoma (NTG). METHODS Sixty-one eyes of 61 patients with NTG and 21 eyes of age-matched healthy control subjects were included in this study. The NTG eyes were divided into the following three groups based on the progression of their visual field defects: mild (mean deviation [MD] greater than -6.0 decibels [dB]), moderate (MD between -6.0 and -12.0 dB), and severe (MD less than -12.0 dB). The ONH BF analysis was performed with laser speckle flowgraphy (LSFG) and included waveform variables such as skew, acceleration time index (ATI), and blowout time. RESULTS In the ONH, LSFG skew variables were significantly lower in the NTG eyes than in the control eyes (P < 0.001), and ATI was significantly higher (P < 0.01), despite similar systemic characteristics in the four groups. The differences were most marked in the mild NTG group. Multiple linear regression analysis showed that MD, average thickness of the circumpapillary retinal nerve fiber layer, and pulse rate were predictive factors for both skew and ATI. A receiver operating characteristic (ROC) curve analysis also revealed that skew (area under the ROC curve, 0.89) and ATI (area under the ROC curve, 0.80) had the greatest power to differentiate normal eyes from eyes with mild NTG. CONCLUSIONS These results suggest that LSFG measurements of waveform changes in ONH BF can differentiate healthy eyes from eyes with NTG, particularly those with mild NTG.

The novel Rho kinase (ROCK) inhibitor K-115: a new candidate drug for neuroprotective treatment in glaucoma.

PURPOSE To investigate the effect of K-115, a novel Rho kinase (ROCK) inhibitor, on retinal ganglion cell (RGC) survival in an optic nerve crush (NC) model. Additionally, to determine the details of the mechanism of K-115s neuroprotective effect in vivo and in vitro. METHODS ROCK inhibitors, including K-115 and fasudil (1 mg/kg/d), or vehicle were administered orally to C57BL/6 mice. Retinal ganglion cell death was then induced with NC. Retinal ganglion cell survival was evaluated by counting surviving retrogradely labeled cells and measuring RGC marker expression with quantitative real-time polymerase chain reaction (qRT-PCR). Total oxidized lipid levels were assessed with a thiobarbituric acid-reactive substances (TBARS) assay. Reactive oxygen species (ROS) levels were assessed by co-labeling with CellROX and Fluorogold. Expression of the NADPH oxidase (Nox) family of genes was evaluated with qRT-PCR. RESULTS The survival of RGCs after NC was increased 34 ± 3% with K-115, a significantly protective effect. Moreover, a similar effect was revealed by the qRT-PCR analysis of Thy-1.2 and Brn3a, RGC markers. Levels of oxidized lipids and ROS also increased with time after NC. NC-induced oxidative stress, including oxidation of lipids and production of ROS, was significantly attenuated by K-115. Furthermore, expression of the Nox gene family, especially Nox1, which is involved in the NC-induced ROS production pathway, was dramatically reduced by K-115. CONCLUSIONS The results indicated that oral K-115 administration delayed RGC death. Although K-115 may be mediated through Nox1 downregulation, we found that it did not suppress ROS production directly. Our findings show that K-115 has a potential use in neuroprotective treatment for glaucoma and other neurodegenerative diseases.

Optic Nerve Head Blood Flow, as Measured by Laser Speckle Flowgraphy, Is Significantly Reduced in Preperimetric Glaucoma

ABSTRACT Purpose: To compare optic nerve head (ONH) blood flow in healthy eyes, eyes with preperimetric glaucoma (PPG), and eyes with mild normal-tension glaucoma (NTG) using laser speckle flowgraphy (LSFG).Methods: In 172 eyes (normal: 44 eyes; PPG: 62 eyes; mild NTG: 66 eyes), LSFG was used to measure mean blur rate in the ONH tissue area (MBRT), an index of capillary blood flow. Multiple regression analysis was performed to determine factors affecting circumpapillary retinal nerve fiber layer thickness (cpRNFLT), mean deviation (MD) and pattern standard deviation (PSD) of the visual field.Results: Despite similar characteristics in age, refractive error and systemic variables among the study groups, MBRT in the normal eyes differed significantly from both the PPG and mild NTG eyes (P = 0.001, P < 0.001, respectively). Multiple regression analysis revealed that MBRT was an independent factor affecting cpRNFLT, MD and PSD (P < 0.001, P = 0.001, P = 0.003, respectively).Conclusion: ONH blood flow was detectibly reduced in eyes with PPG, in close association with structural and visual field damage. This suggests that measuring ONH tissue-area blood flow with LSFG may be a useful way of monitoring glaucoma severity, even in the early stages of glaucoma.

Pulse-Waveform Analysis of Normal Population using Laser Speckle Flowgraphy

Abstract Purpose: Laser speckle flowgraphy (LSFG), a new, non-invasive method of measuring the mean blur rate (MBR) of ocular blood flow, allows for the analysis of the pulse waveform of a heartbeat as it changes dynamically. Here, we investigated the relationship between the pulse waveform and clinical parameters, particularly age. Materials and methods: Sixty eyes of 60 healthy subjects without diabetes were enrolled from among patients undergoing annual health examinations. LSFG, and its analysis software, were used to determine pulse waveform parameters including MBR, skew, blowout score (BOS), blowout time (BOT), rising rate and falling rate in the optic nerve head (ONH), both specifically in the tissue area and in the ONH overall. Fifteen clinical parameters were also recorded, including age and blood pressure, as well as triglyceride and creatinine levels. Results: Skew, BOT and falling rate had a strong correlation (|r| > 0.60) with age, but not with the other clinical parameters. This correlation with age was stronger in the tissue area (BOT: p < 0.0001, r = − 0.68; skew: p < 0.0001, r = 0.65; falling rate: p < 0.0001, r = 0.61) than in the ONH overall (BOT: p < 0.0001, r = −0.67; skew: p < 0.0001, r = 0.60; falling rate: p < 0.0001, r = 0.59). Stepwise multiple regression analysis revealed that tissue area falling rate was an independent factor indicating age, and conversely that age was an independent factor indicating tissue area falling rate. Conclusions: The significant correlation of LSFG-measured tissue area falling rate with age suggests that it may be a new candidate biomarker for age-dependent microcirculation.

The Influence of Posture Change on Ocular Blood Flow in Normal Subjects, Measured by Laser Speckle Flowgraphy

Abstract Purpose: To investigate, using laser speckle flowgraphy (LSFG), the autoregulation of ocular blood flow (BF) in response to posture change. Methods: This study comprised 20 healthy volunteers (mean age 30.0 ± 8.5). The mean blur rate (MBR) of the ocular circulation in the subjects was assessed in both a sitting and a supine position every 2 min over the course of 10 min. Baseline measurements of the MBR at the optic nerve head (ONH) and the choroid were taken in a sitting position. Increases in the MBR ratio in a supine position were calculated with reference to this baseline. Intraocular pressure (IOP), systemic blood pressure and heart rate in the brachial artery were also recorded. Results: In the ONH, the MBR ratio increased significantly over the baseline after 2 min (104.8 ± 5.0%, p = 0.001) and 4 min (104.4 ± 5.6%, p = 0.005), in a supine position, but decreased to the initial level after only 6 min. In the choroid, on the other hand, while the MBR ratio also increased significantly after 2 min in a supine position (113.7 ± 8.1%, p < 0.001), it kept this significant increase over the time course of 10 min. After 10 min in a supine position, IOP increased significantly (p < 0.001), systolic blood pressure decreased significantly (p < 0.001), but diastolic blood pressure did not change significantly compared to the baseline. (p = 0.07) Conclusions: ONH and choroidal circulation have significantly different hemodynamics in response to posture change in healthy volunteers. This finding suggests that LSFG enables us to assess the autoregulation of BF in the ONH.

Correlation between structure/function and optic disc microcirculation in myopic glaucoma, measured with laser speckle flowgraphy.

BackgroundIt is difficult to identify glaucoma in myopic eyes because the configuration of the optic disc varies; yet it is important clinically. Here, we used laser speckle flowgraphy (LSFG) to measure mean blur rate (MBR), representing optic disc microcirculation, and assessed its ability to identify glaucoma in eyes with myopic optic discs.Methods129 eyes (normal disc: 21 eyes; myopic disc: 108 eyes) were enrolled. The eyes were classified as normal or mildly, moderately, or severely glaucomatous with standard automated perimetry (SAP). We determined the relationship between optic nerve head (ONH) MBR, measured with LSFG, mean deviation (MD), measured with SAP, and circumpapillary retinal nerve fiber layer thickness (cpRNFLT), measured with optical coherence tomography (OCT).ResultsONH MBR and cpRNFLT decreased significantly with the severity of glaucoma. MBR was significantly correlated with cpRNFLT and MD (r =0.65 and r =0.63, respectively). A multiple regression analysis revealed that MBR and cpRNFLT were independent factors indicating glaucoma severity. A logistic regression analysis revealed that MBR and cpRNFLT were also independent factors indicating the presence of glaucoma. In a receiver operating characteristic (ROC) analysis, MBR and cpRNFLT could both differentiate between normal and glaucomatous eyes (MBR area under the ROC curve: 0.86, with a cut-off score of 24.0 AU).ConclusionThese results suggest that in addition to cpRNFLT, non-invasive and objective LSFG measurements of MBR may enable the identification of glaucoma and the classification of its severity in eyes with myopic optic discs.

Relative Flow Volume, a Novel Blood Flow Index in the Human Retina Derived From Laser Speckle Flowgraphy

PURPOSE We investigated the accuracy and reproducibility of relative flow volume (RFV), a novel index of blood flow in the human retina derived from laser speckle flowgraphy (LSFG). METHODS Pre- and postbranch retinal RFV measurements were compared in 34 retinal venous bifurcations in 34 healthy volunteers (mean age, 49.0 ± 14.8 years) to determine the accuracy of RFV. Next, the coefficient of variation (COV) of RFV was determined for 30 temporal retinal arteries in a second group of 18 healthy volunteers (mean age, 30.3 ± 7.7 years). Finally, laser Doppler velocimetry (LDV) data were obtained from the same study population and compared to RFV data from the retinal vessels. RESULTS A comparison of RFV measurements in a trunk vessel of the retina and the sum of its two daughter vessels revealed a strong correlation (r = 0.98, P < 0.001). Reproducibility analysis showed that the COV for RFV was 5.9% ± 3.6%. Linear regression analysis revealed that RFV was correlated significantly with LDV measurements of mean retinal blood velocity (vmean) and retinal blood flow (FLDV, vmean, r = 0.61, P < 0.001; FLDV, r = 0.51, P = 0.004, respectively), but not significantly correlated with ocular perfusion pressure (r = -0.04, P = 0.76). CONCLUSIONS These results suggest that RFV values obtained with LSFG can be considered an accurate and reliable index of relative blood flow in the human retina. Thus, RFV, a novel LSFG-derived variable, has potential for assessing retinal blood flow alterations in ocular disease.

3D Evaluation of the Lamina Cribrosa with Swept-Source Optical Coherence Tomography in Normal Tension Glaucoma

Purpose Although the lamina cribrosa (LC) is the primary site of axonal damage in glaucoma, adequate methods to image and measure it are currently lacking. Here, we describe a noninvasive, in vivo method of evaluating the LC, based on swept-source optical coherence tomography (SS-OCT), and determine this method’s ability to quantify LC thickness. Methods This study comprised 54 eyes, including normal (n = 18), preperimetric glaucoma (PPG; n = 18), and normal tension glaucoma (NTG; n = 18) eyes. We used SS-OCT to obtain 3 x 3 mm cube scans of an area centered on the optic disc, and then synchronized reconstructed B- and en-face images from this data. We identified the LC in these B-scan images by marking the visible borders of the LC pores. We marked points on the anterior and posterior borders of the LC in 12 B-scan images in order to create a skeleton model of the LC. Finally, we used B-spline interpolation to form a 3D model of the LC, including only reliably measured scan areas. We calculated the average LC thickness (avgLCT) in this model and used Spearmans rank correlation coefficient to compare it with circumpapillary retinal nerve fiber layer thickness (cpRNFLT). Results We found that the correlation coefficient of avgLCT and cpRNFLT was 0.64 (p < 0.01). The coefficient of variation for avgLCT was 5.1%. AvgLCT differed significantly in the groups (normal: 282.6 ± 20.6 μm, PPG: 261.4 ± 15.8 μm, NTG: 232.6 ± 33.3 μm). The normal, PPG and NTG groups did not significantly differ in age, sex, refractive error or intraocular pressure (IOP), although the normal and NTG groups differed significantly in cpRNFLT and Humphrey field analyzer measurements of mean deviation. Conclusion Thus, our results indicate that the parameters of our newly developed method of measuring LC thickness with SS-OCT may provide useful and important data for glaucoma diagnosis and research.

Effect of Topical Tafluprost on Optic Nerve Head Blood Flow in Patients With Myopic Disc Type

Purpose:To investigate the effect of topical tafluprost on optic disc blood flow in patients with myopic disc. Materials and Methods:Forty-eight eyes in 24 patients with a myopic disc type (oval shaped) optic disc tilted to the temporal, with a crescent peripapillary atrophy were included in this study. Twenty-eight eyes were diagnosed as normal tension glaucoma and 20 eyes were in normal subjects. None had any treatment for glaucoma. Average age was 45.3±11.9 years. One eye was treated with topical tafluprost and the fellow eye served as the control. Ocular blood flow was measured by laser speckle flowgraphy (LSFG-NAVI) at 30, 60, 90, and 120 minutes after tafluprost administration, and the mean blur rate (MBR) on the optic disc was analyzed. Blood pressure and intraocular pressure (IOP) were recorded. Results:In all subjects, topical tafluprost (a) significantly reduced IOP versus baseline from 60 minutes after treatment (baseline: 15.2±3.4 mm Hg, 60 min: 13.3±3.2 mm Hg, P=0.001, 90 min: 13.3±3.6 mm Hg, P=0.002, 120 min: 13.7±3.4 mm Hg, P=0.007); and (b) significantly increased the MBR versus baseline (60 min: +4.3±6.6%, P=0.008, 90 min: +5.0±4.9%, P<0.001, 120 min: +6.7±7.0%, P<0.001). Conclusions:Topical tafluprost increased MBR in the optic nerve head and significantly reduced IOP, effects that may represent beneficial treatment for glaucoma patients with a myopic disc type.

The effect of intravitreal bevacizumab on ocular blood flow in diabetic retinopathy and branch retinal vein occlusion as measured by laser speckle flowgraphy.

Background This study evaluated the effect of intravitreal injection of bevacizumab (IVB) on macular edema associated with diabetic retinopathy (DME) or branch retinal vein occlusion (BRVOME) using laser speckle flowgraphy. Methods A comparative interventional study of 25 eyes from 22 patients with macular edema (DME group: 12 eyes; BRVOME group: 13 eyes) who underwent IVB. Mean blur rate (MBR) was measured in the retinal artery, retinal vein, optic nerve head (ONH), and choroid before and after IVB. Results In the BRVOME group, there was no significant change in MBR in the retinal artery, retinal vein or ONH, but choroidal MBR decreased significantly (P=0.04). In the DME group, the MBR in the retinal artery, retinal vein, ONH, and choroid decreased significantly (P=0.02, P=0.04, P<0.001, and P=0.04, respectively). In the DME group, pre-IVB MBR in the ONH was significantly correlated with post-IVB foveal thickness (R= −0.71, P=0.002). There was no such correlation in the BRVOME group in the ONH. Conclusion IVB had a suppressive effect on circulation in eyes with DME but not in those with BRVOME. This suggests that this noninvasive and objective biomarker may be a useful part of pre-IVB evaluations and decision-making in DME.