Ocular haemodynamics in glaucoma associated with high myopia

The ocular blood flow of a group of high myopic and glaucomatous eyes has been investigated by means of the Color Doppler Imaging (CDI) technique, comparing the results with those of some very myopic eyes without glaucoma, some non-myopic glaucomatous eyes and with a control group. The Ophthalmic Artery (OA), the Short Posterior Ciliary Arteries (SPCAs) and the Central Retinal Artery (CRA) were considered. For every vessel, peak systolic velocity (SV), end-diastolic velocity (DV) and the Pourcelot Resistivity Index were studied. The statistical analysis was performed by means of t-test according to Bonferroni procedure for multiple comparisons. The authors registered in the group of eyes with glaucoma associated with very severe myopia some abnormalities of the OA blood flow systolic velocity which might be interpreted as a vascular risk factor for the pathogenesis of the glaucomatous opticneuropathy; these abnormalities are more severe in glaucoma patients with high myopia than in anage-matched group of glaucoma patients without myopia. This revised version was published online in July 2006 with corrections to the Cover Date.     

Retrobulbar hemodynamic parameters in open-angle and angle-closure glaucoma patients

Purpose

The purpose of this study is to compare the retrobulbar hemodynamic parameters in the ophthalmic artery (OA), central retinal artery (CRA), and posterior cilliary arteries (PCA), in open-angle glaucoma (OAG) and angle-closure glaucoma (ACG) patients.

Patients and methods

A total of 52 eyes from 52 patients with OAG and 25 eyes from 25 ACG patients who met the inclusion/exclusion criteria were included in this cross-sectional study. Peak-systolic velocity, end-diastolic velocity, and Pourcelot resistivity index (RI) were assessed in the OA, CRA, and PCA. Intraocular pressure (IOP) was measured both with the Goldmann applanation tonometer (GAT) and with the Dynamic Contour tonometer (DCT) three times, respectively. Ocular pulse amplitude was measured using DCT.

Results

The RI was significantly higher in both the ophthalmic and short PCA in the OAG patients as compared with that in those ACG patients, P=0.003 and 0.048, respectively. There was no correlation between the IOP measured with GAT and the retrobulbar hemodynamic parameters in either OAG or ACG.

Conclusions

There was an increased resistance to blood flow in the OA of OAG as compared with ACG patients. Additionally, the degree of circulatory disturbance was not related to either the IOP or the visual-field damage.     

A controlled clinical trial of Dorzolamide: a single-centre subset of a multicentre study

Purpose: To assess the safety and intraocular pressure (IOP)-lowering activity of 2% dorzolamide (topical carbonic anhydrase inhibitor), compared to 0.5% timolol and 0.5% betaxolol eyedrops.
Methods: A parallel, masked, randomised one-year clinical trial was conducted in 16 patients with open-angle glaucoma or ocular hypertension, being a subset of a multicentre study which enrolled 523 subjects. Patients had IOP > 22 mmHg in one eye at baseline following washout of ocular hypotensive medications and were then randomised in a 3:l:l ratio to receive 2% dorzolamide thrice daily, 0.5% timolol twice daily or 0.5% betaxolol twice daily respectively. IOP was measured at Hour 2 (morning peak), Hour 5 and Hour 8 (afternoon trough for dorzolamide) at baseline, Weeks 2 and 4 and Months 2, 3, 6, 9 and 12.
Results: Topical dorzolamide 2% solution was well tolerated and safe. Mean IOP for dorzolamide at Hour 2 was 29.1 mmHg at baseline and 20.8 mmHg on treatment at one year, a 28.5% change. Mean IOP for dorzolamide at Hour 8 was 24.5 mmHg at baseline and 20.2 mmHg on treatment at one year, a 17.6% change. Comparable percent changes for timolol and betaxolol were 43.2/25.7 mmHg at Hour 2 and 21.9/13.5 mmHg at Hour 8 respectively.
Conclusions: Dozolamide 2% given thrice daily was well tolerated and safe, with a clinically significant effect on IOP comparable to betaxolol 0.5% twice daily, but not as great as timolol 0.5% twice daily.     

The Circadian Variations in Systemic Blood Pressure, Ocular Perfusion Pressure, and Ocular Blood Flow: Risk Factors for Glaucoma?

Intraocular pressure, a major risk factor for glaucoma, is known to vary throughout the day, yet glaucoma continues to progress in some patients despite it being well controlled. It is important to understand how other glaucomatous risk factors are affected by circadian variations. The purpose of this review is to analyze the literature concerning circadian variations in systemic blood pressure, ocular perfusion pressure, and ocular blood flow and to identify consensus findings regarding their impact on glaucoma. This review suggests that nonphysiologic nocturnal blood pressure dipping and wider circadian fluctuations in ocular perfusion pressure are linked with the development and progression of glaucoma. No consensus concerning circadian variations in ocular blood flow exists in the current literature, and future investigations of nocturnal changes in blood flow and glaucoma progression are required.     

Changes in optic nerve head blood flow and retrobular hemodynamics following calcium-channel blocker treatment of normal-tension glaucoma

Background: Because calcium channel blockers reduce vascularresistance, they may have a clinical application in the treatment ofnormal-tension glaucoma (NTG). This study investigates changes inboth the optic disc blood flow and the hemodynamics of retrobulbarvessels in NTG patients after the systemic administration of a calcium channel blocker. Methods: Twelve eyes of 12 NTG patients (meanage 57 6 ± 15.3 years) were examined before and after a 4-weektreatment with 2 mg b.i.d. oral nilvadipine, an L-typc calcium channel blocker. By scanning laser-Doppler flowmetry (SLDF), we obtained the velocity, flow, and volume from within a 10 × 10 pixel windowplaced on the temporal rim region of the optic disc perfusion map. Byultrasound color Doppler imaging (CDI), we measured the peak systolicvelocity (PSV) and the end diastolic velocity (EDV) of the ophthalmicartery (OA), central retinal artery (CRA), nasal posterior ciliary artery (NPCA), and temporal posterior ciliary artery (TPCA). We then calculated a resistance index (RI) for each vessel. Results: After treatment, the flow and velocity of the optic disc blood flow significantly increased (P < 0.05).Nilvadipine also significantly reduced RIs of the CRA, NPCA, and TPCA(P <0 .05), and increased both the PSV of the NPCA and the EDVs of the CRA, NPCA, and TPCA. The percent change in velocity correlated significantly with the percent changes of the CRA RI and NPCA RI. Conclusions: Oral nilvadipine appears to reduce orbital vascular resistance, which consequentlyincreases the optic disc blood flow. Abbreviations.BP – blood pressure;CRA – central retinal artery;CDI – ultrasound color Doppler imaging;EDV – end diastolic velocity;NPCA – short posterior ciliary arteries located nasal to optic nerve;NTG – normal-tension glaucoma;OA – ophthalmic artery;PP – perfusion pressure;PSV – peak systolic velocity;RI – resistance index;SLDF scanning laser-Doppler flowmetry;TPCA – short posterior ciliary arteries locatedtemporal to optic nerve.     

Short-term effect of dipyridamole on blood flow velocities in the extraocular vessels

Dipyridamole is known to inhibit platelet aggregation and to induce vasodilatation. It has been shown that dipyridamole increases blood flow in various tissues in humans as well as in the eyes of animals. We studied the influence of dipyridamole in a prospective open trial in 23 patients with impaired ocular circulation due to different causes, based on experienced clinical judgement, such as anterior ischemic optic neuropathy, vasospastic syndrome, glaucoma, or central retinal vein occlusion. Blood flow velocities in the ophthalmic artery, central retinal artery and vein, one lateral and one medical posterior ciliary artery were measured using a Siemens Quantum 2000 color Doppler device. Blood flow velocities were measured before and under treatment. Dipyridamole increased blood flow velocities significantly in all vessels measured. Therefore, it seems promising to evaluate the effect of dipyridamole over a longer period in patients with impaired ocular blood flow.     

Pulsatile Ocular Blood Flow: Changes Associated with Scleral Buckling Procedures

Purpose To determine the changes in the pulse amplitude (PA) and the pulsatile ocular blood flow (POBF) after scleral buckling (SB).Methods Retrospectively, we studied 24 patients (average age, 52 years) who had undergone SB to repair a retinal detachment in one eye. The patients were divided into two groups: those in whom SB had been performed less than 6 months earlier (n = 10), and those in whom the procedure had been performed more than 6 months previously (n = 14). In each group, the PA and the POBF were determined with a computerized tonometry system, and the values in the SB eyes were compared with those in the control fellow eyes.Results Within 6 months postoperatively, the mean PA in the SB eyes (0.66 ± 0.30mmHg) was significantly lower than that in the control eyes (1.43 ± 0.34mmHg; P < 0.05). The mean POBF in the SB eyes (349.5 ± 154.1µl/min) was also significantly lower than that in the control eyes (631.0 ± 226.6µl/min; P < 0.05). After more than 6 months postoperatively, there were no significant differences in the PA or the POBF between the SB eyes (1.08 ± 0.49mmHg and 612.4 ± 341.2µl/min, respectively) and the control eyes (1.50 ± 0.51mmHg and 589.5 ± 278.4µl/min, respectively).Conclusions These results indicate that the choroidal blood flow decreases after SB but returns to normal levels after 6 months. Jpn J Ophthalmol 2005;49:162–165 © Japanese Ophthalmological Society 2005     

Effects of Topical Phenylephrine on Blood Flow in the Posterior Segments of Monkey and Aged Human Eyes

Purpose The aim of this study was to evaluate the effects of topical 5% phenylephrine on circulation in the optic nerve head (ONH) of cynomolgus monkeys and in the central retinal artery (CRA) of aged patients.Methods In five monkeys, ONH tissue blood velocity (NB_ONH), determined using the laser speckle method, and intraocular pressure (IOP), blood pressure (BP), and pulse rate (PR) were measured 2h after a single unilateral instillation and after a 7-day twice-daily unilateral instillation of phenylephrine. In 20 aged patients (mean age: 70.4 years), the CRA circulation indices were determined by color Doppler imaging (CDI), and IOP, BP, and PR were measured before and after four serial unilateral instillations at 30-min intervals of phenylephrine.Results In the monkeys, there was no significant change in IOP, BR, or PR, while NB_ONH decreased 2h after a single instillation (P = 0.080) and after a 7-day instillation (P = 0.043). In theaged patients, IOP in the phenylephrine-treated eyes significantly increased (P = 0.022), while the CDI indices, BR, and PR did not. In this CDI assessment, the statistical power to detect significant changes (P < 0.05) in the resistive index was estimated as 4.8% of the standard deviation.Conclusions Topical phenylephrine decreased the ONH tissue blood velocity in monkeys, suggesting possible risks regarding circulation in the posterior portion of the eye. However, these effects were not observed in the CRA circulation in the patients. Jpn J Ophthalmol 2004;48:243–248 © Japanese Ophthalmological Society 2004     

丝裂霉素对兔眼睫状体上皮碳酸酐酶及ATP酶活性的影响

目的:采用酶组织化学方法,观察兔眼巩膜咬切术中应用丝裂霉素(MMC)后,MMC对睫状体上皮细胞分泌房水的功能酶-碳酸酐酶(CA)及ATP酶(ATPase)的影响,以期进一步探讨术后MMC降低眼压的作用机制。方法:在兔眼巩膜咬切术中局部应用0.2mg/ml MMC 0.1ml,术后第7天,分别采用Hasson氏法和硝酸铅法对睫状体上皮细胞的碳酸酐酶及ATP酶进行显色,经光镜观察,并采用计算机图像分析仪对酶的灰度值进行分析。结果:MMC对术区附近睫状体上皮细胞的CA及ATPase活性有抑制作用,而远离术区90°部位及生理盐水对照组酶活性改变不明显。结论:MMC可能通过抑制影响房水分泌的CA及ATPase的活性而减少房水分泌,降低眼压。抑制程度大则可能导致持续性低眼压。眼科学报 1996;12:75—78。     

Measuring and interpreting ocular blood flow and metabolism in glaucoma

There is a growing body of evidence suggesting that vascular dysfunction is related to several prominent ophthalmic diseases, including glaucoma. The vast majority of studies providing data on ocular circulation and disease pathophysiology use a relatively small number of complicated ocular blood flow imaging techniques. Although these imaging technologies are not commonly used in clinical settings, understanding the medical literature characterizing ocular blood flow requires familiarity with their methodology and function. This review highlights the imaging technologies most commonly used to investigate ocular blood flow, including color Doppler imaging, confocal scanning laser ophthalmoscopic angiography with fluorescein and indocyanine green dye, Canon laser blood flowmetry, scanning laser Doppler flowmetry, and retinal photographic oximetry. Each imaging technique's ability to define vascular function and reveal pathology is discussed as are limitations inherent to each technology. The ultimate goal of this review is to provide the physician with a clinically relevant foundation for differentiating the various ocular blood flow outcome measures often presented in the literature and determine how they are related to ocular health and disease.     

Scanning laser Doppler flowmetry in glaucoma

Scanning laser Doppler flowmetry is a new means for the measurement of capillary perfusion. We studied the retinal and neuroretinal rim capillary perfusion with the Heidelberg Retina Flowmeter in one randomly selected eye of 31 healthy volunteers, 42 primary open angle glaucoma (POAG) patients and 17 normal pressure glaucoma (NPG) patients. The reproducibility of the measurements on the temporal and nasal retina and on the disc rim was 19%, 26% and 28% in the unselected control group, 12% in the POAG and 12%, 13% and 10% in the NPG group, respectively. Optic disc flow was significantly higher than retinal flow (p < 0.000001). Differences in corresponding flow values between healthy volunteers and glaucoma patients as well as between POAG and NPG patients were not statistically significant. There was no correlation between the temporal and nasal flow values of the same eyes. The average variation in flow between adjacent frame positions was 18.5%. Actual intraocular pressure and the type of treatment had no influence on the retinal flow. The results suggest that the position of the test-frame is very important for the final result. We could not find any significant difference in the perfusion between glaucomatous and control eyes with the Heidelberg Retina Flowmeter.The authors have no financial interest in the Heidelberg Retina Flowmeter.     

Ocular blood flow in phakic and aphakic monkey eyes

Alterations in regional ocular blood flow produced by topical epinephrine were studied in phakic and aphakic eyes of Macaca arctoides using the radioactive microsphere technique. Three isotopes were used to make sequential blood flow measurements just prior to topical epinephrine administration, 1 hr later and 3 hr later. Significant reductions of flow were found in the iris, ciliary body, and optic nerve head of both phakic and aphakic groups. Choroidal and posterior optic nerve flow decreased significantly in aphakic eyes only. Decreases in flow were flow decreased significantly in aphakic eyes only. Decreases in flow were maximal at 3 hr. Significant changes in retinal flow were not detected. The implications of these findings regarding epinephrine-induced aphakic cystoid macular edema and the suitability of epinephrine or its derivatives in the treatment of glaucoma are discussed.     

The Effect of Tilted Disc Syndrome on Ocular Hemodynamic Measurements

Background: The purpose of this study was to assess ocular hemodynamics in patients with unilateral tilted disc syndrome (TDS) using color Doppler ultrasonography (CDUS). Methods: Fifteen consecutive patients with unilateral TDS and normal-appearing contralateral optic nerves were enrolled. Both eyes of all participants underwent detailed ophthalmological examination including automated visual field testing. CDUS was performed in the eyes with tilted discs and fellow unaffected eyes. Peak systolic velocities, end diastolic velocities, and vessel resistance were measured in the ophthalmic artery (OA), central retinal artery (CRA), nasal posterior ciliary artery (NPCA), and temporal posterior ciliary artery (TPCA). The minimum and maximum blood flow velocities were also measured in the central retinal vein (CRV). Results: No statistically significant differences were found between eyes with tilted discs and fellow normal eyes in terms of OA, CRA, NPCA, or TPCA mean peak systolic or end diastolic velocities, resistivity indices, and the mean maximal and minimal CRV blood flow velocities. Conclusion: Ocular hemodynamic measurements determined by CDUS do not appear to be altered in tilted disc syndrome.     

X-linked Juvenile Retinoschisis in Females and Response to Carbonic Anhydrase Inhibitors: Case Report and Review of the Literature

A 63 year old woman was referred to the retina clinic after her vision failed to improve in her left eye after cataract surgery. X-linked retinoschisis was diagnosed in the patient after her retina exam revealed an area of retinoschisis and a foveal cyst.The OCT confirmed the macular cyst and the ERG showed loss of B waves.The florescein angiogram showed no significant perifoveal leakage. Her foveal cyst resolved after treatment with carbonic anhydrase inhibitors.The patient’s son was examined and his ophthalmologic exam,ERG and imaging findings were consistent with X-linked retinoschisis. However, his bilateral foveal cysts did not respond to treatment with carbonic anhydrase inhibitors. X-linked retinoschisis is a very rare disease in women due to its X-linked recessive inheritance and the foveal cysts associated with it can respond to carbonic anhydrase inhibitors.     

Relaxation of Encircling Buckle Improved Choroidal Blood Flow in a Patient with Visual Field Defect Following Encircling Procedure

Background We report a patient with a visual field defect after retinal reattachment by the encircling procedure for rhegmatogenous retinal detachment. We confirmed improved ocular blood flow after relaxation of the buckle. Case A 24-year-old woman with a visual field defect appearing after an encircling procedure for rhegmatogenous retinal detachment. Observations Before and after relaxing the encircling buckle, we measured tissue blood flow in the fundus of each eye of the patient using a Heidelberg retina flow meter. Preoperative measurements showed a reduction of blood flow at the disc rim in the diseased fundus, while retinal blood flow was not reduced (P = 0.026, disc rim area versus retinal area, one-factor analysis of variance, ANOVA). Indocyanine green angiography showed extensive peripheral filling delay. Electroretinography showed low a-wave and b-wave amplitudes, but normal oscillatory potential. The base value of the electro-oculogram was severely reduced in the right eye. The blood flow values after surgery indicated a significant improvement of blood flow (P = 0.01, one-factor ANOVA). No further progression in the visual field defect was observed, and visual acuity of the right eye improved from 0.8 to more than 1.0. Conclusions These results suggest that the choroidal circulation disturbance, which was found after the encircling procedure, had a plausible role in the development of the visual field defect.