Alon Harris

Special web version!

This short outline reviews interesting contributions in the field of ocular blood flow research in glaucoma presented at the ARVO meeting 2001. Many experts are active in basic and clinical research on the optic nerve blood flow but only few representative presentations can be discussed in this brief overview. Some studies have investigated the important relationship of blood flow changes to alterations in the related anatomical structures. One approach investigated retinal blood flow (RBF) and retinal nerve fiber layer (NFL) thickness changes in a laser induced glaucomatous monkey model using the Heidelberg Retina Flowmeter (HRF) and Optical Coherence Tomography (OCT). The neve fiber layer thickness significantly decreased over time in the experimental glaucomatous eyes versus control eyes in this glaucomatous monkey model.(1) There are various techniques used to evaluate blood flow of the ONH. In many studies there are disagreements between various investigators due to different technologies used for assessment of ocular blood flow in patients. Comparison of existing techniques and evaluating their strengths or weaknesses are consequently of high interest. One study examined features of the Heidelberg retina flowmeter and Laser speckle flowgraphy (LSFG) to quantify the circulation in the same site. (2) The correlation of the results was not significant for the ONH, probably due to the difference of measurement depth of ONH by each method (it is known that SBR value reflects blood flow not only in the retina but also in the choroid), showing at the same time significant correlation between the choroid and retina. These findings suggested that "flow" and "velocity" obtained by HRF might be indicative of blood flow within the choroid as well as in retina. 

The HRF, a well-known confocal scanning laser Doppler flowmetry device, measures blood flow in retinal capillaries and depicts a two-dimensional flow map. Correct interpretation of Scanning Laser Doppler Flowmetry results, technique commonly used in quantification of retinal capillary blood flow, depends also on modern software approaches and its proper utilization. Thus it is particularly important to understand how the background of these automatic approaches works in relation to the real measurement values. A comparison of two HRF flow maps analysis methods, pointwise analysis (PA) with the novel scanning laser Doppler flowmetry data analysis software (SLDF, Mver 3.3) in a single identical data set analyzed before and after glaucoma treatment by both software methods showed differences in the ability of detection of significant drug-induced reduction in blood flow. (3) PA identified a significant drug-induced reduction in blood flow, a difference that the SLDF software was unable to detect. The results point to possible loss of significant clinical information depending on the analysis method used. 

The effects of subclasses of medications such as carbonic anhydrase inhibitors, beta-blockers, alpha-adrenergic agonists, and prostaglandin analogues on optic nerve head, retinal, choroidal, and retrobulbar circulation represent also major contributions to the blood flow related research. Various studies investigated claims for enhancements or reduction of ocular circulation with different classes of substances, among them endothelin-1 because of its supposed role in vasospasm in vascular diseases (4), showing an abnormal increase in plasma endothelin-1 and a significant decrease in retinal blood flow within glaucoma patients (5). One of the studies on the effect of topical brinzolamide on retinal capillary blood flow using HRF in glaucoma patients demonstrated improvement of retinal blood flow (6). Emphasis in clinical research can also be found in studies on the relationship of functional damageand blood flow alterations. Circulation in the ONH neuroretinal rim and cup was significantly correlated to the extent of glaucomatous damage between the eyes of patients with asymmetric damages (7).

Some contributions have been presented on new and futuristic technologies of blood flow evaluation, like the Canon Laser Blood Flowmeter (8), a new instrument capable of measuring large retinal for volumetric blood flow assessment. Improvements in the already established techniques have been proposed, like in a study in an animal model examining the visualisation of intravenously injected ultrasound contrast agent with harmonic ultrasound technique within the range of accepted low transmitting ultrasound power (9). Also attempts to facilitate and automate the quantification of retinal microcirculation from video fluorescein angiograms have been presented during this year's convention (10).

Ocular blood flow measuring devices continue to develop rapidly. There are still however some controversies and uncertainties related to the clinical application of such devices and the utilization surrounding pharmacological perturbations. Overall, our understanding of the vascular aetiology in glaucoma has greatly improved. 

References

(1) Evaluation of Retinal Blood Flow Using the Heidelberg Retina Flowmeter and Nerve Fiber Layer Thickness Using Optical Coherence Tomography in Glaucomatous Monkey Model
R.K. Ghanta^1,2, A. Harris³, E. Hertzmark⁴, H. Pakter¹, J. Simpson¹, V.R.F. Guedes¹, W. Drexler², J.G. Fujimoto², L. Kagemann³, J.S. Schuman¹
New England Eye Center, Tufts University School of Medicine, Boston, MA, USA¹
Elec Eng & Computer Science, Mass Institute of Technology, Cambridge, MA, USA²
Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, USA³
Harvard School of Public Health, Boston, MA, USA⁴.
Program Nr: 85

(2) Correlation between Heidelberg retina flowmeter (HRF) and Laser speckle flowgrafy (LSFG).
T. Okuno , T. Sugiyama , T. Ikeda.
Ophthalmology, Osaka Medical College, Takatsuki, Osaka, Japan.
Program Nr: 462

(3) Heidelberg Retinal Flowmetry: A comparison of New Analysis Technique with SLDF Software Pre and Post Glaucoma Therapy
A. Harris , L. Kagemann , Y. Rotenstreich , C.P. Jonescu-Cuypers , C.A. Ciulla , B. Martin , B. Siesky , L. McCranor , P.O. Sinchai.
Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, USA
Program Nr: 683

(4) Regulation of Human Retinal Blood Flow by Endothelin-1
K. Polak^1,2, A. Luksch¹, B. Frank¹, K. Jandrasits¹, L. Schmetterer^1,3
Dept of Clinical Pharmacology, University Clinic Vienna,Vienna, Austria¹
Department of Ophthalmology, University Clinic Vienna,Vienna, Austria²
Institute of Medical Physics, University of Vienna,Vienna, Austria³
Program Nr: 2819

(5) Studies on the role of endothelin-1 related vasospasm in glaucoma.
M.T. Nicolela¹, S.N. Ferrier¹, T.L. LeVatte¹, M.L. Archibald¹, J. Hanly², R.P. LeBlanc¹, B.C. Chauhan¹
Department of Ophthalmology, Dalhousie University, Halifax, Canada¹
Department of Reumathology, Dalhousie University²
Program Nr: 1702

(6) Retinal blood flow before and after brinzolamide.
M.M. Iester^1,2, M. Altieri¹, P. Vittone², M. Zingirian¹, C.E. Traverso¹
DNVS, Ophthalmology B, University of Genoa, Genoa, Italy¹
Division of Ophthalmolgy, G Gaslini Institute, Genoa, Italy²
Program Nr: 2236

(7) Optic Nerve Blood flow in eyes with asymmetric visual field and optic disc damage
 J.R. Piltz-Seymour, J.E. Grunwald, J. Dupont.
Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, School of Medicine Philadelphia, Pennsylvania, USA
Program Nr: 2231

(8) Retinal Blood Flow in the Normal Human Eye using the Canon Laser Blood Flowmeter.
J.S. Garcia Jr. , P.T. Garcia , R.B. Rosen
Department of Ophthalmology, The New York Eye and Ear Infirmary, New York, NY.
Program Nr: 452

(9) Visualization of perfusion imaging using ultrasound contrast agent and harmonic ultrasound in rabbit eyes
T. Hirokawa, M. Hayashi, H. Murata, M. Takebayashi, K. Fuke, T. Ohki, M. Kajima, T. Naito, S. Yamane, H. Shiota
Department of Ophthalmology, The University of Tokushima, Tokushima, Japan
Program Nr: 2238

(10) Automated Quantification of the Retinal Microcirculation from Video Fluorescein Angiograms.
B. Shoelson , A. Clermont , S.-E. Bursell.
Joslin Diabetes Center, Harvard Medical School, Boston, MA.
Program Nr: 2821

Issue 3-1

Table of Contents Editor's Selection

Change Issue

24-3 (2024) 24-1/2 (2024) 23-4 (2023) 23-3 (2023) 23-2 (2023) 23-1 (2022) 22-4 (2022) 22-3 (2022) 22-2 (2021) 22-1 (2021) 21-4 (2021) 21-3 (2021) 21-2 (2021) 21-1 (2020) 20-4 (2020) 20-3 (2020) 20-2 (2019) 20-1 (2019) 19-4 (2019) 19-3 (2018) 19-2 (2018) 19-1 (2018) 18-4 (2017) 18-3 (2017) 18-2 (2017) 18-1 (2017) 17-4 (2016) 17-3 (2016) 17-2 (2016) 17-1 (2016) 16-4 (2015) 16-3 (2015) 16-2 (2015) 16-1 (2014) 15-4 (2014) 15-3 (2014) 15-2 (2013) 15-1 (2013) 14-4 (2013) 14-3 (2013) 14-2 (2013) 14-1 (2012) 13-4 (2012) 13-3 (2011) 13-2 (2011) 13-1 (2011) 12-4 (2011) 12-3 (2010) 12-2 (2010) 12-1 (2010) 11-4 (2010) 11-3 (2009) 11-2 (2009) 11-1 (2009) 10-4 (2009) 10-3 (2008) 10-2 (2008) 10-1 (2008) 9-4 (2008) 9-3 (2007) 9-2 (2007) 9-1 (2007) 8-4 (2007) 8-3 (2006) 8-2 (2006) 8-1 (2006) 7-3 (2006) 7-2 (2005) 7-1 (2005) 6-3 (2005) 6-2 (2004) 6-1 (2004) 5-3 (2004) 5-2 (2003) 5-1 (2003) 4-3 (2003) 4-2 (2002) 4-1 (2002) 3-3 (2002) 3-2 (2001) 3-1 (2001) 2-3 (2001) 2-2 (2000) 2-1 (2000) 1-3 (2000) 1-2 (1999) 1-1 (1999)

---

advertisement