Elsevier

Survey of Ophthalmology

Volume 42, Issue 6, May–June 1998, Pages 509-533
Survey of Ophthalmology

Review
Assessment of Human Ocular Hemodynamics

https://doi.org/10.1016/S0039-6257(98)00011-3Get rights and content

Abstract

Vascular abnormality and altered hemodynamics play important roles in many ophthalmic pathologies. Much of our knowledge of ocular hemodynamics was gained from invasive animal research, although a number of noninvasive methods suitable for in vivo use in humans have been developed. Data from these methods now produce a significant literature of their own. Understanding the origins of the data and appreciating their limitations can be difficult. Modern hemodynamic assessment techniques each examine a unique facet of the ocular circulation. No single facet provides a complete description of the hemodynamic state of the eye. These methods have contributed a great deal to our understanding of normal hemodynamics. More importantly, they continue to add to our understanding of altered hemodynamics found in disease. Some have found their way into limited clinical practice. The predominant ocular hemodynamic assessment techniques are reviewed with the aims of introducing the fundamental principles behind each, highlighting their inherent advantages and limitations, highlighting their contributions to understanding ocular physiology, and considering their potential to provide signs for diagnosis. (Surv Ophthalmol 42:509–533, 1998.

Section snippets

The Importance of Ocular Hemodynamic Assessment

The potential value of examining ocular circulation has been expounded in recent editorials.240, 241 From the most basic standpoint, the eye offers a unique opportunity to study hemodynamics. It is one of the few locations in the body where capillary blood flow may be observed in humans noninvasively. Various influences are responsible for the control and regulation of the various facets of ocular blood flow, such as metabolic demands, blood nutrients, metabolic byproducts, perfusion pressure,

Ocular vascular anatomy

The only branch of the internal carotid artery outside of the cranium is the ophthalmic artery. The ophthalmic artery enters the posterior globe and supplies the retinal circulation, the uveal circulation, and the extrinsic muscles of the eye. Within the eye there are two distinct circulatory systems, the retinal, which is supplied by the central retinal artery (CRA), and the uveal, which is supplied by ciliary arteries. The retinal system supplies the inner layers of the retina, whereas the

Vessel caliber assessment

Since the development of the ophthalmoscope, the retinal vessels have been evaluated for their health.235 In 1876 Gowers noted the importance of changes in the retinal vessels observed ophthalmoscopically in Bright disease,76 and Moore suggested that the general reduction in size of retinal arteries in arteriosclerosis observed ophthalmoscopically should be considered one of the first signs of the disease.155 The development of fundus photography gave researchers the means to more objectively

Methods summary

Ocular hemodynamic assessment techniques used in humans, which are well represented in the literature were presented in this article. A fundamental problem in comprehending the ocular blood flow literature is the difficulty in comparing the results of similar studies employing different assessment techniques. Each technique evaluates a portion of the ocular circulation in a unique way. Many techniques are directed at entirely different parts of the ocular vasculature. Table 1 summarizes the

Method of Literature Search

The Medline database was used. Searches were conducted on blood flow, ocular blood flow, and for each of the technologies covered in this article. Articles cited in the resulting articles were obtained and were also reviewed. Translations were obtained of non-English publications.

Acknowledgements

The authors wish to thank Dr. Ana Mafalda Pereira and Carol Kagemann for their assistance in the preparation of the manuscript. This work was presented in part at the New Horizons in Glaucoma: Visual Function and Ocular Blood Flow meeting, October, 1993, Portland, Oregon. This work was supported by National Institutes of Health grant EY10180-01 and by an unrestricted grant from Research to Prevent Blindness, Inc.

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