Content area
Full text
About the Authors:
Gilberto Raul Lopez Jaime
Contributed equally to this work with: Gilberto Raul Lopez Jaime, Amir H. Kashani
Affiliation: Doheny Eye Institute, University of Southern California, Los Angeles California, United States of America
Amir H. Kashani
Contributed equally to this work with: Gilberto Raul Lopez Jaime, Amir H. Kashani
* E-mail: [email protected]
Affiliation: Department of Ophthalmology, William Beaumont Hospital and Associated Retinal Consultants P.C., Royal Oak, Michigan, United States of America
Saloomeh Saati
Affiliation: Doheny Eye Institute, University of Southern California, Los Angeles California, United States of America
Gabriel Martin
Affiliation: Reichert Technologies, Buffalo, New York, United States of America
Gerald Chader
Affiliation: Doheny Eye Institute, University of Southern California, Los Angeles California, United States of America
Mark S. Humayun
Affiliations Doheny Eye Institute, University of Southern California, Los Angeles California, United States of America, Department of Ophthalmology, Keck School of Medicine, University of Southern California Los Angeles, Los Angeles, California, United States of America, Departments of Neuroscience and Biomedical Engineering, University of Southern California Los Angeles, Los Angeles, California, United States of America
Introduction
Noninvasive measurement of hemoglobin oxygen saturation (oximetry) has been demonstrated by analysis of oxygenated and deoxygenated hemoglobin absorption spectra. [1] The earliest studies demonstrating this technique showed a difference between arterial and venous retinal oxygen saturation using photographic emulsions and multiple filter systems. [2]–[5] More sophisticated methods were later developed to allow near simultaneous measurements of a few wavelengths (usually between 2–4) to calculate oxygen saturation. [6]–[13] Other methods use rapid serial scanning with liquid tunable filters [14] or confocal scanning laser devices. [15], [16] Sophisticated calibration methods are commonly required for all non-invasive, multi-wavelength oximetry systems since the measured light depends on hemoglobin saturation as well as hematocrit, vessel size, and light scattering. [8], [17], [18],[19] An alternative method, phosphorescence quenching, measures the fluorescence of an oxygen-sensitive probe injected into the vitreous and has also been used to demonstrated retinal tissue oxygen gradients in the rat. This method is probably the most ideal measurement of tissue oxygen metabolism in a research setting but it is not feasible clinically [20].
The application of hyperspectral computed tomographic imaging spectrometry (HCTIS) for measurement of retinal oximetry is able to overcome some of the limitations of earlier methods. Previous animal and...