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Amir H. Kashani, Gilberto Raul Lopez Jaime, Saloomeh Saati, Gerald J. Chader, Rohit Varma, Mark S. Humayun; Variation in Retinal Vascular Oxygen Content Among Human Patients: A Study Using Computed Tomographic Imaging Spectroscopy. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2167.
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To study the variation in human intravascular retinal oxygen saturation in normal and disease states using snapshot hyperspectral computed tomographic spectroscopy (HCTIS).
Sixty-five human subjects were dilated using 2.5% phenylephrine and 1% tropicamide ophthalmic drops for standard fundus photography. Fundus photographs and retinal vascular oxygen measurements (oximetry) were made using a custom made HCTIS coupled to a standard fundus camera as previously described (Kashani AH et al., PLoS One, 2011). Oximetry measurements were made along arteries and veins adjacent to the optic disc to evaluate retinal vascular oxygen content. All comparisons were made using the Student T-test. All procedures were performed under an IRB approved protocol and with informed consent.
The study population consisted of 45 controls, 10 glaucomatous, and 10 diabetic subjects (Age range 35-85; 30% male). Controls were limited to subjects with refractive error less than +/-4D and/or mild-moderate cataracts. In control subjects, mean arterial and venous oxygen saturation was 93±7% and 65±6% (p less than 0.001) respectively. In diabetic subjects mean arterial and venous saturation was 91±6% and 68±5% (p less than 0.001) respectively. In glaucomatous subjects, mean arterial and venous saturation was 93±6% and 66±3% (p less than 0.001) respectively. Within the diabetic group, there was a significant decrease in the arteriovenous difference from 27±6% in diabetics with nonproliferative disease to 14±4% in diabetics with proliferative diabetic retinopathy (p=0.003). There was no statistically significant difference in arterial or venous oxygen saturation between control males and females (p greater than 0.1) or between controls age less than 60 years and those greater than or equal to 60 (p greater than 0.1).
This study utilizes a novel technique (HCTIS) to demonstrate variations in intravascular oxygen content among normal and diseased subjects. Although the study size is small, these data confirm previous findings of decreased arteriovenous difference in diabetic patients and provide useful normative data for future studies. Further investigation with HCTIS may provide novel diagnostic information in the evaluation and management of ischemic retinal diseases.
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