Relating glaucomatous visual field loss to retinal oxygen delivery and metabolism

Purpose To test the hypothesis that visual field (VF) loss is associated with decreased retinal blood flow, oxygen delivery and metabolism, and with increased retinal oxygen extraction fraction (OEF) in glaucomatous individuals. Methods Glaucomatous subjects underwent automated perimetry, dual wavelength scanning laser ophthalmoscopy and Doppler optical coherence tomography imaging in order to measure mean deviation, central retinal arterial and venous diameter equivalents (CRAE and CRVE), oxygen saturation levels and total retinal blood flow (TRBF), respectively. Retinal oxygen delivery, metabolism and extraction fraction were derived from measurements of oxygen saturation and blood flow. Results Twenty eyes of 14 subjects were included in the study. Mean deviation was on average -13.76 +/- 8.70 dB. Mean CRAE and CRVE were 126 +/- 28 and 191 +/- 35 mu m, respectively. Mean TRBF and oxygen delivery were 34.3 +/- 11.7 mu l/min and 6.5 +/- 2.6 mu l O-2/min, respectively. Mean oxygen metabolism and extraction fraction were 2.1 +/- 0.94 mu l O-2/min and 0.34 +/- 0.15, respectively. Visual field (VF) loss was associated with reduced CRAE and CRVE, TRBF and oxygen delivery and associated with increased OEF. Conclusion Combined measurements of retinal blood flow and oxygen saturation in glaucomatous individuals suggest VF loss is associated with impaired oxygen delivery and augmented OEF.