Oxygen saturation measurements of the retinal vasculature in treated asymmetrical primary open-angle glaucoma using hyperspectral imaging

Abstract

Purpose To determine whether there are differences in retinal vascular oxygen saturation measurements, estimated using a hyperspectral fundus camera, between normal eyes and treated eyes of subjects with asymmetrical primary open-angle glaucoma (POAG). Methods A noninvasive hyperspectral fundus camera was used to acquire spectral images of the retina at wavelengths between 556 and 650 nm in 2-nm increments. In total, 14 normal eyes and both eyes of 11 treated POAG subjects were imaged and analyzed using algorithms that use the spectral variation of the optical densities of blood vessels to estimate the oxygen saturation of blood within the retinal vasculature. In the treated POAG group, each of the eyes were categorized, based on the mean deviation of the Humphrey visual-field analyzer result, as either more-advanced or less-advanced, glaucomatous eyes. Unpaired t-tests (twotailed) with Welch's correction were used to compare the mean oxygen saturation between the normal subjects and the treated POAG subgroups. Results In less-advanced and moreadvanced-treated POAG eyes, mean retinal venular oxygen saturations (48.2 ± 21.6% and 42.6 ± 18.8%, respectively) were significantly higher than in normal eyes (27.9 ± 9.9%; P ¼ 0.03 and 0.01, respectively). Arteriolar oxygen saturation was not significantly different between normal eyes and treated POAG eyes. ConclusionsThe increased oxygen saturation of the retinal venules in advancedtreated POAG eyes may indicate reduced metabolic consumption of oxygen in the inner retinal tissues.

Hyperspectral Image Mapping Spectrometry for Retinal Oximetry Measurements in Four Diseased Eyes

“…Geirsdottir, et al used the Oxymap T1 to demonstrate that oxygen saturation in retinal veins decreases with age in healthy eyes [12]. Several studies have found reduced oxygen saturation values in occluded arteries and veins [14–17] and increased venous oxygen saturation in patients with exudative age-related macular degeneration (AMD) [18], advanced primary open-angle glaucoma [19–21], diabetic retinopathy[22–24], and retinitis pigmentosa [25, 26]. For patients with retinitis pigmentosa, increased arterial oxygenation saturation and increased arteriovenous oxygen saturation differences have been observed, with age seemingly affecting these values [27, 28].…”

“…Hyperspectral imaging (HSI) allows for the collection of multiple spectral bands in a single image, and has been increasingly utilized in measuring ocular oximetry [21, 30–36]. HSI is advantageous over two- or three-wavelength oximetry in multiple ways.…”

Rapid prototyping of biomimetic vascular phantoms for hyperspectral reflectance imaging

“…HRI has been studied for monitoring blood perfusion in superficial tissues such as skin wounds, 5 diagnosis of ocular vascular disorders, 6,7 tumor vasculature oximetry for cancer prognosis, 8,9 artery-vein differentiation during surgery, 10 and subcutaneous vasculature visualization for vein inspection and blood withdrawal.…”

The Future of Imaging in Detecting Glaucoma Progression

“…Retinal oxygen saturation was reported to be positively correlated with visual field and RNFL thickness; a negative correlation was seen between oxygen saturation in the choroid plexus and RNFL thickness (69). MSI has also been used to measure increased venular retinal oxygen saturation in POAG compared to healthy subjects (70). Measurements using MSI have illustrated differential light absorption in neuroretinal rim tissue that is associated with visual field sensitivity in POAG (71).…”