Sunday, May 25, 2025
5/25/2025
Tissue Oxygenation in Small Retinal Vessels - Summary Recently, we found extensive remodeling of the microvasculature of the retina, occurring in some diabetic patients much earlier than expected. This provides the potential for novel biomarkers to improve classification of patients for management and cost-effective testing of therapies. However, the equipment is too expensive for most clinics and small practices. These early retinal microvascular changes cannot be seen with routine clinical examination or traditional imaging devices. We propose to reduce the cost and improve ease of use of this technology to allow widespread detection of retinal microvascular changes as biomarkers. Part of the high cost of these devices is the adaptive optics (AO) subsystem, which includes one or more deformable mirrors to compensate for the aberrations of the optics of the human eye. The contrast of retinal images is further improved by scanning the illumination and using confocal detection apertures. By designing a simpler AO imager with only sufficient resolution to provide improved visibility of small vessel lesions, a wider field of view, more compact layout, and greater ease of use can be realized with less challenging optical performance parameters. To provide a clinically useful tool for examination of the retinal microvascular lesions in diabetes and other retinal vascular diseases, along with improving information about oxygen in the retina, we propose 3 Aims. In Aim 1, we will optimize adaptive optics digital light ophthalmoscope (AO-DLO) for high contrast, pseudo-color video imaging of the human retina at high magnification to improve detection of microvascular lesions and quantification of the relative absorption of arterioles and venules. The 3.6 deg AO field of view on a high contrast NIR wide field image will ease the burden of localizing features or montaging AO images taken sequentially, with an acceptable trade off in maximum imaging resolution. The AO-DLO will acquire monochrome images of 10 controls, using alternating red and yellow LED illumination wavelengths that match those used in oximetry. This provides high contrast pseudo-color retinal imaging, good retinal penetration for dark eyes, and strong absorption signals from blood bands. In Aim 2, we will use the AO-DLO to image the retinal microvasculature in 10 controls and 10 diabetic patients with less than severe non-proliferative retinopathy. We will perform parametric studies of aperture size and position, and focal plane, to optimize the reproducibility of the measurements of the relative absorption in 2 visible wavelength bands in with the AO- DLO. These manipulations, along with an exercise regime, will provide information about oxygen extraction in arterioles and venules for capillary networks. In Aim 3, we will image the same subjects with the high resolution Indiana AO-SLO (Burns, 2014), examining vessel walls and lumen, then re-assess placement of oximetry data samples and recompute optical density ratios. This project offers the potential to move high quality adaptive optics retinal imaging into use with more patients, improving the classification of diabetic eyes for management and evaluating therapies.
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