ADAPTIVE OPTICS AND MULTIMODAL IMAGING FOR INFLAMMATORY VITREORETINAL INTERFACE ABNORMALITIES.

Purpose: To investigate changes to the vitreoretinal interface in uveitis with multimodal imaging including adaptive optics.

Methods: Four eyes (four patients) affected by fovea-attached (subtype 1A) or fovea-sparing epiretinal membranes (ERMs) on spectral-domain optical coherence tomography or visible internal limiting membrane (ILM) on infrared scanning laser ophthalmoscope (SLO) fundus imaging were recruited in this pilot study. The microstructure of the vitreoretinal interface was imaged using flood-illumination adaptive optics (FIAO), and the images were compared with the cross-sectional spectral-domain optical coherence tomography data.

Label-Free Imaging of Inflammation at the Level of Single Cells in the Living Human Eye.

Purpose: Putative microglia were recently detected using adaptive optics ophthalmoscopy in healthy eyes. Here we evaluate the use of nonconfocal adaptive optics scanning light ophthalmoscopy (AOSLO) for quantifying the morphology and motility of presumed microglia and other immune cells in eyes with retinal inflammation from uveitis and healthy eyes.

Design: Observational exploratory study.

Comparison between Two Adaptive Optics Methods for Imaging of Individual Retinal Pigmented Epithelial Cells.

The Retinal Pigment Epithelium (RPE) plays a prominent role in diseases such as age-related macular degeneration, but imaging individual RPE cells is challenging due to their high absorption and low autofluorescence emission. The RPE lies beneath the highly reflective photoreceptor layer (PR) and contains absorptive pigments, preventing direct backscattered light detection when the PR layer is intact. Here, we used near-infrared autofluorescence adaptive optics scanning laser ophthalmoscopy (NIRAF AOSLO) and transscleral flood imaging (TFI) in the same healthy eyes to cross-validate these approaches.

Autofluorescent hyperreflective foci on infrared autofluorescence adaptive optics ophthalmoscopy in central serous chorioretinopathy.

Purpose: To test the hypothesis that hyperreflective foci in central serous chorioretinopathy (CSCR) are autofluorescent and may represent macrophages that have engulfed outer retinal fluorophores from the retinal pigment epithelium (RPE) and photoreceptors.

Methods: Enrolled subjects underwent spectral domain and swept-source optical coherence tomography, adaptive optics flood-illumination, and adaptive optics scanning laser ophthalmoscopy (AOSLO), including near-infrared autofluorescence (AO-IRAF). For the AO-IRAF imaging, retinal fluorophores were excited using 795 nm light and collected in an emission band from 814 to 850 nm.

Design of a radial multi-offset detection pattern for phase contrast imaging of the inner retina in humans.

Previous work has shown that multi-offset detection in adaptive optics scanning laser ophthalmoscopy (AOSLO) can be used to image transparent cells such as retinal ganglion cells (RGCs) in monkeys and humans. Though imaging in anesthetized monkeys with high light levels produced high contrast images of RGCs, images from humans failed to reach the same contrast due to several drawbacks in the previous dual-wavelength multi-offset approach. Our aim here was to design and build a multi-offset detection pattern for humans at safe light levels that could reveal transparent cells in the retinal ganglion cell layer with a contrast and acquisition time approaching results only previously obtained in monkeys.

Partial-field illumination ophthalmoscope: improving the contrast of a camera-based retinal imager.

Effective and accurate in vivo diagnosis of retinal pathologies requires high performance imaging devices, combining a large field of view and the ability to discriminate the ballistic signal from the diffuse background in order to provide a highly contrasted image of the retinal structures. Here, we have implemented the partial-field illumination ophthalmoscope, a patterned illumination modality, integrated to a high pixel rate adaptive optics full-field microscope. This non-invasive technique enables us to mitigate the low signal-to-noise ratio, intrinsic of full-field ophthalmoscopes, by partially illuminating the retina with complementary patterns to reconstruct a wide-field image.

Strip-based digital image registration for distortion minimization and robust eye motion measurement from scanned ophthalmic imaging systems.

Retinal image-based eye motion measurement from scanned ophthalmic imaging systems, such as scanning laser ophthalmoscopy, has allowed for precise real-time eye tracking at sub-micron resolution. However, the constraints of real-time tracking result in a high error tolerance that is detrimental for some eye motion measurement and imaging applications. We show here that eye motion can be extracted from image sequences when these constraints are lifted, and all data is available at the time of registration.

Spatial-frequency-based image reconstruction to improve image contrast in multi-offset adaptive optics ophthalmoscopy.

Off-axis detection methods in adaptive optics (AO) ophthalmoscopy can enhance image contrast of translucent retinal structures such as cone inner segments and retinal ganglion cells. Here, we propose a 2D optical model showing that the phase contrast produced by these methods depends on the offset orientation. While one axis provides an asymmetric light distribution, hence high phase contrast, the perpendicular axis provides a symmetric one, thus substantially lower contrast.

Optical Incoherence Tomography: a method to generate tomographic retinal cross-sections with non-interferometric adaptive optics ophthalmoscopes.

We present Optical Incoherence Tomography (OIT): a completely digital method to generate tomographic retinal cross-sections from through-focus image stacks acquired by non-interferometric imaging systems, such as adaptive optics (AO)-ophthalmoscopes. We demonstrate that OIT can be applied to different imaging modalities using back-scattered light, including systems without inherent optical sectioning and, for the first time, multiply-scattered light, revealing a distinctive cross-sectional view of the retina. The axial dimension of OIT cross-sections is given in terms of focus position rather than optical path, as in OCT.

Near infrared adaptive optics flood illumination retinal angiography.

Image-based angiography is a well-adapted technique to characterize vasculature, and has been used in retinal neurovascular studies. Because the microvasculature is of particular interest, being the site of exchange between blood and tissue, a high spatio-temporal resolution is required, implying the use of adaptive optics ophthalmoscopes with a high frame rate. Creating the opportunity for decoupled stimulation and imaging of the retina makes the use of near infrared (NIR) imaging light desirable, while the need for a large field of view and a lack of distortion implies the use of a flood illumination-based setup.

near-infrared autofluorescence imaging of retinal pigment epithelial cells with 757 nm excitation.

We demonstrate near-infrared autofluorescence (NIRAF) imaging of retinal pigment epithelial (RPE) cells in healthy volunteers and patients using a 757 nm excitation source in adaptive optics scanning laser ophthalmoscopy (AOSLO). NIRAF excited at 757 nm and collected in an emission band from 778 to 810 nm produced a robust NIRAF signal, presumably arising from melanin, and revealed the typical hexagonal mosaic of RPE cells at most eccentricities imaged within the macula of normal eyes. Several patterns of altered NIRAF structure were seen in patients, including disruption of the NIRAF over a drusen, diffuse hyper NIRAF signal with loss of individual cell delineation in a case of non-neovascular age-related macular degeneration (AMD), and increased visibility of the RPE mosaic under an area showing loss of photoreceptors.

Higher adaptive optics loop rate enhances axial resolution in nonconfocal ophthalmoscopes.

In this Letter, we propose a way to better understand the impact of dynamic ocular aberrations in the axial resolution of nonconfocal adaptive optics (AO) ophthalmoscopes via a simulation of the 3D PSF in the retina for various AO-loop rates. We then use optical incoherence tomography, a method enabling the generation of tomographic retinal cross sections in incoherent imaging systems, to evaluate the benefits of a fast AO-loop rate on axial resolution and, consequently, on AO-corrected retinal image quality. We used the PARIS AO flood-illumination ophthalmoscope for this study, where retinal images from different focal planes at an AO-loop rate of 10 and 50 Hz were acquired.

High loop rate adaptive optics flood illumination ophthalmoscope with structured illumination capability.

The design and performance of an adaptive optics flood illumination ophthalmoscope (AO-FIO) platform, based on eye motion and dynamic aberrations experimental analysis, are described. The system incorporates a custom-built real-time controller, enabling up to 70 Hz loop rate without jitter, and an AO-corrected illumination capable of projecting high-resolution features in the retina. Wide-field (2.

Pupil motion analysis and tracking in ophthalmic systems equipped with wavefront sensing technology.

Our eyes are constantly in motion, even during "steady" fixation. In ophthalmic systems equipped with wavefront technology, both eye and head motion potentially degrade its performance and/or increase the cost and complexity, as they induce a movement of the entrance optical pupil of the system. Here, we characterize the pupil motion in an aberrometry setting, using a custom, high-speed pupil tracker (478 Hz), and draw conclusions on design considerations of future ophthalmic systems.