Automated image processing pipeline for adaptive optics scanning light ophthalmoscopy

Salmon, Alexander E; Cooper, Robert F.; Chen, Min; Higgins, Brian; Cava, Jenna; Chen, Nickolas; Follett, Hannah M; Gaffney, Mina; Heitkotter, Heather; Heffernan, Elizabeth; Schmidt, Taly Gilat; Carroll, Joseph

doi:10.1364/boe.418079

Cited by 10 publications

(4 citation statements)

References 47 publications

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“…Automatic retinal image montaging has been demonstrated in prior art, but most implementations have focused on obtaining image strips that extend into the periphery along two cardinal axes rather than constructing continuous retinal montages that encompass the entire 5-degree fovea [49,54,55]. For quantifying cone density across the entire fovea, it is advantageous to obtain a continuous map of the photoreceptor mosaic with a diameter larger than 5 degrees centered on the foveola, which is why we implemented the full-field imaging strategy described in Section 5.1.…”

Section: Discussionmentioning

confidence: 99%

High refresh rate display for natural monocular viewing in AOSLO psychophysics experiments

Moon,

Linebach,

Yang

et al. 2024

Preprint

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By combining an external display operating at 360 frames per second with an Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) for human foveal imaging, we demonstrate color stimulus delivery at high spatial and temporal resolution in AOSLO psychophysics experiments. A custom pupil relay enables viewing of the stimulus through a 3-mm effective pupil diameter and provides refractive error correction from -8 to +4 diopters. Performance of the assembled and aligned pupil relay was validated by measuring the wavefront error across the field of view and correction range, and the as-built Strehl ratio was 0.64 or better. High-acuity stimuli were rendered on the external display and imaged through the pupil relay to demonstrate that spatial frequencies up to 54 cycles per degree, corresponding to 20/11 visual acuity, are resolved. The completed external display was then used to render fixation markers across the field of view of the monitor, and a continuous retinal montage spanning 9.4 by 5.4 degrees of visual angle was acquired with the AOSLO. We conducted eye-tracking experiments during free-viewing and high-acuity tasks with polychromatic images presented on the external display. Sub-arcminute eye position uncertainty was achieved, enabling precise localization of the line of sight on the monitor while simultaneously imaging the fine structure of the human central fovea. This high refresh rate display overcomes the temporal, spectral, and field of view limitations of AOSLO-based stimulus presentation, enabling natural monocular viewing of stimuli in psychophysics experiments conducted with AOSLO.

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Section: Discussionmentioning

confidence: 99%

High refresh rate display for natural monocular viewing in AOSLO psychophysics experiments

Moon,

Linebach,

Yang

et al. 2024

Preprint

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“…Reference frames with minimal distortion due to eye movement were selected from each image sequence either manually or automatically (4), for registration and averaging of at least 40 images at each retinal location to increase the signal-to-noise ratio (5). Intraframe motion correction (de-warping) was then applied to remove any residual distortion (6).…”

Section: Methodsmentioning

confidence: 99%

Minimum intensity projection of embossed quadrant-detection images for improved photoreceptor mosaic visualisation

Kalitzeos,

Michaelides,

Dubra

2024

Front. Ophthalmol.

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Non-confocal split-detection imaging reveals the cone photoreceptor inner segment mosaic in a plethora of retinal conditions, with the potential of providing insight to ageing, disease, and response to treatment processes, in vivo, and allows the screening of candidates for cell rescue therapies. This imaging modality complements confocal reflectance adaptive optics scanning light ophthalmoscopy, which relies on the waveguiding properties of cones, as well as their orientation toward the pupil. Split-detection contrast, however, is directional, with each cone inner segment appearing as opposite dark and bright semicircles, presenting a challenge for either manual or automated cell identification. Quadrant-detection imaging, an evolution of split detection, could be used to generate images without directional dependence. Here, we demonstrate how the embossed-filtered quadrant-detection images, originally proposed by Migacz et al. for visualising hyalocytes, can also be used to generate photoreceptor mosaic images with better and non-directional contrast for improved visualisation. As a surrogate of visualisation improvement between legacy split-detection images and the images resulting from the method described herein, we provide preliminary results of simple image processing routines that may enable the automated identification of generic image features, as opposed to complex algorithms developed specifically for photoreceptor identification, in pathological retinas.

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“…However, these metrics are necessarily robust to noise and are designed for image alignment to a reference image, not as descriptors of image quality. While there exist algorithms capable of rejecting poor reference images before alignment based on metrics such as mean intensity, contrast, and sharpness [ 16 , 17 ], the quality of the final registered image is not always related to the quality of the reference image, and ultimately a user is still required to select suitable quality images from a subset of registered and averaged candidate images.…”

Section: Introductionmentioning

confidence: 99%

“…For this reason, no-reference image quality metrics are often more desirable for evaluating AOSLO images. This includes metrics like mean intensity [ 8 , 5 ], contrast [ 6 ], sharpness [ 16 , 17 ], Fourier coefficient energy [ 6 , 7 ], Blind Image Quality Index (BIQI) [ 3 , 20 , 21 ], and Perception-based Image Quality Evaluator (PIQE) [ 21 ]. Many of these have found extensive use in sensorless AO, where they are used as metrics to drive optimization of an AO control loop but are not commonly reported in literature as a descriptive measure.…”

Section: Introductionmentioning

confidence: 99%

Quantifying image quality in AOSLO images of photoreceptors

Brennan,

Heitkotter,

Carroll

et al. 2024

Biomed. Opt. Express

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The use of “quality” to describe the usefulness of an image is ubiquitous but is often subject to domain specific constraints. Despite its continued use as an imaging modality, adaptive optics scanning light ophthalmoscopy (AOSLO) lacks a dedicated metric for quantifying the quality of an image of photoreceptors. Here, we present an approach to evaluating image quality that extracts an estimate of the signal to noise ratio. We evaluated its performance in 528 images of photoreceptors from two AOSLOs, two modalities, and healthy or diseased retinas. The algorithm was compared to expert graders’ ratings of the images and previously published image quality metrics. We found no significant difference in the SNR and grades across all conditions. The SNR and the grades of the images were moderately correlated. Overall, this algorithm provides an objective measure of image quality that closely relates to expert assessments of quality in both confocal and split-detector AOSLO images of photoreceptors.

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Automated image processing pipeline for adaptive optics scanning light ophthalmoscopy

Cited by 10 publications

References 47 publications

High refresh rate display for natural monocular viewing in AOSLO psychophysics experiments

High refresh rate display for natural monocular viewing in AOSLO psychophysics experiments

Minimum intensity projection of embossed quadrant-detection images for improved photoreceptor mosaic visualisation

Quantifying image quality in AOSLO images of photoreceptors

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