Program Abstracts

Invited Session I: Optoretinography

Optoretinography: From Retinal Physiology to Clinical Biomarkers
Ram Sabesan, University of Washington

Optoretinography (ORG) has emerged as a powerful approach for measuring light-evoked functional responses in the eye and bridging the gap between retinal structure and function. Broadly, ORG leverages existing optical imaging modalities, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), to measure stimulus-evoked neural activity non-invasively in the living human eye. When combined with adaptive optics, these techniques enable functional imaging at cellular resolution.

This presentation will provide an overview of recent advances in ORG and the insights they have provided into retinal physiology. Topics will include the fundamental properties of light-evoked responses in photoreceptors, as well as recent work linking these signals to phototransduction, outer retinal biomechanics, and coherent optical scattering. Together, these studies have begun to establish a unified framework for interpreting ORG measurements across imaging modalities. The presentation will also highlight the use of ORG as a sensitive biomarker of retinal disease, capable of detecting functional abnormalities before overt structural changes become apparent. Finally, it will conclude with a discussion of the remaining challenges, open questions, and opportunities for translating functional retinal imaging from the research laboratory into broader clinical practice.

Optoretinography and Beyond: Imaging Neural and Vascular Function in the Human Retina
Pedro Mecê, Institut Langevin, Paris

Optoretinography (ORG) is emerging as a powerful approach for probing retinal function non-invasively. This presentation will highlight two complementary imaging strategies to extend cellular-resolution functional retinal imaging over large fields and at high speed.

We will first present time-domain full-field optical coherence tomography (FFOCT) for measuring stimulus-evoked photoreceptor responses over a 5° × 5° field at up to 500 Hz, with the aim of extending cellular ORG toward more scalable and clinically applicable measurements.

We will then consider retinal function from a broader physiological perspective. Neural activation is accompanied by vascular responses (neurovascular coupling) that regulate local blood supply and metabolic support, providing complementary information on retinal function. Adaptive-optics rolling-slit ophthalmoscopy (AO-RSO), a phase-contrast method developed in our group, provides cellular-scale imaging over approximately 4.5° × 3° at up to 200 Hz. Direct visualization and tracking of vessel walls over time reveal stimulus-evoked vasodilation during neurovascular coupling.

Together, these developments illustrate how functional retinal imaging may evolve from the measurement of photoreceptor activity toward a more integrated assessment of neural and vascular function, with potential applications in retinal and neurodegenerative disease.

Techniques and applications of optoretinography in combination with adaptive optics scanning laser ophthalmoscopy
Jessica Morgan, University of Pennsylvania

Optoretinography is an emerging technique for high resolution assessment of retinal function through noninvasive imaging. This presentation will describe techniques and applications of optoretinography in combination with adaptive optics scanning laser ophthalmoscopy (AOSLO).

A custom-built, multimodal AOSLO was used to image the photoreceptors before, during, and after calibrated stimuli of 545 nm light were delivered to the retina. AOSLO videos were registered and cone intensities extracted. Population optoretinogram (ORG) measurements were made by normalizing, standardizing, and aggregating cones intensities to detect changes in cone intensities following stimulation. ORGs from patients with choroideremia and retinitis pigmentosa were compared with normal ORGs across retinal eccentricities.

In normal controls, the ORG was repeatable, decreased with eccentricity, and its action spectrum corresponded with the photopic luminosity function. In choroideremia patients, ORGs were severely reduced at all retinal locations in comparison to controls. Retinitis pigmentosa patients also exhibited severely reduced ORGs, especially at retinal locations approaching the transition zone of photoreceptor loss.

Optoretinography demonstrates promise as an objective biomarker of cone function in health and disease. Future applications of optoretinography include its use as a secondary outcome measure in clinical trials testing novel therapeutics for retinal disease.

Differential Coherence as an Optoretinographic Tool
Lawrence Sincich, The University of Alabama at Birmingham

Cone photoreceptors have stimulus-driven morphological changes that can alter their optical reflectance. In conjunction with adaptive optics, we are exploring how differential coherence imaging (DCI) may be used to measure positional shifts in reflective surfaces after stimulation with light in the living eye. Such shifts are expected to occur as interference effects from surface pairs lying within the coherence length of an imaging light source.

DCI images were created by subtracting successive frames during imaging with high (11.1 µm, λ = 840±10.5 nm) and low coherence (5 µm, λ ≈ 848±50 nm) sources of balanced intensity reflected from the eye. Imaging trials lasted 6 s, with a stimulus flashed for 0.5 s containing green light (543±11 nm, 0.9-20 µW). DCI reflectivity changes were compared to images processed from an adjacent area of unstimulated retina, acting as a control.

We found DCI signals—resolved at the single cone level—driven by visual stimulation in 3 tested subjects. DCI signals were detectable within 1 trial and are consistent with the movement of reflective surfaces positioned less than 10 µm apart. The signal likely arises from the inner/outer segment junction or from the outer segment tip adjacent to the retinal pigment epithelium. The DCI approach holds promise as a new optoretinographic tool for revealing photoreceptor responses.

Contributed Session 1

AO-SLO photopic optoretinography with silent substitution flicker
Sirui Liu, University of Oxford

Optoretinography (ORG) is an emerging technique for measuring light-evoked responses of photoreceptors using AO-OCT or AO-SLO. While conventional ORG requires repeated dark adaptation and intense flashes, the light-adapted flicker ORG has recently shown promise in OCT. Through experimental measurements and computational modelling, we assess the feasibility of measuring the light-adapted flicker ORG in AO-SLO. We measured the AO-SLO ORG from two human participants with normal colour vision in response to achromatic, L-, M-, and S-cone-isolating flicker. Data were compared to control conditions that used a steady background matched to the flicker mean. Existing biophysical models of stimulus-evoked outer segment changes were integrated with a two-beam interference model and an AO-SLO data capture model (Emulated Retinal Image Capture, ERICA). The framework reproduced published responses under the dark-adapted flash paradigm and was then used to predict responses for the photopic silent-substitution flicker paradigm, enabling verification and optimisation of downstream analysis. Stimulus-driven frequency-locked cone reflectance oscillations were observed from both participants but with considerable trial-to-trial variability. Modelling suggested that image registration and segmentation errors contributed more substantially than measurement noise, emphasising the need for optimisation in image processing to improve robustness of the photopic AO-SLO ORG.

Adaptive optics imaging reveals transport dynamics of mitochondria in ganglion cell axons

Derek Power, University of Rochester

Mitochondria are essential organelles that provide ATP to meet the high metabolic demands of the retina. Their proper localization and transport are critical for neuronal homeostasis and visual function. However, direct visualization of mitochondrial transport in the live mammalian retina has remained largely inaccessible due to insufficient resolution. Here, we extend adaptive optics scanning light ophthalmoscopy (AOSLO) to the subcellular scale to visualize mitochondrial axonal transport in vivo.

We resolve and track individual fluorescent mitochondria undergoing axoplasmic transport in retinal ganglion cell axons, representing the first direct observation of this process in ophthalmoscopy. Imaging was performed in 2 mito:mKate2 mice expressing fluorescently labeled mitochondria throughout the retina acquiring 5-minute videos of the nerve fiber layer within 10° of the optic disc. We reveal mitochondrial transport in both anterograde and retrograde directions with velocities of 0.86±0.15 µm/s (mean±SD) and 0.91±0.1 µm/s, respectively (n=5 mitochondria each). Continuous transport occurred throughout nerve fibers with no evidence of stalling. These findings establish organelle-scale AOSLO imaging as the first non-invasive approach for directly visualizing axonal mitochondrial transport in the living mammalian retina. This approach opens new opportunities to investigate metabolic and neurodegenerative diseases characterized by impaired mitochondrial localization and transport.

Longitudinal AOSLO in vivo imaging reveals RGC dendritic remodeling in a mouse photoreceptor degeneration model
Soumaya Belhadj, University of Pittsburgh

In disease of the outer retina, photoreceptor loss drives maladaptive plasticity of surviving inner retinal circuits, corrupting the processing of electrophysiological responses to light from surviving photoreceptors in early-stage disease and from artificial vision methods relying on functional retinal ganglion cells (RGC) in late-stage disease. This remodeling induces dynamic changes in RGC circuits, which have so far only been observed in terminal experiments. Here, we investigate RGC dendritic reorganization in the same cells, tracked over time during homeostasis and degeneration using adaptive optics scanning light ophthalmoscopy (AOSLO).

We used 2 WT and 3 rd1 Thy1-YFP transgenic mice expressing YFP in a sparse subset of RGCs, enabling isolation of individual dendritic arbors. 3 to 4 individual RGCs/mouse were imaged across 5 timepoints spanning postnatal day (P) 45 to P170. Fluorescence (111 µW 488 nm) was acquired using a custom AOSLO.

In healthy mice, dendritic arbors remained stable across all sessions. In the rd1 strain we detected in vivo dendritic remodeling in 30% of the RGCs imaged, emerging between P70 and P90 and continuing throughout P171. The changes observed were subtle and consisted of dendrite retraction ranging from 20 to 86 µm, preceded by extension in some cases, and overall structure reorganization. This work shows the magnitude and evolution of dendritic remodeling in homeostasis and degeneration that can be now tracked in vivo.

The Relationship Between Acuity and Cone Density Decline Across the Foveola
Krishnaveni Nagarajan, University of Rochester

Cone density declines with eccentricity even within the central 1deg foveola. Here, we examined how the decline in cone density from the preferred retinal locus to 25 arcmin eccentricity relates to the decline in visual acuity. Cone density was measured from retinal images acquired with an Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO). Acuity thresholds were measured with a 4AFC Tumbling E task under diffraction-limited conditions with AOSLO, and under natural optical conditions using a digital Dual Purkinje Image eye tracker with refractive errors corrected by a Badal optometer.

Under diffraction-limited viewing, acuity was close to the cone-mosaic Nyquist sampling limit, and the slope of acuity decline closely matched that of cone-density decline across the foveola. Notably, the estimated number of stimulated cones remained constant across eccentricities when stimuli were scaled to each observer's acuity threshold, suggesting that threshold performance depends on maintaining a comparable cone-sampling pool across foveolar eccentricities. Under natural optical conditions, acuity also declined with eccentricity, but this decline was substantially shallower than under diffraction-limited conditions and did not correlate with the decline in cone density across subjects. Acuity across the foveola was therefore not uniform, even under normal viewing conditions in the presence of optical aberrations.

Frequency selective post-microsaccadic perceptual enhancements in the fovea
Zoe Stearns, University of Rochester

Microsaccades compensate for non-uniform sensitivity within the foveola by redirecting the preferred locus of fixation (PLF) and enhancing fine spatial vision before their onset. Whether perception is further enhanced after microsaccade landing remains unknown. We measured post-microsaccadic visual discrimination at the landing site and further away from it. Eye movements were recorded with a digital Dual-Purkinje Image eye tracker while observers (N=10) freely viewed five Gabors spanning 2.5°. At random times, all Gabors reversed phase and one also changed orientation. Contrast was adjusted so that orientation discrimination was at threshold during fixation at the PLF. Performance was compared during steady fixation and 0-100 ms after microsaccade landing for stimuli near the PLF (≤15 arcmin) or farther away (20-40 arcmin), and for low and high spatial frequencies. Visual discrimination improved immediately after microsaccade landing relative to baseline. The enhancement was confined to the PLF and was selective for high spatial frequencies; performance increased ~20 ms after landing, whereas for low spatial frequencies performance remained unchanged. These results show that microsaccades lead to post-microsaccadic perceptual enhancements, these modulations are spatial-frequency selective and are localized at the microsaccade landing site, indicating that they are driven by extraretinal signals.

Translating fixation stability measurements from lab to practice: Comparing clinical devices to a laboratory eye-tracker
Riley Wiland, University of Houston

Fixational eye movements are widely studied for their potential as biomarkers of ocular and neurologic disease. However, the laboratory-based instruments used in most research are not routinely available in clinical practice, limiting clinical translation of these findings. We compared fixation stability estimates from two clinically available devices with those obtained using a research-grade eye-tracker. Fixation stability under monocular viewing conditions was assessed in participants with a range of diagnosed ocular conditions known to affect visual function and age-matched controls (n=20) via three devices: Eyelink 1000+, Nidek MP-3, and Cirrus 6000 OCT. Nidek and OCT measurements were evaluated against Eyelink using linear mixed-effects models of log-transformed 68% BCEA, accounting for paired eye measurements. Agreement between devices was evaluated using repeated-measures Bland-Altman (BA) analyses. Eyelink BCEA significantly predicted both Nidek (β = 0.66, 95% CI 0.37-0.95, p < 0.001) and OCT (β = 0.61, 95% CI 0.24-0.99, p = 0.003) measurements. BA analyses showed that both Nidek (mean log difference = -0.80; 95% LOA: -1.50 to -0.09) and OCT (mean log difference = -0.27; 95% LOA: -1.15 to 0.61) systematically underestimated Eyelink BCEA. Both clinical instruments demonstrated a significant relationship with Eyelink estimates while showing systematic bias. These findings support the feasibility of estimating fixation stability using clinically available instruments.

Invited Session II: Chromatic Mechanisms in Myopia

Temporal Constraints on Antagonistic Chromatic and Achromatic Mechanisms in Emmetropization
Frances Rucker, New England College of Optometry

The emmetropization mechanism uses longitudinal chromatic aberration (LCA) to guide ocular growth through a blue/yellow chromatic pathway but can also regulate growth in monochromatic light via an achromatic mechanism. Because myopia develops when axial elongation exceeds the optical power of the eye, understanding how these pathways interact is important. We tested whether temporal frequency differentially engages chromatic and achromatic emmetropization mechanisms to produce antagonistic growth responses. Chicks were exposed to visual stimuli that varied in temporal frequency, spectral composition, and contrast. At low temporal frequencies, high-contrast blue/yellow chromatic stimulation reduced axial growth, whereas achromatic stimulation increased growth. At high temporal frequencies simulating blur produced by LCA, greater contrast in short- than long-wavelength channels paradoxically increased growth, consistent with the predicted sign of the LCA signal. In contrast, high-contrast achromatic stimulation without short-wavelength cone stimulation generated a stop signal that inhibited growth. These findings demonstrate that chromatic and achromatic emmetropization mechanisms have distinct temporal tuning and generate opposing signals that regulate axial elongation. Without sufficient short-wavelength or high-frequency stimulation, the balance shifts toward increased eye growth, providing a potential mechanism for the development of myopia.

Developing chromatic signals as a therapy for myopia control
Safal Khanal, The University of Alabama at Birmingham

Myopia, or nearsightedness, affects approximately 36% of children and adolescents worldwide, and the prevalence continues to increase. Although current interventions can slow myopia progression, their effectiveness remains incomplete, and substantial progression continues in many children. New approaches targeting the biological mechanisms that regulate eye growth are urgently needed. Growing evidence suggests that the spectral composition of light plays a critical role in emmetropization, raising the possibility that specific wavelengths could be harnessed as a therapy for myopia control.

In this talk, I will present evidence across species demonstrating how emmetropization responds to chromatic signals in the visual environment and how selective spectral manipulation can alter eye growth and refractive development. I will then describe preclinical findings, including our work in tree shrews, that have informed the development of a wavelength-based light therapy for childhood myopia, as well as emerging clinical evidence supporting this approach. Finally, I will discuss potential retinal mechanisms underlying wavelength-dependent regulation of eye growth, including evidence from our human studies that myopia may be associated with altered retinal responses to chromatic signals. Understanding how the retina encodes wavelength signals that regulate eye growth may provide a mechanistic foundation for developing effective light therapies for myopia control in children.

Longitudinal Chromatic Aberration as a Cue for Detecting the Sign of Defocus
Geunyoung Yoon, University of Houston

While several optical cues have been proposed, understanding how the visual system detects the sign of defocus remains critical to elucidating the mechanisms underlying emmetropization. Longitudinal chromatic aberration (LCA) is an optical property of the eye that serves as a vital cue for this process. Because different wavelengths of light focus at distinct distances, LCA generates systematic chromatic signals that differentiate myopic from hyperopic defocus. This talk examines how the visual system leverages these signals to guide two distinct physiological processes: accommodation and choroidal thickness modulation. By employing a spatial light modulator visual simulator, we manipulated ocular LCA to be increased, corrected, or reversed. We will present evidence on whether LCA acts as a common optical cue for detecting the direction of optical error, linking retinal image signals to short-term accommodation and, potentially, to the longer-term mechanisms governing myopia development.

How could the eye use chromatic cues to guide refractive development?
Timothy Gawne, The University of Alabama at Birmingham

In childhood and up through young adulthood, the eye uses visual cues to determine the magnitude and sign of defocus, and adjusts its rate of axial elongation to first achieve, and then actively maintain, sharp focus – a process termed ememtropization. Increasingly our modern visual environment is interfering with this process, and there is an epidemic of myopia (nearsightedness), where the eye has elongated too much for its optics. Myopia does not just require glasses or contact lenses but negatively impacts the quality of life and is a major risk factor for later sight-threatening disease.

In this talk I will cover the evidence that the primary visual cue used by emmetropization is a chromatic one, that exploits naturally occurring Longitudinal Chromatic Aberration (LCA). Experiments on tree shrews – small diurnal animals closely related to primates – have shown that if the chromatic cues for defocus are manipulated, sharp focus itself can be over-ridden, and an eye can be forced to become hyperopic or myopic. The rules likely do not correspond to those of perceptual psychophysics, this is another system that combines different wavelength sensitive photoreceptors, the continually changing focus with wavelength due to LCA, and the spatial and chromatic structure of the external environment. Understanding this process opens the possibility of ‘talking’ to the post-natal developing eye and convincing it to halt excessive elongation.

Contributed Session II

Altered retinal light response in retinoic acid-induced myopic mice
Sabina Poudel, University of Rochester

The signaling pathways linking visual input to myopic eye growth remain poorly understood. Previous work shows elevated all-trans retinoic acid (atRA) in visually induced myopia and that exogenous atRA induces myopia in mice, but whether atRA alters retinal function is unknown. Here, we measured retinal ganglion cell (RGC) responses in atRA-induced myopia using a pigmented RARE-LacZ line reporting RA signaling activity (Rossant et al,1991). Mice received sugar pellets with atRA (25mg/kg, n=11) or sugar pellets (control, n=9) from P30-P47. Refraction (RE) and axial length (AL) were measured weekly by photorefraction and OCT. At endpoint, ex vivo RGC light responses were recorded by multielectrode arrays with white-light steps (16µW/cm2) and temporal contrast modulation. LacZ expression was assessed by immunofluorescence. Compared to controls, atRA-fed mice developed myopic shift and eye elongation (RE:-10.2±1.8D; AL:+50±12µm). Myopic retinas showed reduced ON (10%) and increased OFF (54%) peak firing rates compared to controls, lowering ON/OFF response ratio (1.56 vs 2.61). atRA-fed retinas also showed reduced contrast-evoked responses, particularly at high contrasts and dorsal retina (by 23% at 0.5-1.0 contrast). LacZ expression localized to Muller glia with regional increases in atRA-fed sclera. These findings show retinal functional changes accompanying RA-induced myopic eye growth and motivate studying how RA signaling and retinal function interact in myopia development.

Task engagement modulates BOLD responses in early visual cortex
Philipp Kreyenmeier, National Institutes of Health

Neurons in early visual cortex (EVC) are selective for low-level visual features. Yet, even in the absence of visual stimulation, EVC exhibits intrinsic hemodynamic responses that are related to the task structure. The origin and function of these task-related responses are poorly understood. We ask whether task-related activity reflects changes in brain states, such as task engagement and arousal.

Participants alternated between periods of engagement in a visual task and periods of rest (under controlled visual stimulation) while we recorded eye movements and functional magnetic resonance imaging (fMRI). In different variations of the experiment, we tested the role of temporal predictability, the decision, and the motor response.

We found that saccades and blinks were suppressed while pupil size increased during task engagement, reflecting periodic fluctuations in arousal state. fMRI-BOLD responses in EVC showed a similar periodic modulation. EVC exhibited increases in response amplitude during rest, when subjects were disengaged from the task and in a low arousal state. These task-related responses were widespread and persisted across experiments:1) when subjects did not make a manual response, 2) when the timing of the task was unpredictable, and 3) when accounting for task-related blinking.

Our findings show that task-related BOLD activity in EVC reflects changes in brain state, independent of visual stimulation, predictive processes, blinking, and manual responses.

Convexity biases persist in stereoscopically viewed structure-from-motion surfaces
Ryne Choi, York University

A bias toward interpreting surfaces as convex rather than concave has been observed in many areas of vision science, including in structure-from-motion (SFM), where it can override both a rigid motion bias and perspective image cues. Binocular disparity, however, specifies the sign of surface curvature without the depth-reversal ambiguity of orthographic SFM. We asked whether the convexity bias observed in SFM persists when binocular disparity specifies a concave surface. Observers viewed stereoscopically presented random-dot half-spheres that were static or rotated back and forth about a vertical axis. Binocular disparity was manipulated by uniformly scaling every point’s image disparity by a gain parameter termed disparity gain (DG), ranging from 0 (no disparity) to 1 (the geometrically correct disparity). On each trial, observers indicated whether the surface appeared convex or concave. Psychometric functions for the proportion of “convex” responses to concave stimuli were fit to estimate the DG producing 50% convex responses (PSE). PSEs were substantially higher for moving than static stimuli, indicating that greater disparity was required to overcome the convexity bias. For several observers, this bias was so powerful that convex responses remained dominant even at the highest disparity levels. Our results show that models of cue integration must account for the influence of strong shape priors even in the presence of highly reliable cues such as binocular disparity.

The role of visuomotor contingency in stereoscopic depth perception
Jie Z. Wang, University of Rochester

Stereopsis is commonly viewed as a spatial process based on retinal disparities between static images. However, incessant inter-saccadic eye movements during fixation cause retinal disparities to change over time. Recent work has shown that these temporal disparity modulations are essential for normal stereoscopic sensitivity. Here, we show that stereopsis depends not only on dynamic disparity signals, but also on their congruence with oculomotor signals. Observers judged whether the upper or lower half of a vertically slanted surface appeared closer while binocular eye movements were recorded with a digital DPI eye tracker. A custom gaze-contingent display updated stimuli in real time to disrupt the natural visuomotor contingency. Three viewing conditions were interleaved: “Stabilized” eliminated disparity modulations by moving the stimuli with the eyes; “Reconstructed” compensated for current eye movements and replayed previously recorded eye motions; and “Flipped-vergence” inverted vergence-induced disparity and eliminated version-induced disparity. Eliminating disparity modulations greatly impaired performance. Reintroducing disparity modulations partially restored performance, showing that passive exposure is beneficial but insufficient for normal sensitivity. Performance declined even further in the Flipped-vergence condition. These results point to a critical role of visuomotor contingency together with dynamic disparity modulations in stereoscopic depth perception.

Perceptual inference of object motion and depth: how cueing one variable influences estimation of the other
Vitaly Lerner, University of Rochester

When an observer moves, the same retinal motion can be interpreted as arising from a stationary object or a moving object at a different depth. The strategy used by the brain to infer object depth and motion remains an open question. In ambiguous cases, a-priori knowledge of depth can facilitate detection of object motion by disambiguating the contributions of self- and object motion to retinal velocity. Similarly, a-priori knowledge of object motion can facilitate depth perception. To investigate the use of a-priori knowledge of one variable to infer another, we trained macaque monkeys to discriminate depth sign (nearer or farther than the fixation point) and object motion (stationary or moving in the world) during self-motion in a virtual environment. Monkeys are also trained to associate depth sign and object motion with specific visual cues. On a portion of trials in the depth discrimination task, the object motion is given by the cue, and vice versa. Preliminary results indicate that motion cueing has a stronger impact on decisions about depth than vice versa, with this mechanism being gated by the alignment of retinal motion and self-motion. Furthermore, we record neuronal activity in brain areas known for their contributions to perception of motion and depth: middle temporal area (MT) and medial superior temporal (MST) cortex, to study how such crossmodal perceptual cues modulate the neural dynamics underlying perception of object depth and motion in the world.

High-Precision Stereoacuity Assessment in VR Using STRIVE (STereo Random-dot Interactive Virtual Environment)
Triya Belani, Rochester Institute of Technology

Accurate measurement of stereoacuity is essential for understanding binocular depth perception and its role in visuomotor behavior. Common clinical tests (e.g., Randot, Frisby) retain potential monocular depth cues, are resolution-limited, and have a physical format that is an obstacle to development and modification. We present STRIVE, a real-time, depth-map-driven random-dot stereogram framework that can convert any interactive VR task in Unity into a disparity-isolated environment. STRIVE provides precise disparity control and enables manipulation of competing depth cues. To validate the framework, 13 adults with normal binocular vision completed a three-alternative forced-choice depth discrimination task. Stereo thresholds estimated using an adaptive staircase followed by a method of constant stimuli yielded thresholds of 6.9–28.5 arcsec, with low within-participant variability (SD = 2.1 arcsec) and good test–retest reliability (ICC(2,1) = 0.862). In contrast, Randot thresholds showed floor effects and clustered at only three discrete levels. An additional evaluation using the adaptive QUEST+ procedure yielded thresholds comparable to the method of constant stimuli while requiring substantially fewer trials and less testing time. These findings indicate that STRIVE provides a rapid and accurate measure of stereoacuity that is comparable to RANDOT, making it a suitable tool for stereovision studies in dynamic and interactive environments.

Invited Session III: Multisensory Cue Integration in Real and Virtual Environments

Multisensory cue use during navigation in virtual reality: What role does vision play?
Sarah Creem-Regehr, The University of Utah

Effective navigation depends on integrating information from multiple sensory systems, including vision, hearing, and the proprioceptive and vestibular signals generated during movement (body-based cues). Visual landmarks are a reliable and heavily weighted spatial cue but their reliability may be reduced in environmental contexts that lack visual landmarks or with individual vision loss. I will present studies that address how multisensory cues are used in navigation when visual landmarks are not (or less) available. Participants completed a virtual reality homing task. They walked to a home location, and then walked two more legs of a triangle with landmarks present. They then walked back to home under four conditions: single cues, both cues, and a conflict condition in which the landmarks were covertly shifted. One experiment paired auditory landmarks with body-based cues (no visual landmarks); another combined auditory and visual landmarks under degraded (blurred) vision; two additional experiments reduced visibility of visual landmarks with gaze-contingent central or peripheral scotomas. Participants generally showed multisensory benefits, with reduced navigation variability when two cues were available. However, different patterns of navigation accuracy, precision, and cue-weighting varied across manipulations, suggesting that individuals can flexibly adapt their use of sensory information to compensate for vision loss in different contexts.

Multisensory Integration Across Real and Simulated Environments: Applications to Aging and Clinical Populations
Jennifer Campos, University Health Network

The Challenging Environment Assessment Laboratories at KITE, Toronto Rehabilitation Institute comprise a suite of advanced virtual reality, motion simulation, and environmental simulation systems. These include immersive, multisensory projection-based displays, motion platforms, climate-controlled spaces, and Canada’s most advanced driving simulator. Together, these laboratories allow visual, auditory, vestibular, proprioceptive, and environmental information to be systematically manipulated while perception and behaviour are examined under controlled yet functionally meaningful conditions.

Our research uses these technologies to investigate fundamental principles of multisensory processing, including how the brain combines and weights sensory cues across different tasks and environments. A particular focus is understanding how these processes change with older age and in populations with sensory, cognitive, or neurological impairments. By varying the availability, reliability, and congruence of individual sensory cues, simulated environments provide a powerful means of examining sensory integration and reweighting while retaining greater complexity and ecological relevance than is often possible under traditional laboratory protocols and reductionistic conditions.

These technologies also support the study of multisensory function during everyday activities, including standing, walking, navigation, and driving. This helps bridge the gap between basic research on perception and its application to real-world function, safety, and rehabilitation.

In this talk, I will briefly introduce the laboratory infrastructure and present examples of research examining visual–vestibular integration and sensory weighting in younger and older adults, as well as altered multisensory responses in clinical populations, including individuals with persistent symptoms following concussion. Together, these examples will illustrate how virtual and simulated environments can advance fundamental understanding of multisensory integration while supporting research focused on injury prevention, rehabilitation, and healthy aging.

Vision, proprioception, and memory in naturalistic reaching: evidence from stroke, schizophrenia, and aging
Duje Tadin, University of Rochester

Our actions are guided by multiple sensory signals and cognitive goals. Even something as simple as reaching for a coffee mug involves a coordinated use of proprioception, vision and even working memory. Advances in VR make it possible to systematically probe the sensory and cognitive factors in reaching while retaining much its natural complexity.

In a series of VR studies, we investigated the effects of visual and proprioceptive cues, as well as working memory demands, on reaching behavior. We manipulated whether the participant's hand was rendered, so that reaches were either visually guided (vision plus proprioception) or proprioceptively isolated (hand not rendered during the reach phase). Working memory was assessed by introducing a delay between target disappearance and movement initiation. As expected, both removing vision and adding memory demands reduced reach accuracy.

Next, we used this approach to study the naturalistic reaching behavior in cerebral stroke, schizophrenia, and senescence. We found that patients with cerebral stroke performed worse than age-matched controls, but only when proprioception was isolated. This demonstrates vision's ability to mask kinesthetic impairments. In schizophrenia, visually guided and proprioception-only reaching behaviors were typical, with impairments only appearing when memory demands were introduced. Finally, we found that all of these behaviors were preserved in older adults. Together, we show that a single naturalistic VR paradigm can dissociate distinct sources of reaching impairment — proprioceptive in stroke, mnemonic in schizophrenia, and neither in healthy aging — yielding condition-specific behavioral signatures.

Characterizing perceptual performance bottlenecks in virtual environments
Jovan Kemp, NYU Abu Dhabi

Virtual displays have transformed perception research by enabling precise control over the rendering of naturalistic cues. However, the displays themselves introduce signals that may distort the very behaviours they are designed to study and therefore limit the generalizability of the results. In this talk, we present a series of experiments conducted via virtual displays that reveal systematic and unexpected results about the visual processing of 3D cues. We then rule out the possibility that these results emerge from artifacts of using a virtual environment.

First, we examined depth perception from static monocular and binocular cues for 3D shape. We presented objects at different viewing distances in cue-isolated, or combined conditions. The results point to systematic biases from veridical depth that depend on the viewing condition. While such biases may emerge from flatness cues produced by the display we determined that the flatness cues could not account for the deviations from veridical depth perception.

Second, we examined the integration of binocular cues for motion-in-depth both in isolation and in combination. We used a rendering technique that allowed the binocular positional and velocity components to be completely isolated. We tested participants’ ability to detect direction in depth at different locations across the visual field. We found systematic differences in performance that depended on the binocular cue type and visual field location. Similar to the preceding experiments, properties of the virtual display could not account for these results . We conclude that the results found in these experiments are generalisable to perceptual behavior in the physical world.

Invited Session IV: Visual Development and Plasticity Across Health and Disease

Adaptive Plasticity After Vision Loss: Perceptual and Oculomotor Reorganization in Macular Degeneration
Marcello Maniglia, Rochester Institute of Technology

The human brain remains remarkably plastic throughout adulthood, allowing the visual system to adapt to profound changes in sensory input. Macular degeneration (MD), a leading cause of irreversible central vision loss, provides a unique model for investigating visual reorganization following sensory disruption.

Adaptation to central vision loss has traditionally been examined from two perspectives. Vision science has emphasized altered sensory input and perceptual mechanisms supporting performance, while clinical optometry has focused on oculomotor control and new fixation strategies. These perspectives have defined rehabilitation approaches targeting visual abilities or eye movements.

In this talk, using eye tracking, gaze-contingent paradigms, and psychophysics, I will present work examining how perceptual and oculomotor systems contribute to adaptation in patients with MD and simulated scotomas. These studies reveal substantial variability in adaptation and suggest that compensatory behaviors cannot be explained solely by sensory processing or fixation control.

Instead, emerging evidence suggests that adaptation reflects coordinated reorganization across multiple interacting systems, including sensory processing, oculomotor control, attention, and task-dependent mechanisms. This perspective reframes MD as a model for understanding adult adaptive plasticity and may inform rehabilitation approaches that engage multiple mechanisms of adaptation.

Developmental Neuroplasticity in Sight Loss and Sight Rescue
Tessa Dekker, University College London

How does visual experience shape brain development, and how does the brain adapt when that experience is altered? A robust learning system must balance stability of core neural architecture with the flexibility to learn from new experience. With the advent of gene, cell and retinal implant therapies, understanding these principles has become increasingly important for determining how restored retinal signals are transformed into meaningful vision.

I will present research tracing neural stability and plasticity across typical visual development, congenital sight loss and emerging sight-restoration therapies. Using neuroimaging and behavioural methods, we examine how the visual system reorganises—or resists change—when input is lost or restored through treatment. I will focus on work in children with achromatopsia, a congenital disorder in which cone photoreceptors are present but non-functional from birth, undergoing pioneering gene therapy. We first characterise cortical adaptations to lifelong rod-only vision and then investigate how rescued cone signals propagate through the visual system after treatment. Together, these studies provide new insights into how the developing and mature brain responds to restored sensory input, highlighting both the promise of sight-restoration therapies, and the neuroplasticity constraints that we need to consider to promote functional recovery.

Where and how is auditory motion represented within hMT+ in early blindness?
Woon Ju Park, Georgia Institute of Technology

Following early blindness, the human brain undergoes extensive cross-modal reorganization. A well-known example is area hMT+, which processes visual motion in sighted individuals but responds to auditory and tactile motion in early blind. In this talk, I will present a series of studies examining the anatomical localization and functional properties of these auditory motion responses. First, combining quantitative and functional MRI, I compare the anatomically defined, myelin-rich hMT+ with functionally defined auditory motion responses in early blind individuals. This reveals that the functional responses to auditory motion are displaced from the anatomical localization and do not coincide with the highly myelinated MT proper. Second, I show that this anatomically defined hMT+ retains stronger functional connectivity with occipital visual cortex, whereas the functionally defined auditory motion region is instead more strongly connected with other regions. Finally, I demonstrate that auditory motion responses within functional hMT+ differ qualitatively from visual motion responses in the sighted: they lack genuine object-motion selectivity, likely due to fundamental constraints of auditory input itself. Together, these findings show that cortical reorganization following early blindness is shaped by pre-existing connectivity patterns and the statistical structure of the available sensory input, constraining both where and how auditory motion comes to be represented in hMT+.

Receptive field mapping of the developing visual streams and the role of visuospatial attention in childhood
Jesse Gomez, Princeton University

How does development of visuospatial attention result from local computations in visual cortex? The human visual system contains what is referred to as the dorsal visual stream, a collection of retinotopic maps that play a key role in our ability to deploy visuospatial attention. However, the developmental emergence of the dorsal stream has never been mapped. We created two novel, child-friendly videogames designed to help us model and quantify population receptive fields (pRF). In this talk, we’ll answer two separate questions regarding pRFs: (1) How do static pRF properties of the dorsal visual stream change from childhood to adulthood? (2) Does a pRF’s ability to dynamically change size and position with the deployment of visual attention undergo protracted maturation? In data from both children and adults, I will show that the sampling of visual space undergoes protracted expansion, with field maps in later stages of the dorsal stream sampling significantly more peripheral space into adulthood. Furthermore, left and right hemispheres become increasingly symmetric in their sampling of contralateral space, correlating with behavioral biases in visuospatial attention measured with a line-bisection task in the same participants. These data provide some of the first neural correlates underlying imbalanced spatial attention observed in young children and lay the groundwork for understanding how atypical development contributes to various visual behavior deficits.

Contributed Session III

Colorimetric Awakening

Mark Fairchild, Rochester Institute of Technology

Industrial colorimetry dates back to the the 1920s with the establishment of the CIE and their XYZ system of colorimetry. The CIE system was only indirectly linked to visual physiology for several important practical reasons and due to a paucity of quantitative data on the mechanisms of human color vision. Inertia, and many strict international standards, have resulted in the passage of a century with great advancements in the understanding and quantification of human color vision not being incorporated into industrial color measurement practices. This presentation describes the perspective of a color scientist, with formal training in vision science, after four decades working at the intersection of visual neuroscience and industrial colorimetry. What if we could start anew and build a system of practical colorimetry incorporating much of what has been learned about the visual system in the last century? How would the system be constructed? What predictions would it make? And could it effectively replace current CIE colorimetry and color appearance models with a system that would also be useful for visual psychophysics and neurophysiology? The author believes the answer to these questions is “YES!” and describes the framework and implementation of such a system. Would the CIE be able to adopt such a system for international standards in the foreseeable future? Probably not. Despite that, the framework might be useful to researchers and practitioners in many fields.

Reverse Accommodation in Eyes Implanted with Standard Monofocal IOLs

Austin Roorda, University of Waterloo

Purpose: To measure accommodation in eyes with monofocal IOLs (mIOL). mIOLs are widely thought to offer no accommodation, but evidence is mounting that ‘reverse accommodation’ may be present.

Methods: We used FIAT, a custom-built Shack-Hartmann wavefront sensor, on 78 eyes with mIOLs (Alcon AcrySof IQ - SN60WF). Aberrations were measured at 30 fps while patients focused on near (0.3 – 0.6 m) and distant (> 4m) targets alternately presented for 6 sec each over a span of 36 secs. Refractive state was quantified as the defocus that conferred the highest Strehl ratio for each wavefront frame. The sign of accommodation was computed by comparing the average refractive state between the near and distant target presentations. Accommodation range was computed as the maximum difference in refractive state between near and distant targets.

Results: 40 of 78 eyes with mIOLs exhibited reverse accommodation of > -0.5 D, and the overall average was -0.41D, which can be caused by a ~0.2 mm posterior shift of the mIOL.

Discussion: Reverse accommodation in mIOLs may compromise near vision for millions of individuals worldwide. This finding also sets a new bar for accommodating IOLs (aIOLs) since an aIOL that offers just 0.5 D of accommodation in effect has nearly a 1D range over an mIOL, offering significantly improved near vision.

Conclusion: Optical measures using a device that elicits strong accommodative effort has revealed a small but significant level of reverse accommodation in mIOLs.

Laser-written diffractive soft contact lenses for reversing ocular longitudinal chromatic aberration

Len Zheleznyak, Clerio Vision & University of Rochester

Longitudinal chromatic aberration (LCA) has been proposed as an optical cue for the sign of defocus that may guide emmetropization. Because the eye's native LCA is positive, accommodative lag at near causes short wavelengths to be closer to focus than long wavelengths, producing higher retinal contrast at shorter wavelengths. Reversing ocular LCA would invert this chromatic cue, causing an under-accommodated near target to produce the chromatic signature of distance. In this study, we introduce diffractive soft contact lenses that modulate ocular LCA. Contact lenses were fabricated by laser-induced refractive index change (LIRIC), a femtosecond laser technique that writes subsurface diffractive phase profiles. Because diffractive optics have a negative Abbe number (-3.45), positive diffractive power produces LCA opposite in sign to the eye. Lenses with 1.5, 2.0, 3.0, 6.0 D diffractive power were characterized on a custom multi-wavelength Badal bench (470-700 nm). Measured LCA (2.77, 3.78, 5.31, and 11.37 D/µm) closely matched theoretical predictions (2.73, 3.64, 5.45, 10.91 D/µm). For an average eye, the 1.5 and 2.0 D lenses would partially reduce native LCA, the 3.0 D lens neutralize it, and the 6.0 D lens reverse its sign. These results establish a wearable platform for manipulating chromatic defocus cues relevant to myopia development. Ongoing work is evaluating image quality and visual performance with future studies assessing accommodation and myopia-control efficacy.

Counterintuitively Enhanced Masking Performance in Adults Born Preterm

Zahide Pamir, Bilkent University

Preterm birth is associated with reduced performance across diverse visual tasks, yet the underlying neural mechanisms remain poorly understood. One candidate mechanism is cortical reentrant processing (CRP), which comprises the feedforward and feedback flow of information. Visual masking paradigms provide a powerful tool for investigating these bidirectional processing dynamics. Developmental evidence shows that young infants detect masked stimuli better than older infants or adults, suggesting that visual perception in early infancy relies predominantly on feedforward processing and feedback circuits are not yet fully mature. As these circuits continue to develop after birth, they may be especially vulnerable to disruption following preterm birth, leading to persistent alterations in CRP. To test this hypothesis, we employed an object substitution masking paradigm. Adults born at term (N = 23) and preterm (N = 19) completed a four-alternative forced-choice contour discrimination task under five trailing mask durations (0, 50, 100, 150, and 300 ms). Overall, participants born preterm showed significantly higher discrimination accuracy than those born at term (72% vs. 60%). These findings reveal a counterintuitive improvement in visual masking performance among adults born preterm. Rather than indicating superior perceptual ability, reduced susceptibility to masking likely reflects atypical maturation of cortical feedback mechanisms following preterm birth.

Impact of Occipital Stroke and Recovery on Visual Metacognition

Matthew Cavanaugh, University of Rochester

Stroke damage to early visual cortex causes loss of vision over large portions of the peripheral field of view. Here we asked if downstream areas involved in decision-making and metacognition accurately interpret information from cortically-blinded fields. Specifically, we assessed orientation discrimination in adult, chronic stroke patients: 9 naïve and 15 after motion discrimination training. Orientation data and confidence reports were fit with CASANDRE (Confidence as a Noisy Decision Reliability Estimate) to calculate meta-uncertainty (metaU), with higher metaU equated to noisier confidence computations. In naïve patients, performance was poorer in the blind than intact hemifields (p<0.001). However, confidence matched performance in both locations, leading to low metaU (0.7±1.3 and 1.2±1.5, respectively; p=0.33), and suggesting that the adult metacognitive system spontaneously adapts to correctly process activity from the residual visual circuitry post-stroke. After motion training, orientation discrimination recovered in 6/15 patients. CASANDRE fitting in 4 improved and 4 unimproved patients revealed similar metaU in the 2 groups (1.8±2.2 and 1.4±2.2, respectively; p=0.81), despite large differences in final thresholds. Thus, the metacognitive system seems to successfully track processing changes that underlie training-induced recovery, suggesting appropriate read-out and integration of restored processing abilities into each person’s cognitive framework.

Adaptive optics reveals rare subset of immune cells that initiate uveitis

Kosha Dholakia, University of Rochester

Recent imaging innovations have directly visualized immune cells in the retina using phase contrast adaptive optics. Yet questions remain about which cells evoke the early inflammatory response that compromises vision. Here we study the impact of CD4 T cells as a rare class of immune cells that initiate experimental autoimmune uveitis (EAU). To initiate EAU, 3 GFP+ mice were immunized against interphotoreceptor retinoid-binding protein. GFP+ CD4 T cells were harvested and 2 million cells were injected into healthy C57BL/6J mice. Micron-level retinal imaging was performed with phase contrast AOSLO (796 nm, 192 uW) and GFP fluorescence (488 nm, 111 uW)). Host mice were imaged at baseline 1,3 and 7 days after injection. T cell speed and size was measured using a custom MATLAB script and manually using ImageJ. Successful transfer of CD4 T cells was shown by imaging fluorescent donor cells in injected mice. T cell speed was (27.2±11.8 mm/s, 10 cells 6 arteries) and 22.8±11.1 mm/s (12 cells, in 6 veins) at day 3 after injection, yet no rolling or extravasated cells were observed. Seven days after injection, rolling cells were seen in veins (8.2±1.4 um/s, 5 cells) and extravasated GFP+ T cells <5 deg. of optic disc. These cells had a granular appearance (15.7±2.4 um diameter, n=5) and dynamically surveyed retinal tissue. This dynamic visualization, enabled by adaptive optics, reveals the early sustained localization of CD4 T cells in the retina as an initiating step in EAU.

Program Abstracts

Invited Session I: Optoretinography

Optoretinography: From Retinal Physiology to Clinical BiomarkersRam Sabesan, University of Washington

Optoretinography and Beyond: Imaging Neural and Vascular Function in the Human RetinaPedro Mecê, Institut Langevin, Paris

Techniques and applications of optoretinography in combination with adaptive optics scanning laser ophthalmoscopyJessica Morgan, University of Pennsylvania

Differential Coherence as an Optoretinographic ToolLawrence Sincich, The University of Alabama at Birmingham

Contributed Session 1

AO-SLO photopic optoretinography with silent substitution flickerSirui Liu, University of Oxford

Adaptive optics imaging reveals transport dynamics of mitochondria in ganglion cell axons

Derek Power, University of Rochester

Longitudinal AOSLO in vivo imaging reveals RGC dendritic remodeling in a mouse photoreceptor degeneration modelSoumaya Belhadj, University of Pittsburgh

The Relationship Between Acuity and Cone Density Decline Across the FoveolaKrishnaveni Nagarajan, University of Rochester

Frequency selective post-microsaccadic perceptual enhancements in the foveaZoe Stearns, University of Rochester

Translating fixation stability measurements from lab to practice: Comparing clinical devices to a laboratory eye-trackerRiley Wiland, University of Houston