How similar are the eye movement patterns of different subjects when free viewing dynamic natural scenes? We collected a large database of eye movements from 54 subjects on 18 high-resolution videos of outdoor scenes and measured their variability using the Normalized Scanpath Saliency, which we extended to the temporal domain. Even though up to about 80% of subjects looked at the same image region in some video parts, variability usually was much greater. Eye movements on natural movies were then compared with eye movements in several control conditions. “Stop-motion” movies had almost identical semantic content as the original videos but lacked continuous motion. Hollywood action movie trailers were used to probe the upper limit of eye movement coherence that can be achieved by deliberate camera work, scene cuts, etc. In a “repetitive” condition, subjects viewed the same movies ten times each over the course of 2 days. Results show several systematic differences between conditions both for general eye movement parameters such as saccade amplitude and fixation duration and for eye movement variability. Most importantly, eye movements on static images are initially driven by stimulus onset effects and later, more so than on continuous videos, by subject-specific idiosyncrasies; eye movements on Hollywood movies are significantly more coherent than those on natural movies. We conclude that the stimuli types often used in laboratory experiments, static images and professionally cut material, are not very representative of natural viewing behavior. All stimuli and gaze data are publicly available at http://www.inb.uni-luebeck.de/tools-demos/gaze.

Purpose. To determine whether multivariate, functional principal component analysis of the size and shape of retinal pigment epithelial (RPE) cell morphology allows discrimination of mouse RPE genotypes and age. Methods. Flatmounts of RPE sheets obtained from C57BL/6J (n = 50) and rd10 (n = 61) mice at postnatal days 30 to 720 were stained for zonula occludens-1 (ZO-1) and imaged with confocal microscopy. A total of 111 flatmounts were prepared. Twenty-one morphometric measurements were made on tiled, composite images of complete flatmounts, including cell location, area, and eccentricity, using automated image analysis software for quantitatively measuring cell phenotypes. Results. In young (≤61-day-old) C57BL/6J mice, the RPE morphology resembled a regular hexagonal array of cells of uniform size throughout the retina, except near the ciliary body, where the shapes of RPE resembled a soft network. Old (≥180-day-old) C57BL/6J eyes had a subpopulation of large cells. A clear disruption of the regular cell size and shape appeared in rd10 mutants. Aspect ratio and cell area gave rise to principal components that predictively classified mouse age and genotype. Conclusions. Quantitative differences in the RPE sheet morphology allowed discrimination of rd10 from C57BL/6J strains despite the confounding effect of aging. This has implications for RPE sheet morphology as a potential early biomarker for diagnosis of eye disease and prognosis of the eye at early stages when disease is subtle. We conclude that an RPE cell's area and aspect ratio are very early quantitative indicators that predict progression to advanced RPE disease as manifested in rd10.

Significance: Deprivation of vision during typical age-defined critical periods results in seemingly irreversible changes in neural organization and behavior in animals and humans. We describe visual development in a unique population of patients who were blind during typical critical periods before removal of bilateral cataracts. The rarity of such cases has previously limited empirical investigations of this issue. Surprisingly, we find substantial improvement after sight onset in contrast sensitivity, a basic visual function that has well-understood neural underpinnings. Our results show that the human visual system can retain plasticity beyond critical periods, even after early and extended blindness.

The fundamental role of the visual system is to guide behavior in natural environments. To optimize information transmission, many animals have evolved a non-homogeneous retina and serially sample visual scenes by saccadic eye movements. Such eye movements, however, introduce high-speed retinal motion and decouple external and internal reference frames. Until now, these processes have only been studied with unnatural stimuli, eye movement behavior, and tasks. These experiments confound retinotopic and geotopic coordinate systems and may probe a non-representative functional range. Here we develop a real-time, gaze-contingent display with precise spatiotemporal control over high-definition natural movies. In an active condition, human observers freely watched nature documentaries and indicated the location of periodic narrow-band contrast increments relative to their gaze position. In a passive condition under central fixation, the same retinal input was replayed to each observer by updating the video's screen position. Comparison of visual sensitivity between conditions revealed three mechanisms that the visual system has adapted to compensate for peri-saccadic vision changes. Under natural conditions we show that reduced visual sensitivity during eye movements can be explained simply by the high retinal speed during a saccade without recourse to an extra-retinal mechanism of active suppression; we give evidence for enhanced sensitivity immediately after an eye movement indicative of visual receptive fields remapping in anticipation of forthcoming spatial structure; and we demonstrate that perceptual decisions can be made in world rather than retinal coordinates.