Large Visual Angle Research Articles

Validation of widefield aberrometer for global peripheral aberration scanning

Aberrometers based on Hartmann-Shack wavefront sensing methods have been widely used in the assessment of aberrations in the human eye, a crucial aspect in addressing or adjusting peripheral vision for myopia control, among other applications. Nevertheless, most available aberrometers exhibit limitations such as slow scanning speeds and restricted visual fields when measuring peripheral aberrations. Even the fastest scanning capabilities of commercialized aberrometer are confined to limited visual field and meridians. In this paper, a novel scanning aberrometer for efficient measurement of human eye peripheral aberrations is developed. This instrument allows the measurement of a large visual field angle up to ± 50° and takes all meridian scanning into account, which means it is a widefield aberrometer that can scan the peripheral aberrations globally. Due to the use of the precision motorized rotation stage, both the meridional and visual field angular resolutions of this instrument can be lower to 1°. During the entire measurement process, the subject only needs to focus on a single fixation target. No eye turn or head turn is required. By the instrument installation completed in April 2023, it stands as the only peripheral aberration scanning aberrometer capable of measuring up to a 50° visual field at all meridians using a single fixation target and achieving high angular resolution.

Optical modeling of the entire visual field of the eye.

Vision is rarely evaluated scientifically at very large visual angles, despite being used continuously in everyday life. Furthermore, raytrace calculations indicate that peripheral optical properties are different for a pseudophakic eye, and even though this is rarely noted by patients, it is probably the cause of bothersome "negative dysphotopsia." Simplified paraxial parameters that characterize the basic properties of phakic and pseudophakic eyes are collected together here as a baseline, and then raytracing is used to show that input angles of about 60°, which correspond to obstruction by the nose, eyebrow, and cheek, illuminate a retinal hemisphere. At larger angles in the temporal direction, the image with an intraocular lens (IOL) reaches a limit due to vignetting at about a 90° input angle to the optical axis, in comparison to 105° with the Gullstrand-Emsley eye model, and 109° for the most realistic gradient index crystalline lens model. Scaling the far peripheral vision region more accurately may lead to benefits relating to intraocular lenses, diseases of the peripheral retina, widefield fundus images, and myopia prevention.

Effect of a 7.0 mm intraocular lens optic on peripheral retinal illumination with implications for negative dysphotopsia.

To use optical modeling to compare a 6.0 mm and 7.0 mm intraocular lens (IOL) optic diameters on peripheral retinal illumination with implications for negative dysphotopsia. Mayo Clinic, Rochester, Minnesota, and Simpson Optics LLC, Arlington, Texas. Model eye. Ray-tracing software was used to simulate retinal illumination from an extended light source for a pseudophakic eye with in-the-bag biconvex IOLs (refractive index [n] = 1.46 and 1.55) and a 2.5 mm pupil. Ray-tracing diagrams and simulated retina illumination profiles were compared using the 6.0 mm and 7.0 mm optic diameter IOLs. Retinal locations were scaled to relative visual angles from 70 to 110 degrees horizontally. A 7.0 mm optic (n = 1.46) expands the image field by 2.8 degrees compared with a 6.0 mm optic. High-angle input light misses a 7.0 mm optic at a larger visual angle than a 6.0 mm optic, shifting illumination of the peripheral retina by this light anteriorly by 5.6 degrees. Consequently, a region of nonilluminated peripheral nasal retina is enlarged and shifted peripherally using a 7.0 mm optic (visual angle, 86.3 to 96.3 degrees) compared with a 6.0 mm optic (visual angle, 83.5 to 90.7 degrees). Similar illumination changes were seen modeling a 1.55 n IOL. A narrow dark region in the nasal retina when using a 6.0 mm optic is changed to a broader, more peripheral dark region when using a 7.0 mm optic. An extended, more peripheral dark nasal region may make a temporal shadow less bothersome and explain lower negative dysphotopsia rates using a 7.0 mm optic.

P‐29: Wide Visual Angle Anti‐Reflection Film

A wide visual angle anti‐reflection film with low reflection property under zero visual angles and more than 40 degree to 70 degree visual angle was developed. In addition, due to the functional layer in the wide visual angle anti‐reflection film, the new film can reduce the angular reflective color shift at large visual angle.

The Effect of Color on Letter Discrimination Can Be Modulated by the Global/Local Processing and Attention Level

This study explored whether the color of letters could influence letter discrimination task performances and whether this effect of color could be modulated by processing level (global vs. local) and attention level of color (color-attended vs. color-unattended). We used the Navon letters in red, green, or white as stimuli at a relatively small (Experiment 1) or large visual angle (Experiments 2, 3, and 4). Each experiment included two tasks: color-attended task in which participants were told to respond only to target letters in a designated color; color-unattended task in which color was task-irrelevant. Experiment 1 found that the responses to red stimuli were significantly faster than those to the other color stimuli in the color-attended task. In Experiment 2, the same pattern occurred only at the local level in the color-attended task. Experiments 3 and 4 further controlled the brightness and chroma of stimuli and the results replicated the enhancement effect of red at the local level in the color-attended task and demonstrated an interference effect of red and green in the color-unattended task. These results suggested that red facilitated letter discrimination at the local processing level, reflecting the effect of avoidance motivation evoked by red on cognition and behavior which was consistent with color-in-context model. Moreover, this study found that the effect of color was modulated by attention level of color, and the interference effect of color in the color-unattended task confirmed that the color effect might mainly arise from controlled processes but not automatic processes.

Immersive screens change attention width but not perception or decision-making performance in natural and basic tasks

In the last decades, a number of studies have examined people's perceptual and attentional capabilities using flat screen displays. The completion of studies using curved displays/screens has been neglected so far, despite their advantage of creating a more immersive and life-like experience. In two studies, we analysed possible performance differences between subjects' perceptual and attentional capabilities during a decision-making task whilst viewing life-size stimuli on large flat and curved immersive screens. In Study 1, participants performed an attention-demanding shape discrimination task. In Study 2, participants performed a more naturalistic football-specific discrimination task. Results of both studies revealed no differences in perception and decision making between screen conditions, but that attention can be directed across greater visual angles on immersive screens compared to flat screens. The findings suggest that attention can be directed across a larger visual angle on curved screens compared to flat screens probably because curved screens distort the image less than flat screens. This study has implications for the use of flat screens in studies that examine perceptual and attentional capabilities in the visual periphery.

Smaller visual angles show greater benefit of letter boldness than larger visual angles

Research has shown that fonts viewed at a smaller visual angle benefit from greater letter boldness. Since small and large visual angles operate on different spatial frequencies, we examined whether the effect was dependent on font size. By applying a paradigm of single-letter exposure across two experiments, we showed that fonts of thinner letter strokes and of extreme boldness decreased recognition for all tested font sizes, and that there was a positive effect of boldness at small visual angles which did not occur at large visual angles. The paper provides evidence that bolder fonts are less effective at improving recognition at larger visual angles, and that over a scale of font weights there is a drop-off at the lightest and the heaviest extremes at all tested font sizes.

SNR optimized 31 P functional MRS to detect mitochondrial and extracellular pH change during visual stimulation.

SummaryEnergy metabolism of the human visual cortex was investigated by performing 31P functional MRS.IntroductionThe human brain is known to be the main glucose demanding organ of the human body and neuronal activity can increase this energy demand. In this study we investigate whether alterations in pH during activation of the brain can be observed with MRS, focusing on the mitochondrial inorganic phosphate (Pi) pool as potential marker of energy demand.MethodsSix participants were scanned with 16 consecutive 31P‐MRSI scans, which were divided in 4 blocks of 8:36 minutes of either rest or visual stimulation. Since the signals from the mitochondrial compartments of Pi are low, multiple approaches to achieve high SNR 31P measurements were combined. This included: a close fitting 31P RF coil, a 7 T‐field strength, Ernst angle acquisitions and a stimulus with a large visual angle allowing large spectroscopy volumes containing activated tissue.ResultsThe targeted resonance downfield of the main Pi peak could be distinguished, indicating the high SNR of the 31P spectra. The peak downfield of the main Pi peak is believed to be connected to mitochondrial performance. In addition, a BOLD effect in the PCr signal was observed as a signal increase of 2–3% during visual stimulation as compared to rest. When averaging data over multiple volunteers, a small subtle shift of about 0.1 ppm of the downfield Pi peak towards the main Pi peak could be observed in the first 4 minutes of visual stimulation, but no longer in the 4 to 8 minute scan window. Indications of a subtle shift during visual stimulation were found, but this effect remains small and should be further validated.ConclusionOverall, the downfield peak of Pi could be observed, revealing opportunities and considerations to measure specific acidity (pH) effects in the human visual cortex.

Gaze and the Eye Pupil Adjust to Imagined Size and Distance.

Pupillary responses and associated vergence eye movements were monitored during imagery of objects of differing sizes ("large" or "small") from varying distances ("near" or "far"). Objects' imagined size and distance affected oculomotor behavior. Objects visualized as "far" resulted in the larger pupil dilations and smaller visual angle, while small objects imagined "near" were associated with smaller pupils in contrast to relatively larger pupils when imagined as "far" away. Furthermore, near objects resulted in larger visual angle, and particularly, vergence adjustments were observed that were dependent on imagined size and distance of the small objects. The findings are consistent with the idea that imagery emulates perception, also at the embodied level of oculomotor behaviors.

Why colour is complex: Evidence that bees perceive neither brightness nor green contrast in colour signal processing

Honey bees ( Apis mellifera Linnaeus, 1758) potentially rely on a variety of visual cues when searching for flowers in the environment. Both chromatic and achromatic (brightness) components of flower signals have typically been considered simultaneously to understand how flower colours have evolved. However, it is unclear whether honey bees actually use brightness information in their colour perception. We investigated whether free-flying honey bees can process brightness cues in achromatic stimuli when presented at a large visual angle of 28° to ensure colour processing. We found that green contrast (modulation of the green receptor against the background) and brightness contrast (modulation of all three receptors against the background) did not have a significant effect on the proportion of correct choices made by bees, indicating that they did not appear to use brightness cues in a colour processing context. Our findings also reveal that, even at a small visual angle, honeybees do not reliably process single targets solely based on achromatic information, at least considering values up to 60% modulation of brightness. We discuss these findings in relation to proposed models of bee colour processing. Therefore, caution should be taken when interpreting elemental components of complex flower colours as perceived by different animals.

Iris characteristics affecting far peripheral vision and negative dysphotopsia

To evaluate how the iris obstructs rays at large visual angles. Simpson Optics, Arlington, Texas, USA, and Spektrum Eye Clinic, Wroclaw, Poland. Retrospective case study. Anterior segment optical coherence tomography (AS-OCT) (Visante) images were exported for normal, short, and long eyes and eyes with negative dysphotopsia. Iris characteristics were manually identified, including the maximum iris thickness and its distance from the pupil, and the gap between the iris and intraocular lens (IOL). Ray-tracing software was used for optical modeling. The study comprised AS-OCT images of 63 eyes (21 normal eyes, 20 short eyes, and 19 long eyes, as well as 3 eyes with negative dysphotopsia). Preoperative and postoperative iris dimensions were similar, with a mean maximum thickness of 0.47mm±0.08 (SD) at 0.94±0.19mm radially from the pupillary margin. The mean pupillary plane distance from the corneal epithelium moved from 3.23±0.50mm preoperatively to 3.99±0.26mm postoperatively, and the mean gap between the posterior iris and the IOL was 0.50±0.24mm, with a systematic increase with axial length for both parameters. The anterior iris surface obstructed light at very large angles and contributed to the limiting visual angle for rays focused by the IOL (although light from lower angles also bypassed the IOL). Models for the eyes with negative dysphotopsia had dark retinal regions between the focused image and peripheral light for small pupils. Rays at very large angles can be obstructed by theanterior iris surface, which can be modeled to have a triangular profile near the pupillary margin. This limits the visual field for light focused by the IOL.

11-10 広視野に提示した視標に対する頭部および眼球運動と手の動きの協調特性(第11部門 ヒューマンインフォメーション(視覚特性および映像・画像評価))

11-10 広視野に提示した視標に対する頭部および眼球運動と手の動きの協調特性(第11部門 ヒューマンインフォメーション(視覚特性および映像・画像評価))

The effect of spatial luminance distribution on dark adaptation.

Recent studies show that dark adaptation in the visual system depends on local luminance levels surrounding the viewing direction. These studies, however, do not explain to what extent veiling luminance is responsible for the outcome. To address the latter, in this study dark adaptation was measured for three different spatial luminance distributions surrounding a target to be detected, while keeping the veiling luminance at the location of the target equivalent. The results show that a background with bright areas close to the viewing direction yields longer adaptation times than a background with bright areas at a larger visual angle. Therefore, we conclude that dark adaptation is affected to a great extent by local luminance, even when controlling for veiling luminance. Based on our results, a simple but adequate model is proposed to predict the adaptation luminance threshold for backgrounds having a nonuniform luminance distribution.

Significance of Camouflage, Chromatic Acuity and Contour in the Design of Pseudoisochromatic Plates

PurposePseudoisochromatic plates use a pseudo‐chaotic pattern of image dots to conceal the contour of colour optotypes. By our study we wantto improve the understanding of functional principles of pseudoisochromatic plates.MethodsThe circular elements of red/green pseudoisochromatic plates were varied in size and degree of pseudo‐chaotic arrangement. Illuminated by standard white D 65, colour optotypes were presented to daltonians and to normal observers, and the rates of failure and success in recognition were recorded.ResultsRecognition of pseudoisochromatic optotypes is related to the size of elements in a non‐ linear way. Towards small visual angles, colour optotype recognition may improve due to fusion of the perceived colour of adjacent small elements. Towards large visual angles, colour optotype recognition may again improve due to detection of the individual colours of elements. Weakening of contours by defocus may improve the recognition of colour optotypes due to loss of camouflage. Loss of camouflage also occurs with a more regular, less pseudo‐chaotic arrangement of image dots, thus facilitating the recognition of colour optotypes.ConclusionsBesides the colours themselves, arrangement and size of coloured elements need careful consideration in designing pseudoisochromatic plates. In application of the plates defocusing has to be avoided.

Vignetting and negative dysphotopsia with intraocular lenses in "far peripheral vision".

At very large visual angles, vignetting can occur at the edge of an intraocular lens (IOL), because it is much smaller than the natural crystalline lens that it replaces. Ray trace calculations show that, by 80-90deg of input visual angle, it is possible that about half the light is no longer focused by the IOL. This may create curved, peripheral, shadowlike regions, which are a clinical characteristic of negative dysphotopsia. The imaging characteristics for this "far peripheral vision" region are different from those of a phakic eye, whether or not negative dysphotopsia is experienced.

Double image in far peripheral vision of pseudophakic eye as source of negative dysphotopsia.

Some intraocular lens (IOL) patients report seeing "dark shadows" at visual angles that are larger than 60°-70°. Raytrace models of the pseudophakic eye show that light starts to miss the IOL at large visual angles because the implant diameter of about 6mm is much smaller than the natural crystalline lens diameter of 9.5mm. This light forms a second displaced image on the peripheral retina. To evaluate the appearance of the image, raytrace software was used to image an illuminated window onto the highly curved retina, and a method was developed to project the image back to object space for evaluation on a flat surface. Only a single schematic eye was evaluated monochromatically and the low resolution of the peripheral retina was not modeled, but the simulated images depict a shadow-like phenomenon at similar visual angles to reports of "negative dysphotopsia."

Comparison of methods to quantify posterior capsule opacification using forward and backward light scattering

To compare forward and backward light scattering measurements to quantify posterior capsule opacification (PCO). Vienna Institute for Research in Ocular Surgery, Vienna, Austria. Prospective single-center study. This observational study comprised consecutive patients scheduled for neodymium:YAG (Nd:YAG) capsulotomy for regeneratory PCO. The corrected distance visual acuity (CDVA) using Early Treatment of Diabetic Retinopathy Study charts and the contrast sensitivity under mesopic and photopic conditions using Pelli-Robson charts were assessed before an Nd:YAG capsulotomy was performed. Retroillumination images, rotating Scheimpflug scans (Pentacam HR), and straylight meter (C-Quant) and point-spread function (PSF) meter (Optical Quality Analysis System) measurements were performed before and after Nd:YAG capsulotomy. The study enrolled 50 eyes of 50 patients. The mean uncorrected distance visual acuity and CDVA were 0.76 logMAR ± 0.18 (SD) and 0.68 ± 0.2 logMAR, respectively. The mean log contrast sensitivity (logCS) was 1.2 ± 0.15 logCS under photopic conditions and 1.05 ± 0.15 logCS under mesopic conditions. There was a moderate correlation between the Scheimpflug score and the Automated Quantification of After-Cataract score (r(2) = 0.37, P=.03). Furthermore, a moderate and close to significant correlation between the PSF meter and the straylight meter was observed (r(2) = 0.32; P=.07). Each of the 4 devices assesses different aspects of a patient's quality of vision. Further developments should focus on methods that measure forward scatter of light in a large visual angle and are not too patient or examiner dependent.

Hydrogen concentration of co-deposited carbon film produced in the vicinity of LHD divertor tiles

In order to investigate the hydrogen retention and desorption behavior in co-deposited carbon film , a unique sample holder was mounted on the plasma-facing wall close to the graphite divertor tiles in the LHD during the 13th experimental campaign. The amount of deposited carbon for the sample with a large visual angle against the divertor tile was much larger than that with a small visual angle. The amount of retained hydrogen increased with the film thickness, but not proportional to the thickness. The carbon films contained boron caused by boronization and the retained hydrogen was trapped mainly by C–H and B–H bonds. Hydrogen concentration for the carbon film with a large visual angle against the graphite tile was much smaller than that with a small visual angle, possibly owing to the difference of the ratio of hydrogen influx to carbon influx.

Exploring the Effects of Display Characteristics on Presence and Emotional Responses of Game Players

Large displays are becoming ubiquitous and one important property of large displays is that they afford larger visual angles and physically larger screen sizes. However, there has been little investigation of the effects of large displays on users; furthermore, few studies have employed physiological measures, nor isolated the effects on presence and emotional responses of large visual angle and physically large screen size. This study, then, examines specifically the effects of these two properties of large displays on presence and emotional responses, using physiological as well as subjective methods. The results indicate that the larger visual angle offered by a large display can increase the sense of presence, engagement, and emotional responses when players are playing games. More interestingly, the physically larger sizes offered by a large display seem to also be able to affect these player experiences, even at identical visual angles with small displays.

Honeybees (Apis mellifera) Learn Color Discriminations via Differential Conditioning Independent of Long Wavelength (Green) Photoreceptor Modulation

BackgroundRecent studies on colour discrimination suggest that experience is an important factor in how a visual system processes spectral signals. In insects it has been shown that differential conditioning is important for processing fine colour discriminations. However, the visual system of many insects, including the honeybee, has a complex set of neural pathways, in which input from the long wavelength sensitive (‘green’) photoreceptor may be processed either as an independent achromatic signal or as part of a trichromatic opponent-colour system. Thus, a potential confound of colour learning in insects is the possibility that modulation of the ‘green’ photoreceptor could underlie observations.Methodology/Principal FindingsWe tested honeybee vision using light emitting diodes centered on 414 and 424 nm wavelengths, which limit activation to the short-wavelength-sensitive (‘UV’) and medium-wavelength-sensitive (‘blue’) photoreceptors. The absolute irradiance spectra of stimuli was measured and modelled at both receptor and colour processing levels, and stimuli were then presented to the bees in a Y-maze at a large visual angle (26°), to ensure chromatic processing. Sixteen bees were trained over 50 trials, using either appetitive differential conditioning (N = 8), or aversive-appetitive differential conditioning (N = 8). In both cases the bees slowly learned to discriminate between the target and distractor with significantly better accuracy than would be expected by chance. Control experiments confirmed that changing stimulus intensity in transfers tests does not significantly affect bee performance, and it was possible to replicate previous findings that bees do not learn similar colour stimuli with absolute conditioning.ConclusionOur data indicate that honeybee colour vision can be tuned to relatively small spectral differences, independent of ‘green’ photoreceptor contrast and brightness cues. We thus show that colour vision is at least partly experience dependent, and behavioural plasticity plays an important role in how bees exploit colour information.