Binocular Field Research Articles

Lifestyle shapes bird of prey binocular visual field

Swooping toward a victim with its vicious talons extended, a bird of prey homes in for the kill with meticulous precision. ‘Birds, particularly birds of prey [raptors], are believed to forage primarily using visual cues’, says vision scientist Simon Potier from Lund University, Sweden, who was inspired by his father's love of birds of prey to take up falconry as a small child. Yet, Potier explains that it was not clear how the birds use the region where the views from the two eyes overlap (the binocular zone) during their rapier-like attacks. As the hunting strategies of birds of prey span low-speed scavenging to high-speed aerial and ground prey capture, Potier, Francesco Bonadonna and Olivier Duriez from Université de Montpellier, France, and an international team of collaborators wondered whether the binocular vision of these precision hunters might vary depending on their lifestyle.Potier turned to his own collection of almost 60 birds at Les Ailes de l'Urga theme park in France and other birds from Le Grand Parc du Puy du Fou to measure the binocular visual fields of birds ranging from carrion-feeding vultures to predatory Cooper's hawks and eagles that target victims on the ground. ‘We used a non-invasive procedure to measure visual field characteristics in alert birds’, says Potier, recalling the difficulty of holding the large eagles steady for 20 min while measuring the limit of the view from each eye in order to calculate the binocular region where the visual fields overlapped. ‘The experience of the falconers who helped was essential’, he says. In addition, he had to custom build individual bill holders for each species to keep their heads in place, ‘which took me quite some time to fit perfectly’, he laughs. However, Potier was relieved when the birds appeared unfazed after they were released: ‘Directly after the experiment, they still flew to me, which indicates that they were not stressed’, he smiles.Initially, Potier and his colleagues had anticipated that the binocular visual fields of the hunters would be wider than those of the scavengers, as the hunters have to precisely target a moving victim with their talons while the scavengers’ aim may not need to be as precise. However, the width of the binocular visual fields was remarkably similar. The contrasts were more apparent when the team plotted the full projections of the binocular region, showing that the zone above the beak where the view from the two eyes overlapped tapered more rapidly in the ground-hunting eagles than it did in Cooper's hawks (which target birds on the wing) and the scavenging vultures. There was also an extensive blind zone above the heads of the ground predators – which do not have to outmanoeuvre agile targets on the wing. Considering the various hunting strategies and differences in the head shapes of the 15 species, Potier and his colleagues suspect that the ridge of bone that shades the eyes of the ground-hunting species could partially obscure the upper portion of their binocular field to produce the large blind zone. In addition, their short, but wide, powerful beaks appear to shade the lower portion of their view.‘Our results show that the binocular field configuration is specialized to foraging tactics in raptors’, says Potier, who is keen to scrutinise the vision of the almost exclusively terrestrial secretary bird. ‘They have very large eyes… I would love to estimate their visual field’, he muses.

Thalamocortical Circuits and Functional Architecture.

The thalamocortical pathway is the main route of communication between the eye and the cerebral cortex. During embryonic development, thalamocortical afferents travel to L4 and are sorted by receptive field position, eye of origin, and contrast polarity (i.e., preference for light or dark stimuli). In primates and carnivores, this sorting involves numerous afferents, most of which sample a limited region of the binocular field. Devoting abundant thalamocortical resources to process a limited visual field has a clear advantage: It allows many stimulus combinations to be sampled at each spatial location. Moreover, the sampling efficiency can be further enhanced by organizing the afferents in a cortical grid for eye input and contrast polarity. We argue that thalamocortical interactions within this eye-polarity grid can be used to represent multiple stimulus combinations found in nature and to build an accurate cortical map for multidimensional stimulus space.

Changes in lateral ocular movement after two muscle exotropia surgery

Objective This study was to identify the surgical procedures associated with changes of lateral eye movement to help inform surgical planning for patients with concomitant exotropia. Methods The medical records of 87 concomitant exotropia surgical procedures that were performed at Henan Eye Hospital from June 2014 to August 2015 were retrospectively reviewed.The deviation angle was measured by prism and alternate cover test.Photographs and arc campimeter was used to obtain changes of abduction and lateral monocular fixation field respectively.Data were compared preoperatively and postoperatively among five groups based on the surgical procedures.The surgical procedures were 0 mm for control group (61 eyes), 8 mm unilateral rectus recession for lateral rectus recession (LR) group (27 eyes), 5-6 mm recession/4-5 mm resection for small amount recess-resect (R-R) group (24 eyes), 7-8 mm recession/5-6 mm resection for medium amount R-R group (29 eyes) and 8-10 mm recession/7-8 mm resection for large amount R-R group (33 eyes). The minimum follow-up period was 6 months.Informed consent was signed from each patient or the guardian. Results The success, overcorrection and undercorrection rate was 81.61%, 5.56% and 12.64%, respectively.Mean preoperative abduction of each group was (11.86±1.11)mm in the control group, (12.04±0.68)mm in the LR group, (11.58±1.06)mm in the small amount R-R group, (11.86±0.93)mm in the medium amount R-R group and (12.22±0.60)mm in the large amount R-R group.The postoperative mean abduction of each group was (11.81±1.03), (11.81±0.70), (10.78±1.05), (10.54±1.07) and (9.90±0.82)mm, respectively.Mean abduction among the five groups was not significantly different preoperatively (F=1.85, P=0.12), while it was significantly different postoperatively (F=28.04, P=0.00). The abduction between control group and small amount R-R group was not significantly different postoperatively (P=0.99), but the abduction of control group was significantly greater than that of all the R-R groups (all at P=0.00). Mean lateral monocular fixation field of each group preoperatively was (50.82±3.30)° in control group, (51.48±2.39)° in LR group, (50.13±3.51)° in small amount R-R group, (51.06±2.90)° in medium amount R-R group and (52.09±2.61)° in large amount R-R group.The postoperative mean lateral monocular fixation field of each group was (50.52±3.51)°, (50.11±2.36)°, (46.38±3.67)°, (44.00±3.00)°, (41.84±2.46)°, respectively.Preoperative lateral monocular fixation field among the five groups was not significantly different (F=1.75, P=0.14), while postoperative difference was significant (F=55.75, P=0.00). Lateral monocular fixation field between control group and LR group was not significantly different postoperatively (P=0.57), but the mean lateral monocular fixation field of control group was significantly greater than that of all the R-R groups (all at P=0.00). Conclusions The successful alignment rate of unilateral recess/resect procedure is satisfying, but it can also create abduction deficit especially in large surgical amounts eye.Patients with binocular vision will be sensitive to diplopia in side gaze; in such cases, the consequences of recess/resect procedure should be considered particularly to avoid decrease of the binocular single vision field. Key words: Exotropia, concomitant/surgery; Ocular movement/Abduction; Stereopsis; Monocular vision field; Treatment outcomes

Callosal Influence on Visual Receptive Fields Has an Ocular, an Orientation-and Direction Bias.

One leading hypothesis on the nature of visual callosal connections (CC) is that they replicate features of intrahemispheric lateral connections. However, CC act also in the central part of the binocular visual field. In agreement, early experiments in cats indicated that they provide the ipsilateral eye part of binocular receptive fields (RFs) at the vertical midline (Berlucchi and Rizzolatti, 1968), and play a key role in stereoscopic function. But until today callosal inputs to receptive fields activated by one or both eyes were never compared simultaneously, because callosal function has been often studied by cutting or lesioning either corpus callosum or optic chiasm not allowing such a comparison. To investigate the functional contribution of CC in the intact cat visual system we recorded both monocular and binocular neuronal spiking responses and receptive fields in the 17/18 transition zone during reversible deactivation of the contralateral hemisphere. Unexpectedly from many of the previous reports, we observe no change in ocular dominance during CC deactivation. Throughout the transition zone, a majority of RFs shrink, but several also increase in size. RFs are significantly more affected for ipsi- as opposed to contralateral stimulation, but changes are also observed with binocular stimulation. Noteworthy, RF shrinkages are tiny and not correlated to the profound decreases of monocular and binocular firing rates. They depend more on orientation and direction preference than on eccentricity or ocular dominance of the receiving neuron's RF. Our findings confirm that in binocularly viewing mammals, binocular RFs near the midline are constructed via the direct geniculo-cortical pathway. They also support the idea that input from the two eyes complement each other through CC: Rather than linking parts of RFs separated by the vertical meridian, CC convey a modulatory influence, reflecting the feature selectivity of lateral circuits, with a strong cardinal bias.

The Orientation of Visual Space from the Perspective of Hummingbirds.

Vision is a key component of hummingbird behavior. Hummingbirds hover in front of flowers, guide their bills into them for foraging, and maneuver backwards to undock from them. Capturing insects is also an important foraging strategy for most hummingbirds. However, little is known about the visual sensory specializations hummingbirds use to guide these two foraging strategies. We characterized the hummingbird visual field configuration, degree of eye movement, and orientation of the centers of acute vision. Hummingbirds had a relatively narrow binocular field (~30°) that extended above and behind their heads. Their blind area was also relatively narrow (~23°), which increased their visual coverage (about 98% of their celestial hemisphere). Additionally, eye movement amplitude was relatively low (~9°), so their ability to converge or diverge their eyes was limited. We confirmed that hummingbirds have two centers of acute vision: a fovea centralis, projecting laterally, and an area temporalis, projecting more frontally. This retinal configuration is similar to other predatory species, which may allow hummingbirds to enhance their success at preying on insects. However, there is no evidence that their temporal area could visualize the bill tip or that eye movements could compensate for this constraint. Therefore, guidance of precise bill position during the process of docking occurs via indirect cues or directly with low visual acuity despite having a temporal center of acute vision. The large visual coverage may favor the detection of predators and competitors even while docking into a flower. Overall, hummingbird visual configuration does not seem specialized for flower docking.

Visual field shape and foraging ecology in diurnal raptors.

Birds, particularly raptors, are believed to forage primarily using visual cues. However, raptor foraging tactics are highly diverse - from chasing mobile prey to scavenging - which may reflect adaptations of their visual systems. To investigate this, we studied the visual field configuration of 15 species of diurnal Accipitriformes that differ in such tactics, first focusing on the binocular field and blind area by using a single-traits approach, and then exploring the shape of the binocular field with a morphometric approach. While the maximum binocular field width did not differ between species with different foraging tactics, the overall shape of their binocular fields did. In particular, raptors chasing terrestrial prey (ground predators) had a more protruding binocular field and a wider blind area above the head than did raptors chasing aerial or aquatic prey and obligate scavengers. Ground predators that forage on mammals from above have a wide but short bill - which increases ingestion rate - and a large suborbital ridge to avoid sun glare. This may explain the protruding binocular field and the wide blind area above the head. By contrast, species from the two other groups have long but narrow bills used to pluck, flake or tear food and may need large visual coverage (and reduced suborbital ridges) to increase their foraging efficiency (e.g. using large visual coverage to follow the escaping prey in three dimensions or detect conspecifics). We propose that binocular field shape is associated with bill and suborbital ridge shape and, ultimately, foraging strategies.

Expansion of binocular fields in the treatment of lateral rectus paresis

Expansion of binocular fields in the treatment of lateral rectus paresis

Orbital trapdoor fractures: different clinical profiles between adult and paediatric patients

BackgroundTo compare clinical findings of orbital trapdoor fractures between adult and paediatric patients.MethodsPaediatric patients were categorised into two groups by age: children (0–9 years) and adolescents (10–19 years). Adult patients...

Robotic assembly of smartphone back shells with eye-in-hand visual servoing

Abstract Research concerning smartphone assembly has attracted increasing attention from the manufacturing industry. This paper presents an automatic back shell assembly system using real-time visual servoing in an eye-in-hand configuration. Look-then-move and look-and-move control approaches are sequentially proposed to handle distal and proximal assembly tasks, respectively. During distal assembly, binocular vision is employed to assist a robotic manipulator to locate and reconstruct the positions and orientations of a cellular phone and its back shell in the work space. After lifting the back shell up and then reaching the top of the cellular phone, there is no binocular field of view. A seemingly novel way of 3-D reconstruction by two uniocular fields of view of the two cameras is proposed. With the pair of monocular vision sensors, two monocular visual servo control laws are employed sequentially to perform the proximal assembly task autonomously. Based on the experimental results, the robotic manipulator can be driven to hold the back shell by a vacuum absorption device and position it precisely onto the smartphone to accomplish the automatic assembly task even if the vision system is only roughly calibrated. The proposed control approach for distal and proximal assembly appears to be efficient, flexible, and reliable for potential applications in industrial manufacturing.

Incarceration of the inferior oblique muscle branch of the oculomotor nerve in patients with orbital floor trapdoor fracture.

To examine the clinical characteristics of patients with concomitant incarceration of the inferior oblique muscle branch of the oculomotor nerve who had suffered from an orbital floor trapdoor fracture with orbital fat incarceration. Fifty-nine patients were retrospectively reviewed. Concomitant inferior oblique muscle branch incarceration was diagnosed by inferior oblique muscle underaction on the Hess chart and a missing inferior oblique muscle branch on computed tomographic images on baseline examination. Eleven patients (18.6%) were diagnosed with concomitant branch incarceration. The patients with branch incarceration were all under 19years of age, and were younger than those without branch incarceration (P=0.026). There were no significant differences between the groups in terms of cause of injury, presence of concomitant medial wall fracture, hypoesthesia of the cheek region, or ocular and periocular complications (P>0.050). All patients with branch incarceration underwent surgical reduction, whereas 16 of 48 patients without branch incarceration were observed without surgery (P=0.021). Although preoperative binocular single vision field was smaller in patients with branch incarceration (P=0.026), it improved after surgery, comparable to that of patients without branch incarceration (P=0.079). Concomitant incarceration of inferior oblique muscle branch of the oculomotor nerve occurred in 18.6% of patients who had suffered from an orbital floor trapdoor fracture with orbital fat incarceration. Patients with branch incarceration were all under 19years of age. Branch incarceration resulted in a smaller binocular single vision field, which considerably improved after surgical reduction.

Comparison of optomotor and optokinetic reflexes in mice

During animal locomotion or position adjustments, the visual system uses image stabilization reflexes to compensate for global shifts in the visual scene. These reflexes elicit compensatory head movements (optomotor response, OMR) in unrestrained animals or compensatory eye movements (optokinetic response, OKR) in head-fixed or unrestrained animals exposed to globally rotating striped patterns. In mice, OMR are relatively easy to observe and find broad use in the rapid evaluation of visual function. OKR determinations are more involved experimentally but yield more stereotypical, easily quantifiable results. The relative contributions of head and eye movements to image stabilization in mice have not been investigated. We are using newly developed software and apparatus to accurately quantitate mouse head movements during OMR, quantitate eye movements during OKR, and determine eye movements in freely behaving mice. We provide the first direct comparison of OMR and OKR gains (head or eye velocity/stimulus velocity) and find that the two reflexes have comparable dependencies on stimulus luminance, contrast, spatial frequency, and velocity. OMR and OKR are similarly affected in genetically modified mice with defects in retinal ganglion cells (RGC) compared with wild-type, suggesting they are driven by the same sensory input (RGC type). OKR eye movements have much higher gains than the OMR head movements, but neither can fully compensate global visual shifts. However, combined eye and head movements can be detected in unrestrained mice performing OMR, suggesting they can cooperate to achieve image stabilization, as previously described for other species.NEW & NOTEWORTHY We provide the first quantitation of head gain during optomotor response in mice and show that optomotor and optokinetic responses have similar psychometric curves. Head gains are far smaller than eye gains. Unrestrained mice combine head and eye movements to respond to visual stimuli, and both monocular and binocular fields are used during optokinetic responses. Mouse OMR and OKR movements are heterogeneous under optimal and suboptimal stimulation and are affected in mice lacking ON direction-selective retinal ganglion cells.

Avian binocular vision: It's not just about what birds can see, it's also about what they can't.

With the exception of primates, most vertebrates have laterally placed eyes. Binocular vision in vertebrates has been implicated in several functions, including depth perception, contrast discrimination, etc. However, the blind area in front of the head that is proximal to the binocular visual field is often neglected. This anterior blind area is important when discussing the evolution of binocular vision because its relative length is inversely correlated with the width of the binocular field. Therefore, species with wider binocular fields also have shorter anterior blind areas and objects along the mid-sagittal plane can be imaged at closer distances. Additionally, the anterior blind area is of functional significance for birds because the beak falls within this blind area. We tested for the first time some specific predictions about the functional role of the anterior blind area in birds controlling for phylogenetic effects. We used published data on visual field configuration in 40 species of birds and measured beak and skull parameters from museum specimens. We found that birds with proportionally longer beaks have longer anterior blind areas and thus narrower binocular fields. This result suggests that the anterior blind area and beak visibility do play a role in shaping binocular fields, and that binocular field width is not solely determined by the need for stereoscopic vision. In visually guided foragers, the ability to see the beak—and how much of the beak can be seen—varies predictably with foraging habits. For example, fish- and insect-eating specialists can see more of their own beak than birds eating immobile food can. But in non-visually guided foragers, there is no consistent relationship between the beak and anterior blind area. We discuss different strategies—wide binocular fields, large eye movements, and long beaks—that minimize the potential negative effects of the anterior blind area. Overall, we argue that there is more to avian binocularity than meets the eye.

The Hawk-Eyed Songbird: Retinal Morphology, Eye Shape, and Visual Fields of an Aerial Insectivore.

Swallows are a unique group of songbirds because they are active-pursuit predators that execute all aspects of hunting prey in flight: search, detection, pursuit, and capture. We show that swallows have evolved a visual system that is unlike that of any other studied songbird. Swallows have a bifoveate retina that provides sharp lateral and frontal vision, an unusually long eye that enhances spatial resolution, a large posterior blind area, and a narrow binocular field. We also show that swallows and diurnal raptors (hawks and falcons) have converged on a similar visual configuration but that, interestingly, predatory songbirds that ambush prey (flycatchers) have not converged on the same suite of traits. Despite the commonly held belief that predators rely on binocular vision, the temporal (frontally projecting) fovea present in swallows-but not present in other songbirds-is likely not involved in binocular vision. Instead, swallows have four nonoverlapping foveae in a 100° arc around the beak, which can improve the tracking of frontally located aerial prey that are engaging in evasive maneuvers. Overall, vision in pursuit predators reflects the complex sensory demands of hunting in the air at high speeds and emphasizes the importance of acute frontal vision in predators.

White‐headed Vulture Trigonoceps occipitalis shows visual field characteristics of hunting raptors

The visual fields of the Aegypiinae vultures have been shown to be adapted primarily to meet two key perceptual challenges of their obligate carrion‐feeding behaviour: scanning the ground and preventing the sun's image falling upon the retina. However, field observations have shown that foraging White‐headed Vultures Trigonoceps occipitalis are not exclusively carrion‐feeders; they are also facultative predators of live prey. Such feeding is likely to present perceptual challenges that are additional to those posed by carrion‐feeding. Binocularity is the key component of all visual fields and in birds it is thought to function primarily in the accurate placement and time of contact of the talons and bill, especially in the location and seizure of food items. We determined visual fields in White‐headed Vultures and compared them with those of two species of carrion‐eating Gyps vultures. The visual field of White‐headed Vultures has more similarities with those of predatory raptors (e.g. accipitrid hawks) than with the taxonomically more closely related Gyps vultures. Maximum binocular field width in White‐headed Vultures (30°) is significantly wider than that in Gyps vultures (20°). The broader binocular fields in White‐headed Vultures probably facilitate accurate placement and timing of the talons when capturing evasive live prey.

Binocular vs. monocular hue perception

Hue perception has been shown to differ for the same stimulus when presented to the temporal and the nasal areas of the retina. The present study investigated perceptual differences in stimuli viewed binocularly or monocularly in the peripheral retina to determine how hue information combines across the two retinas for a stimulus falling on the temporal retina of one eye and the nasal retina of the other. A hue-scaling procedure was utilized to ascertain hue perception for three color- and binocular-normal observers viewing monochromatic stimuli (450–670nm, 20nm steps) ranging in size from 1.0° to 3.7°. Peripherally-presented binocular stimuli fell upon the nasal retina of one eye and the temporal retina of the other. Hue-scaling results indicated that peripheral binocular hue and saturation perceptions for smaller stimuli were more similar to those of stimuli falling on the temporal retina in the monocular condition. Hue-scaling data were also used to determine perceptive field sizes for the four elemental hues. Binocular perceptive field sizes were more similar to those obtained for stimuli falling on the temporal retina in the monocular conditions. Eye dominance did not appear to have an effect on hue perception. The results seem to indicate that visual information from the temporal retina is weighted more heavily when information from the two eyes is combined cortically. This finding may relate to differences in V1 cortical activation for stimuli presented to the nasal retina versus the temporal retina.

ОЦЕНКА КЛИНИКО-ФУНКЦИОНАЛЬНОГО РЕЗУЛЬТАТА МУЛЬТИФОКАЛЬНОЙ КОНТАКТНОЙ КОРРЕКЦИИ У ПАЦИЕНТОВ С ПРЕСБИОПИЕЙ И МИОПИЧЕСКОЙ РЕФРАКЦИЕЙ

The aim of the study was to evaluate the effectiveness of multifocal contact lens correction in patients with presbyopia and myopic refractive error. The study involved 45patients with myopia ranging in age from 43 to 56years in conditions of habitual monofocal contact lens correction, a month after the selection and wearing multifocal contact lenses. Contact correction was carried out according to standard procedures taking into account the accuracy of contact lens fitting, with carrying out functional tests for the “dry eye” syndrome and evaluation of corneal epithelial thickness (Optovue, USA). The as-sessment of the following parameters of visual perception was made: far, near and middle distance (monocular and binocular) visual acuity, the spatial contrast sensitivity, stereovision (I & II Lang test), the area of binocular interaction field (binarymeter), the quality of vision (VF-14 test ). The use of multifocal contact lenses for the correction of presbyopia with the initial myopic refraction ensures high functional results at different distances. Patients with a myopic refraction, previously used contact lenses, easy pass to multifocal correction option. The greatest satisfaction by achieved vision noted in those patients who had achieved refraction (–)0.5diopters. In the selection of contact lenses in older patients the thickness of the corneal epithelium and tear film validity must be taken into account.

The risk of pedestrian collisions with peripheral visual field loss.

Patients with peripheral field loss complain of colliding with other pedestrians in open-space environments such as shopping malls. Field expansion devices (e.g., prisms) can create artificial peripheral islands of vision. We investigated the visual angle at which these islands can be most effective for avoiding pedestrian collisions, by modeling the collision risk density as a function of bearing angle of pedestrians relative to the patient. Pedestrians at all possible locations were assumed to be moving in all directions with equal probability within a reasonable range of walking speeds. The risk density was found to be highly anisotropic. It peaked at ≈45° eccentricity. Increasing pedestrian speed range shifted the risk to higher eccentricities. The risk density is independent of time to collision. The model results were compared to the binocular residual peripheral island locations of 42 patients with forms of retinitis pigmentosa. The natural residual island prevalence also peaked nasally at about 45° but temporally at about 75°. This asymmetry resulted in a complementary coverage of the binocular field of view. Natural residual binocular island eccentricities seem well matched to the collision-risk density function, optimizing detection of other walking pedestrians (nasally) and of faster hazards (temporally). Field expansion prism devices will be most effective if they can create artificial peripheral islands at about 45° eccentricities. The collision risk and residual island findings raise interesting questions about normal visual development.

A “Wide” Variety: Effects of Horizontal versus Vertical Display on Assortment Processing, Perceived Variety, and Choice

The authors investigate how horizontal versus vertical displays of alternatives affect assortment processing, perceived variety, and subsequent choice. Horizontal (vs. vertical) displays are easier to process due to a match between the human binocular vision field (which is horizontal in direction) and the dominant direction of eye movements required for processing horizontal displays. It is demonstrated that this processing fluency allows people to browse information more efficiently, which increases perceived assortment variety and ultimately leads to more variety being chosen, and if the number of options chosen is allowed to vary, it leads to more options chosen. It is shown that because people see more variety in a horizontal (vs. vertical) display, they process a horizontal assortment more extensively. When more variety is positive, they find the choice task easier and have a higher level of satisfaction and confidence about their choices. When more variety is not necessarily positive, for example, in a choice of a single most-preferred option, these effects disappear. Two field studies, an eye-tracking study, and two lab studies support these conclusions.

‘I didn't see that coming’: simulated visual fields and driving hazard perception test performance

BackgroundEvidence is limited regarding specific types of visual field loss associated with unsafe driving. We use novel gaze‐contingent software to examine the effect of simulated visual field loss on computer‐based driving hazard detection with the specific aim of testing the impact of scotomata located to the right and left of fixation.MethodsThe ‘hazard perception test’ is a component of the UK driving licence examination, which measures speed of detecting 15 different hazards in a series of real‐life driving films. We have developed a novel eye‐tracking and computer set up capable of generating a realistic gaze‐contingent scotoma simulation (GazeSS) overlaid on film content. Thirty drivers with healthy vision completed three versions of the hazard perception test in a repeated measures experiment. In two versions, GazeSS simulated a scotoma in the binocular field of view to the left or right of fixation. A third version was unmodified to establish baseline performance.ResultsParticipants' mean baseline hazard perception test score was 51 ± 7 (out of 75). This reduced to 46 ± 9 and 46 ± 11 when completing the task with a binocular visual field defect located to the left and right of fixation, respectively. While the main effect of simulated visual field loss on performance was statistically significant (p = 0.007), there were no average differences in the experimental conditions where a scotoma was located in the binocular visual field to the right or left of fixation.ConclusionSimulated visual field loss impairs driving hazard detection on a computer‐based test. There was no statistically significant difference in average performance when the simulated scotoma was located to the right or left of fixation of the binocular visual field, but certain types of hazard caused more difficulties than others.

Driving with central field loss III: vehicle control

BackgroundVisual impairment associated with central field loss may make vehicle control more difficult due to the degraded view of the road. We evaluated how central field loss affects vehicle control in a driving simulator.MethodsNineteen participants with binocular central field loss (acuity 6/9 to 6/60) and 15 controls with normal vision drove 10 scenarios, each about eight to 12-minutes. Speed, lane offset and steering wheel reversal rate were measured on straights, left and right curves, along city (approximately 50-km/h) and rural highway (approximately 100-km/h) routes. Following distance was measured on two city straight segments.ResultsSubjects with central field loss had higher steering wheel reversal rates (0.55 versus 0.45 reversals per second, p = 0.015), suggesting that the steering task was more demanding for them, requiring more steering corrections; however, they did not differ in other performance measures. Nearly all maintained a safe following distance, although they were more likely than controls with normal vision to lose sight of the lead car in scenarios that required following a car.ConclusionsMost measures of vehicle control did not significantly differ between participants with central field loss and those with normal vision; however, the higher steering wheel reversal rates suggest that, in compensating for their vision impairment, drivers with central field loss had to allocate extra steering effort to maintain their lane position, which in turn could reduce attentional resources for other driving tasks.