What do patients with glaucoma see: a novel iPad app to improve glaucoma patient awareness of visual field loss.

Purpose: Glaucoma patients with peripheral vision loss have in the past subjectively described their field loss as 'blurred' or 'no vision compromise'. We developed an iPad app for patients to self-characterise perception within areas of glaucomatous visual field loss.

Methods: Twelve glaucoma patients with visual acuity ≥20/40 in each eye, stable and reliable Humphrey Visual Field (HVF) over 2 years were enrolled.

Convergence and divergence to radial optic flow in infancy.

Research finds a relationship between the development of depth perception and ocular motion functions including smooth pursuit and ocular following response. Infants' reactions to looming stimuli also suggest sensitivity to optic flow information that specifies relative distance. With radial optic flow, an expanding flow field elicits involuntary convergent eye movements while a contracting one elicits involuntary divergent eye movements.

Aging does not affect integration times for the perception of depth from motion parallax.

To successfully navigate throughout the world, observers must rapidly recover depth information. One depth cue that is especially important for a moving observer is motion parallax. To perceive unambiguous depth from motion parallax, the visual system must integrate information from two different proximal signals, retinal image motion and a pursuit eye movement.

The effects of aging on the perception of depth from motion parallax.

Successful navigation in the world requires effective visuospatial processing. Unfortunately, older adults have many visuospatial deficits, which can have severe real-world consequences. Although some of these age effects are well documented, some others, such as the perception of depth from motion parallax, are poorly understood.

A Pursuit Theory Account for the Perception of Common Motion in Motion Parallax.

The visual system uses an extraretinal pursuit eye movement signal to disambiguate the perception of depth from motion parallax. Visual motion in the same direction as the pursuit is perceived nearer in depth while visual motion in the opposite direction as pursuit is perceived farther in depth. This explanation of depth sign applies to either an allocentric frame of reference centered on the fixation point or an egocentric frame of reference centered on the observer.

Motion parallax thresholds for unambiguous depth perception.

The perception of unambiguous depth from motion parallax arises from the neural integration of retinal image motion and extra-retinal eye movement signals. It is only recently that these parameters have been articulated in the form of the motion/pursuit ratio. In the current study, we explored the lower limits of the parameter space in which observers could accurately perform near/far relative depth-sign discriminations for a translating random-dot stimulus.

Modeling depth from motion parallax with the motion/pursuit ratio.

The perception of unambiguous scaled depth from motion parallax relies on both retinal image motion and an extra-retinal pursuit eye movement signal. The motion/pursuit ratio represents a dynamic geometric model linking these two proximal cues to the ratio of depth to viewing distance. An important step in understanding the visual mechanisms serving the perception of depth from motion parallax is to determine the relationship between these stimulus parameters and empirically determined perceived depth magnitude.

In pursuit of perspective: does vertical perspective disambiguate depth from motion parallax?

Motion parallax provides a dynamic, unambiguous, monocular visual depth cue. However, the lateral image motion in computer-generated motion parallax displays is depth-sign ambiguous. While mounting evidence indicates that the visual system uses an extra-retinal signal from the pursuit system to disambiguate depth, vertical perspective is a potential confound because it co-varies with the stimulus translation that produces the pursuit signal.

The role of eye movements in depth from motion parallax during infancy.

Motion parallax is a motion-based, monocular depth cue that uses an object's relative motion and velocity as a cue to relative depth. In adults, and in monkeys, a smooth pursuit eye movement signal is used to disambiguate the depth-sign provided by these relative motion cues. The current study investigates infants' perception of depth from motion parallax and the development of two oculomotor functions, smooth pursuit and the ocular following response (OFR) eye movements.

Integration time for the perception of depth from motion parallax.

The perception of depth from relative motion is believed to be a slow process that "builds-up" over a period of observation. However, in the case of motion parallax, the potential accuracy of the depth estimate suffers as the observer translates during the viewing period. Our recent quantitative model for the perception of depth from motion parallax proposes that relative object depth (d) can be determined from retinal image motion (dθ/dt), pursuit eye movement (dα/dt), and fixation distance (f) by the formula: d/f≈dθ/dα.

Visual depth from motion parallax and eye pursuit.

A translating observer viewing a rigid environment experiences "motion parallax", the relative movement upon the observer's retina of variously positioned objects in the scene. This retinal movement of images provides a cue to the relative depth of objects in the environment, however retinal motion alone cannot mathematically determine relative depth of the objects. Visual perception of depth from lateral observer translation uses both retinal image motion and eye movement.

MT neurons combine visual motion with a smooth eye movement signal to code depth-sign from motion parallax.

The capacity to perceive depth is critical for an observer to interact with his or her surroundings. During observer movement, information about depth can be extracted from the resulting patterns of image motion on the retina (motion parallax). Without extraretinal signals related to observer movement, however, depth-sign (near versus far) from motion parallax can be ambiguous.

The motion/pursuit law for visual depth perception from motion parallax.

One of vision's most important functions is specification of the layout of objects in the 3D world. While the static optical geometry of retinal disparity explains the perception of depth from binocular stereopsis, we propose a new formula to link the pertinent dynamic geometry to the computation of depth from motion parallax. Mathematically, the ratio of retinal image motion (motion) and smooth pursuit of the eye (pursuit) provides the necessary information for the computation of relative depth from motion parallax.

The development of depth perception from motion parallax in infancy.

Little is known about infants' perception of depth from motion parallax, even though it is known that infants are sensitive both to motion and to depth-from-motion cues at an early age. The present experiment assesses whether infants are sensitive to the unambiguous depth specified by motion parallax and, if so, when this sensitivity first develops. Eleven infants were followed longitudinally from 8 to 29 weeks.

First and second-order motion perception after focal human brain lesions.

Perception of visual motion includes a first-order mechanism sensitive to luminance changes and a second-order motion mechanism sensitive to contrast changes. We studied neural substrates for these motion types in 142 subjects with visual cortex lesions, 68 normal controls and 28 brain lesion controls. On first-order motion, the visual cortex lesion group performed significantly worse than normal controls overall and in each hemifield, but second-order motion did not differ.

Concordant eye movement and motion parallax asymmetries in esotropia.

The role of eye movements in the perception of depth from motion was investigated in esotropia. Elevated motion parallax thresholds have been shown in strabismus [Thompson, A. M.

The pursuit theory of motion parallax.

Although motion parallax is closely associated with observer head movement, the underlying neural mechanism appears to rely on a pursuit-like eye movement signal to disambiguate perceived depth sign from the ambiguous retinal motion information [Naji, J. J., & Freeman, T.

Disruption of eye movements by ethanol intoxication affects perception of depth from motion parallax.

Motion parallax, the ability to recover depth from retinal motion generated by observer translation, is important for visual depth perception. Recent work indicates that the perception of depth from motion parallax relies on the slow eye movement system. It is well known that ethanol intoxication reduces the gain of this system, and this produces the horizontal gaze nystagmus that law enforcement's field sobriety test is intended to reveal.

Depth from motion parallax scales with eye movement gain.

Recent findings suggest that the slow eye movement system, the optokinetic response (OKR) in particular, provides the extra-retinal signal required for the perception of depth from motion parallax (Nawrot, 2003). Considering that both the perception of depth from motion parallax (Ono, Rivest & Ono, 1986; Rivest, Ono & Saida, 1989) and the eye movements made in response to head translations (Schwarz & Miles 1991; Paige, Telford, Seidmen, & Barnes, 1998) appear to scale with viewing distance, changes in perceived depth from motion parallax were studied as a function of viewing distance. If OKR is used in the perception of depth from motion parallax, a change in the OKR signal, caused by a change in viewing distance, should accompany a change in perceived depth from motion parallax.

Disorders of motion and depth.

Damage to the human homologue of area MT produces a motion perception deficit similar to that found in the monkey with MT lesions. Even temporary disruption of MT processing with transcranial magnetic stimulation can produce a temporary akinetopsia [127]. Motion perception deficits, however, also are found with a variety of subcortical lesions and other neurologic disorders that can best be described as causing a disconnection within the motion processing stream.

Eye movements provide the extra-retinal signal required for the perception of depth from motion parallax.

It has been unclear whether the perception of depth from motion parallax is an entirely visual process or whether it requires extra-retinal information such as head movements, vestibular activation, or eye movements. Using a motion aftereffect and static test stimulus technique to eliminate visual cues to depth, this psychophysical study demonstrates that the visual system employs a slow eye movement signal, optokinetic response (OKR) in particular, for the unambiguous perception of depth from motion parallax. A vestibular signal, or vestibularly driven eye movement signal is insufficient for unambiguous depth from motion parallax.