Interocular Phase Disparity Tuning of Binocular Contrast Summation Depends on Carrier Spatial Frequency and Orientation.

Significance: Binocular summation is a sensitive metric of binocular integration. As such, characterization of the mechanisms underlying binocular summation is a key step in translating and applying this knowledge to abnormal binocular systems afflicted with strabismus and amblyopia.

Purpose: Computational models of binocular summation have advocated the operation of mechanisms sensitive to the interocular phase disparity of first-order carrier gratings.

The effect of letter string length and report condition on letter recognition accuracy.

Purpose: Letter sequence recognition accuracy has been postulated to be limited primarily by low-level visual factors. The influence of high level factors such as visual memory (load and decay) has been largely overlooked. This study provides insight into the role of these factors by investigating the interaction between letter sequence recognition accuracy, letter string length and report condition.

Binocular capture: the role of non-linear position mechanisms.

When monocular Vernier targets are presented with binocular disparate elements, an increase in vertical separation elevates alignment thresholds and also shifts its perceived visual direction towards the visual direction of the binocular disparate surround. This observation has been termed binocular capture. There is increasing evidence that this shift in the visual direction of the monocular target may be related to the type of position encoding mechanism involved in processing the relative position signal.

Binocular capture: the effects of spatial frequency and contrast polarity of the monocular target.

The influence of binocular disparate targets on the perceived visual direction of adjacent monocular targets has been termed "binocular capture". The magnitude of capture increases significantly with increasing vertical separation between monocular targets. This study sets out to elucidate the interaction between spatial frequency content, contrast polarity and vertical separation between monocular targets to establish the roles of the monocular target's positional uncertainty and the underlying position-encoding mechanism in the production of binocular capture.

Spatial scaling of the binocular capture effect.

Purpose: Binocular "capture" occurs when the perceived visual direction of a monocular stimulus is displaced in the direction of the cyclopean visual direction of nearby binocular targets. This effect increases with the vertical separation of broadband monocular stimuli. The present study investigated whether the "capture" effect exhibits a systematic relationship with the spatial frequency composition of monocular lines and vertical separation.

Psychophysical measurements of referenced and unreferenced motion processing using high-resolution retinal imaging.

Background: Motion detection thresholds with a stationary frame of reference are significantly lower than unreferenced motion thresholds. To account for this, previous studies have postulated the existence of compensatory mechanisms, driven by the presence of a surround, that cancel the effects of eye movements. In the present study we used an adaptive optics scanning laser ophthalmoscope (AOSLO) to investigate the effects of retinal jitter due to fixation eye movements on referenced and unreferenced motion thresholds.

The utility of clinical electrophysiology in a case of nonorganic vision loss.

Background: Nonorganic vision loss (NOVL) usually refers to reports of acuity reduction, field constrictions, or both without any associated organic pathology. Regardless of the underlying cause, the primary concern of the eye care practitioner is to demonstrate visual potential better than suggested by the patient's subjective reports.

Case Report: This article presents a case report of a 43-year-old woman with NOVL.

Refractive error and visual impairment in African children in South Africa.

Purpose: To assess the prevalence of refractive error and visual impairment in school-aged African children in South Africa.

Methods: Random selection of geographically defined clusters was used to identify a sample of children 5 to 15 years of age in the Durban area. From January to August 2002, children in 35 clusters were enumerated through a door-to-door survey and examined in temporary facilities.