Absence Of Motion Research Articles

Mixed-state causal modeling for statistical KL-based motion texture tracking

We are interested in the modeling and tracking of dynamic or motion textures, which refer to dynamic contents that can be classified as a texture with motion (fire, smoke, crowd of people). Experimentally we observe that they depict motion maps with values of a mixed type: a discrete value at zero (absence of motion) and continuous non-null motion values. We thus introduce a temporal mixed-state Markov model for the characterization of motion textures from which a set of 13 parameters is extracted as the descriptive feature of the dynamic content. Then, a motion texture tracking strategy is proposed using the conditional Kullback–Leibler (KL) divergence between mixed-state probability densities, which allows us to estimate the position using a statistical matching approach.

MO-D-BRB-05: A Computational Method for Estimating the Dosimetric Effect of Intra-Fraction Motion on Step-And-Shoot IMRT and Compensator Plans

Purpose:Organ motion during intensity‐modulated radiation therapy (IRMT) treatment can cause dose deviations. To investigate the extent of these dosimetric changes a computational model was developed and validated, allowing for estimations of the impact of motion. Method and Materials: A Matlab program was written to simulate the effect of a motion track on the dose profile of both step‐and‐shoot IMRT and solid state compensator treatment plans. Static fluence maps for each segment were exported from the treatment planning system. These maps were shifted for each monitor unit delivered according to the motion track position at the time of delivery. These motion‐encoded fluence maps were then recombined and used to calculate the motion‐encoded dose. To validate the accuracy of the motion‐encoded dose profile the treatment plan was delivered to a cylindrical ‘cheese’ phantom mounted on a four‐dimensional motion phantom, programmed to create the motion track. EDR‐2 film measured the planar dose, with the resultant dose distribution being compared to the code‐predicted distribution using a gamma index analysis (3% dose difference, 3mm distance‐to‐agreement). A series of motion tracks incorporating both step‐function shifts and sinusoidal motion were tested. Results: The code was shown to accurately predict the film's dose distribution for all of the tested motion tracks, both for the step‐and‐shoot IMRT and compensator plans. The average gamma analysis pass rate for the motion‐encoded dose profiles was 98.3±0.7. In the absence of motion, static delivery pass rates were 98.7±0.2. Conclusion: A computational technique has been developed allowing for predictions of the dosimetric effect of intra‐fraction motion. This technique has the potential to be used to evaluate a given plan's sensitivity to organ motion. This information could be used as a tool for selecting the optimal treatment modality or for plan optimization. Conflict of Interest: This work was funded in part by .decimal

Illusory conjunction between continuous and discrete changes in the absence of motion

Illusory conjunction between continuous and discrete changes in the absence of motion

Motion processing with wide-field neurons in the retino-tecto-rotundal pathway.

The retino-tecto-rotundal pathway is the main visual pathway in non-mammalian vertebrates and has been found to be highly involved in visual processing. Despite the extensive receptive fields of tectal and rotundal wide-field neurons, pattern discrimination tasks suggest a system with high spatial resolution. In this paper, we address the problem of how global processing performed by motion-sensitive wide-field neurons can be brought into agreement with the concept of a local analysis of visual stimuli. As a solution to this problem, we propose a firing-rate model of the retino-tecto-rotundal pathway which describes how spatiotemporal information can be organized and retained by tectal and rotundal wide-field neurons while processing Fourier-based motion in absence of periodic receptive-field structures. The model incorporates anatomical and electrophysiological experimental data on tectal and rotundal neurons, and the basic response characteristics of tectal and rotundal neurons to moving stimuli are captured by the model cells. We show that local velocity estimates may be derived from rotundal-cell responses via superposition in a subsequent processing step. Experimentally testable predictions which are both specific and characteristic to the model are provided. Thus, a conclusive explanation can be given of how the retino-tecto-rotundal pathway enables the animal to detect and localize moving objects or to estimate its self-motion parameters.

Quantification of non–water‐suppressed MR spectra with correction for motion‐induced signal reduction

Intrascan subject movement in clinical MR spectroscopic examinations may result in inconsistent water suppression that distorts the metabolite signals, frame-to-frame variations in spectral phase and frequency, and consequent reductions in the signal-to-noise ratio due to destructive averaging. Frame-to-frame phase/frequency corrections, although reported to be successful in achieving constructive averaging, rely on consistent water suppression, which may be difficult in the presence of intrascan motion. In this study, motion correction using non-water-suppressed data acquisition is proposed to overcome the above difficulties. The time-domain matrix-pencil postprocessing method was used to extract water signals from the non-water-suppressed spectroscopic data, followed by phase and frequency corrections of the metabolite signals based on information obtained from the water signals. From in vivo experiments on seven healthy subjects at 3.0 T, quantification of metabolites using the unsuppressed water signal as a reference showed improved correlation with water-suppressed data acquired in the absence of motion (R(2) = 0.9669; slope = 0.94). The metabolite concentrations derived using the proposed approach were in good agreement with literature values. Computer simulations under various degrees of frequency and phase variations further demonstrated robust performance of the time-domain postprocessing approach.

Eye-catching crowds

Populated virtual environments need to be simulated with as much variety as possible. By identifying the most salient parts of the scene and characters, available resources can be concentrated where they are needed most. In this paper, we investigate which body parts of virtual characters are most looked at in scenes containing duplicate characters or clones . Using an eye-tracking device, we recorded fixations on body parts while participants were asked to indicate whether clones were present or not. We found that the head and upper torso attract the majority of first fixations in a scene and are attended to most. This is true regardless of the orientation, presence or absence of motion, sex, age, size, and clothing style of the character. We developed a selective variation method to exploit this knowledge and perceptually validated our method. We found that selective colour variation is as effective at generating the illusion of variety as full colour variation. We then evaluated the effectiveness of four variation methods that varied only salient parts of the characters. We found that head accessories, top texture and face texture variation are all equally effective at creating variety, whereas facial geometry alterations are less so. Performance implications and guidelines are presented.

Long term outcome of anterior cervical discectomy and fusion using coral grafts

To determine the long term efficacy of coral grafts in anterior cervical discectomy and fusion. In this prospective longitudinal study, All patients presenting with myelopathy and/or radiculopathy due to discal hernia or cervical spondylosis underwent anterior cervical microdiscectomy, arthrodesis with coral, and stabilization with anterior cervical locking plates. Clinical and radiological post-operative evaluations were performed at 2 days, 3, 6, and 12 months, and then yearly. The visual analogue scale was used for the evaluation of pain. Fusion was defined as the absence of motion on dynamic imaging combined with the disappearance of radio-lucent lines around the graft. The mean follow-up period was 44 months. In 83.3%, 91.2% and 93.7% of patients there was a satisfactory outcome for neck pain, arm pain, and motor deficit, respectively. The overall complication rate was 17.5%, all of which were transient. Additional surgery was required in nine cases. The occurrence of complications is correlated with less satisfactory outcomes for both neck and arm pain. While 95.5% of patients expressed overall satisfaction with their surgery, 70.5% stated that they had returned to their previous activities. The fusion rate was 45%; which was not correlated with clinical outcome and more likely in patients with of cervical spondylosis and one-level arthrodesis. Despite satisfactory clinical results and a long follow-up period, coral implants yield low fusion rates, particularly in patients with discal hernia of two-level arthrodesis. The use of coral grafts cannot be recommended when fusion is one of the post-operative endpoints.

Diagnosing Cervical Fusion: A Comprehensive Literature Review

Study DesignComprehensive literature review.PurposeTo document the criteria for fusion utilized in these studies to determine if a consensus on the definition of a solid fusion exists.Overview of LiteratureNumerous studies have reported on fusion rates following anterior cervical arthrodesis. There is a wide discrepancy in the fusion rates in these studies. While factors such as graft type, Instrumentation, and technique play a factor in fusion rate, another reason for the difference may be a result of differences in the definition of fusion following anterior cervical spine surgery.MethodsA comprehensive English Medline literature review from 1966 to 2004 using the key words "anterior," "cervical," and "fusion" was performed. We divided these into two groups: newer studies done between 2000 and 2004, and earlier studies done between 1966 and 2000. These articles were then analyzed for the number of patients, follow-up period, graft type, and levels fused. Moreover, all of the articles were examined for their definition of fusion along with their fusion rate.ResultsIn the earlier studies from 1966 to 2000, there was no consensus for what constituted a solid fusion. Only fifteen percent of these studies employed the most stringent definition of a solid fusion which was the presence of bridging bone and the absence of motion on flexion and extension radiographs. On the other hand, the later studies (2000 to 2004) used such a definition a majority (63%) of the time, suggesting that a consensus opinion for the definition of fusion is beginning to form.ConclusionsOur study suggests that over the past several years, a consensus definition of fusion is beginning to form. However, a large percentage of studies are still being published without using stringent fusion criteria. To that end, we recommend that all studies reporting on fusion rates use the most stringent criteria for solid fusion following anterior cervical spine surgery: the absence of motion on flexion/extension views and presence of bridging trabeculae on lateral x-rays. We believe that a universal adoption of such uniform criteria will help to standardize such studies and make it more possible to compare one study with another.

Judging beforehand the possibility of passing under obstacles without motion: the influence of egocentric and geocentric frames of reference

Previous studies have shown that the perception of the earth-based visual horizon, also named Gravity Referenced Eye Level (GREL), is modified by body tilt around a trans-ocular axis. Here, we investigated whether estimates of the elevation of a luminous horizontal line presented on a screen in otherwise darkness and estimates of the possibility of passing under are identically related to body tilt in absence of motion. Results showed that subjects overestimated the elevation of the projected line, whatever their body orientation. In the same way, subjects also overestimated their capacity of passing under the line. Both estimates appeared as a linear function of body tilt, that is, forward body tilt yielded increased overestimations, and backward body tilt yielded decreased overestimations. More strikingly, the linear effect of body tilt upon these estimates is comparable to that previously observed for direct GREL judgements. Overall, these data strongly suggest that the perception of the elevation of a visible obstacle and the perception of the ability of passing under in otherwise darkness shared common processes which are intimately linked to the GREL perception. The effect of body tilt upon these perceptions may illustrate an egocentric influence upon the semi-geocentric frame of reference required to perform the task. Possible interactions between egocentric and geocentric frames of reference are discussed.

Performance of ultrasound based measurement of 3D displacement using a curvilinear probe for organ motion tracking

Three-dimensional (3D) soft tissue tracking is of interest for monitoring organ motion during therapy. Our goal is to assess the tracking performance of a curvilinear 3D ultrasound probe in terms of the accuracy and precision of measured displacements. The first aim was to examine the depth dependence of the tracking performance. This is of interest because the spatial resolution varies with distance from the elevational focus and because the curvilinear geometry of the transducer causes the spatial sampling frequency to decrease with depth. Our second aim was to assess tracking performance as a function of the spatial sampling setting (low, medium or high sampling). These settings are incorporated onto 3D ultrasound machines to allow the user to control the trade-off between spatial sampling and temporal resolution. Volume images of a speckle-producing phantom were acquired before and after the probe had been moved by a known displacement (1, 2 or 8 mm). This allowed us to assess the optimum performance of the tracking algorithm, in the absence of motion. 3D speckle tracking was performed using 3D cross-correlation and sub-voxel displacements were estimated. The tracking performance was found to be best for axial displacements and poorest for elevational displacements. In general, the performance decreased with depth, although the nature of the depth dependence was complex. Under certain conditions, the tracking performance was sufficient to be useful for monitoring organ motion. For example, at the highest sampling setting, for a 2 mm displacement, good accuracy and precision (an error and standard deviation of <0.4 mm) were observed at all depths and for all directions of displacement. The trade-off between spatial sampling, temporal resolution and size of the field of view (FOV) is discussed.

Success of junctional anterior cervical discectomy and fusion

Background context Junctional breakdown has long been a consideration for surgeons when performing an arthrodesis in the cervical spine. Numerous authors have reported symptomatic junctional disease after fusion with varying degrees of reoperation. To our knowledge, there are no large series recording the fusion rate using instrumentation as an adjuvant to bone grafting. Purpose To determine the fusion rate when arthrodesis is performed in the setting of junctional stenosis using iliac crest autograft and instrumentation. Study design/setting This is a retrospective review performed on patients at the senior author's institution. Patient sample The patient population consisted of a consecutive series of patients undergoing an elective anterior-only cervical arthrodesis for junctional stenosis. Outcome measures The primary outcome is a physiologic measure from dynamic radiographs. Fusion was assessed by the absence of motion and radiolucent lines at the bone graft interface. Methods During the study period, a total of 56 consecutive patients underwent anterior treatment for junctional cervical stenosis. Forty-nine of these patients were treated with an anterior discectomy and instrumented arthrodesis using iliac crest autograft, and seven underwent a corpectomy. We retrospectively reviewed the patients' charts and radiographs to determine the fusion rate. Results A solid fusion was obtained in 81.6% of patients in the study group. In patients undergoing a single-level arthrodesis adjacent to a one-level fusion, the fusion rate was 95.2%. The fusion rate significantly dropped in patients with longer preexisting fusion segments. In patients with a two- or three-level fusions preoperatively, the union rate was 81.3% and 57.1%, respectively. Conclusions Anterior cervical discectomy and arthrodesis yields a high fusion rate for cervical stenosis adjacent to a single-level fusion. A multilevel preexisting fusion segment leads to a significant decline in successfully achieving a solid adjacent fusion despite using iliac crest autograft and instrumentation.

Evolution of the Carter constant for inspirals into a black hole: Effect of the black hole quadrupole

We analyze the effect of gravitational radiation reaction on generic orbits around a body with an axisymmetric mass quadrupole moment $Q$ to linear order in $Q$, to the leading post-Newtonian order, and to linear order in the mass ratio. This system admits three constants of the motion in absence of radiation reaction: energy, angular momentum along the symmetry axis, and a third constant analogous to the Carter constant. We compute instantaneous and time-averaged rates of change of these three constants. For a point particle orbiting a black hole, Ryan has computed the leading order evolution of the orbit's Carter constant, which is linear in the spin. Our result, when combined with an interaction quadratic in the spin (the coupling of the black hole's spin to its own radiation reaction field), gives the next to leading order evolution. The effect of the quadrupole, like that of the linear spin term, is to circularize eccentric orbits and to drive the orbital plane towards antialignment with the symmetry axis. In addition we consider a system of two point masses where one body has a single mass multipole or current multipole of order $l$. To linear order in the mass ratio, to linear order in the multipole, and to the leading post-Newtonian order, we show that there does not exist an analog of the Carter constant for such a system (except for the cases of an $l=1$ current moment and an $l=2$ mass moment). Thus, the existence of the Carter constant in Kerr depends on interaction effects between the different multipoles. With mild additional assumptions, this result falsifies the conjecture that all vacuum, axisymmetric spacetimes possess a third constant of the motion for geodesic motion.

Electron Paramagnetic Resonance Spectroscopy of Site-directed Spin Labels Reveals the Structural Heterogeneity in the N-terminal Domain of ApoA-I in Solution

Apolipoprotein A-I (apoA-I) is the major protein constituent of high density lipoprotein (HDL) and plays a central role in phospholipid and cholesterol metabolism. This 243-residue long protein is remarkably flexible and assumes numerous lipid-dependent conformations. Consequently, definitive structural determination of lipid-free apoA-I in solution has been difficult. Using electron paramagnetic spectroscopy of site-directed spin labels in the N-terminal domain of apoA-I (residues 1-98) we have mapped a mixture of secondary structural elements, the composition of which is consistent with findings from other in-solution methods. Based on side chain mobility and their accessibility to polar and non-polar spin relaxers, the precise location of secondary elements for amino acids 14-98 was determined for both lipid-free and lipid-bound apoA-I. Based on intermolecular dipolar coupling at positions 26, 44, and 64, these secondary structural elements were arranged into a tertiary fold to generate a structural model for lipid-free apoA-I in solution.

Oculomotor Instabilities in Zebrafish Mutantbelladonna: A Behavioral Model for Congenital Nystagmus Caused by Axonal Misrouting

A large fraction of homozygous zebrafish mutant belladonna (bel) larvae display a reversed optokinetic response (OKR) that correlates with failure of the retinal ganglion cells to cross the midline and form the optic chiasm. Some of these achiasmatic mutants display strong spontaneous eye oscillations (SOs) in the absence of motion in the surround. The presentation of a stationary grating was necessary and sufficient to evoke SO. Both OKR reversal and SO depend on vision and are contrast sensitive. We built a quantitative model derived from bel fwd (forward) eye behaviors. To mimic the achiasmatic condition, we reversed the sign of the retinal slip velocity in the model, thereby successfully reproducing both reversed OKR and SO. On the basis of the OKR data, and with the support of the quantitative model, we hypothesize that the reversed OKR and the SO can be completely attributed to RGC misrouting. The strong resemblance between the SO and congenital nystagmus (CN) seen in humans with defective retinotectal projections implies that CN, of so far unknown etiology, may be directly caused by a projection defect.

Expandable cylindrical cages in the cervical spine: a review of 22 cases

Expandable cylindrical cages (ECCs) have been utilized successfully to reconstruct the thoracic and lumbar spine. Their advantages include ease of insertion, reduced endplate trauma, direct application/maintenance of interbody distraction force, and one-step kyphosis correction. The authors present their experience with ECCs in the reconstruction of the cervical spine in patients with various pathological conditions. Data obtained in 22 patients were reviewed retrospectively. A standard anterior cervical corpectomy was performed in all cases. Local vertebral body bone was harvested for use as graft material. Patients underwent pre- and postoperative assessment involving the visual analog scale (VAS), Nurick grading system for determining myelopathy disability, and radiographic studies to determine cervical kyphosis/lordosis and cage subsidence. Fusion was defined as the absence of motion on flexion-extension x-ray films. Sixteen patients presented with spondylotic myelopathy, two with osteomyelitis, two with fracture, one with tumor metastasis, and one with severe stenosis. Fourteen patients underwent supplemental posterior spinal fusion, seven underwent single-level corpectomy, and 15 patients underwent multilevel corpectomy. No perioperative complications occurred. The mean follow-up period was 22 months. In 11 patients with preexisting kyphosis (mean deformity +19 degrees), the mean correction was 22 degrees. There was no statistically significant difference in subsidence between single- and multilevel corpectomy or between 360 degrees fusion and anterior fusion alone. The VAS scores improved by 35%, and the Nurick grade improved by 31%. The fusion rate was 100%. The preliminary results support the use of ECCs in the cervical spine in the treatment of patients with various disease processes. No significant subsidence was noted, and pain and functional scores improved in all cases. Expandable cylindrical cages appear to be well suited for cervical reconstruction and for correcting sagittal malalignment.

An advantage for detecting dynamic targets in natural scenes

In the present study, we tested the extent to which observers use dynamic information to detect targets in natural scenes. For this purpose, we used composite stimuli in which target sequences were superimposed onto distractor sequences. We varied target visibility in the composite sequence, and the presence or absence of motion. Across four experiments, we found a dynamic advantage for target detection: Observers performed more accurately with dynamic than static target scenes. This advantage depended on the availability of target motion, irrespective of whether the target was upright or inverted in the image plane (Experiments 1-4). The magnitude of this advantage also depended on the availability of segmentation cues (Experiments 1 and 2) and on the distractors used (Experiments 2 and 4). Overall, the dynamic advantage reported extends previous work using isolated dynamic objects to more complex scenes.

Resorbable Polylactic Acid Interbody Spacers with Vertebral Autograft for Anterior Cervical Discectomy and Fusion

Resorbable polylactic acid spinal implants have recently become commercially available. These spacers carry the advantages of allowing for clear visualization of new bone growth, eliminating the risk of pathogen transmission, and providing for consistent biomechanical quality. However, previously published reports on the use of these spacers have all utilized bone morphogenetic proteins to supplement the fusion. This report describes our early experience with the use of these devices for interbody reconstruction in anterior cervical discectomy with fusion. Twenty patients underwent an anterior cervical discectomy with fusion at 30 levels during an 18-month period. All patients were implanted with polylactic acid interbody spacers using the Smith-Robinson technique. Supplementary anterior cervical plating was applied using unicortical semiconstrained screws, and the spacers were filled with vertebral endplate autograft bone shavings. Seven of the patients were smokers, and three were diabetics. Radiographic fusion was determined with dynamic cervical spine x-rays, and clinical responses were determined using the Medical Outcomes Study Short-Form 36-Item Health Survey, Odom's criteria, Nurick scores, and functional outcome swallowing score dysphagia scores. Follow-up averaged 11.6 months. Of the 9 patients with myelopathy, all experienced clinical improvement, with the mean Nurick score improving from 2.7 to 1.3. Of the 14 patients who had radiculopathy, 9 had complete resolution of symptoms, 4 experienced some improvement, and 1 had no improvement. All 20 patients demonstrated radiographic fusion at last follow-up as demonstrated by bridging bone between the vertebral bodies and the absence of motion on dynamic x-rays. Resorbable polylactic acid interbody spacers are safe and effective for anterior cervical discectomy and fusion. Use of locally harvested vertebral endplate bone packed within the spacer is sufficient to promote fusion in anterior cervical discectomy with fusion.

Spin-current-induced magnetization reversal in magnetic nanowires with constrictions

We have performed experiments on current-induced domain-wall motion (CIDWM) in the case of the domain walls (DW) trapped within the nanoscale constrictions in patterned NiFe structures. Direct observation of current-induced magnetization reversal was achieved and critical current densities jc were measured in the presence of easy-axis magnetic fields. The direction of CIDWM was found to be along the direction of the electron motion in absence of an applied magnetic field and in the direction of the field when in the presence of even relatively weak fields. Data for the field dependence of jc for both uniform and fast rising pulses suggest that the current, regardless of polarity, assists in the depinning of the DW. Only for the dc case does the data strongly reveal the influence of the electron pressure in promoting or hindering DW motion.

Nonuniform Upwelling in a Shallow-Water Model of the Antarctic Bottom Water in the Brazil Basin*

Abstract A numerical model based on the shallow-water equations is developed to represent the flow of Antarctic Bottom Water (AABW) in the Brazil Basin (southwest Atlantic Ocean). The aim is twofold. First, an attempt is made to identify in a model that includes both simplified dynamics and realistic bathymetry (at 1/6° resolution) the impacts of the elevated diapycnal mixing rates near the Mid-Atlantic Ridge (MAR) documented by dissipation data of the Deep Basin Experiment (DBE). To this end, different assumptions regarding the distribution of the velocity across the AABW layer interface (w) are considered. Second, the extent to which the shallow-water model can replicate observations relative to AABW circulation in the basin, in particular the trajectory and velocity of neutrally buoyant floats released in the AABW during the DBE, is examined. The model flows are characterized by small Rossby numbers, except in the northward-flowing western boundary current where kinetic energy is largely concentrated. To interpret the flows, model streamlines are compared with isopleths of linear potential vorticity f/h0 of the shallow-water theory (f is the planetary vorticity and h0 is the layer thickness in the absence of motion). The f/h0 contours are oriented northwest–southeast in the western part of the basin and southwest–northeast in the eastern part, reflecting the bowl-shaped topography of the Southern Hemisphere basin. With a spatially uniform (positive) w, the ubiquitous vortex stretching produces a flow to the southeast, consistent with the Stommel–Arons theory. This flow occurs in most of the basin interior, even in the east where f/h0 contours converge to the northeastern end of the basin. With strongly positive w near the ridge and zero or slightly negative w elsewhere, the flow follows more closely f/h0 contours in the western interior and intersects them near the ridge. The confinement of the diapycnal mass flux near the MAR drastically reduces the southward flow in the interior or even reverses its direction, leading to a circulation quite distinct from that of the Stommel– Arons theory. The model results compare favorably to some (but not all) hydrographic estimates of AABW circulation patterns and rates. On the other hand, the model streamlines and velocities show important differences with, respectively, the trajectory and the velocity of the floats launched in the AABW layer. The prescription of vanishing w in the interior does not systematically improve the fit of the model streamlines to the float trajectories, and the model velocities simulated with spatially uniform w or spatially variable w are on average smaller by one order of magnitude than the float velocities. A variety of mechanisms, which are not included in the numerical experiments, may explain the differences between the model results and the float data.

Sources of normal and anomalous motion in retinoscopy.

Besides the classic "with," "against," and "neutral" absence of motion, retinoscopic reflexes can display anomalous "with" motion in myopia. A model is presented that explains the source of this anomalous motion, as well as quantifies the appearance of retinoscopic motion in myopia and hyperopia. Various 2 x 2 matrices were created to describe schematic eyes for a +20 D trial lens, a Gullstrand #1 schematic eye, and an infant schematic eye. Rays from the retinoscope were traced paraxially through these matrices over a full transit of the retinoscope beam across the pupil. Retinal position of the edge of the reflex visible to the observer was plotted as a function of pupil sizes from 2 mm to 16 mm for -5.00 D and +2.00 D refractive errors for the +20 D trial lens. The edge of the retinoscopic reflex could be formed by one of two sources: the edge of the retinoscope beam itself, or the shadow cast by the beam against the edge of the pupil. Anomalous "with" motion arose in myopia when the edge of the reflex was formed by the edge of the beam. The edge of the beam was also visible in hyperopia but did not create anomalous motion. The retinoscope peephole was not involved in the formation of the edge of the reflex. The degree of anomalous motion increased with greater myopia and pupil size. Measured pupil sizes needed to completely eliminate anomalous motion agreed well with those predicted by the model, except at the largest pupil sizes. The limit for anomalous motion depended only on pupil size, refractive error, and working distance but not on whether the system matrix represented the trial lens, a Gullstrand #1 eye, or an infant eye. Seeing the edge of the beam at large pupil sizes during retinoscopy creates anomalous "with" motion in myopia but may make the reflex easier to see in hyperopia. Anomalous "with" motion in myopia can be managed by adjustment of pupil size, working distance, or net corrected refractive error. Aside from possible effects of aberrations, retinoscopic motion appears to be consistent across various paraxial optical systems for a given refractive error and pupil size.