Steady Gaze Research Articles

Insect vision: A steady gaze over different landscapes

To gather visual information effectively, animals must stabilize images when they move. But closely related fruit fly species sometimes occupy strikingly diverse visual habitats. A new study shows that they have adopted gaze strategies tailored to their different visual worlds.

MHealth technology identifies visual impairment in young children.

mHealth technology identifies visual impairment in young children.

Ye Shall Bear Witness: An Ethics of Survival in W.G. Sebald’s Rings of Saturn

In Rings of Saturn, W.G. Sebald uses the concept of the Roche limit—the nearest a satellite can come to the object it orbits without being consumed by that object’s gravity— to draw a boundary around human suffering so that in bearing witness, we shall not be destroyed.By using lists to create literary fractals—geometric designs that are self-similar at a fractional dimension—Sebald dramatizes that limit as an equilibrium that art must hold between distance from and proximity to human suffering. He asks readers not merely to bear witness but to find the proximity at which we can hold a steady gaze, unflinching, without being consumed by that suffering. At the Roche limit, we are bound by what we see but not consumed.

Directional differences in head stabilisation in Acanthodactylus pardalis lizards

Running inevitably causes the animal trunk to undulate. The consequential head rotations have to be stabilised in space for a steady gaze and an accurate sense of self-motion for balance. The ecology and anatomy of the species determine the necessity to stabilise the head in yaw, pitch, and roll direction. Terrestrial lizards, running with a sprawled body posture, are especially prone to undulations in the horizontal (yaw) plane. Measurements on an experimental oscillation platform show that Acanthodactylus pardalis lizards stabilise their head less in pitch direction (54% stabilisation) than in yaw and roll direction (66% and 64% stabilisation, respectively). Because we performed these experiments in darkness, the lizards based their head stabilisation on vestibular information. Hence, we hypothesised that their vestibular system is less sensitive in pitch direction than in yaw and roll direction. Yet, this was not confirmed by a detailed Fluid-Structure Interaction model of the membranous labyrinth, which showed that not pitch sensitivity (88% of yaw sensitivity), but roll sensitivity (73% of yaw sensitivity) is the lowest. So why is the head stabilisation in darkness almost as good in roll direction as in yaw direction? While this may be due to neurological nonlinearities, it seems worth noticing that the moment of inertia is lowest in roll direction due to the elongated head shape. Hence, less torque is needed to stabilise a head rotation in roll direction than in the other two directions.

Acquired nystagmus.

Nystagmus is the repetitive to and fro movement of the eyes, which may be physiological or pathological. The movements can be horizontal, vertical, torsional or a combination of these movements. It starts by a slow movement of the eye away from the visual target. The second movement brings the eye back to the visual target. If this second movement is quick, the nystagmus is called jerk nystagmus. If the second movement is slow, the nystagmus is said to be pendular. Maintaining steady gaze is dependent upon visual fixation, the vestibulo-ocular reflex and the gaze-holding neural integrator system. Pathological nystagmus typically presents with the symptom of oscillopsia, which is the illusory movement of the surrounding environment. Nystagmus that develops outside of early infancy is termed acquired nystagmus. There may be serious underlying pathology that will require further investigation and management. This article reviews the terminology, pathophysiology, causes and treatment of acquired nystagmus.

Reflections on Fifty Years of The Bluest Eye

Reflections on Fifty Years of The Bluest Eye Stephanie Li (bio) This year will mark fifty years since Toni Morrison’s first novel, The Bluest Eye (1970), was published by Holt, Rinehart & Winston. In the past five decades, the cover of Morrison’s book has featured an array of pensive and melancholy black girls. They are often posed against shades of elusive sky or denim blue. The girls are always presented alone, completely detached from any community or connection to others. Often they wear hats as if to cover the hair that must be as hated as their dark skin and brown eyes. The collective effect of these images is to suggest that black girlhood is not just tragic, but profoundly solitary. For anyone familiar with the first edition of The Bluest Eye, these images are necessarily disappointing—too obvious to capture any of Morrison’s eloquence or wisdom. By contrast, the original publication cover contains no visual image at all. Instead it looks like the first page of the book, with the opening paragraphs of the novel printed in full. These paragraphs contain no reference to Pecola’s desire for blue eyes. Rather, Pecola is presented in relation to others. Claudia, the text’s narrator, laments with her sister the horror of Pecola’s pregnancy and stillborn baby. They mention her father, who impregnated Pecola in a desperate, profoundly misguided display of love. Moreover, their concern [End Page 682] with the marigolds that do not grow in their garden implicitly roots Pecola to the natural world. While the front cover of the first edition is filled only with words, the back is devoted entirely to an image. It features a black and white photograph of Morrison’s imposing face. Her portrait extends across the entire back of the book and just as Morrison’s name is not featured on the front jacket, only on the spine, her name is also absent on the back cover. By eliminating her name from the front and back of the book, Morrison reminds us that this text is less about her than about us. To this end, she looks evenly at the reader, eyes level and unsurprised. While Morrison’s large afro exceeds the frame of the photograph, it is her face that is most striking. Her closed lips do not smile, but she does not radiate anger or frustration. This is a woman who has never wanted blue eyes. Although she too is presented alone, she is the very opposite of the girls that populate contemporary covers of Morrison’s novel. The steady gaze that emanates from the book’s back cover implies a deep connection to others, if not to us, her readers, then to a community that has sustained and loved her. The original cover’s absence of a lone black girl reflecting on her tragic fate suggests one way that The Bluest Eye has evolved in our cultural imagination since its original publication. The book has come to signify most readily as a commentary on the idealization of white beauty and the self-hatred this perpetuates in the African American community. And certainly, Morrison’s book has much to say about the pernicious master narratives of beauty and race. But to accept that this is the most important insight of The Bluest Eye leads to dangerous claims that Pecola’s self-hatred is a thing of the past. The diversification of lines of Barbie dolls and other popular toys marketed for children has led some to contend that whiteness is no longer the uncontested standard of beauty. Now we have Beyoncé, Serena Williams, and Lupita Nyong’o on the cover of Vogue. And briefly we had Sasha and Malia dolls named in honor of the Obama daughters before their mother rightly protested the commercialization of her children. With these images before her, might a Pecola Breedlove of the twenty-first century not pine for blue eyes at all? I’d like to suggest that this question elides a more central concern of the novel and its implications fifty years since its publication. Let’s return then to the original cover of The Bluest Eye, which has very little to...

Dynamic text presentation on smart glasses: A pilot evaluation in age-related macular degeneration

We suggest a low-vision reading aid based on user-customized text presented on a head-mounted display (HMD), and make an initial comparison to optical aids in participants with age-related macular degeneration (AMD). Biomimetic scrolling, a novel method of text presentation which mimics the natural movements of the eye while reading, was previously invented: while the user maintains a steady gaze, text is scrolled horizontally across the display in a series of pauses and steps that resemble the natural fixations and saccades of reading. This method, along with rapid serial visual presentation, continuous scrolling, and static text, was presented on smart glasses to 23 participants with macular disease. Reading speed and subjective preference of the smart glasses was compared to reading text printed on paper using the participants’ habitual optical reading aid. Reading using smart glasses, the mean (±standard error) maximum reading speed was 122 ± 15 words per minute (wpm), compared to 74 ± 9 wpm using each participants’ habitual optical magnifier. This is a statistically significant difference as confirmed by a paired-sample t-test, t(17) = –4.61, p < .001. In total, 70% of the participants preferred reading from the smart glasses compared to reading from paper, and 84% found doing so easier. Data from this small patient cohort with AMD have demonstrated enhanced reading performance using dynamic text presented on a spectacle type HMD-device. Loss of reading ability marks a major decline in quality of life and independent functioning. Dynamic text presentation, including biomimetic scrolling, on smart glasses could improve reading performance for the visually impaired.

Eye position signals in the dorsal pulvinar during fixation and goal-directed saccades.

Sensorimotor cortical areas contain eye position information thought to ensure perceptual stability across saccades and underlie spatial transformations supporting goal-directed actions. One pathway by which eye position signals could be relayed to and across cortical areas is via the dorsal pulvinar. Several studies have demonstrated saccade-related activity in the dorsal pulvinar, and we have recently shown that many neurons exhibit postsaccadic spatial preference. In addition, dorsal pulvinar lesions lead to gaze-holding deficits expressed as nystagmus or ipsilesional gaze bias, prompting us to investigate the effects of eye position. We tested three starting eye positions (-15°, 0°, 15°) in monkeys performing a visually cued memory saccade task. We found two main types of gaze dependence. First, ~50% of neurons showed dependence on static gaze direction during initial and postsaccadic fixation, and might be signaling the position of the eyes in the orbit or coding foveal targets in a head/body/world-centered reference frame. The population-derived eye position signal lagged behind the saccade. Second, many neurons showed a combination of eye-centered and gaze-dependent modulation of visual, memory, and saccadic responses to a peripheral target. A small subset showed effects consistent with eye position-dependent gain modulation. Analysis of reference frames across task epochs from visual cue to postsaccadic fixation indicated a transition from predominantly eye-centered encoding to representation of final gaze or foveated locations in nonretinocentric coordinates. These results show that dorsal pulvinar neurons carry information about eye position, which could contribute to steady gaze during postural changes and to reference frame transformations for visually guided eye and limb movements.NEW & NOTEWORTHY Work on the pulvinar focused on eye-centered visuospatial representations, but position of the eyes in the orbit is also an important factor that needs to be taken into account during spatial orienting and goal-directed reaching. We show that dorsal pulvinar neurons are influenced by eye position. Gaze direction modulated ongoing firing during stable fixation, as well as visual and saccade responses to peripheral targets, suggesting involvement of the dorsal pulvinar in spatial coordinate transformations.

Eye Movement Disorders and the Cerebellum.

The cerebellum works as a network hub for optimizing eye movements through its mutual connections with the brainstem and beyond. Here, we review three key areas in the cerebellum that are related to the control of eye movements: (1) the flocculus/paraflocculus (tonsil) complex, primarily for high-frequency, transient vestibular responses, and also for smooth pursuit maintenance and steady gaze holding; (2) the nodulus/ventral uvula, primarily for low-frequency, sustained vestibular responses; and (3) the dorsal vermis/posterior fastigial nucleus, primarily for the accuracy of saccades. Although there is no absolute compartmentalization of function within the three major ocular motor areas in the cerebellum, the structural-functional approach provides a framework for assessing ocular motor performance in patients with disease that involves the cerebellum or the brainstem.

Sonia's Call

Kabir says, “If you don't break your ropes while you're alivedo you think ghosts will do it after?”I read it in a book of poems.Now, in autumn's morning light I wonder. What ifAll of life is an invitationTo this momentTo this day of the goldening green marshAnd the call of falling leaves? What ifLetting go is all we really needTo learn?Would we pay to practice?Perhaps that's what we've done here,With Sonia, when trying something new. It seems to me the space between the letting goAnd moving forward, is eternal. That's where you'll find Sonia now.Her steady gaze, solid ground for bigger lives,If we dare. What ifthere is nothingnew to try?Only now. This moment,full of freedom and despair.How do we live more boldly now,in the afternoon light of Wellfleet woods?And now?And now?And now …— 1 October 2017

Access Nollywood

Access Nollywood

Head-Eye Coordination at a Microscopic Scale

Humans explore static visual scenes by alternating rapid eye movements (saccades) with periods of slow and incessant eye drifts [1-3]. These drifts are commonly believed to be the consequence of physiological limits in maintaining steady gaze, resulting in Brownian-like trajectories [4-7], which are almost independent in the two eyes [8-10]. However, because of the technical difficulty of recording minute eye movements, most knowledge on ocular drift comes from artificial laboratory conditions, in which the head of the observer is strictly immobilized. Little is known about eye drift during natural head-free fixation, when microscopic head movements are also continually present [11-13]. We have recently observed that the power spectrum of the visual input to the retina during ocular drift is largely unaffected by fixational head movements [14]. Here we elucidate the mechanism responsible for this invariance. We show that, contrary to common assumption, ocular drift does not move the eyes randomly, but compensates for microscopic head movements, thereby yielding highly correlated movements in the two eyes. This compensatory behavior is extremely fast, persists with one eye patched, and results in image motion trajectories that are only partially correlated on the two retinas. These findings challenge established views of how humans acquire visual information. They show that ocular drift is precisely controlled, as long speculated [15], and imply the existence of neural mechanisms that integrate minute multimodal signals.

Craquelure, and: Handiwork

Craquelure, and: Handiwork Robert B. Shaw (bio) CRAQUELURE The ancestors were more relaxed than some when sitting for their portraits, given that the painter was their son, presumably performing gratis. In their Sunday best, they peer shrewdly from their his-and-hers twin ovals now exactly as they’ve done for something like a century-and-a-half. His formal white cravat, the filmy bands depending from her lace cap set off healthy complexions, features glowing with composure, hair brushed to a sheen; in short, the earmarks of prosperous middle age. A bead of white glimmering from each pupil works to bring their eyes to life. When I first pondered them, flanking my grandparents’ fireplace, they did not seem approachable by children— too venerable, even though their brows were mostly free of wrinkles. Now I find I’ve not only approached them but outpaced them, drawn past their age that day they gave their son his chance to practice on familiar subjects. Immunity to mutability confers on anyone a great advantage, and for years I credited them with it. Their sameness cast a spell of reassurance on any of the parlors they were hung in. Children of the latest generation have had their turn at being sobered by them, subdued to order by their steady gaze. Lately, though, by sidling close enough to give them a more skeptical inspection, [End Page 66] I’ve seen what doesn’t show up at a distance: clinging to each unworried face a wealth of radiating fissures forming nets of lines as delicate as hairs that once were snugged together on the artist’s brush-tip, the one he favored for his finest strokes to show posterity his parents’ eyebrows. Imagine filaments as fine as those, spreading a weft, on each a weightless veil, as if to compensate, year after year, for all the wrinkles that would never show in either likeness anchored to its canvas. An aging on the surface of the paint or in the once-protective coat of varnish belies their images’ arrested aging. By now I’m used to this, but at the moment it first came home to me, I thought of times I’d made my way with care across a sheet of pond ice till the cracks began to fan out from my feet, warning me to back off. Thank you, great, great Grandmother and Grandfather, for offering a modicum of caution along with your unruffled optimism. No doubt you found this out before I did: sooner or later, cracks are bound to come, however safe our customary frames prompt us to feel; the ice cannot be trusted beyond a point we only recognize on reaching it. Here, there’s no turning back. [End Page 67] HANDIWORK Against the back wall of our garage my grandfather built a long workbench on which whatever else we wanted to have built for us would assume form beneath hands that knew the ways of wood— which meant his, plainly. My lefthanded father had no knack for carpentry, nor liking, either, but was more than willing if the old man had a mind to put tools smartly through their paces. Coffee tables, cupboard shelves and doors, bookcases, trellises and easels, more and less structural joinery filled his hours when he visited. He let me heft with my untutored hands the implements that in his hands were like deft bodily extensions. The handles I liked most to handle looked like lemon jelly petrified. Even now I have a mental grasp of gear going about its business capably, or hung ready to hand on hooks, or stowed on shelves: the sharp ones he warned me about (planes, chisels, saws), the three hammers (tack, claw, and ballpeen); screwdrivers and wrenches in their ranked sizes, and the spirit level with its bubble that would never tell a lie. Most of all I liked (I wonder why) the pencil that he marked lumber with. Flat, unfaceted, so it would not roll out of sight or onto the floor, its wooden shaft glowed tomato red. He scored a dark line to guide his saw; on each graphite track the saw bit down. Sawdust from his cuts gleamed...

Laughter of Demons

Laughter of Demons Nii Ayikwei Parkes (bio) This is not a literary study. It is a collection of thoughts by one writer about another writer whose company he enjoys. I believe these things are permitted and good. Actually, this is about laughter, plain, conversation-interrupting laughter, the laughter of a particular man, the laughter of Ben Okri. Why? Well, whenever I think I haven’t seen Ben Okri for a while, that it would be nice to see him, I think primarily of his laughter. That is not to say that there is nothing to Ben but his laughter, far from it, but for me it is his mirth that carries the rest of him—the hat, the steady gaze, that gluttonous intellect. It is the lightness that inhabits his laughter that ennobles his best work; insight is a hard sell when you’re frowning. There is an encounter in Ben’s book of impossibility, Dangerous Love, where Doctor Okocha, wizened by ogogoro, tells the hero that his life will be full of surprises, that miracles happen where there has been suffering. In a way, Okocha’s words reflect my experience of Ben’s laughter; his brooding look makes his gregarious laughter a miracle, a surprise of gaping proportions. Our first meeting was a solemn affair, dictated by the weight of the occasion—we were both speaking at the mayor’s vigil for victims of the July 7, 2005, bombings in London. There was space for defiant smiles, not buoyant laughter. Our second was almost four years later in April, a perfect fourth pitched atop Kensington’s Roof Gardens. We were there at the invitation of the British Council, celebrating innovation. I identified him across the room by his iconic black beret and made my way over to pay my respects. It was only meant to be a quick hello—just a quick hello and a retreat; I didn’t want him asking me the kinds of questions that established writers ask writers whose books are about to be published. He was speaking to a lady who was completely in his thrall. I cut in awkwardly; waiting has never been my forte. To compensate, I made a wry comment. The lady giggled. Ben began to laugh. Now, I must make my position on the word “began” in narrative clear: I don’t like it. I tell my writing students, they either do or they don’t; if they begin, you have to tell us when they end. However, in this case, it is appropriate. Ben began to laugh. I say that because he laughed in waves. He started, stopped, and started again. Watching his eyes, I realized that I had triggered something; the joke for him was beyond my comment—he was mentally riffing. I caught his fever and fell into laughter too. Musically, Ben’s laugh has a wonderful quality—it’s a mellifluous, rhythmic explosion that carries well, a joyful call, a call for the community to share. Even in that room, abuzz with pockets of conversation, clinking glasses, mobile phone beeps and rights, the sound of air kisses and expensive heels clicking in the direction of opportunity, it caused a stir. People stopped to stare. [End Page 1012] The ability to laugh like Ben did on that Kensington Roof—like Ben does often—signals humility and a capacity for abstraction, the ability to empathize with someone’s perception of the world for long enough to “get it.” Let’s face it, there are more bad jokes in the world than good ones and even the good ones have to be delivered well. I happen to know I don’t tell jokes at all, the odd sly comment is about as funny as I get. What I realized in that moment was that our humor-triggers, like our stories, don’t belong to us. In 2011, twenty years after The Famished Road was published, Sam Jordison wrote something in the Guardian that made me wonder if he lacked a basic capacity for understanding. I can relate to someone not liking The Famished Road, no problem. What I can’t understand, as someone who has lived through drought, is...

Acute episodic centrally maintained vestibulopathy in a patient with multiple sclerosis managed with brain and vestibular rehabilitative approach: a case report

Event Abstract Back to Event Acute episodic centrally maintained vestibulopathy in a patient with multiple sclerosis managed with brain and vestibular rehabilitative approach: a case report Troy May1 and Derek Barton2* 1 May Chiropractic Clinic, United States 2 Carrick Institute, United States Background A 31-year-old female patient presented to a functional neurology clinic with an idiopathic acute episode of vertigo which was constant and of varying intensity beginning four days prior. The patient reported a sensation of spinning to the left and falling backward and rated the level of disorientation she felt as 6/10 with 10 being severely disoriented. She reported head pain over the right parietal region and a seven year history of multiple sclerosis confirmed by MRI. The patient stated she was unable to work and had difficulty eating due to her level of disorientation. Methods Neurological examination revealed unsteady and guarded gait, mild slurring of speech, and distressed demeanor. The patient demonstrated an inability to hold steady gaze with square wave intrusions during gaze holding assessment. She also had horizontal square wave jerks during pursuit testing with pursuits to the left being more difficult. Romberg test was positive with the patient falling backward and to the left. The patient had intersegmental dysfunction of the upper cervical spine. The patient was diagnosed with a centrally maintained vestibulopathy and a treatment plan was implemented immediately. The patient received five right Halmagyi head thrusts and three three-second passes of upward optokinetic stimuli. Gaze stability exercises were then performed in the horizontal plane with passive sinusoidal movements to a central target. Gaze stability was first performed supine and then in a seated position. Manipulation of the second cervical vertebra was also performed. Results The patient experienced immediate improvement of her subjective complaints of disorientation and head pain. She rated her level of disorientation as 2/10 following Halmagyi head thrusts. Objective improvements were seen in the patient's ability to hold steady gaze on a target during gaze fixation and Romberg testing was performed without any fall. The patient followed up for the next two days in the office with only a minor increase in symptoms. The patient was treated with a similar protocol and given at-home therapy exercises of horizontal 1x viewing for two minutes every two hours. Conclusions This case follows the treatment of a centrally maintained vestibular issue in a patient suffering from multiple sclerosis. The patient experienced immediate relief from her symptoms after a protocol utilizing brain activation and vestibular stimulation. Further investigation is necessary to determine if this approach would be beneficial for a larger population of multiple sclerosis patients suffering with vertigo issues. Keywords: Multiple Sclerosis, Vertigo, Dizziness, Neuro rehabilitation, falls Conference: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration, Orlando, Florida, United States, 10 Dec - 14 Dec, 2015. Presentation Type: Poster Presentation Topic: Case Reports for Poster Presentation Citation: May T and Barton D (2015). Acute episodic centrally maintained vestibulopathy in a patient with multiple sclerosis managed with brain and vestibular rehabilitative approach: a case report. Front. Neurol. Conference Abstract: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration. doi: 10.3389/conf.fneur.2015.58.00027 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 31 Oct 2015; Published Online: 02 Nov 2015. * Correspondence: Dr. Derek Barton, Carrick Institute, Cape Canaveral, FL, United States, derekabarton@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Troy May Derek Barton Google Troy May Derek Barton Google Scholar Troy May Derek Barton PubMed Troy May Derek Barton Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Viewing condition dependence of the gaze-evoked nystagmus in Arnold Chiari type 1 malformation

Saccadic eye movements rapidly shift gaze to the target of interest. Once the eyes reach a given target, the brainstem ocular motor integrator utilizes feedback from various sources to assure steady gaze. One of such sources is cerebellum whose lesion can impair neural integration leading to gaze-evoked nystagmus. The gaze evoked nystagmus is characterized by drifts moving the eyes away from the target and a null position where the drifts are absent. The extent of impairment in the neural integration for two opposite eccentricities might determine the location of the null position. Eye in the orbit position might also determine the location of the null. We report this phenomenon in a patient with Arnold Chiari type 1 malformation who had intermittent esotropia and horizontal gaze-evoked nystagmus with a shift in the null position. During binocular viewing, the null was shifted to the right. During monocular viewing, when the eye under cover drifted nasally (secondary to the esotropia), the null of the gaze-evoked nystagmus reorganized toward the center. We speculate that the output of the neural integrator is altered from the bilateral conflicting eye in the orbit position secondary to the strabismus. This could possibly explain the reorganization of the location of the null position.

高频采样下人眼波像差特性研究

Temporal properties of ocular wave aberrations are researched to improve the performance of eye aberration correction based on adaptive optical systems and the result for retinal imaging. Using a Shack-Hartmann wavefront sensor at a sampling rate of 330 Hz and exposure time of 3 ms, an optical system is constructed to detect human eye's wave aberration. The averaged root mean square (RMS) of detecting errors of the system is proved to be 0.01 by error analysis and an experiment on schematic eye. Detection results show that the existence of fluctuations of ocular wave aberration above 150 Hz can probably impact the performance of adaptive optics systems for wave aberration correction. These fluctuations can be reduced by increasing the detection and exposure times of the detector. In order to reach the diffraction limit, for eyes in the state of steady gaze, correction residual error RMS of adaptive optical system is less than /14, when detecting exposure time is 3 ms and detecting correction period is less than 45 ms. while the detecting correction period can increase to 62 ms as long as the exposure time is set to 6 ms. Analysis on tilt aberration proves that exposure time of high resolution retinal imaging should be less than 9 ms to avoid horizontal movements. Weighting the tradeoff between aberration fluctuation and horizontal movements, exposure times of detection and imaging are both set to about 6 ms.

EPA-1112 - Can eye movements be used as a marker for major depression?

No externally validated tests are available for routine use to confirm clinical diagnosis of major psychiatric disorders. Eye movement abnormalities that distinguish schizophrenia and bipolar disorder have only recently been described. Evidence of oculomotor dysfunction specific to endogenous major depressive disorder (MDD) would represent discovery of a significant endophenotypic interface between psychotic and affective disorders. Out-patients meeting DSM criteria for MDD (n=68, F:M=40:28, median age=49 (IQR 38-57) years) participated in a series of tasks while eye movements were recorded using an EyeLink 1000 infra-red video tracker. Patients' characteristics at time of assessment included median illness duration of 13 years (IQR= 7-23; n=53 available cases), HADS anxiety=11 (IQR 7-15) and depression=9 (IQR 4-11), BDI=27 (IQR 16-33), BPRS= 25 (IQR 20-29) and estimated IQ= 106 (IQR 96-118; n=42). Performance measures from smooth pursuit, picture viewing, and steady fixation were analysed alongside data from controls, schizophrenia, and bipolar disorder cases. A neural network was able to delineate the clinical and control groups with sensitivity=90.4% and specificity=97.1%. Multivariate tests of group differences post hoc revealed that MDD cases were on average poorest in maintaining steady gaze during the fixation task, mirroring the neuropsychological evidence for dysregulation of executive function in prefrontal brain regions. Bipolar and unipolar affective cases performed similarly on smooth pursuit and picture viewing tests, but were systematically different from schizophrenia and control groups. If differences are replicated in further cases, the MDD eye movement marker could be an important tool for psychiatric research, allowing for easier delineation of the major disorders.

Active Vision: Fixational Eye Movements Help Seeing Space in Time

The significance of the miniature eye movements that we make during visual fixation has been intensely debated for the last 80 years. Recent studies have revealed that these motions of the eyes fulfill an important functional role: helping to extract useful information from natural scenes.

Pharmacological tests of hypotheses for acquired pendular nystagmus

Acquired pendular nystagmus (APN) occurs with multiple sclerosis (MS) and oculopalatal tremor (OPT); distinct features of the nystagmus have led to the development of separate models for their pathogenesis. APN in MS has been attributed to instability in the neural integrator, which normally ensures steady gaze. APN in OPT may result from electrotonic coupling between neurons in the hypertrophied inferior olivary nucleus, which induces maladaptive learning in cerebellar cortex. We tested these two hypotheses by analyzing the effects of gabapentin, memantine, and baclofen on both forms of nystagmus. No drug changed the dominant frequency of either form of APN, but the variability of frequency was affected with gabapentin and memantine in patients with OPT. The amplitude of APN in both MS and OPT was reduced with gabapentin and memantine, but not baclofen. Analyzing the effects of drug therapies on ocular oscillations provides a novel approach to test models of nystagmus.