Prehension of a flanked target in individuals with amblyopia.

yesPurpose: Reduced binocularity is a prominent feature of amblyopia and binocular cues are thought to be important for prehension. We examine prehension in individuals with amblyopia when the target-object was flanked, thus mimicking everyday prehension. Methods: amblyopes (n=20, 36.4±11.7 years; 6 anisometropic, 3 strabismic, 11 mixed) and visually-normal controls (n=20, 27.5±6.3 years) reached forward, grasped and lifted a cylindrical target-object that was flanked with objects on either (lateral) side of the target, or in front and behind it in depth. Only 6 amblyopes (30%) had measurable stereoacuity. Trials were completed in binocular and monocular viewing, using the better eye in amblyopic participants. Results: Compared to visual normals, amblyopes displayed a longer overall movement time (p=0.031), lower average reach velocity (p=0.021), smaller maximum aperture (p=0.007) and longer durations between object contact and lift (p=0.003). Differences between groups were more apparent when the flankers were in front and behind, compared to either side, as evidenced by significant group-by-flanker configuration interactions for reach duration (p<0.001), size and timing of maximum aperture (p≤0.009), end-of-reach to object-contact (p<0.001), and between object contact and lift (p=0.044), suggesting that deficits are greatest when binocular cues are richest. Both groups demonstrated a significant binocular advantage, in that in both groups performance was worse for monocular compared to binocular viewing, but interestingly, amblyopic deficits in binocular viewing largely persisted during monocular viewing with the better eye. Conclusions: These results suggest that amblyopes either display considerable residual binocularity or that they have adapted to make good use of their abnormal binocularity

Binocular summation and other forms of non-dominant eye contribution in individuals with strabismic amblyopia during habitual viewing

YesAdults with amblyopia ('lazy eye'), long-standing strabismus (ocular misalignment) or both typically do not experience visual symptoms because the signal from weaker eye is given less weight than the signal from its fellow. Here we examine the contribution of the weaker eye of individuals with strabismus and amblyopia with both eyes open and with the deviating eye in its anomalous motor position. The task consisted of a blue-on-yellow detection task along a horizontal line across the central 50 degrees of the visual field. We compare the results obtained in ten individuals with strabismic amblyopia with ten visual normals. At each field location in each participant, we examined how the sensitivity exhibited under binocular conditions compared with sensitivity from four predictions, (i) a model of binocular summation, (ii) the average of the monocular sensitivities, (iii) dominant-eye sensitivity or (iv) non-dominant-eye sensitivity. The proportion of field locations for which the binocular summation model provided the best description of binocular sensitivity was similar in normals (50.6%) and amblyopes (48.2%). Average monocular sensitivity matched binocular sensitivity in 14.1% of amblyopes' field locations compared to 8.8% of normals'. Dominant-eye sensitivity explained sensitivity at 27.1% of field locations in amblyopes but 21.2% in normals. Non-dominant-eye sensitivity explained sensitivity at 10.6% of field locations in amblyopes but 19.4% in normals. Binocular summation provided the best description of the sensitivity profile in 6/10 amblyopes compared to 7/10 of normals. In three amblyopes, dominant-eye sensitivity most closely reflected binocular sensitivity (compared to two normals) and in the remaining amblyope, binocular sensitivity approximated to an average of the monocular sensitivities. Our results suggest a strong positive contribution in habitual viewing from the non-dominant eye in strabismic amblyopes. This is consistent with evidence from other sources that binocular mechanisms are frequently intact in strabismic and amblyopic individuals

A Limited Role for Suppression in the Central Field of Individuals with Strabismic Amblyopia.

yesBackground: Although their eyes are pointing in different directions, people with long-standing strabismic amblyopia typically do not experience double-vision or indeed any visual symptoms arising from their condition. It is generally believed that the phenomenon of suppression plays a major role in dealing with the consequences of amblyopia and strabismus, by preventing images from the weaker/deviating eye from reaching conscious awareness. Suppression is thus a highly sophisticated coping mechanism. Although suppression has been studied for over 100 years the literature is equivocal in relation to the extent of the retina that is suppressed, though the method used to investigate suppression is crucial to the outcome. There is growing evidence that some measurement methods lead to artefactual claims that suppression exists when it does not. Methodology/Results: Here we present the results of an experiment conducted with a new method to examine the prevalence, depth and extent of suppression in ten individuals with strabismic amblyopia. Seven subjects (70%) showed no evidence whatsoever for suppression and in the three individuals who did (30%), the depth and extent of suppression was small. Conclusions: Suppression may play a much smaller role in dealing with the negative consequences of strabismic amblyopia than previously thought. Whereas recent claims of this nature have been made only in those with micro-strabismus our results show extremely limited evidence for suppression across the central visual field in strabismic amblyopes more generally. Instead of suppressing the image from the weaker/deviating eye, we suggest the visual system of individuals with strabismic amblyopia may act to maximise the possibilities for binocular co-operation. This is consistent with recent evidence from strabismic and amblyopic individuals that their binocular mechanisms are intact, and that, just as in visual normals, performance with two eyes is better than with the better eye alone in these individuals

The functional impact of amblyopia and its associated conditions : an investigation of the potential disability associated with amblyopia and its associated conditions.

In the past decade, considerable attention has been paid to examination of the impact of amblyopia, and strabismus, upon the lives of the individuals. Although an extensive amount of literature exists regarding amblyopia and its associated visual defects, little is known about the contribution of the amblyopic eye in the habitual viewing condition (i.e. both eyes viewing). The purpose of these studies was to determine whether amblyopes are disadvantaged in the performance of tasks under habitual viewing conditions, highlighting any functional differences which may exist as a consequence of amblyopia. Secondly, the work aimed to investigate whether the amblyopic eye contributes to the habitual performance of these tasks. A simple light detection task, in a dichoptic arrangement based upon blue/yellow stimuli viewed through yellow filters, was used to investigate the above two aims and investigate the degree of interocular suppression in amblyopic participants. Using a 3D motion analysis system performance was assessed for an obstacle crossing task (adaptive gait) and a task of reaching for and grasping of an isolated object and in a ¿cluttered¿ environment. Fine motor skills were assessed in a threading a needle task. On the whole it was found that amblyopes are not disadvantaged under habitual viewing conditions, and in cases where differences were found to exist this appeared to be in tasks requiring speed and accuracy. Consistently across all studies it was found that the amblyopic eye contributed in a positive manner, thus, as in visual normals, two eyes are better than one

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Not AvailableLignocellulose is an important carbohydrate feedstock polymer for societally-acceptable second generation ethanol production. Delignification of lignocellulose is the foremost step towards accessing the sugars that can be fermented for ethanol production. Hence, the relative efficacies of single organosolv acid pretreatments, consisting of acetic and propionic acids, for delignification of corn stover have been optimized. It was observed that amongst the pretreatments involving single organosolv agent, 40% acetic acid resulted in maximum lignin reduction. The co-pretreatment consisting of Hydrogen peroxide and acetic acid resulted in more delignification (90.2% as compared to 75.7% in case of acetic acid alone), though found to be a costlier pretreatment. On the other hand, 40% acetic acid being low-cost and with an additional advantage of acetic acid recovery through distillation offered an economical choice for organosolv pretreatment of corn stover. This work thus guides the development of a cost-effective pretreatment regime for delignification of corn stover.Not Availabl

The functional impact of amblyopia and its associated conditions : an investigation of the potential disability associated with amblyopia and its associated conditions

In the past decade, considerable attention has been paid to examination of the impact of amblyopia, and strabismus, upon the lives of the individuals. Although an extensive amount of literature exists regarding amblyopia and its associated visual defects, little is known about the contribution of the amblyopic eye in the habitual viewing condition (i.e. both eyes viewing). The purpose of these studies was to determine whether amblyopes are disadvantaged in the performance of tasks under habitual viewing conditions, highlighting any functional differences which may exist as a consequence of amblyopia. Secondly, the work aimed to investigate whether the amblyopic eye contributes to the habitual performance of these tasks. A simple light detection task, in a dichoptic arrangement based upon blue/yellow stimuli viewed through yellow filters, was used to investigate the above two aims and investigate the degree of interocular suppression in amblyopic participants. Using a 3D motion analysis system performance was assessed for an obstacle crossing task (adaptive gait) and a task of reaching for and grasping of an isolated object and in a 'cluttered' environment. Fine motor skills were assessed in a threading a needle task. On the whole it was found that amblyopes are not disadvantaged under habitual viewing conditions, and in cases where differences were found to exist this appeared to be in tasks requiring speed and accuracy. Consistently across all studies it was found that the amblyopic eye contributed in a positive manner, thus, as in visual normals, two eyes are better than one.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Sensitivity of the amblyopic eye of the 10 strabismic amlyopes when the dominant eye viewed through the yellow filter (orange filled circles, dashed line) or had translucent occlusion (blue open squares, solid line).

<p>Error bars represent ±1 standard deviation of the mean. Negative values on the eccentricity axis correspond to visual field locations to the left of the fixation point. P-values are from the regression analysis comparing the two viewing conditions within each region separated by the vertical dotted lines. P = n/a signifies that no data are present from the yellow filter viewing condition due to the horizontal adjustment described in the text. The vertical red arrow indicates the location which corresponds to the straight ahead position of the strabismic eye when the dominant eye was fixating through the yellow filter.</p

Clinical details of strabismic amblyopic participants.

<p>Monocular visual acuity (VA, logMAR) are presented for left (L) and right (R) eyes under both habitual and optimal refractive conditions for the amblyopic eye (AE) and fellow eye (FE). The refractive correction worn habitually by each participant is also shown as Optimal (same as optimal refaction), None (no correction worn) or detailed in other cases. Oculomotor status and measurements at near viewing are presented and stereoacuity is given in seconds of arc (negative indicates worse than 600″) on the Frisby stereo acuity test. Eccentric fixation (EF) was measured in strabismic amblyopes using an interocular afterimage transfer method and the results are presented in degrees nasal (N) or degrees temporal (T). In visual normals, ocular dominance was determined with the Kay-pictures Dominant Eye Test (<a href="http://www.kaypictures.co.uk/dominant.html" target="_blank">www.kaypictures.co.uk/dominant.html</a>) and was classified as the eye that was used for sighting on at least two of the three presentations. The presence of abnormal retinal correspondence (ARC) was inferred from the results of the Bagolini lens test. On this basis only two participants (DF & GR) were diagnosed as displaying ARC. All four extropes are primary rather than consecutive exotropes. Abbreviations: AE = Amblyopic Eye, FE = Fellow Eye, Dom = Dominant Eye, XOT = Exotropia, SOT = Esotropia, Sup = suppression, DS = Dioptre Sphere, Δ = Prism Dioptres.</p

Summary of results obtained in visual normals (top, (a)) and in strabismic amblyopes (bottom, (b)).

<p>To account for the fact that in normals and strabismic amblyopes, the dominant eye may be the right or left eye, the results for some participants have been flipped so that the dominant eye is always the right eye, and the non-dominant eye is always the left eye. Locations corresponding to the blind spot (BS) in each eye were excluded from this analysis and are thus shown as gaps in the figure. Each bar corresponds to a visual field location in degrees to the left or right of the straight ahead position. The proportion of each bar that is black in colour indicates the proportion of normals (a) or strabismic amblyopes (b) for whom the binocular summation (Binoc Summ) model provided the closest estimate of binocular sensitivity actually exhibited at that field location. The proportion of individuals for whom the average monocular sensitivity is closest to binocular sensitivity is coded in blue (Ave), and red and yellow (NDE) colours represent the proportions where, respectively, the dominant (DE) and non-dominant (NDE) eye sensitivity is closest to the binocular sensitivity actually exhibited.</p

Outcomes of modelling results at each location as a function of exponent (n).

<p>The proportion of visual field locations best described by each of the four models for strabismic amblyopic and visual normal groups as a function of the exponent(n) used in the Binocular Summation modelling using equation <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0077871#pone.0077871-Frandsen1" target="_blank">[1]</a>. The numbers are the percentages of individual locations over the ten participants in each group in which the measured binocular visual field sensitivity was closest to the modelled Binocular summation (BinocSumm), the sensitivity in the Dominant Eye (DE), the sensitivity in the Non-dominant Eye (NDE) or the average of the sensitivities of the dominant and non-dominant eyes (Ave).</p