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Optometry and Vision Science : Official... Feb 2019Ophthalmic imaging instruments that require stable fixation can benefit by using Bessel beams in the form of monitor-based Bessel images. (Comparative Study)
Comparative Study
SIGNIFICANCE
Ophthalmic imaging instruments that require stable fixation can benefit by using Bessel beams in the form of monitor-based Bessel images.
PURPOSE
The purpose of this study was to investigate fixation stability using laser Bessel and Gaussian beams and monitor-based images of these targets.
METHODS
The right eyes of 16 participants were presented with seven fixation targets: monitor-based images of a bull's eye/cross hair, a Gaussian beam, a Bessel beam with four rings and a Bessel beam with three rings; laser Gaussian beam, laser Bessel beam with four rings, and laser Bessel beam with three rings. Participants fixated target centers for five runs, in which each run presented the seven targets for 20 seconds each. An Eye Tribe tracker sampled eye positions at 30 Hz. Standard deviations along horizontal (σx) and vertical meridians (σy) and areas of bivariate contour ellipses (BCEAs) of fixation positions were calculated, and statistical significances of target differences for these parameters were determined.
RESULTS
Average σx, σy, and BCEAs ranged from 0.26 to 0.35°, 0.38 to 0.55°, and 0.78 to 1.31 degrees, respectively. Target differences in σx (χ6 = 13.0, P = .04), (σy) (χ6 = 36.819, P < .001), and BCEA (χ6 = 34.406, P < .001) were statistically significant. There were significant post hoc differences between some of the target pairs for σy and BCEA, but not for σx. Monitor-based Bessel beam targets provided significantly smaller σy and BCEAs than the bull's eye/cross hair combination and the monitor- and laser-based Gaussian beam targets.
CONCLUSIONS
Monitor-based images of Bessel beams provided better fixation targets than did a bull's eye/cross hair combination, monitor-based Gaussian images, and laser Gaussian beams, but no claim can be made that laser Bessel beams provide better fixation targets than do laser Gaussian beams. Monitor-based Bessel images should be useful for ophthalmic imaging instruments requiring stable fixation.
Topics: Adolescent; Adult; Diagnostic Imaging; Eye Movements; Female; Fixation, Ocular; Humans; Light; Male; Young Adult
PubMed: 30601363
DOI: 10.1097/OPX.0000000000001328 -
PloS One 2023Good fixation of filigree specimens for micro-CT examinations is often a challenge. Movement artefacts, over-radiation or even crushing of the specimen can easily occur....
Good fixation of filigree specimens for micro-CT examinations is often a challenge. Movement artefacts, over-radiation or even crushing of the specimen can easily occur. Since different specimens have different requirements, we scanned, analysed and compared 19 possible fixation materials under the same conditions in the micro-CT. We focused on radiodensity, porosity and reversibility of these fixation materials. Furthermore, we have made sure that all materials are cheap and easily available. The scans were performed with a SkyScan 1173 micro-CT. All dry fixation materials tested were punched into 5 mm diameter cylinders and clamped into 0.2 ml reaction vessels. A voxel size of 5.33 μm was achieved in a 180° scan in 0.3° steps. Ideally, fixation materials should not be visible in the reconstructed image, i.e., barely binarised. Besides common micro-CT fixation materials such as styrofoam (-935 Hounsfield Units) or Basotect foam (-943 Hounsfield Units), polyethylene air cushions (-944 Hounsfield Units), Micropor foam (-926 Hounsfield Units) and polyurethane foam, (-960 Hounsfield Units to -470 Hounsfield Units) have proved to be attractive alternatives. Furthermore, more radiopaque materials such as paraffin wax granulate (-640 Hounsfield Units) and epoxy resin (-190 Hounsfield Units) are also suitable as fixation materials. These materials often can be removed in the reconstructed image by segmentation. Sample fixations in the studies of recent years are almost all limited to fixation in Parafilm, Styrofoam, or Basotect foam if the fixation type is mentioned at all. However, these are not always useful, as styrofoam, for example, dissolves in some common media such as methylsalicylate. We show that micro-CT laboratories should be equipped with various fixation materials to achieve high-level image quality.
Topics: X-Ray Microtomography; Polystyrenes; Polyethylene; Artifacts; Paraffin
PubMed: 37315002
DOI: 10.1371/journal.pone.0286039 -
European Journal of Orthopaedic Surgery... Apr 2015Whether external or plating fixation is more appropriate for high-energy tibial plateau fractures is still being disputed, our aim was to test the hypothesis whether... (Comparative Study)
Comparative Study Review
OBJECTIVE
Whether external or plating fixation is more appropriate for high-energy tibial plateau fractures is still being disputed, our aim was to test the hypothesis whether external fixation can provide a fair outcome with fewer complications, when compared to the results with previously reported data of plating fixation for high-energy tibial plateau fractures.
METHODS
An Ovid of Medline, Embase, and Cochrane Library search was conducted for the relevant English orthopedic journals, and eligible studies, including twenty-four case series and one comparative study containing 885 patients associated with 892 fractures, were enrolled.
RESULTS
The results showed there were a higher proportion of men, open fractures, malunion, knee instability, and posttraumatic arthritis occurred in external fixation group than those in plating group (P=0.007, P=0.000, P=0.024, P=0.006, P=0.000, respectively), while valgus deformity happened at a significantly higher rate in plate group (P=0.014). No significant differences were found between the two groups in terms of age, Schatzker type, follow-up, mean time to union, mean range of knee motion, and rate of reoperation. With regard to the functional and radiological outcome assessment, despite what assessment tools were used, most of these studies presented less than 90% good/excellent results in their high-energy fracture series. Besides, there was a trend for patients in plating group to have a higher risk than those in external fixation group in terms of heterotopic ossification and local irritation (1.23 vs 0.17%, 4 vs 1.94%, accordingly).
CONCLUSIONS
Although lack of good quality randomized control trials, there are rather enough samples supporting the current available results. Meanwhile, future multicentered, randomized, controlled studies should be implemented to test these outcomes.
Topics: Arthritis; Bone Plates; Epiphyses; External Fixators; Fracture Fixation, Internal; Fractures, Malunited; Genu Valgum; Humans; Intra-Articular Fractures; Joint Instability; Knee Joint; Tibial Fractures
PubMed: 25217410
DOI: 10.1007/s00590-014-1528-7 -
Orthopedic Research and Reviews 2020Lateral humeral condyle fractures are the second most common elbow fractures in children. Both K-wire fixation and screw fixation have been advocated as suitable... (Review)
Review
OBJECTIVE
Lateral humeral condyle fractures are the second most common elbow fractures in children. Both K-wire fixation and screw fixation have been advocated as suitable treatment options for displaced fractures. This study aimed to identify which fixation method was associated with the best functional outcomes.
METHODS
A systematic review was conducted. Studies reporting functional outcomes following surgical fixation of lateral condyle fractures were included for review. The primary outcome measure was functional outcome. The secondary outcome measure was major complications. A narrative analysis was undertaken, as meta-analysis was felt to be inappropriate due to the differences between included studies.
RESULTS
Ten retrospective non-randomised, comparative studies were eligible and included. No randomised-controlled trials were identified. The highest rate of excellent functional outcomes was seen with screw fixation (120/126 [95%]), compared with K-wire fixation (135/162 [86%]). The incidence of major complications was comparable, with complications in 6/95 (6%) of screw fixations and 6/141 (4%) K-wire fixations. A small sample of data on closed reduction demonstrated excellent functional results in 73 of 76 (96%) of patients. Closed reduction of displaced fractures is associated with a significant learning curve however.
CONCLUSION
The evidence was of poor quality and comprised of retrospective case series. This prevented meta-analysis and any firm conclusions being drawn from the available data. Screw fixation may be associated with improved functional outcomes. Complication rates between the two methods are comparable. Further prospective studies are recommended.
PubMed: 32273780
DOI: 10.2147/ORR.S215742 -
Psychological Science Sep 2022Perceptual processes underlying individual differences in face-recognition ability remain poorly understood. We compared visual sampling of 37 adult...
Perceptual processes underlying individual differences in face-recognition ability remain poorly understood. We compared visual sampling of 37 adult super-recognizers-individuals with superior face-recognition ability-with that of 68 typical adult viewers by measuring gaze position as they learned and recognized unfamiliar faces. In both phases, participants viewed faces through "spotlight" apertures that varied in size, with face information restricted in real time around their point of fixation. We found higher accuracy in super-recognizers at all aperture sizes-showing that their superiority does not rely on global sampling of face information but is also evident when they are forced to adopt piecemeal sampling. Additionally, super-recognizers made more fixations, focused less on eye region, and distributed their gaze more than typical viewers. These differences were most apparent when learning faces and were consistent with trends we observed across the broader ability spectrum, suggesting that they are reflective of factors that vary dimensionally in the broader population.
Topics: Adult; Facial Recognition; Humans; Individuality
PubMed: 36044042
DOI: 10.1177/09567976221096320 -
Seeing and Perceiving 2012Several definitions, measurements, and implicit meanings of 'fixation stability' have been used in clinical vision research, leading to some confusion. One definition... (Comparative Study)
Comparative Study Review
Several definitions, measurements, and implicit meanings of 'fixation stability' have been used in clinical vision research, leading to some confusion. One definition concerns eye movements observed within fixations (i.e., within periods separated by saccades) when observing a point target: drift, microsaccades and physiological tremor all lead to some degree of within-fixation instability. A second definition relates to eye position during multiple fixations (and saccades) when patients fixate a point target. Increased between-fixation variability, combined with within-fixation instability, is known to be associated with poorer visual function in people with retinal disease such as age-related macular degeneration. In this review article, methods of eye stability measurement and quantification are summarised. Two common measures are described in detail: the bivariate contour ellipse area (BCEA) and the within-isolines area. The first measure assumes normality of the underlying positions distribution whereas the second does not. Each of these measures can be applied to two fundamentally different kinds of eye position data collected during a period of target observation. In the first case, mean positions of eye fixations are used to obtain an estimate of between-fixation variability. In the second case, often used in clinical vision research, eye position samples recorded by the eyetracker are used to obtain an estimate that confounds within- and between-fixation variability. We show that these two methods can produce significantly different values of eye stability, especially when reported as BCEA values. Statistical techniques for describing eye stability when the distribution of eye positions is multimodal and not normally distributed are also reviewed.
Topics: Eye Movements; Fixation, Ocular; Humans; Vision, Low
PubMed: 22370759
DOI: 10.1163/187847611X620955 -
Clinical Cases in Mineral and Bone... 2015Distal femoral fractures have typically a bimodal occurrence: in young people due to a high-energy trauma and in older people related to a low-energy trauma. These... (Review)
Review
Distal femoral fractures have typically a bimodal occurrence: in young people due to a high-energy trauma and in older people related to a low-energy trauma. These fractures are associated to a very high morbidity and mortality in elderly. Distal femoral fractures might be treated with plates, intramedullary nails, external fixations, and prosthesis. However, difficulties in fracture healing and the rate of complications are important clinical issues. The purpose of this retrospective review was to present our experience in treatment of distal femoral fracture in a sample of older people in order to evaluate the technical pitfalls and strategies used to face up the fractures unsuccessfully treated with locking plates. We included people aged more than 65 years, with a diagnosis of distal femoral fracture, treated with locking plates. We considered 'unsuccessfully treated' the cases with healing problems or hardware failures. Of the 12 patients (9 females and 3 males; mean aged 68.75 ± 3.31 years) included, we observed 3 'unsuccessfully cases', 2 due to nonunions and 1 due to an early hardware failure, all treated using a condylar blade plate with a bone graft. One patient obtained a complete fracture healing after 1 year and in the other cases there was a nonunion. We observed as most common technical pitfalls: inadequate plate lengthening, fracture bridging, and number of locking screws. The use of locking plates is an emerging technique to treat these fractures but it seems more challenging than expected. In literature there is a lack of evidences about the surgical management of distal femoral fractures that is still an important challenge for the orthopaedic surgeon that has to be able to use all the fixation devices available.
PubMed: 27134634
DOI: 10.11138/ccmbm/2015.12.3s.054 -
Journal of Vision Jan 2017Microsaccades are high-velocity fixational eye movements, with special roles in perception and cognition. The default microsaccade detection method is to determine when...
Microsaccades are high-velocity fixational eye movements, with special roles in perception and cognition. The default microsaccade detection method is to determine when the smoothed eye velocity exceeds a threshold. We have developed a new method, Bayesian microsaccade detection (BMD), which performs inference based on a simple statistical model of eye positions. In this model, a hidden state variable changes between drift and microsaccade states at random times. The eye position is a biased random walk with different velocity distributions for each state. BMD generates samples from the posterior probability distribution over the eye state time series given the eye position time series. Applied to simulated data, BMD recovers the "true" microsaccades with fewer errors than alternative algorithms, especially at high noise. Applied to EyeLink eye tracker data, BMD detects almost all the microsaccades detected by the default method, but also apparent microsaccades embedded in high noise-although these can also be interpreted as false positives. Next we apply the algorithms to data collected with a Dual Purkinje Image eye tracker, whose higher precision justifies defining the inferred microsaccades as ground truth. When we add artificial measurement noise, the inferences of all algorithms degrade; however, at noise levels comparable to EyeLink data, BMD recovers the "true" microsaccades with 54% fewer errors than the default algorithm. Though unsuitable for online detection, BMD has other advantages: It returns probabilities rather than binary judgments, and it can be straightforwardly adapted as the generative model is refined. We make our algorithm available as a software package.
Topics: Algorithms; Bayes Theorem; Fixation, Ocular; Humans; Saccades; Visual Perception
PubMed: 28114483
DOI: 10.1167/17.1.13 -
Psychological Reports Aug 2010The present pilot study examined psychosexual fixations and defense mechanisms in a sample of young Japanese women. The Lexical Rorschach count and the Defense...
The present pilot study examined psychosexual fixations and defense mechanisms in a sample of young Japanese women. The Lexical Rorschach count and the Defense Mechanisms Inventory were administered to 24 female college students. Sadism on the Lexical Rorschach count was positively correlated with Reversal of Affect. Phallic fixation on the Lexical Rorschach count was positively correlated with Projection. Psychoanalytic hypotheses about the associations between psychosexual fixations and defense mechanisms were partially confirmed.
Topics: Adolescent; Aggression; Asian People; Cross-Cultural Comparison; Defense Mechanisms; Dependency, Psychological; Female; Gender Identity; Humans; Japan; Libido; Male; Personality Inventory; Psychometrics; Psychosexual Development; Social Dominance; Social Identification; Social Values; Young Adult
PubMed: 20923051
DOI: 10.2466/02.09.PR0.107.4.79-86 -
Journal of Eye Movement Research 2023The aim of the study was to analyze the stability of dominant and non-dominant eye fixations, as well as the influence of development on fixation stability. The study...
The aim of the study was to analyze the stability of dominant and non-dominant eye fixations, as well as the influence of development on fixation stability. The study analyzed fixation stability in 280 school-age children, ranging in age from 7 to 12 years old. Fixation stability was determined by calculating the bivariate contour ellipse area (BCEA). During the fixation task, eye movements were recorded using the Tobii Pro Fusion eye tracking device at a 250 Hz sampling frequency. The results indicate that the fixation stability of dominant and non-dominant eyes, as well as the fixation stability of each eye regardless of dominance, improves as children grow older. It was found that for 7 and 8- year-old children, fixation in the dominant eye is significantly more stable than in the non-dominant eye, while in older children, there is no significant difference in fixation stability between the dominant and non-dominant eye.
PubMed: 38370528
DOI: 10.16910/jemr.16.3.6