Fixation stability after surgical treatment of strabismus and biofeedback fixation training in amblyopic eyes

Background Visual fixation may be affected in amblyopic patients and, moreover, its stability may be associated with the effects of amblyopic treatments on visual performance in patients with strabismus. Therefore, fixation stability is a relevant biomarker that might predict the recurrence of amblyopia after a therapeutic intervention. Microperimetric biofeedback fixation training (BFT) can stabilize visual fixation in adult patients with central vision loss. It was the purpose of the present study to evaluate the effects of BFT on fixation stability in adult amblyopic patients after surgical intervention to treat strabismus. Methods Participants were 12 patients with strabismus (mean age = 29.6 ± 8.5 years; 6 females) and 12 healthy volunteers (mean age = 23.8 ± 1.5 years; 9 females). The protocol included ophthalmological and microperimetric follow-ups to measure fixation stability and macular sensitivity. BFT was applied monocularly to four amblyopic eyes either on the spontaneous preferential retinal locus or to a fixation area closer to the anatomical fovea after surgical treatment of strabismus. Results Baseline measurements showed significantly altered microperimetric average threshold in amblyopic eyes compared to fellow eyes (p = 0.024) and compared to control eyes (p < 0.001). Fixation was unstable in amblyopic eyes compared to control eyes (p < 0.001). Fixation stability did not significantly change after surgical alignment of strabismus (p = 0.805). BFT applied to operated eyes resulted in a more stable fixation with improvements of about 50% after three months of training. Conclusions Fixation stability improvements following BFT highlight its potential use in adult amblyopic eyes after the surgical alignment of the strabismus. Future investigations may also consider applying this method in combination with standard treatments to improve vision in amblyopic patients.

The efficacy of biofeedback visual rehabilitation therapy in patients with infantile nystagmus syndrome: A retrospective study

Objective: To report fixation stability changes in patients with different forms of infantile nystagmus syndrome (INS), who have undergone a visual rehabilitation through biofeedback fixation training (BFT) with microperimetry (MP). Design: Retrospective study. Methods: Patients 6 to 12 years-old with INS who performed BFT with MP. Initially 10 once-weekly followed by eight twice-weekly sessions of BFT during a minimum of 6 months period were performed. Visual acuity (VA) and MP fixation stability indices were analyzed, including displacement from fixation point (P1, P2) and percentage of retinal loci used during fixation attempt (BCEA 63% and 95%). Statistical analysis was conducted at baseline (BL), 10 weeks (W10) and 6 months (M6). Results: Twelve patients (mean age 8.9 years.) with INS completed the whole training session. All patients showed significant improvement in the mean BCEA fixation area (deg2): For BCEA@95% BL was 78.0, 46.1 at W10, and 27.4 at M6 ( p-value = 0.004). For BCEA@63% BL was 27.3, 15.4 in W10, and 9.17 at M6 ( p = 0.01). The ANOVA test for the FS indices of P1 and P2, as well as for BCVA showed no significant difference when compared at the same intervals. Conclusion: Fixation stability (FS) indices of BCEAs (63% and 95%) improved at W10 and M6, while P1 and P2 showed significant improvement at W10 but not at M6, probably because BCEA involves a much larger area than P1 and P2. VA did not show significant improvement at any time point.

Biomechanical Evaluation of a New Fixation Type in 3D-Printed Periacetabular Implants using a Finite Element Simulation

Pelvic implants require complex geometrical shapes to reconstruct unusual areas of bone defects, as well as a high mechanical strength in order to endure high compressive loads. The electron beam melting (EBM) method is capable of directly fabricating complex metallic structures and shapes based on digital models. Fixation design is important during the 3D printing of pelvic implants, given that the fixation secures the pelvic implants to the remaining bones, while also bearing large amounts of the loads placed on the bone. In this study, a horseshoe-shaped plate fixation with a bridge component between two straight plates is designed to enhance the mechanical stability of pelvic implants. The aim of this study is to investigate the biomechanics of the horseshoe-shaped plate fixation in a 3D-printed pelvic implant using a finite element (FE) simulation. First, computed tomography (CT) scans were acquired from a patient with periacetabular bone tumors. Second, 3D FE implant models were created using the patient’s Digital Imaging and Communications in Medicine (DICOM) data. Third, a FE simulation was conducted and the stress distribution between a conventional straight-type plate model, and the horseshoe-shaped plate model was compared. In both of the models, high-stress regions were observed at the iliac fixation area. In contrast, minimal stress regions were located at the pubic ramus and ischium fixation area. The key finding of this study was that the maximal stress of the horseshoe-shaped plate model (38.6 MPa) was 21% lower than that of the straight-type plate model (48.9 MPa) in the iliac fixation area. The clinical potential for the application of the horseshoe-shaped plate fixation model to the pelvic implant has been demonstrated, although this is a pilot study.

ARTICULATION AND BACKSIDE WEAR ANALYSIS AFTER LONG-TERM IN VITRO WEAR SIMULATION OF VITAMIN E STABILIZED POLYETHYLENE ACETABULAR LINERS WITH A PRESS-FIT LOCKING MECHANISM

A previous retrieval study analyzed the backside wear of short-term implanted liners against in vitro tested liners of similar life in service and showed comparable results among both groups, with no significant backside wear due to micro-motion.The purpose — to obtain a picture of the overall wear (articulation and backside surfaces) of 0.1% vitamin e blended polyethylene liners, with a locking mechanism based on a press-fit cone in combination with a rough titanium conical inner surface in the fixation area, under a 20 million cycles hip wear simulation.Materials and Methods. A semi-quantitative method was used in order to assess the damage on the backside of the liners and a 3d measuring machine to assess the creep and wear at the articulation surface.Results. The total average backside wear score was 22.00±2.59 from a maximum total score of 147 after 5 million cycles (mc), increased to 31.92±5.57 after 10 mc, but showed no further increment after 15 and 20 mc. The reference liners (subjected only to axial load) showed similar wear scores and modes as the liners under wear simulation (axial load and movement). Small scratches produced during insertion and removal were clearly seen at the rim (fixation) area and no considerable abrasion was observed. The machining marks on the convex surface were always visible. Regarding the articulation surface, a steady state wear rate of 7 µm/year was measured.Conlusion. These results determined that most of the backside wear produced on the liners occurred during their insertion and removal rather than during their life in service. Moreover, the wear at the articulation surface was similar to that seen in vivo at short- and mid-term on highly cross-linked polyethylene liners with and without vitamin e content.

Leukocyte Image Segmentation Using Novel Saliency Detection Based on Positive Feedback of Visual Perception

This paper presents a novel method for salient object detection in nature image by simulating microsaccades in fixational eye movements. Due to a nucleated cell usually stained that is salient obviously, the proposed method is suitable to segment nucleated cell. Firstly, the existing fixation prediction method is utilized to produce an initial fixation area. Followed EPELM (ensemble of polyharmonic extreme learning machine) is trained on-line by the pixels sampling from the fixation and nonfixation area. Then the model of EPELM could be used to classify image pixels to form new binary fixation area. Depending upon the updated fixation area, the procedure of “pixel sampling-learning-classification” could be performed iteratively. If the previous binary fixation area and the latter one were similar enough in iteration, it indicates that the perception is saturated and the loop should be terminated. The binary output in iteration could be regarded as a kind of visual stimulation. So the multiple outputs of visual stimuli can be accumulated to form a new saliency map. Experiments on three image databases show the validity of our method. It can segment nucleated cells successfully in different imaging conditions.

The new method for the treatment of relative amblyopia in the patients presenting with optical nystagmus

Aim. The objective of the present study was to develop the method for the pleoptical treatment of relative amblyopia in the children presenting with optical nystagmus with the use of sinoptophore under conditions of nystagmus blockade. The secondary objective was to evaluate the effectiveness of the proposed method. Materials and methods. The newly developed technique for the pleoptical treatment of relative amblyopia consisted of the blockade of nystagmus by conversion effort and the application of the light pulses to the central fovea of the retina under control of bifoveal fusion. Results. The proposed method was employed to treat 21 patients presenting with optical nystagmus and relative amblyopia at the age varying from 5 to 10 years. In 18 children, the changes in the parameters of nystagmus were evaluated from its amplitude and fixation area density on the retina by means of microperimetry using the NIDEK Microperimeter-MP1 apparatus. The study revealed the tendency toward the improvement of binocular visual acuity, both corrected and uncorrected (by 0.14±0.09 and 0.12±0.07 on the average, respectively), and of the absolute accommodation volume (by 2.88±1.9 diopters). The inverse relationship between the motor parameters of nystagmus and visual acuity was documented. Conclusion. The proposed new method for the pleoptical treatment of relative amblyopia consists of blockade of nystagmus by conversion effort and the delivery of the light pulses to the central fovea of the retina in both eyes under control of bifoveal fusion on sinoptofphore. The method allowed to improve both the functional (enhanced visual acuity) and motor (amplitude and fixation area density) characteristics of nystagmus.

Study on Novice Drivers' Fixation Features under Different Car-Following Risk Levels

Through early interviews 22 common traffic scenes were found and leveled by questionnaires. Six scenes of low-risk, medium risk and high risk were selected and implemented in the simulation software using the software of Creator, Vega, C++, etc. Simulation experiments were conducted to analyze the novice drivers fixation features under different levels of risk based on the designed real car simulation platform. The results showed that both novice and experienced drivers saccade times are more than 3 times greater than the fixation times, suggesting that drivers visual search are found mainly in saccadic movement other than watch movement. In potentially dangerous environment, experience drivers always reduce fixation time and increase saccade time to make early warnings of danger that may arise, while novice drivers saccade time and fixation time are relatively stable. Novice drivers concern more about the dashboard regardless of the level of risk in any scenarios comparatively. In the three levels of risk conditions, novice drivers watching areas are more concentrate, namely, their fixation area mostly focus on some certain areas while ignoring other areas, such as rearview mirror and traffic signals.