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Talsma HE, Kruijt CC, de Wit GC, Zwerver SHL, van Genderen MM. Nystagmus Characteristics in Albinism: Unveiling the Link to Foveal Hypoplasia and Visual Acuity. Invest Ophthalmol Vis Sci 2023; 64:30. [PMID: 38133506 PMCID: PMC10746925 DOI: 10.1167/iovs.64.15.30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 11/21/2023] [Indexed: 12/23/2023] Open
Abstract
Purpose The purpose of this study was to describe the association among nystagmus characteristics, foveal hypoplasia, and visual acuity in patients with albinism. Methods We studied nystagmus recordings of 50 patients with albinism. The nystagmus waveform was decomposed into two types: dominantly pendular and dominantly jerk. We correlated the nystagmus type, amplitude, frequency, and percentage of low velocity (PLOV) to Snellen visual acuity and foveal hypoplasia grades. Results The grade of foveal hypoplasia and visual acuity showed a strong correlation (r = 0.87, P < 0.0001). Nystagmus type and PLOV had the strongest significant (P < 0.0001) correlation with visual acuity (r = 0.70 and r = -0.56, respectively) and with foveal hypoplasia (r = 0.76 and r = -0.60, respectively). Patients with pendular nystagmus type had the lowest PLOV, and the highest grade of foveal hypoplasia (P < 0.0001). Severe foveal hypoplasia (grade 4), was almost invariably associated with pendular nystagmus (86%). Conclusions Foveal hypoplasia grade 4 is associated with pendular nystagmus, lower PLOV, and worse visual acuity. Based on these results, nystagmus recordings at a young age may contribute to predicting visual outcomes.
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Affiliation(s)
- Herman E. Talsma
- Bartiméus Diagnostic Center for Complex Visual Disorders, Zeist, The Netherlands
| | - Charlotte C. Kruijt
- Bartiméus Diagnostic Center for Complex Visual Disorders, Zeist, The Netherlands
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands
| | - Gerard C. de Wit
- Bartiméus Diagnostic Center for Complex Visual Disorders, Zeist, The Netherlands
| | - Stefan H. L. Zwerver
- Bartiméus Diagnostic Center for Complex Visual Disorders, Zeist, The Netherlands
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboudumc, Nijmegen, The Netherlands
| | - Maria M. van Genderen
- Bartiméus Diagnostic Center for Complex Visual Disorders, Zeist, The Netherlands
- Department of Ophthalmology, University Medical Center Utrecht, Utrecht, The Netherlands
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Huang L, Zhou Y, Chen W, Lin P, Xie Y, He K, Zhang S, Wu Y, Li N. Correlations of FRMD7 gene mutations with ocular oscillations. Sci Rep 2022; 12:9914. [PMID: 35705619 PMCID: PMC9200781 DOI: 10.1038/s41598-022-14144-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 05/11/2022] [Indexed: 11/30/2022] Open
Abstract
Mutations in the FERM domain containing 7 (FRMD7) gene have been proven to be responsible for infantile nystagmus (IN). The purpose of this study is to investigate FRMD7 gene mutations in patients with IN, and to evaluate the nystagmus intensity among patients with and without FRMD7 mutations. The affected males were subdivided into three groups according to whether or not having FRMD7 mutations and the types of mutations. Fifty-two mutations were detected in FRMD7 in 56 pedigrees and 34 sporadic patients with IN, including 28 novel and 24 previous reported mutations. The novel identified mutations further expand the spectrum of FRMD7 mutations. The parameters of nystagmus intensity and the patients’ best corrected visual acuity were not statistically different among the patients with and without identified FRMD7 mutations, and also not different among patients with different mutant types. The FERM-C domain, whose amino acids are encoded by exons 7, 8 and 9, could be the harbor region for most mutations. Loss-of-function is suggested to be the common molecular mechanism for the X-linked infantile nystagmus.
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Affiliation(s)
- Lijuan Huang
- Department of Ophthalmology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, 362000, China.,Department of Ophthalmology, Beijing Children's Hospital, Capital Medical University, No 56. Nan Li Shi Rd, Xicheng District, Beijing, 100045, China
| | - Yunyu Zhou
- Department of Ophthalmology, Beijing Children's Hospital, Capital Medical University, No 56. Nan Li Shi Rd, Xicheng District, Beijing, 100045, China
| | - Wencong Chen
- Department of Biostatistics, Vanderbilt University Medical Center, 2525 West End Avenue, Suite 1100, Nashville, TN, 37203, USA
| | - Ping Lin
- Department of Ophthalmology, Xi'an Children's Hospital, Xi'an, 710002, China
| | - Yan Xie
- Department of Ophthalmology, Beijing Children's Hospital, Capital Medical University, No 56. Nan Li Shi Rd, Xicheng District, Beijing, 100045, China
| | - Kaiwen He
- Department of Ophthalmology, Beijing Children's Hospital, Capital Medical University, No 56. Nan Li Shi Rd, Xicheng District, Beijing, 100045, China
| | - Shasha Zhang
- Department of Ophthalmology, Xi'an Children's Hospital, Xi'an, 710002, China
| | - Yuyu Wu
- Department of Ophthalmology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, 362000, China.
| | - Ningdong Li
- Department of Ophthalmology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, 362000, China. .,Department of Ophthalmology, Beijing Children's Hospital, Capital Medical University, No 56. Nan Li Shi Rd, Xicheng District, Beijing, 100045, China. .,Department of Ophthalmology, Xi'an Children's Hospital, Xi'an, 710002, China. .,Key Laboratory of Major Diseases in Children, Ministry of Education, Beijing, 100045, China. .,Department of Ophthalmology, Children's Hospital, Capital Institute of Pediatrics, Beijing, 100020, China.
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Hertle RW, Kelleher C, Bruckman D, McNinch N, Ricker I, Bouhenni R, Wiseman K. Analysis of anomalous head posturing in patients with infantile nystagmus syndrome. J AAPOS 2021; 25:145.e1-145.e5. [PMID: 34087474 DOI: 10.1016/j.jaapos.2021.02.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/15/2021] [Accepted: 02/15/2021] [Indexed: 10/21/2022]
Abstract
PURPOSE To investigate anomalous head posturing in patients with INS. METHODS This was a prospective, cohort analysis of clinical and anomalous head posture (AHP) data in 34 patients with INS and an AHP. Particular outcome measures included measurement of AHP in three dimensions of pitch (anterior posterior flexion/extension), yaw (lateral rotation), and roll (lateral flexion) during best-corrected binocular acuity testing and during their subjective sense of straight. Patients were also queried as to their subjective sense of head posture in forced straight position and in their preferred AHP. The paired t test was used to determine significance in differences between measures. RESULTS A total of 34 patients (19 males [56%]) 9-56 years of age (mean, 16.5 ± 6) were included. Associated systemic or ocular system deficits were present in 30 patients (88%). AHP during best-corrected visual acuity testing averaged 16.5° ± 8.20° (range, 10°-51°), which was significantly different from the mean voluntary "comfortable" position only in the pitch and roll directions (P < 0.001). There was a significant noncongruous response during subjective response to head posturing with most sensing their head as "crooked" (76.5%) when manually straightened (P = 0.001). CONCLUSIONS The clinical AHP of patients with INS exists in all three spatial dimensions of pitch, yaw, and roll. Although the visual system may be causally related to the onset, amount, and direction of a compensatory AHP in patients with INS, its persistence over time or after surgical intervention is likely due to a combination of visual system (eg, nystagmus, strabismus) and nonvisual system (egocentric and musculo-skeletal) factors.
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Affiliation(s)
- Richard W Hertle
- Akron Children's Hospital Vision Center, Akron, Ohio; The Considine Research Institute, Akron Children's Hospital, Akron, Ohio; Northeast Ohio Medical College, Rootstown, Ohio.
| | - Cecily Kelleher
- Akron Children's Hospital Vision Center, Akron, Ohio; The Considine Research Institute, Akron Children's Hospital, Akron, Ohio
| | - David Bruckman
- Center for Populations Health Research, Cleveland Clinic, Cleveland, Ohio
| | - Neil McNinch
- The Considine Research Institute, Akron Children's Hospital, Akron, Ohio
| | - Isabel Ricker
- Akron Children's Hospital Vision Center, Akron, Ohio; The Considine Research Institute, Akron Children's Hospital, Akron, Ohio
| | - Rachida Bouhenni
- Akron Children's Hospital Vision Center, Akron, Ohio; The Considine Research Institute, Akron Children's Hospital, Akron, Ohio; Northeast Ohio Medical College, Rootstown, Ohio
| | - Kelly Wiseman
- Akron Children's Hospital Vision Center, Akron, Ohio; The Considine Research Institute, Akron Children's Hospital, Akron, Ohio
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Abadi RV, Akman OE, Arblaster GE, Clement RA. Analysing nystagmus waveforms: a computational framework. Sci Rep 2021; 11:9761. [PMID: 33963228 PMCID: PMC8105328 DOI: 10.1038/s41598-021-89094-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 04/21/2021] [Indexed: 12/03/2022] Open
Abstract
We present a new computational approach to analyse nystagmus waveforms. Our framework is designed to fully characterise the state of the nystagmus, aid clinical diagnosis and to quantify the dynamical changes in the oscillations over time. Both linear and nonlinear analyses of time series were used to determine the regularity and complexity of a specific homogenous phenotype of nystagmus. Two-dimensional binocular eye movement recordings were carried out on 5 adult subjects who exhibited a unilateral, uniplanar, vertical nystagmus secondary to a monocular late-onset severe visual loss in the oscillating eye (the Heimann-Bielschowsky Phenomenon). The non-affected eye held a central gaze in both horizontal and vertical planes (± 10 min. of arc). All affected eyes exhibited vertical oscillations, with mean amplitudes and frequencies ranging from 2.0°-4.0° to 0.25-1.5 Hz, respectively. Unstable periodic orbit analysis revealed only 1 subject exhibited a periodic oscillation. The remaining subjects were found to display quasiperiodic (n = 1) and nonperiodic (n = 3) oscillations. Phase space reconstruction allowed attractor identification and the computation of a time series complexity measure-the permutation entropy. The entropy measure was found to be able to distinguish between a periodic oscillation associated with a limit cycle attractor, a quasiperiodic oscillation associated with a torus attractor and nonperiodic oscillations associated with higher-dimensional attractors. Importantly, the permutation entropy was able to rank the oscillations, thereby providing an objective index of nystagmus complexity (range 0.15-0.21) that could not be obtained via unstable periodic orbit analysis or attractor identification alone. These results suggest that our framework provides a comprehensive methodology for characterising nystagmus, aiding differential diagnosis and also permitting investigation of the waveforms over time, thereby facilitating the quantification of future therapeutic managements. In addition, permutation entropy could provide an additional tool for future oculomotor modelling.
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Affiliation(s)
- Richard V Abadi
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK.
| | - Ozgur E Akman
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK.
| | - Gemma E Arblaster
- Orthoptics Department, NHS Foundation Trust, Sheffield Teaching Hospitals, Sheffield, UK
- Division of Ophthalmology and Orthoptics, Health Sciences School, University of Sheffield, Sheffield, UK
| | - Richard A Clement
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
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Rosengren W, Nyström M, Hammar B, Stridh M. Waveform characterisation and comparison of nystagmus eye-tracking signals. Physiol Meas 2021; 42:015004. [PMID: 33412529 DOI: 10.1088/1361-6579/abd98f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Pathological nystagmus is a symptom of oculomotor disease where the eyes oscillate involuntarily. The underlying cause of the nystagmus and the characteristics of the oscillatory eye movements are patient specific. An important part of clinical assessment in nystagmus patients is therefore to characterise different recorded eye-tracking signals, i.e. waveforms. APPROACH A method for characterisation of the nystagmus waveform morphology is proposed. The method extracts local morphologic characteristics based on a sinusoidal model, and clusters these into a description of the complete signal. The clusters are used to characterise and compare recordings within and between patients and tasks. New metrics are proposed that can measure waveform similarity at different scales; from short signal segments up to entire signals, both within and between patients. MAIN RESULTS The results show that the proposed method robustly can find the most prominent nystagmus waveforms in a recording. The method accurately identifies different eye movement patterns within and between patients and across different tasks. SIGNIFICANCE In conclusion, by allowing characterisation and comparison of nystagmus waveform patterns, the proposed method opens up for investigation and identification of the underlying condition in the individual patient, and for quantifying eye movements during tasks.
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Abstract
Mathematical modeling of nystagmus oscillations is a technique with applications in diagnostics, treatment evaluation, and acuity testing. Modeling is a powerful tool for the analysis of nystagmus oscillations but quality assessment of the input data is needed in order to avoid misinterpretation of the modeling results. In this work, we propose a signal quality metric for nystagmus waveforms, the normalized segment error (NSE). The NSE is based on the energy in the error signal between the observed oscillations and a reconstruction from a harmonic sinusoidal model called the normalized waveform model (NWM). A threshold for discrimination between nystagmus oscillations and disturbances is estimated using simulated signals and receiver operator characteristics (ROC). The ROC is optimized to find noisy segments and abrupt waveform and frequency changes in the simulated data that disturb the modeling. The discrimination threshold, 𝜖, obtained from the ROC analysis, is applied to real recordings of nystagmus data in order to determine whether a segment is of high quality or not. The NWM parameters from both the simulated dataset and the nystagmus recordings are analyzed for the two classes suggested by the threshold. The optimized 𝜖 yielded a true-positive rate and a false-positive rate of 0.97 and 0.07, respectively, for the simulated data. The results from the NWM parameter analysis show that they are consistent with the known values of the simulated signals, and that the method estimates similar model parameters when performing analysis of repeated recordings from one subject.
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Abstract
Eye tracking is a useful tool when studying the oscillatory eye movements associated with nystagmus. However, this oscillatory nature of nystagmus is problematic during calibration since it introduces uncertainty about where the person is actually looking. This renders comparisons between separate recordings unreliable. Still, the influence of the calibration protocol on eye movement data from people with nystagmus has not been thoroughly investigated. In this work, we propose a calibration method using Procrustes analysis in combination with an outlier correction algorithm, which is based on a model of the calibration data and on the geometry of the experimental setup. The proposed method is compared to previously used calibration polynomials in terms of accuracy, calibration plane distortion and waveform robustness. Six recordings of calibration data, validation data and optokinetic nystagmus data from people with nystagmus and seven recordings from a control group were included in the study. Fixation errors during the recording of calibration data from the healthy participants were introduced, simulating fixation errors caused by the oscillatory movements found in nystagmus data. The outlier correction algorithm improved the accuracy for all tested calibration methods. The accuracy and calibration plane distortion performance of the Procrustes analysis calibration method were similar to the top performing mapping functions for the simulated fixation errors. The performance in terms of waveform robustness was superior for the Procrustes analysis calibration compared to the other calibration methods. The overall performance of the Procrustes calibration methods was best for the datasets containing errors during the calibration.
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Imai T, Takimoto Y, Okumura T, Higashi-Shingai K, Takeda N, Kitamura K, Kalubi B, Fujikado T, Hirota M, Midoh Y, Nakamae K, Inohara H. Visual Target Strategies in Infantile Nystagmus Patients With Horizontal Jerk Waveform. Front Neurol 2018; 9:622. [PMID: 30104998 PMCID: PMC6077220 DOI: 10.3389/fneur.2018.00622] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 07/10/2018] [Indexed: 11/24/2022] Open
Abstract
The aim of this study was to propose a new pathophysiological hypothesis for involuntary eye oscillation in infantile nystagmus (IN): patients with IN exhibit impaired gaze fixation, horizontal smooth pursuit and optokinetic nystagmus (OKN) and use saccadic eye movements for these underlying impairments. In order to induce saccades, they make enough angle between gaze and target by precedent exponential slow eye movements. IN consists of the alternate appearance of the saccade and the slow eye movements. Unlike most previous theories, IN is therefore considered a necessary strategy allowing for better vision and not an obstacle to clear vision. In five patients with IN, eye movements were analyzed during the smooth pursuit test, saccadic eye movement test, OKN test and vestibulo-ocular reflex (VOR) test. Their gaze fixation, horizontal smooth pursuit, OKN and the last half of the slow phase of VOR were impaired. The lines obtained by connection of the end eye positions of fast phase of nystagmus coincided with the trajectories of targets. The findings indicate that patients followed the target by the fast but not the slow phase of nystagmus, which supports our hypothesis. By setting the direction of slow phase of nystagmus opposite to the direction of the OKN stimulation, enough angle can be effectively made between the gaze and target for the induction of saccade. This is the mechanism of reversed OKN response. In darkness and when eyes are closed, IN weakens because there is no visual target and neither the saccade for catching up the target or slow phase for induction of the saccade is needed.
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Affiliation(s)
- Takao Imai
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | | | - Tomoko Okumura
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | | | - Noriaki Takeda
- Department of Otorhinolaryngology - Head and Neck Surgery, Tokushima University Graduate School of Medicine, Tokushima, Japan
| | - Koji Kitamura
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Bukasa Kalubi
- Medical Education Center, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Takashi Fujikado
- Department of Ophthalmology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Masakazu Hirota
- Department of Ophthalmology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yoshihiro Midoh
- Department of Information Systems Engineering, Osaka University Graduate School of Information Science and Technology, Osaka, Japan
| | - Koji Nakamae
- Department of Information Systems Engineering, Osaka University Graduate School of Information Science and Technology, Osaka, Japan
| | - Hidenori Inohara
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
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Nij Bijvank JA, Petzold A, Balk LJ, Tan HS, Uitdehaag BMJ, Theodorou M, van Rijn LJ. A standardized protocol for quantification of saccadic eye movements: DEMoNS. PLoS One 2018; 13:e0200695. [PMID: 30011322 PMCID: PMC6047815 DOI: 10.1371/journal.pone.0200695] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 07/02/2018] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE Quantitative saccadic testing is a non-invasive method of evaluating the neural networks involved in the control of eye movements. The aim of this study is to provide a standardized and reproducible protocol for infrared oculography measurements of eye movements and analysis, which can be applied for various diseases in a multicenter setting. METHODS Development of a protocol to Demonstrate Eye Movement Networks with Saccades (DEMoNS) using infrared oculography. Automated analysis methods were used to calculate parameters describing the characteristics of the saccadic eye movements. The two measurements of the subjects were compared with descriptive and reproducibility statistics. RESULTS Infrared oculography measurements of all subjects were performed using the DEMoNS protocol and various saccadic parameters were calculated automatically from 28 subjects. Saccadic parameters such as: peak velocity, latency and saccade pair ratios showed excellent reproducibility (intra-class correlation coefficients > 0.9). Parameters describing performance of more complex tasks showed moderate to good reproducibility (intra-class correlation coefficients 0.63-0.78). CONCLUSIONS This study provides a standardized and transparent protocol for measuring and analyzing saccadic eye movements in a multicenter setting. The DEMoNS protocol details outcome measures for treatment trial which are of excellent reproducibility. The DEMoNS protocol can be applied to the study of saccadic eye movements in various neurodegenerative and motor diseases.
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Affiliation(s)
- J. A. Nij Bijvank
- Department of Ophthalmology, Neuro-ophthalmology Expertise Center, Amsterdam UMC - VUmc, Amsterdam, The Netherlands
- Department of Neurology, MS Center and Neuro-ophthalmology Expertise Center, Neuroscience Amsterdam, Amsterdam UMC - VUmc, Amsterdam, The Netherlands
- * E-mail:
| | - A. Petzold
- Department of Ophthalmology, Neuro-ophthalmology Expertise Center, Amsterdam UMC - VUmc, Amsterdam, The Netherlands
- Department of Neurology, MS Center and Neuro-ophthalmology Expertise Center, Neuroscience Amsterdam, Amsterdam UMC - VUmc, Amsterdam, The Netherlands
- Moorfields Eye Hospital and The National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - L. J. Balk
- Department of Neurology, MS Center and Neuro-ophthalmology Expertise Center, Neuroscience Amsterdam, Amsterdam UMC - VUmc, Amsterdam, The Netherlands
| | - H. S. Tan
- Department of Ophthalmology, Neuro-ophthalmology Expertise Center, Amsterdam UMC - VUmc, Amsterdam, The Netherlands
| | - B. M. J. Uitdehaag
- Department of Neurology, MS Center and Neuro-ophthalmology Expertise Center, Neuroscience Amsterdam, Amsterdam UMC - VUmc, Amsterdam, The Netherlands
| | - M. Theodorou
- Moorfields Eye Hospital and The National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - L. J. van Rijn
- Department of Ophthalmology, Neuro-ophthalmology Expertise Center, Amsterdam UMC - VUmc, Amsterdam, The Netherlands
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Avramidis E, Akman OE. Optimisation of an exemplar oculomotor model using multi-objective genetic algorithms executed on a GPU-CPU combination. BMC SYSTEMS BIOLOGY 2017; 11:40. [PMID: 28340582 PMCID: PMC5364688 DOI: 10.1186/s12918-017-0416-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 03/02/2017] [Indexed: 11/10/2022]
Abstract
BACKGROUND Parameter optimisation is a critical step in the construction of computational biology models. In eye movement research, computational models are increasingly important to understanding the mechanistic basis of normal and abnormal behaviour. In this study, we considered an existing neurobiological model of fast eye movements (saccades), capable of generating realistic simulations of: (i) normal horizontal saccades; and (ii) infantile nystagmus - pathological ocular oscillations that can be subdivided into different waveform classes. By developing appropriate fitness functions, we optimised the model to existing experimental saccade and nystagmus data, using a well-established multi-objective genetic algorithm. This algorithm required the model to be numerically integrated for very large numbers of parameter combinations. To address this computational bottleneck, we implemented a master-slave parallelisation, in which the model integrations were distributed across the compute units of a GPU, under the control of a CPU. RESULTS While previous nystagmus fitting has been based on reproducing qualitative waveform characteristics, our optimisation protocol enabled us to perform the first direct fits of a model to experimental recordings. The fits to normal eye movements showed that although saccades of different amplitudes can be accurately simulated by individual parameter sets, a single set capable of fitting all amplitudes simultaneously cannot be determined. The fits to nystagmus oscillations systematically identified the parameter regimes in which the model can reproduce a number of canonical nystagmus waveforms to a high accuracy, whilst also identifying some waveforms that the model cannot simulate. Using a GPU to perform the model integrations yielded a speedup of around 20 compared to a high-end CPU. CONCLUSIONS The results of both optimisation problems enabled us to quantify the predictive capacity of the model, suggesting specific modifications that could expand its repertoire of simulated behaviours. In addition, the optimal parameter distributions we obtained were consistent with previous computational studies that had proposed the saccadic braking signal to be the origin of the instability preceding the development of infantile nystagmus oscillations. Finally, the master-slave parallelisation method we developed to accelerate the optimisation process can be readily adapted to fit other highly parametrised computational biology models to experimental data.
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Affiliation(s)
- Eleftherios Avramidis
- Centre for Systems, Dynamics and Control, College of Engineering, Mathematics and Physical Sciences, University of Exeter, North Park Road, Exeter, EX4 4QF, UK.,Department of Electronic Engineering, National University of Ireland, Maynooth, Ireland
| | - Ozgur E Akman
- Centre for Systems, Dynamics and Control, College of Engineering, Mathematics and Physical Sciences, University of Exeter, North Park Road, Exeter, EX4 4QF, UK.
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