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Ghasia F, Tychsen L. Inter-Ocular Fixation Instability of Amblyopia: Relationship to Visual Acuity, Strabismus, Nystagmus, Stereopsis, Vergence, and Age. Am J Ophthalmol 2024; 267:230-248. [PMID: 38944136 DOI: 10.1016/j.ajo.2024.06.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 03/21/2024] [Accepted: 06/14/2024] [Indexed: 07/01/2024]
Abstract
PURPOSE Amblyopia damages visual sensory and ocular motor functions. One manifestation of the damage is abnormal fixational eye movements. Tiny fixation movements are normal; however, when these exceed a normal range, the behavior is labeled "fixation instability" (FI). Here we compare FI between normal and amblyopic subjects, and evaluate the relationship between FI and severity of amblyopia, strabismus angle, nystagmus, stereopsis, vergence, and subject age. METHODS Fixation eye movements were recorded using infrared video-oculography from 47 controls (15.3 ± 12.2 years of age) and 104 amblyopic subjects (13.3 ± 11.2 years of age) during binocular and monocular viewing. FI and vergence instability were quantified as the bivariate contour ellipse area (BCEA). We also calculated the ratio of FI between the 2 eyes: right eye/left eye for controls, amblyopic eye/fellow eye for amblyopes. Multiple regression analysis evaluated how FI related to a range of visuo-motor measures. RESULTS During binocular viewing, the FI of fellow and amblyopic eye, vergence instability, and inter-ocular FI ratios were least in anisometropic and most in mixed amblyopia (P < .05). Each correlated positively with the strabismus angle (P < .01). During monocular viewing, subjects with deeper amblyopia (P < .01) and larger strabismus angles (P < .05) had higher inter-ocular FI ratios. In all, 27% of anisometropic and >65% of strabismic/mixed amblyopes had nystagmus. Younger age and nystagmus increased FI and vergence instability (P < .05) but did not affect the inter-ocular FI ratios (P > .05). CONCLUSIONS Quantitative recording of perturbed eye movements in children reveal a major functional deficit linked to amblyopia. Imprecise fixation, measured as inter-ocular FI ratios, may be used as a robust marker for amblyopia and strabismus severity. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.
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Affiliation(s)
- Fatema Ghasia
- From the Neurosciences and Ocular Motility Laboratory (F.G.), Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA.
| | - Lawrence Tychsen
- Department of Ophthalmology and Visual Sciences (L.T.), St Louis Children's Hospital at Washington University School of Medicine, St. Louis, Missouri, USA
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Cakir GB, Murray J, Dulaney C, Ghasia F. Multifaceted Interactions of Stereoacuity, Inter-Ocular Suppression, and Fixation Eye Movement Abnormalities in Amblyopia and Strabismus. Invest Ophthalmol Vis Sci 2024; 65:19. [PMID: 38470326 PMCID: PMC10941996 DOI: 10.1167/iovs.65.3.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 02/19/2024] [Indexed: 03/13/2024] Open
Abstract
Purpose Amblyopic and strabismus subjects experience inter-ocular suppression, impaired stereoacuity, and increased fixation instability. The purpose of the study was to investigate factors affecting suppression and stereoacuity and examine their relationship to fixation eye movement (FEM) abnormalities. Methods We recruited 14 controls and 46 amblyopic subjects (anisometropic = 18, strabismic = 14, and mixed = 14) and 11 subjects with strabismus without amblyopia. We utilized the dichoptic motion coherence test to quantify suppression, and stereoacuity was assessed using the Titmus Fly test. We recorded FEMs using high-resolution video-oculography and classified subjects that did not have nystagmus (n = 27) versus those with nystagmus (n = 32; fusion maldevelopment nystagmus [FMN], n = 10) and nystagmus that did not meet the criteria of FMN (n = 20). We also recorded FEMs under dichoptic viewing (DcV) at varied fellow eye (FE) contrasts and computed the amplitude and velocity of the fast and slow FEMs and vergence instability. Results Inter-ocular suppression and stereoacuity deficits were closely correlated with an amblyopic eye (AE), visual acuity, and strabismus angle. Subjects with nystagmus displayed more pronounced stereoacuity deficits than those without nystagmus. Strabismic subjects with and without amblyopia, who demonstrated a fixation switch at 100% FE contrast, had lower inter-ocular suppression than subjects lacking a fixation switch under DcV. Amplitude of fast FEMs and velocity of slow FEMs, and vergence instability were increased as the FE contrast was lowered in both amblyopic and strabismic subjects. Conclusions The current study highlights the intricate relationships between AE visual acuity, eye deviation, and FEM abnormalities on suppression and stereoacuity deficits and underscores the need to evaluate FEM abnormalities while assessing dichoptic treatment outcomes.
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Affiliation(s)
- Gokce Busra Cakir
- Ocular Motility & Vision Neurosciences Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Jordan Murray
- Ocular Motility & Vision Neurosciences Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Cody Dulaney
- Ocular Motility & Vision Neurosciences Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Fatema Ghasia
- Ocular Motility & Vision Neurosciences Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
- Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
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Lotze A, Love K, Velisar A, Shanidze NM. A low-cost robotic oculomotor simulator for assessing eye tracking accuracy in health and disease. Behav Res Methods 2024; 56:80-92. [PMID: 35948762 PMCID: PMC9911554 DOI: 10.3758/s13428-022-01938-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/21/2022] [Indexed: 12/24/2022]
Abstract
Eye tracking accuracy is affected in individuals with vision and oculomotor deficits, impeding our ability to answer important scientific and clinical questions about these disorders. It is difficult to disambiguate decreases in eye movement accuracy and changes in accuracy of the eye tracking itself. We propose the EyeRobot-a low-cost, robotic oculomotor simulator capable of emulating healthy and compromised eye movements to provide ground truth assessment of eye tracker performance, and how different aspects of oculomotor deficits might affect tracking accuracy and performance. The device can operate with eccentric optical axes or large deviations between the eyes, as well as simulate oculomotor pathologies, such as large fixational instabilities. We find that our design can provide accurate eye movements for both central and eccentric viewing conditions, which can be tracked by using a head-mounted eye tracker, Pupil Core. As proof of concept, we examine the effects of eccentric fixation on calibration accuracy and find that Pupil Core's existing eye tracking algorithm is robust to large fixation offsets. In addition, we demonstrate that the EyeRobot can simulate realistic eye movements like saccades and smooth pursuit that can be tracked using video-based eye tracking. These tests suggest that the EyeRobot, an easy to build and flexible tool, can aid with eye tracking validation and future algorithm development in healthy and compromised vision.
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Affiliation(s)
- Al Lotze
- Smith-Kettlewell Eye Research Institute, 2318 Fillmore Street, San Francisco, CA, 94115, USA
| | | | - Anca Velisar
- Smith-Kettlewell Eye Research Institute, 2318 Fillmore Street, San Francisco, CA, 94115, USA
| | - Natela M Shanidze
- Smith-Kettlewell Eye Research Institute, 2318 Fillmore Street, San Francisco, CA, 94115, USA.
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Cantó-Cerdán M, Martínez-Abad A, Siverio-Colomina A, Díez R, Amesty MA. Comparative Analysis of Strabismus Measurement Using a Video Oculagraphy System and Alternate Prism Cover Test. Asia Pac J Ophthalmol (Phila) 2023; 12:582-590. [PMID: 37974329 DOI: 10.1097/apo.0000000000000641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 08/23/2023] [Indexed: 11/19/2023] Open
Abstract
PURPOSE The aim of the study was to compare distance vision measurements obtained with video oculography (VOG) and an alternate prism cover test (APCT). DESIGN Single-center, retrospective, and cross-sectional. METHODS Eighty-seven subjects with strabismus were included. All patients underwent an optometric examination. The measurement of strabismus in distance vision was performed with the best optical correction using the APCT and the VOG GazeLab. Subjects were divided according to the type of strabismus; 41 were esotropic and 46 were exotropic. RESULTS The general comparison of APCT and VOG showed a mean difference of 0.60±2.74 prism diopters (Δ), not observing statistical differences between both methods ( P =0.059) and presenting a correlation of 0.976 ( P <0.001). Using APCT, the mean amount of esotropia for the group was 18.31±11.64 Δ and that of exotropia was 19.62±8.80 Δ. Compared with the VOG, the mean value of esotropia for the group was 18.65±11.65 Δ and that of exotropia was 19.48±8.62 Δ. The means are statistically different for the esotropia group ( P =0.005) but not for the exotropia group ( P =0.318). There was a high direct correlation between the methods of measurement for both the esotropic ( R =0.980; P <0.001) and exotropic patients ( R =0.975; P <0.001). Bland-Altman analysis shows a mean difference of 1.37±2.76 Δ for the esotropia patients and 0.31±2.66 Δ for the exotropic patients, respectively. CONCLUSIONS This study demonstrated comparable results in measuring strabismus between VOG and APTC for esotropia and exotropia, with an excellent correlation between both methods and good agreement, especially in subjects with exotropia.
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Huang Y, Liu Z, Wang M, Gao L, Wu Y, Hu J, Zhang Z, Yan FF, Deng D, Huang CB, Yu M. Cortical Reorganization After Optical Alignment in Strabismic Patients Outside of Critical Period. Invest Ophthalmol Vis Sci 2023; 64:5. [PMID: 37535007 PMCID: PMC10408769 DOI: 10.1167/iovs.64.11.5] [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: 03/22/2023] [Accepted: 07/17/2023] [Indexed: 08/04/2023] Open
Abstract
PURPOSE To measure visual crowding, an essential bottleneck on object recognition and reliable psychophysical index of cortex organization, in older children and adults with horizontal concomitant strabismus before and after strabismus surgery. METHODS Using real-time eye tracking to ensure gaze-contingent display, we examined the peripheral visual crowding effects in older children and adults with horizontal concomitant strabismus but without amblyopia before and after strabismus surgery. Patients were asked to discriminate the orientation of the central tumbling E target letter with flankers arranged along the radial or tangential axis in the nasal or temporal hemifield at different eccentricities (5° or 10°). The critical spacing value, which is the minimum space between the target and the flankers required for correct discrimination, was obtained for comparisons before and after strabismus surgery. RESULTS Twelve individuals with exotropia (6 males, 21.75 ± 7.29 years, mean ± SD) and 15 individuals with esotropia (6 males, 24.13 ± 5.96 years) participated in this study. We found that strabismic individuals showed significantly larger critical spacing with nasotemporal asymmetry along the radial axis that related to the strabismus pattern, with exotropes exhibiting stronger temporal field crowding and esotropes exhibiting stronger nasal field crowding before surgical alignment. After surgery, the critical spacing was reduced and rebalanced between the nasal and temporal hemifields. Furthermore, the postoperative recovery of stereopsis was associated with the extent of nasotemporal balance of critical spacing. CONCLUSIONS We find that optical realignment (i.e., strabismus surgery) can normalize the enlarged visual crowding effects, a reliable psychophysical index of cortical organization, in the peripheral visual field of older children and adults with strabismus and rebalance the nasotemporal asymmetry of crowding, promoting the recovery of postoperative stereopsis. Our results indicated a potential of experience-dependent cortical organization after axial alignment even for individuals who are out of the critical period of visual development, illuminating the capacity and limitations of optics on sensory plasticity and emphasizing the importance of ocular correction for clinical practice.
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Affiliation(s)
- Yiru Huang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong, China
| | - Zitian Liu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong, China
| | - Mingqin Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong, China
| | - Le Gao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong, China
| | - Yanyan Wu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong, China
| | - Jingyi Hu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong, China
| | - Zhenyu Zhang
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences (CAS), Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Fang-Fang Yan
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences (CAS), Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Daming Deng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong, China
| | - Chang-Bing Huang
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences (CAS), Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Minbin Yu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong, China
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Summers AI, Morrison DG, Chandler DL, Henderson RJ, Chen AM, Leske DA, Walker KR, Li Z, Melia BM, Bitner DP, Kurup SP, Allen M, Phillips PH, Nash DL, Grigorian AP, Kraus CL, Miller AM, Titelbaum JR, Kraker RT, Holmes JM, Cotter SA. A Pilot Randomized Clinical Trial of Base-in Relieving Prism Spectacle Treatment of Intermittent Exotropia. Optom Vis Sci 2023; 100:432-443. [PMID: 37399233 PMCID: PMC10534203 DOI: 10.1097/opx.0000000000002039] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2023] Open
Abstract
SIGNIFICANCE This pilot randomized trial, the first to evaluate a specific base-in relieving prism treatment strategy for childhood intermittent exotropia, did not support proceeding to a full-scale clinical trial. Defining and measuring prism adaptation in children with intermittent exotropia are challenging and need further study. PURPOSE This study aimed to determine whether to proceed to a full-scale trial of relieving base-in prism spectacles versus refractive correction alone for children with intermittent exotropia. METHODS Children 3 years old to those younger than 13 years with distance intermittent exotropia control score of ≥2 points on the Intermittent Exotropia Office Control Scale (Strabismus 2006;14:147-150; 0 [phoria] to 5 [constant]), ≥1 episode of spontaneous exotropia, and 16 to 35∆ by prism-and-alternate-cover test, who did not fully prism adapt on a 30-minute in-office prism-adaptation test were randomized to base-in relieving prism (40% of the larger of distance and near exodeviations) or nonprism spectacles for 8 weeks. A priori criteria to conduct a full-scale trial were defined for the adjusted treatment group difference in mean distance control: "proceed" (≥0.75 points favoring prism), "uncertain" (>0 to <0.75 points favoring prism), or "do not proceed" (≥0 points favoring nonprism). RESULTS Fifty-seven children (mean age, 6.6 ± 2.2 years; mean baseline distance control, 3.5 points) received prism (n = 28) or nonprism (n = 29) spectacles. At 8 weeks, mean control values were 3.6 and 3.3 points in prism (n = 25) and nonprism (n = 25) groups, respectively, with an adjusted difference of 0.3 points (95% confidence interval, -0.5 to 1.1 points) favoring nonprism (meeting our a priori "do not proceed" criterion). CONCLUSIONS Base-in prism spectacles, equal to 40% of the larger of the exodeviations at distance or near, worn for 8 weeks by 3- to 12-year-old children with intermittent exotropia did not yield better distance control than refractive correction alone, with the confidence interval indicating that a favorable effect of 0.75 points or larger is unlikely. There was insufficient evidence to warrant a full-scale randomized trial.
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Affiliation(s)
| | | | | | | | - Angela M Chen
- Southern California College of Optometry at Marshall B. Ketchum University, Fullerton, California
| | | | | | - Zhuokai Li
- Jaeb Center for Health Research, Tampa, Florida
| | | | | | - Sudhi P Kurup
- Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
| | - Megan Allen
- Illinois College of Optometry, Chicago, Illinois
| | | | | | | | | | | | | | | | - Jonathan M Holmes
- University of Arizona-Tucson, Tucson, Arizona for the PEDIG Study Group
| | - Susan A Cotter
- Southern California College of Optometry at Marshall B. Ketchum University, Fullerton, California
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Ma MML, Scheiman M. Divergence excess and basic exotropia types of intermittent exotropia: a major review. Part 1: prevalence, classification, risk factors, natural history and clinical characteristics. Strabismus 2023; 31:97-128. [PMID: 37489263 DOI: 10.1080/09273972.2023.2227681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
INTRODUCTION Intermittent exotropia (IXT) is a common form of strabismus. It is an outward deviation of one eye typically when viewing at distance. Symptoms include, but are not limited to double vision, eyes feeling tired, excessive blinking, and reduced quality of life. Its clinical characteristics are distinctive from other types of strabismus. This paper provides a comprehensive review of prevalence, classification, risk factors, natural history and clinical characteristics of the divergence excess and basic exotropia types of IXT. METHODS Search strategies involving combination of keywords including intermittent exotropia, exotropia, divergences excess, basic exotropia, prevalence, incidence, classification, terminology, risk factor, natural history, observation, angle of deviation, control, control score, symptom, quality of life, suppression, anomalous retinal correspondence, AC/A, accommodative convergence/accommodation, accommodative convergence, convergence, accommodation, vergence, incomitance and vertical were used in Medline. All English articles from 1900/01/01 to 2020/09/01 were reviewed. The reference list of the identified article was also checked for additional relevant article. Studies focused on animal model or strabismus associated with neurologic disorder or injury were excluded. RESULTS The estimated prevalence of IXT in children ranges from 0.1% to 3.7%. Hypoxia at birth and being female are potential risk factors of IXT. Using validated measures of control, multicenter prospective studies showed that the rate of conversion from IXT to constant exotropia is low. The angle of deviation is the most reported outcome measure in studies of IXT. It is often used to represent the severity of the condition and has been suggested as one of the four core outcomes for studies of the surgical management of IXT. Control of exodeviation is one of the four suggested core outcomes for study of surgery of IXT and is considered the main parameter of disease severity. Several validated tools for quality of life score are available to evaluate the subjective severity of IXT. DISCUSSION We reviewed the prevalence, classification, risk factors, natural history and clinical characteristics of the divergence excess and basic exotropia types of IXT. Further research into these areas, especially its clinical characteristics (e.g. suppression, dual retinal correspondence), will increase our understanding of this condition and potentially lead to better management of this common form of strabismus.
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Affiliation(s)
- Martin Ming-Leung Ma
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou
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Economides JR, Dilbeck MD, Gentry TN, Horton JC. Ambulatory Monitoring With Eye Tracking Glasses to Assess the Severity of Intermittent Exotropia. Am J Ophthalmol 2023; 250:120-129. [PMID: 36681174 PMCID: PMC10266486 DOI: 10.1016/j.ajo.2023.01.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/11/2023] [Accepted: 01/12/2023] [Indexed: 01/19/2023]
Abstract
PURPOSE To explore the utility of eye tracking glasses in patients with intermittent exotropia as a means for quantifying the occurrence of exotropia, defined as the percentage of time that the eyes are misaligned. DESIGN Prospective observational study. METHODS Eye tracking glasses were used to obtain 68 recordings in 44 ambulatory patients with a history of intermittent exotropia. Vergence angle was monitored for up to 12 hours to document the occurrence of exotropia. RESULTS Intermittent exotropia was present in 31 of 44 patients. They had a mean exotropia of 19.3 ± 5.3° and a mean occurrence of 40% (range 3-99%). There was a moderate correlation between the magnitude of exotropia and its occurrence (r = 0.59). In 13 patients the occurrence of exotropia was <1%; they were deemed to have an exophoria only. In 35 of 44 cases, families reported an occurrence of intermittent exotropia greater than that measured by the eye tracking glasses. CONCLUSIONS Eye tracking glasses may be a useful tool for quantifying the severity of intermittent exotropia and for defining more precisely its clinical features.
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Affiliation(s)
- John R Economides
- From the Department of Ophthalmology, University of California, San Francisco, San Francisco, California, USA
| | - Mikayla D Dilbeck
- From the Department of Ophthalmology, University of California, San Francisco, San Francisco, California, USA
| | - Thomas N Gentry
- From the Department of Ophthalmology, University of California, San Francisco, San Francisco, California, USA
| | - Jonathan C Horton
- From the Department of Ophthalmology, University of California, San Francisco, San Francisco, California, USA..
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Ghasia F, Wang J. Amblyopia and fixation eye movements. J Neurol Sci 2022; 441:120373. [PMID: 36007287 DOI: 10.1016/j.jns.2022.120373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 07/05/2022] [Accepted: 07/31/2022] [Indexed: 11/29/2022]
Abstract
Amblyopia is a neurodevelopmental disorder caused by abnormal visual experience in early life that affects 3-5% of the population. Amblyopia results in a host of monocular and binocular visual afferent function deficits including reduced visual acuity, contrast sensitivity, depth perception, interocular suppression, and efferent function abnormalities such as unstable and inaccurate fixation. Conventional treatments such as patching therapy and newer dichoptic treatments are not always successful as 30-40% of patients experience recurrence/regression of amblyopia. There are numerous review articles focused on visual afferent function deficits and treatment modalities and outcomes in amblyopia. Recently, the advent of high spatial and temporal resolution eye trackers has spurred studies on fixation eye movements (FEMs) in healthy controls and neurologic and ophthalmic disorders. In this focused review, we will summarize studies evaluating FEM abnormalities in amblyopia. We will first describe the common devices and techniques used to quantify fixation abnormalities, and then highlight the importance of systematically evaluating the eye movements under different viewing conditions and describe the parameters crucial in assessing FEM abnormalities in amblyopia. We will summarize the evidence suggesting that FEM abnormalities are not limited to the amblyopic eye only but also affects the fellow eye and that FEM abnormalities can serve as biomarkers to predict the impact of amblyopia on visual functions. Beyond diagnosis, we will discuss the treatment and prognostic implications of the evaluation of FEM abnormalities in clinical practice.
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Affiliation(s)
- Fatema Ghasia
- Cleveland Clinic, Cleveland, OH, United States of America.
| | - Jingyun Wang
- SUNY College of Optometry, NY, New York, United States of America
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Irsch K, Guyton DL, Geary RB, Tian J, Gramatikov BI, Ying HS. Disconjugacy of Eye Movements during Attempted Fixation: A Sufficient Marker for Amblyopia? Klin Monbl Augenheilkd 2022; 239:1206-1212. [DOI: 10.1055/a-1933-3150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Abstract
Background To investigate whether detection of disconjugacy of eye movements during attempted fixation, or interocular position instability, may serve as a single sensitive test for
amblyopia.
Patients/Methods and Material Binocular eye movements were recorded at 500 Hz using the EyeLink 1000 eye tracker (SR Research Ltd., Kanata, Ontario, Canada) and analyzed using
EyeLink software and Matlab (MathWorks, Natick, MA, USA). Eight subjects (four amblyopes, one successfully treated amblyope, and three non-amblyopes: 7 – 44 years) were asked to fixate on a
stationary cross subtending 0.5° at 57 cm. Interocular position instability was quantified by calculating the minimum area bivariate contour ellipse (BCEA) encompassing 68% of the difference
between right and left eye position points during 20-second viewing epochs. For statistical analysis, BCEA values, as well as visual acuity and stereoacuity, were normalized by base-10
logarithm transformation.
Results The amblyopic subjects with persistent vision loss (one anisometropic, two strabismic, one deprivation; uncorrected visual acuity range 20/60 – 20/300, corrected stereoacuity
range nil-400 arcsec) showed significantly higher interocular position instability (larger 68% BCEAs) than the non-amblyopic subjects (uncorrected visual acuity range 20/20 – 20/800,
corrected stereoacuities of 20 arcsec) and the successfully treated strabismic amblyope (to the 20/20 level of visual acuity and 70 arcsec of stereoacuity) during binocular viewing trials;
p < 0.01. Interocular position stability was strongly correlated with stereoacuity (in that better stereoacuity was associated with lower 68% BCEAs; r = 0.95), but not with visual acuity
(r = 0.20).
Conclusion Interocular position instability appears to differentiate amblyopic from non-amblyopic subjects and appears to improve after successful treatment. Interocular position
instability may therefore prove to be a single sensitive test for the presence of amblyopia. As a difference measure, it is inherently less susceptible to head motion and calibration error,
as well as to conjugate eye motion, and as such is expected to be somewhat immune to latent nystagmus. Interocular position instability may also be useful to guide treatment, especially in
preverbal children, and to assess the efficacy of novel treatments. Further research is required to establish optimal interocular position instability thresholds and to determine how
specific this measure is to amblyopia.
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Affiliation(s)
- Kristina Irsch
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Vision Institute – CNRS, INSERM, Sorbonne University, Paris, France
| | - David L. Guyton
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Robert B. Geary
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
| | - Jing Tian
- School of Medicine, University of Maryland Baltimore, Baltimore, Maryland, United States
| | - Boris I. Gramatikov
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
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Chaturvedi I, Sharma P. Commentary: Automated strabismus measurement - Orthoptics with an edge! Indian J Ophthalmol 2022; 70:3628-3629. [PMID: 36190060 PMCID: PMC9789810 DOI: 10.4103/ijo.ijo_1501_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Isha Chaturvedi
- Comprehensive Services, Centre for Sight Eye Institute, Dwarka, New Delhi, India
| | - Pradeep Sharma
- Strabismus Pediatric and Neuro-Ophthalmology Services, Centre for Sight, Safdarjung Enclave, New Delhi, India,Correspondence to: Dr. Pradeep Sharma, Director Strabismus Pediatric and Neuro-Ophthalmology Services, Centre for Sight, Safdarjung Enclave, New Delhi, India. E-mail:
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Milla-Barrios M, Piñero DP, Molina-Martín A. Fixation Pattern Analysis With Microperimetry In Strabismic Subjects: A Pilot Study. Semin Ophthalmol 2022; 37:699-706. [PMID: 35666653 DOI: 10.1080/08820538.2022.2085513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVE Strabismic amblyopia is a motor and sensory deficit produced by unilateral constant strabismus and binocular imbalance. The aim of this study was to analyse the retinal fixation pattern using microperimetry in subjects with strabismus with and without amblyopia associated, and to compare the results with those obtained in normal subjects. METHODS Prospective comparative study conducted at the Optometric Clinic of the University of Valencia and Oftalvist Alicante (Spain) including 46 eyes with ages from 3 to 16 years. Three groups were differentiated: patients with persistent strabismic amblyopia after occlusion and active therapy (group 1, 7 patients, 30.4%), strabismic patients without amblyopia (group 2, 8 patients, 34.8%) and a control group (8 patients, 34.8%). Microperimetric analysis was performed with the Macular Integrity Assessment (MAIA) system (Centervue, Padova, Italy) and using the following parameters: P1% and P2% fixation indexes, and the ellipse areas (BCEA) for 95% and 63% of points for the first 10 seconds, 30 seconds, 60 seconds, and the total examination time. RESULTS Significant differences were found between groups for dominant eyes in P2 calculated at 30 (p = .04) and 60 seconds (p = .03). However, these differences between groups in non-dominant eyes were close to statistical significance (p = .07 and p = .08). Specifically, P2 was significantly lower in group 1 compared to control group (p = .01). Best corrected visual acuity was found to be significantly correlated (p ≤ .04) with total P1 (dominant eye, r = -0.51; non-dominant eye, r = -0.50), total P2 (dominant eye, r = -0.50; non-dominant eye, r = -0.50), and BCEA63 (dominant eye, r = 0.50; non-dominant eye, r = 0.40) and BCEA95 (dominant eye, r = 0.50; non-dominant eye, r = 0.40) measured at 10 seconds. CONCLUSIONS The preliminary results of this study seem to indicate that subjects with strabismus have fixation instability regardless of the presence or absence of amblyopia.
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Affiliation(s)
| | - David P Piñero
- Group of Optics and Visual Perception, Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain.,Advanced Clinic Optometry Unit, Department of Ophthalmology, Vithas Medimar International Hospital, Alicante, Spain
| | - Ainhoa Molina-Martín
- Group of Optics and Visual Perception, Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
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Kim SY, Moon BY, Cho HG, Yu DS. Quantitative Evaluation of the Association Between Fixation Stability and Phoria During Short-Term Binocular Viewing. Front Neurosci 2022; 16:721665. [PMID: 35368249 PMCID: PMC8965591 DOI: 10.3389/fnins.2022.721665] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 02/11/2022] [Indexed: 11/29/2022] Open
Abstract
Purpose Fixation stability for binocular anomalies with a phoria cannot be detected by direct observations. This study aimed to quantitatively evaluate fixation stability using an eye tracker rather than direct directions in binocular vision with abnormal and normal phorias. Methods Thirty-five and 25 participants with abnormal and normal phoria, respectively, were included in the study. The horizontal and vertical gaze points and convergence were recorded for 10 s using a remote eye tracker while binocularly viewing a target on a display screen 550 mm away. Fixation stability was quantified using bivariate contour ellipse areas (BCEA). Results The fixation stability for all participants-based evaluations as a single cluster in the abnormal phoria group was lower than that in the normal phoria group (p = 0.005). There was no difference between the two groups in the evaluation based on the BCEA for each participant-based evaluation (p = 0.66). Fixation stability was also more related to convergence for the abnormal phoria group than for the normal phoria group (r = 0.769, p < 0.001; r = 0.417, p = 0.038, respectively). Conclusion As the first study to evaluate fixation stability using an eye-tracker to differentiate between abnormal and normal phoria for non-strabismus, these findings may provide evidence for improving the evaluation of binocular vision not detected with clinical diagnostic tests.
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Murray J, Gupta P, Dulaney C, Garg K, Shaikh AG, Ghasia FF. Effect of Viewing Conditions on Fixation Eye Movements and Eye Alignment in Amblyopia. Invest Ophthalmol Vis Sci 2022; 63:33. [PMID: 35212720 PMCID: PMC8883146 DOI: 10.1167/iovs.63.2.33] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Accepted: 02/01/2022] [Indexed: 11/24/2022] Open
Abstract
Purpose Patients with amblyopia are known to have fixation instability, which arises from alteration of physiologic fixation eye movements (FEMs) and nystagmus. We assessed the effects of monocular, binocular, and dichoptic viewing on FEMs and eye alignment in patients with and without fusion maldevelopment nystagmus (FMN). Methods Thirty-four patients with amblyopia and seven healthy controls were recruited for this study. Eye movements were recorded using infrared video-oculography during (1) fellow eye viewing (FEV), (2) amblyopic eye viewing (AEV), (3) both eye viewing (BEV), and (4) dichoptic viewing (DcV) at varying fellow eye (FE) contrasts. The patients were classified per the clinical type of amblyopia and FEM waveforms into those without nystagmus, those with nystagmus with and without FMN. Fixational saccades and intersaccadic drifts, quick and slow phases of nystagmus, and bivariate contour ellipse area were analyzed in the FE and amblyopic eye (AE). Results We found that FEMs are differentially affected with increased amplitude of quick phases of FMN observed during AEV than BEV and during DcV at lower FE contrasts. Increased fixation instability was seen in anisometropic patients at lower FE contrasts. Incomitance of eye misalignment was seen with the greatest increase during FEV. Strabismic/mixed amblyopia patients without FMN were more likely to demonstrate a fixation switch where the AE attends to the target during DcV than patients with FMN. Conclusions Our findings suggest that FEM abnormalities modulate with different viewing conditions as used in various amblyopia therapies. Increased FEM abnormalities could affect the visual function deficits and may have treatment implications.
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Affiliation(s)
- Jordan Murray
- Visual Neurosciences and Ocular Motility Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Palak Gupta
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States
- Daroff-Dell'Osso Ocular Motility Laboratory, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, United States
| | - Cody Dulaney
- Visual Neurosciences and Ocular Motility Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Kiran Garg
- Case Western Reserve University, Cleveland, Ohio, United States
| | - Aasef G Shaikh
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States
- Daroff-Dell'Osso Ocular Motility Laboratory, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, United States
- Department of Neurology, Neurological Institute, University Hospitals, Cleveland, Ohio, United States
| | - Fatema F Ghasia
- Visual Neurosciences and Ocular Motility Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
- Daroff-Dell'Osso Ocular Motility Laboratory, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, United States
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15
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Cai X, Chen Z, Liu Y, Deng D, Yu M. A Dichoptic Optokinetic Nystagmus Paradigm for Interocular Suppression Quantification in Intermittent Exotropia. Front Neurosci 2021; 15:772341. [PMID: 34924941 PMCID: PMC8678071 DOI: 10.3389/fnins.2021.772341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 11/04/2021] [Indexed: 11/13/2022] Open
Abstract
Purposes: To investigate the effectiveness of a dichoptic optokinetic nystagmus (dOKN) test to objectively quantify interocular suppression in intermittent exotropia (IXT) patients during the states of orthotropia and exodeviation. Methods: The OKN motion in subjects (15 controls and 59 IXT subjects) who viewed dichoptic oppositely moving gratings with different contrast ratios was monitored and recorded by an eye tracker. Interocular suppression in control subjects was induced using neutral density (ND) filters. The OKN direction ratios were fitted to examine the changes of interocular suppression in subjects under different viewing states. Two established interocular suppression tests (phase and motion) were conducted for a comparative study. Results: The dOKN test, which requires a minimal response from subjects, could accurately quantify the interocular suppression in both IXT and control subjects, which is in line with the established interocular suppression tests. Overall, although comparative, the strength of interocular suppression detected by the dOKN test (0.171 ± 0.088) was stronger than those of the phase (0.293 ± 0.081) and the motion tests (0.212 ± 0.068) in the control subjects with 1.5 ND filters. In IXT patients, when their eyes kept aligned, the dOKN test (0.58 ± 0.09) measured deeper visual suppression compared with the phase (0.73 ± 0.17) or the motion test (0.65 ± 0.14). Interestingly, strong interocular suppression (dOKN: 0.15 ± 0.12) was observed in IXT subjects during the periods of exodeviation, irrespective of their binocular visual function as measured by synoptophore. Conclusion: The dOKN test provides efficient and objective quantification of interocular suppression in IXT, and demonstrates how it fluctuates under different eye positions.
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Affiliation(s)
- Xiaoxiao Cai
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Zidong Chen
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Yanping Liu
- Guangdong Provincial Key Laboratory of Social Cognitive Neuroscience and Mental Health, Department of Psychology, Sun Yat-sen University, Guangzhou, China
| | - Daming Deng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Minbin Yu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
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Candy TR, Cormack LK. Recent understanding of binocular vision in the natural environment with clinical implications. Prog Retin Eye Res 2021; 88:101014. [PMID: 34624515 PMCID: PMC8983798 DOI: 10.1016/j.preteyeres.2021.101014] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 09/26/2021] [Accepted: 09/29/2021] [Indexed: 10/20/2022]
Abstract
Technological advances in recent decades have allowed us to measure both the information available to the visual system in the natural environment and the rich array of behaviors that the visual system supports. This review highlights the tasks undertaken by the binocular visual system in particular and how, for much of human activity, these tasks differ from those considered when an observer fixates a static target on the midline. The everyday motor and perceptual challenges involved in generating a stable, useful binocular percept of the environment are discussed, together with how these challenges are but minimally addressed by much of current clinical interpretation of binocular function. The implications for new technology, such as virtual reality, are also highlighted in terms of clinical and basic research application.
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Affiliation(s)
- T Rowan Candy
- School of Optometry, Programs in Vision Science, Neuroscience and Cognitive Science, Indiana University, 800 East Atwater Avenue, Bloomington, IN, 47405, USA.
| | - Lawrence K Cormack
- Department of Psychology, Institute for Neuroscience, and Center for Perceptual Systems, The University of Texas at Austin, Austin, TX, 78712, USA.
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17
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Huang X, Lee SJ, Kim CZ, Choi SH. An automatic screening method for strabismus detection based on image processing. PLoS One 2021; 16:e0255643. [PMID: 34343204 PMCID: PMC8330949 DOI: 10.1371/journal.pone.0255643] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 07/20/2021] [Indexed: 11/18/2022] Open
Abstract
Purpose This study aims to provide an automatic strabismus screening method for people who live in remote areas with poor medical accessibility. Materials and methods The proposed method first utilizes a pretrained convolutional neural network-based face-detection model and a detector for 68 facial landmarks to extract the eye region for a frontal facial image. Second, Otsu’s binarization and the HSV color model are applied to the image to eliminate the influence of eyelashes and canthi. Then, the method samples all of the pixel points on the limbus and applies the least square method to obtain the coordinate of the pupil center. Lastly, we calculated the distances from the pupil center to the medial and lateral canthus to measure the deviation of the positional similarity of two eyes for strabismus screening. Result We used a total of 60 frontal facial images (30 strabismus images, 30 normal images) to validate the proposed method. The average value of the iris positional similarity of normal images was smaller than one of the strabismus images via the method (p-value<0.001). The sample mean and sample standard deviation of the positional similarity of the normal and strabismus images were 1.073 ± 0.014 and 0.039, as well as 1.924 ± 0.169 and 0.472, respectively. Conclusion The experimental results of 60 images show that the proposed method is a promising automatic strabismus screening method for people living in remote areas with poor medical accessibility.
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Affiliation(s)
- Xilang Huang
- Department of Artificial Intelligent Convergence, Pukyong National University, Busan, Korea
| | - Sang Joon Lee
- Department of Ophthalmology, Kosin University College of Medicine, Busan, Korea
| | - Chang Zoo Kim
- Department of Ophthalmology, Kosin University College of Medicine, Busan, Korea
- Kosin Innovative Smart Healthcare Research Center, Kosin University Gospel Hospital, Busan, Korea
- * E-mail: (CZK); (SHC)
| | - Seon Han Choi
- Department of Artificial Intelligent Convergence, Pukyong National University, Busan, Korea
- * E-mail: (CZK); (SHC)
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Jayakaran P, Aman W, Fernando U, Hackfath K, McPherson A, Williams M, Mitchell L. Sensory organization for postural control in children with strabismus-A systematic review and meta-analysis. Gait Posture 2021; 88:94-104. [PMID: 34015547 DOI: 10.1016/j.gaitpost.2021.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 04/29/2021] [Accepted: 05/05/2021] [Indexed: 02/02/2023]
Abstract
BACKGROUND Postural control requires the interaction of somatosensory, vestibular and visual systems to prevent disequilibrium. Children with strabismus have an impaired visual input which can lead to postural control deficits. RESEARCH QUESTION Does strabismus affect sensory organization for postural control in children? METHODS A systematic comprehensive search of multiple electronic databases for relevant articles was performed using a predetermined search strategy. Peer-reviewed journal publications that assessed sensory organization and postural performance in children with strabismus were included in this review. Methodological quality of the articles was evaluated using the modified Downs and Black quality assessment tool. A total of 10 articles were included in this review. RESULTS Eight of the 10 articles reviewed were included in the meta-analysis. Meta-analysis for Centre of Pressure CoP velocity (n = 3) (eyes open, stable support), was statistically significant (P = 0.01) in favor of controls over children with strabismus (MD, 3.08; 95 % CI -0.66, 5.51). Meta-analysis for CoP surface area (n = 5) (eyes open, stable support) was also statistically significant (P < 0.001) in favor of the control group (MD, 130.14; 95 % CI 70.01, 190.260). Meta-analysis with standardized mean difference (n = 6) for eyes open vs closed, stable support was statistically significant (P = 0.02) in favor of eyes open (MD, -0.94; 95 % CI, -1.74, -0.15). Overall, there was a high level of heterogeneity throughout the studies. SIGNIFICANCE This is the first systematic review of its kind to collate and synthesize evidence on the effect of strabismus on postural control in children. This review suggests that postural control performance in children with strabismus is inferior to that of age-matched control children. Further investigation is needed to understand the influence of the three sensory systems.
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Affiliation(s)
| | - Wali Aman
- School of Physiotherapy, University of Otago, Dunedin, New Zealand
| | - Udari Fernando
- School of Physiotherapy, University of Otago, Dunedin, New Zealand
| | - Kristen Hackfath
- School of Physiotherapy, University of Otago, Dunedin, New Zealand
| | | | - Mike Williams
- School of Physiotherapy, University of Otago, Dunedin, New Zealand
| | - Logan Mitchell
- Dunedin School of Medicine, University of Otago, Dunedin, New Zealand; Marinato Clinic (Ophthalmology), Dunedin, New Zealand
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19
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Economides JR, Adams DL, Horton JC. Interocular Suppression in Primary Visual Cortex in Strabismus. J Neurosci 2021; 41:5522-5533. [PMID: 33941649 PMCID: PMC8221600 DOI: 10.1523/jneurosci.0044-21.2021] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 04/22/2021] [Accepted: 04/27/2021] [Indexed: 11/21/2022] Open
Abstract
People with strabismus acquired during childhood do not experience diplopia (double vision). To investigate how perception of the duplicate image is suppressed, we raised two male monkeys with alternating exotropia by disinserting the medial rectus muscle in each eye at age four weeks. Once the animals were mature, they were brought to the laboratory and trained to fixate a small spot while recordings were made in primary visual cortex (V1). Drifting gratings were presented to the receptive fields of 500 single neurons for eight interleaved conditions: (1) right eye monocular; (2) left eye monocular; (3) right eye's field, right eye fixating; (4) right eye's field, left eye fixating; (5) left eye's field, right eye fixating; (6) left eye's field, left eye fixating; (7) both eyes' fields, right eye fixating; (8) both eyes' fields, left eye fixating. As expected, ocular dominance histograms showed a monocular bias compared with normal animals, but many cells could still be driven via both eyes. Overall, neuronal responses were not affected by switches in ocular fixation. Individual neurons exhibited binocular interactions, but mean population indices indicated no net interocular suppression or facilitation. Even neurons located in cortex with reduced cytochrome oxidase (CO) activity, representing portions of the nasal visual field where perception is suppressed during binocular viewing, showed no net inhibition. These data indicate that V1 neurons do not appear to reflect strabismic suppression and therefore the elimination of diplopia is likely to be mediated at a higher cortical level.SIGNIFICANCE STATEMENT In patients with strabismus, images fall on non-corresponding points in the two retinas. Only one image is perceived, because signals emanating from the other eye that convey the duplicate image are suppressed. The benefit is that diplopia is prevented, but the penalty is that the visual feedback required to adjust eye muscle tone to realign the globes is eliminated. Here, we report the first electrophysiological recordings from the primary visual cortex (V1) in awake monkeys raised with strabismus. The experiments were designed to reveal how perception of double images is avoided.
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Affiliation(s)
- John R Economides
- Program in Neuroscience, Department of Ophthalmology, University of California, San Francisco, California 94143
| | - Daniel L Adams
- Program in Neuroscience, Department of Ophthalmology, University of California, San Francisco, California 94143
| | - Jonathan C Horton
- Program in Neuroscience, Department of Ophthalmology, University of California, San Francisco, California 94143
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20
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Gantz L, Millodot M, Roth GL. Analysis of Alphabet Patterns of Deviations Found in Patients Without Strabismus in Primary Position. CLINICAL OPTOMETRY 2020; 12:49-56. [PMID: 32256138 PMCID: PMC7094002 DOI: 10.2147/opto.s197783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 02/21/2020] [Indexed: 06/11/2023]
Abstract
AIM To detect alphabet patterns in a group of patients without strabismus and to determine whether they induced any convergence insufficiency type symptoms. METHODS Data on subjective refraction, distance and near heterophoria, distance and near positive fusional vergence (BO), near point of convergence (NPC), measurements of upgaze and downgaze made 45° above and below the primary position with alternate cover test and a prism bar at a distance of 37.5 cm, were collected from participants of two clinics. Symptoms were assessed using the 15-item Convergence Insufficiency Symptoms Survey (CISS) to determine a symptom score. Association between alphabet patterns and the other variables was analyzed using parametric and non-parametric tests. RESULTS Out of 122 patients, 14 were found to present an alphabet pattern. Defining a V pattern exophoria ≥15-prism dioptre or ≥10-prism dioptre deviation, three patients (2.5%) and 12 patients (9.8%) were identified, respectively. In addition, one case resembled an X pattern and another a diamond pattern. The refraction, distance and near heterophoria, positive fusional vergence and CISS scores were not significantly different in the participants with V pattern compared to those without V pattern. CONCLUSION Alphabet patterns, especially V type, were demonstrated in approximately 11.5% of a sample of 122 non-strabismus patients. These alphabet patterns were found not to be associated with convergence insufficiency-like symptoms.
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Affiliation(s)
- Liat Gantz
- Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel
| | - Michel Millodot
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | - Gary Lewis Roth
- Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel
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Kang SL, Beylergil SB, Otero-Millan J, Shaikh AG, Ghasia FF. Fixational Eye Movement Waveforms in Amblyopia: Characteristics of Fast and Slow Eye Movements. J Eye Mov Res 2019; 12. [PMID: 33828757 PMCID: PMC7962684 DOI: 10.16910/jemr.12.6.9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Fixational eye movements comprise of fast microsaccades alternating with slow intersaccadic drifts. These physiologic eye movements play an important role in visual perception. Amblyopic patients are known to have fixation instability, particularly of the amblyopic eye. We examined eye movement abnormalities that contribute to this instability. We
found that fixation stability is affected by the presence of fusion maldevelopment nystagmus (FMN). However, some amblyopes can have nystagmus without nasally directed slow
phases and reversal in direction of the quick phase on ocular occlusion, features seen in
FMN. In patients without nystagmus, we found increased amplitude of fixational saccades
and inter-saccadic drifts. We categorized amblyopia patients by type (anisometropic,
strabismic, or mixed) and eye movement waveform (no nystagmus, nystagmus without
FMN, and FMN). We found specific fast and slow eye movement abnormalities of the
fellow and amblyopic eye during fellow, amblyopic and both eyes viewing conditions
across eye movement waveforms and types of amblyopia. These eye movement abnormalities can serve as biomarkers that can predict the impact of amblyopia as measured by
visual acuity and stereopsis. Evaluation of fixational eye movements in amblyopia could
be important to diagnose these common eye diseases and predict treatment effectiveness.
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Affiliation(s)
- Sarah L Kang
- Case Western Reserve University School of Medicine, Cleveland, USA
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Birch EE, Kelly KR, Giaschi DE. Fellow Eye Deficits in Amblyopia. J Binocul Vis Ocul Motil 2019; 69:116-125. [PMID: 31161888 PMCID: PMC6673659 DOI: 10.1080/2576117x.2019.1624440] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 05/23/2019] [Accepted: 05/23/2019] [Indexed: 10/26/2022]
Abstract
Amblyopia is a neurodevelopmental disorder of the visual system, as a result of discordant visual experience during infancy or early childhood. Because amblyopia is typically defined as monocularly reduced visual acuity accompanied by one or more known amblyogenic factors, it is often assumed that the fellow eye is normal and sufficient for tasks like reading and eye-hand coordination. Recent scientific evidence of ocular motor, visual, and visuomotor deficits that are present with fellow eye monocular viewing and with binocular viewing calls this assumption into question. This clinical update reviews the research that has revealed fellow ocular motor and visual deficits and the effect that these deficits have on an amblyopic child's visuomotor and visuocognitive skills. We need to understand how to prevent and rehabilitate the effects of amblyopia not only on the nonpreferred eye but also on the fellow eye.
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Affiliation(s)
- Eileen E Birch
- Crystal Charity Ball Pediatric Vision Laboratory, Retina Foundation of the Southwest, Dallas, TX, USA
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, 11 USA
| | - Krista R Kelly
- Crystal Charity Ball Pediatric Vision Laboratory, Retina Foundation of the Southwest, Dallas, TX, USA
| | - Deborah E Giaschi
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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Zhou L, Zhou Q, Bi H, Chen Y, Chen Z, Wu H, Huang Z, Zhang B. The Stereoacuity-Dependent Concordance between Preferred Fixating Eye and Sighting Dominant Eye in Paediatric Intermittent Exotropia. Curr Eye Res 2019; 44:948-954. [PMID: 31045457 DOI: 10.1080/02713683.2019.1606249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Objective: To investigate if the concordance between sighting dominance and fixation preference depends on stereoacuity in children with intermittent exotropia (IXT). Methods: A total of 160 children (aged 7.24 ± 2.14 years, range 4-13 years) with the basic type of IXT at distance participated in the study. Binocular fusion and vergence were evaluated with synoptophore. Stereoacuity was assessed using the Titmus stereo test. The hole-in-the-card test was used to determine sighting dominance, while the eye of fixation preference was determined by the cover-uncover test. The chi-squared test was used to evaluate whether a distribution was different from the chance distribution. The Kappa value was computed to quantify the concordance between fixation preference and sighting dominance. Results: The mean deviations were 19 ± 4.58 prism diopters (PD) and 18.9 ± 4.47 PD for at distance and near, respectively. The mean amplitude of divergence was 5.34 ± 1.89 PD, and the mean amplitude of convergence was 14.08 ± 4.96 PD. Subjects were categorized as having either good (40-60 seconds of arc, n = 41), moderate (80-140 seconds of arc, n = 46), poor (≥ 200 seconds of arc, n = 45), or having no measurable stereoacuity (n = 28). The concordance between sighting dominance and fixation preference was high in subjects with good (Kappa = 0.858) or moderate (kappa = 0.812) stereoacuity, but it decreased quickly in subjects with poor stereoacuity (kappa = 0.496) or no stereopsis (kappa = 0.563). Conclusions: In pediatric patients with IXT, the concordance between sighting dominance and fixation preference depends on stereoacuity. The results from these two tests become increasingly incongruent as stereoacuity deteriorated.
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Affiliation(s)
- Lu Zhou
- Department of Ophthalmology, Affiliated Children's Hospital of Nanjing Medical University , Nanjing , China.,Department of Ophthalmology, Jinling Clinical Medical College of Nanjing Medical University , Nanjing , China
| | - Qing Zhou
- Department of Ophthalmology, Affiliated Children's Hospital of Nanjing Medical University , Nanjing , China
| | - Hua Bi
- College of Optometry, Nova Southeastern University , Davie , FL , USA
| | - Yanxu Chen
- Department of Ophthalmology, Affiliated Children's Hospital of Nanjing Medical University , Nanjing , China
| | - Zhijun Chen
- Department of Ophthalmology, Affiliated Children's Hospital of Nanjing Medical University , Nanjing , China
| | - Haoran Wu
- Aier School of Ophthalmology, Central South University , Changsha , China
| | - Zhenping Huang
- Department of Ophthalmology, Jinling Clinical Medical College of Nanjing Medical University , Nanjing , China
| | - Bin Zhang
- College of Optometry, Nova Southeastern University , Davie , FL , USA
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Ban JH, Moon SH. The Analysis of Ocular Deviations between Dominant and Non-dominant Eye Using Video-oculography in Intermittent Exotropia. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2019. [DOI: 10.3341/jkos.2019.60.7.685] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Ji Hoon Ban
- Department of Ophthalmology, Busan Paik Hospital, Inje University College of Medicine, Busan, Korea
- T2B Infrastructure Center for Ocular Disease, Busan Paik Hospital, Inje University College of Medicine, Busan, Korea
| | - Sung Hyuk Moon
- Department of Ophthalmology, Busan Paik Hospital, Inje University College of Medicine, Busan, Korea
- T2B Infrastructure Center for Ocular Disease, Busan Paik Hospital, Inje University College of Medicine, Busan, Korea
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Peripheral sensory information and postural control in children with strabismus. Gait Posture 2018; 65:197-202. [PMID: 30558930 DOI: 10.1016/j.gaitpost.2018.07.173] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 06/14/2018] [Accepted: 07/17/2018] [Indexed: 02/02/2023]
Abstract
BACKGROUND Sensory feedback from the visual system along with the vestibular and somatosensory systems is essential for the regulation of normal postural control. Children with strabismus and, therefore, with abnormal binocular vision, may have an altered perception of space and use different sets of cues to determine depth perception when compared with children without strabismus. OBJECTIVE To explore the postural control of children with and without strabismus, when the three sensory systems are challenged. METHOD Forty-six children (21 with strabismus and 25 age-matched controls) aged between 5 and 10 years completed ophthalmic screening and then underwent assessment for postural control, which included Paediatric Balance Scale (PBS) and six conditions of the Sensory Organization Test (SOT). Four primary outcome measures were: PBS summary score, Equilibrium Score (ES), Strategy Score (SS) and Sensory Analysis Score of the SOT. RESULTS A significant difference (P < 0.05) was observed between the strabismus and non-strabismus group in the PBS and, ES and SS of SOT condition 1. The Sensory Analysis scores were significantly different (P = 0.03) between the groups for 'Somatosensory'. Simple linear regression analysis suggested that the strabismus condition was significantly (P ≤ 0.02) associated with the PBS and, the ES and SS of condition 1, with a variance of 14.6%, 16.1% and 12.8%, respectively. Subgroup analysis suggested that age was a significant (P ≤ 0.001) correlate for balance scores in non-strabismus group (R2 ranged from 32% to 58.4%), but not for the strabismus group. SIGNIFICANCE Postural control in children with strabismus is not equivalent to that of children without strabismus, when their somatosensory system is challenged. Additionally, the functional balance performance of children with strabismus is lower than their counterparts without strabismus. Collectively, the results suggest that the usual improvement in balance performance with increasing age is observed in children without strabismus but not in children with strabismus.
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Fixation instability during binocular viewing in anisometropic and strabismic children. Exp Eye Res 2018; 183:29-37. [PMID: 30006273 DOI: 10.1016/j.exer.2018.07.013] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/16/2018] [Accepted: 07/09/2018] [Indexed: 11/22/2022]
Abstract
PURPOSE Strabismus or anisometropia disrupts binocularity and results in fixation instability, which is increased with amblyopia. Fixation instability has typically been assessed for each eye individually. Recently, vergence instability was reported in exotropic adults and monkeys during binocular viewing. We evaluated fixation instability during binocular viewing in children treated for anisometropia and/or strabismus. METHODS 160 children age 4-12 years with treated esotropia and/or anisometropia (98 amblyopic, 62 nonamblyopic) were compared to 46 age-similar controls. Fixation instability was recorded during binocular fixation of a 0.3 deg diameter dot for 20 s using a 500 Hz remote video binocular eye tracker (EyeLink 1000; SR Research). The bivariate contour ellipse area (BCEA; log deg2) for fixation instability was calculated for each eye (nonpreferred, preferred) and for vergence instability (left eye position - right eye position). Best-corrected visual acuity, Randot Preschool stereoacuity, and extent of suppression scotoma (Worth 4-Dot) were also obtained. RESULTS When binocularly viewing, both amblyopic and nonamblyopic children treated for anisometropia and/or strabismus had larger fixation instability and vergence instability than controls. Amblyopia primarily added to the instability of the nonpreferred eye. Anisometropic children had less nonpreferred eye instability and vergence instability than those with strabismus or combined mechanism. Nonpreferred eye instability and vergence instability were related to poorer stereoacuity and a larger suppression scotoma. Preferred eye instability was not related to any visual outcome measure. No relationships were found with visual acuity. CONCLUSIONS Fixation instability and vergence instability during binocular viewing suggests that discordant binocular visual experience during childhood, especially strabismus, interferes with ocular motor development. Amblyopia adds to instability of the nonpreferred eye. Vergence instability may limit potential for recovery of binocular vision in these children.
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Park N, Park B, Oh M, Moon S, Kim M. A quantitative analysis method for comitant exotropia using video-oculography with alternate cover. BMC Ophthalmol 2018; 18:80. [PMID: 29566654 PMCID: PMC5863817 DOI: 10.1186/s12886-018-0747-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 03/16/2018] [Indexed: 12/02/2022] Open
Abstract
Background The purpose of this study was to evaluate the efficacy of a quantitative analysis method for comitant exotropia using video-oculography (VOG) with alternate cover. Methods Thirty-four subjects with comitant exotropia were included. Two independent ophthalmologists measured the angle of ocular deviation using the alternate prism cover test (APCT). The video files and data of changes in ocular deviation during the alternate cover test were obtained using VOG. To verify the accuracy of VOG, the value obtained using VOG and the angle of a rotating model eye were compared, and a new linear equation was subsequently derived using these data. The calculated values obtained using VOG were compared with those obtained using the APCT. Results Rotation of the model eye and the values obtained using VOG demonstrated excellent positive correlation (R = 1.000; p < 0.001). A simple linear regression model was obtained: rotation of the model eye = 0.978 × value obtained using VOG for a model eye – 0.549. The 95% limit of agreement for inter-observer variability was ±4.63 prism diopters (PD) for APCT and that for test-retest variability was ±3.56 PD for the VOG test. The results of APCT and calculated VOG test demonstrated a strong positive correlation. Bland-Altman plots revealed no overall tendency for the calculated values obtained from VOG to differ from those obtained using APCT. Conclusions VOG with alternate cover is a non-invasive and accurate tool for quantitatively measuring and recording ocular deviation. In particular, it is independent of the proficiency of the examiner and, can therefore, be useful in the absence of skilled personnel. Trial registration ClinicalTrial.gov, NCT03119311, Date of registration: 04/17/2017, Date of enrolment of the first participant to the trial: 04/25/2017.
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Affiliation(s)
- Nohae Park
- Department of Ophthalmology, Busan Paik Hospital, Inje University College of Medicine, 75 Bokji-ro, Busanjin-gu, Busan, 47392, Republic of Korea
| | - Byunggun Park
- Department of Ophthalmology, Busan Paik Hospital, Inje University College of Medicine, 75 Bokji-ro, Busanjin-gu, Busan, 47392, Republic of Korea
| | - Minkyung Oh
- Department of Pharmacology, Busan Paik Hospital, Inje University College of medicine, Busan, Republic of Korea
| | - Sunghyuk Moon
- Department of Ophthalmology, Busan Paik Hospital, Inje University College of Medicine, 75 Bokji-ro, Busanjin-gu, Busan, 47392, Republic of Korea.
| | - Myungmi Kim
- Department of Ophthalmology, Yeungnam University College of Medicine, Daegu, Republic of Korea
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Mihara M, Hayashi A, Fujita K, Kakeue K, Tamura R. Fixation stability of the upward gaze in patients with myasthenia gravis: an eye-tracker study. BMJ Open Ophthalmol 2018; 2:e000072. [PMID: 29354719 PMCID: PMC5751864 DOI: 10.1136/bmjophth-2017-000072] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 09/29/2017] [Accepted: 10/30/2017] [Indexed: 11/14/2022] Open
Abstract
Objective To quantify fixation stability of the upward gaze in patients with myasthenia gravis (MG) using an eye tracker. Methods and analysis In this study, 21 normal subjects, 5 patients with MG with diplopia, 5 patients with MG without diplopia and 6 patients with superior oblique (SO) palsy were included. Subjects fixated on a target in the upward direction for 1 min. The horizontal (X) and vertical (Y) eye positions were recorded using an eye tracker. Fixation stability was first quantified using the bivariate contour ellipse areas (BCEA) of fixation points as an index of whole stability. Then, the SDs of the X and Y eye positions (SDX and SDY, respectively) were quantified as indices of directional stability, with the data divided into three 20 s fractions to detect temporal fixation fluctuation. Results BCEAs were larger in patients with MG (both with and without diplopia) than normal subjects and patients with SO palsy, without significant differences among the three 20 s fractions. Compared with normal subjects, SDXs were larger only in patients with MG with diplopia; SDYs were larger in both patients with MG with and without diplopia. In addition, SDYs in patients with MG with diplopia were larger than those in patients with MG without diplopia and patients with SO palsy. Furthermore, a significant difference among the three 20 s fractions was detected for SDYs in patients with MG with diplopia. Conclusion Patients with MG, especially those with diplopia, exhibit fixation instability in the upward gaze. Non-invasive quantification of fixation stability with an eye tracker is useful for precisely identifying MG-specific fatigue characteristics. Trial registration number UMIN000023468; pre-results.
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Affiliation(s)
- Miharu Mihara
- Department of Ophthalmology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.,Department of Integrative Neuroscience, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Atsushi Hayashi
- Department of Ophthalmology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Kazuya Fujita
- Department of Ophthalmology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Ken Kakeue
- Department of Ophthalmology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Ryoi Tamura
- Department of Integrative Neuroscience, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
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Adams DL, Economides JR, Horton JC. Incomitance and Eye Dominance in Intermittent Exotropia. Invest Ophthalmol Vis Sci 2017; 58:4049-4055. [PMID: 28813578 PMCID: PMC5559177 DOI: 10.1167/iovs.17-22155] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To determine if the deviation angle changes in subjects with intermittent exotropia as they alternate fixation between the right and left eye in primary gaze. Methods In this prospective observational cohort study, 37 subjects with intermittent exotropia were tested for evidence of incomitance. The position of each eye was recorded with a video tracker during fixation on a small central target. A cover-uncover test was performed by occluding one eye with a shutter that passed infrared light, allowing continuous tracking of both eyes. The deviation angle was measured during periods of right eye and left eye fixation. Incomitance was assessed as a function of eye preference, fixation stability, and exotropia variability. Results The mean exotropia was 18.2° ± 8.1°. A difference between right exotropia and left exotropia was detectable in 16/37 subjects. Allowing for potential tracking error, the incomitance had a mean amplitude of 1.7°. It was not related to a difference in accommodative effort, eye preference, fixation stability, or variability in deviation. Conclusions Comitance is regarded as a feature that distinguishes strabismus from paralytic or restrictive processes. Unexpectedly, eye tracking during the cover-uncover test showed that incomitance is present in approximately 40% of subjects with intermittent exotropia. It averages 10% of the exotropia, and can equal up to 5°. When substantial, it may be worth considering when planning surgical correction.
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Affiliation(s)
- Daniel L Adams
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States.,Center for Mind/Brain Sciences, The University of Trento, Trento, Italy
| | - John R Economides
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States
| | - Jonathan C Horton
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States
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Ghasia FF, Otero-Millan J, Shaikh AG. Abnormal fixational eye movements in strabismus. Br J Ophthalmol 2017; 102:253-259. [PMID: 28698242 DOI: 10.1136/bjophthalmol-2017-310346] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 04/11/2017] [Accepted: 05/06/2017] [Indexed: 11/03/2022]
Abstract
INTRODUCTION Fixational saccades are miniature eye movements that constantly change the gaze during attempted visual fixation. Visually guided saccades and fixational saccades represent an oculomotor continuum and are produced by common neural machinery. Patients with strabismus have disconjugate binocular horizontal saccades. We examined the stability and variability of eye position during fixation in patients with strabismus and correlated the severity of fixational instability with strabismus angle and binocular vision. METHODS Eye movements were measured in 13 patients with strabismus and 16 controls during fixation and visually guided saccades under monocular viewing conditions. Fixational saccades and intersaccadic drifts were analysed in the viewing and non-viewing eye of patients with strabismus and controls. RESULTS We found an increase in fixational instability in patients with strabismus compared with controls. We also found an increase in the disconjugacy of fixational saccades and intrasaccadic ocular drift in patients with strabismus compared with controls. The disconjugacy was worse in patients with large-angle strabismus and absent stereopsis. There was an increase in eye position variance during drifts in patients with strabismus. Our findings suggest that both fixational saccades and intersaccadic drifts are abnormal and likely contribute to the fixational instability in patients with strabismus. DISCUSSION Fixational instability could be a useful tool for mass screenings of children to diagnose strabismus in the absence of amblyopia and latent nystagmus. The increased disconjugacy of fixational eye movements and visually guided saccades in patients with strabismus reflects the disruption of the fine-tuning of the motor and visual systems responsible for achieving binocular fusion in these patients.
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Affiliation(s)
- Fatema F Ghasia
- Daroff-Del'Osso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, Ohio, USA
| | - Jorge Otero-Millan
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Aasef G Shaikh
- Department of Neurology, Case Western Reserve University, Cleveland, Ohio, USA.,Neurology Service, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, USA.,Neurology, Daroff-Del'Osso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, Ohio, USA
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Economides JR, Adams DL, Horton JC. Capturing the Moment of Fusion Loss in Intermittent Exotropia. Ophthalmology 2017; 124:496-504. [PMID: 28081943 PMCID: PMC5685669 DOI: 10.1016/j.ophtha.2016.11.039] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 11/29/2016] [Accepted: 11/29/2016] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To characterize eye movements made by patients with intermittent exotropia when fusion loss occurs spontaneously and to compare them with those induced by covering 1 eye and with strategies used to recover fusion. DESIGN Prospective study of a patient cohort referred to our laboratory. PARTICIPANTS Thirteen patients with typical findings of intermittent exotropia who experienced frequent spontaneous loss of fusion. METHODS The position of each eye was recorded with a video eye tracker under infrared illumination while fixating on a small central near target. MAIN OUTCOME MEASURES Eye position and peak velocity measured during spontaneous loss of fusion, shutter-induced loss of fusion, and recovery of fusion. RESULTS In 10 of 13 subjects, the eye movement made after spontaneous loss of fusion was indistinguishable from that induced by covering 1 eye. It reached 90% of full amplitude in a mean of 1.75 seconds. Peak velocity of the deviating eye's movement was highly correlated for spontaneous and shutter-induced events. Peak velocity was also proportional to exotropia amplitude. Recovery of fusion was more rapid than loss of fusion, and often was accompanied by interjection of a disconjugate saccade. CONCLUSIONS Loss of fusion in intermittent exotropia is not influenced by visual feedback. Excessive divergence tone may be responsible, but breakdown of alignment occurs via a unique, pathological type of eye movement that differs from a normal, physiological divergence eye movement.
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Affiliation(s)
- John R Economides
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California
| | - Daniel L Adams
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California; Center for Mind/Brain Sciences, The University of Trento, Trento, Italy
| | - Jonathan C Horton
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California.
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Abstract
Disrupting binocular vision in infancy leads to strabismus and oftentimes to a variety of associated visual sensory deficits and oculomotor abnormalities. Investigation of this disorder has been aided by the development of various animal models, each of which has advantages and disadvantages. In comparison to studies of binocular visual responses in cortical structures, investigations of neural oculomotor structures that mediate the misalignment and abnormalities of eye movements have been more recent, and these studies have shown that different brain areas are intimately involved in driving several aspects of the strabismic condition, including horizontal misalignment, dissociated deviations, A and V patterns of strabismus, disconjugate eye movements, nystagmus, and fixation switch. The responses of cells in visual and oculomotor areas that potentially drive the sensory deficits and also eye alignment and eye movement abnormalities follow a general theme of disrupted calibration, lower sensitivity, and poorer specificity compared with the normally developed visual oculomotor system.
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Affiliation(s)
- Vallabh E Das
- College of Optometry, University of Houston, Houston, Texas 77204;
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Jung J, Klaehn L, Brodsky MC. Stability of human binocular alignment in the dark and under conditions of nonfixation. J AAPOS 2016; 20:353-7. [PMID: 27346855 DOI: 10.1016/j.jaapos.2016.05.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 05/26/2016] [Accepted: 05/31/2016] [Indexed: 11/15/2022]
Abstract
PURPOSE To evaluate the stability of human binocular alignment under conditions of altered fixation and luminance. METHODS Horizontal binocular alignment in 8 healthy orthotropic subjects was measured using infrared video-oculography (VOG) under conditions of binocular fixation and luminance change. Each testing condition was preceded by a binocular fixation period in room light (475 lux) to define the baseline binocular alignment. Binocular alignment was then measured in darkness without fixation, in room light through a semitranslucent filter that precluded fixation, and in darkness with a distant fixational target. We used the signed rank test to determine statistically whether these experimental conditions induced significant binocular alignment change from each baseline binocular alignment. RESULTS The mean horizontal binocular alignment in the dark without fixation was similar to baseline binocular alignment (0.2° ± 2.8°; P = 0.4). The mean horizontal binocular alignment without fixation in room light was also similar to baseline binocular alignment (-1.4° ± 1.6°; P = 0.08). The mean horizontal binocular alignment in the dark when a fixational target was provided showed an exodrift compared to baseline alignment (2.3° ± 1.0°; P = 0.0004). CONCLUSIONS The human brain does not require visual input to maintain binocular alignment on a short-term basis. The resilience of binocular alignment probably reflects the presence of phoria adaptation.
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Affiliation(s)
- Jaeho Jung
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota
| | - Lindsay Klaehn
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota
| | - Michael C Brodsky
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota; Department of Neurology, Mayo Clinic, Rochester, Minnesota.
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