Article

Intermittent Exotropia Treatment with Dichoptic Visual Training Using a Unique Virtual Reality Platform

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Abstract

We evaluated the effect of dichoptic visual training based on a unique virtual reality (VR) platform mounted display in patients with intermittent exotropia (IXT). A total of 25 IXT patients (8 men, 17 women) with a mean age of 12.3 years (range, 5-39 year) were recruited. The Hirschberg test, prism and alternate cover testing (with accommodative targets for fixation at 33 cm in all patients), perceptual eye position (PEP), and stereopsis were evaluated after 1, 3, and 6 months of dichoptic visual neuroplasticity training with a computer-controlled perceptual examination evaluation system. Data collected before and after training were evaluated using SPSS software. After 6 months of perceptual training, a new order stereopsis was established, and eye positions were improved in all 25 patients. After training for 1 and 6 months, the horizontal PEP pixels were much lower than those pretraining, respectively (Δ1-0 = -0.53, p = 0.028; Δ6-0 = -0.80, p = 0.018). There was no statistically significant difference between pretraining and 3 months after training in horizontal PEP (Δ3-0 = -0.29, p = 0.370). There was no significant difference between pretraining and post-training in vertical PEP (p > 0.05). There were significant differences between pretraining and post-training in the cornea's optical reflection and prism diopters (p < 0.01). Dichoptic visual neuroplasticity training based on a VR platform is an effective nonsurgical treatment in patients with IXT. With the VR treatment, the degree of strabismus and stereopsis was improved in IXT patients. Perceptual training with VR can remove obstacles in the visual processing channel and repair defects in visual function. The clinical manifestations of improvement were the decrease in the degree of strabismus and the re-establishment of stereopsis.

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... In intermittent exotropic patients, with VR training, the misalignment was decreased and the stereopsis was improved. 33 In our former study, the VR technique was also used to recover the binocular function in postoperative intermittent exotropies. 8 In this preliminary study, we explored the possibility of AR and VR training for improvement of binocular vision in postoperative strabismic patients and provided a potential alternative choice of vision therapy through a short-term perceptual training. ...
... Perceptual training can reduce the suppression/noise of visual processing channels, amplify the vision signal of the strabismic eye, enhance central control, and thus remove the obstacle in the visual processing channel and repair the defect of binocular function. 33 Besides the treatment of amblyopia and strabismus, VR and AR were also applied in other aspects in vision fields, such as low vision, 23,34 glaucoma, [35][36][37] diagnosing strabismus, 38,39 and testing binocular imbalance. 40,41 Though the long-term perceptual training with VR or AR could improve PEP in intermittent exotropes or postoperative intermittent exotropes, 8,33 one short-term training based on VR or AR had no effect on PEP of postoperative strabismic patients in this study. ...
Article
The study aimed to explore the potential effect of short-term visual perceptual training based on virtual reality (VR) and augmented reality (AR) platforms in postoperative strabismic patients. We enrolled 236 postoperative strabismic patients, among whom 111 patients received VR-based training, and 125 patients received AR-based training. The stereoacuity of 1.5 m and dynamic stereopsis were improved by VR training; meanwhile, AR training exhibited more improvement in stereoacuity of 0.8 and 1.5 m, dynamic and coarse stereopsis. It was suggested that the visual perceptual training based on VR and AR technology can be potentially applied in postoperative strabismus treatment to promote the recovery of binocular vision.
... MD is a sensitive indicator of diffuse visual field damage in response to glaucoma. In line with our pilot study 8 and the previous study from others, 11,13,[15][16][17][18] visual training activated residual visual function, improved visual field defects, and enlarged the visual field in patients. We have an interesting example of this. ...
... Patients use the binocular VR push-pull training system to perform the training at home, and it is an uninvasive therapy. At present, activating neuroplasticity by visual training has been widely used in amblyopia and strabismus treatment, 16,21,22 but there are no relevant reports on the application of binocular VR training in the field of glaucoma and our study is the first of a few of this type. However, our study has the following limitations: (a) the visual field data change was not statistically significant at 3 months of training compared with 1 month of training. ...
Article
Visual field defect caused by glaucoma seriously affects the quality of life of patients, and clinically, this type of visual field defect has been considered to be irreversible. The aim of this study is to use binocular virtual reality training (VR training) to repair visual field defect in glaucoma patients, improve the quality of life of patients, and provide a new therapeutic strategy for the rehabilitation of glaucoma. Seventy glaucoma patients (median 56, range 15-84 years) were recruited and divided into control and training groups. Fifty-four patients' data were analyzed. The training group (n = 30) received binocular VR training for 3 months. The control group (n = 24) maintained the conventional treatment without any other intervention. Their visual field index (VFI) and mean defect (MD), and retinal nerve fiber layer average thickness (RNFL) and ganglion cell layer average thickness (GCL) average thickness before training and during followup were analyzed. In the training group, the VFI value (Z = 3.277; p = 0.001) and MD value (Z = 3.913; p < 0.0001) were significantly improved after 1 month of training. After 3 months of training, the VFI value (Z = 3.761; p < 0.0001) and MD value (Z = 3.133; p = 0.002) were significantly improved. There was no significant difference with the changes of average thickness of RNFL (p = 0.350) and GCL average (p = 0.383) after 3 months of training; whereas in the control group, except for a further reduction in GCL average thickness (Z = 3.158; p = 0.002) compared with the baseline data, the other followup data were not statistically significant compared with the baseline data. Our data suggested that binocular VR training can significantly improve the visual field defect of glaucoma patients but warrants further study with large sample size. Clinical Trail registration number: ChiCTR1900027909.
... VR programs could improve the visual acuities of children and adults with amblyopia and reduce the deviation angle in patients with intermittent exotropia. [12][13][14] However, VR applications have not been developed to train residents for diagnosing strabismus. ...
... Žiak et al. 12 reported that the mean best-corrected visual acuity of adult patients with amblyopia improved with dichoptic training. Li et al. 14 reported that the degree of strabismus and stereopsis improved with dichoptic visual training using a VR platform in patients with intermittent exotropia. Nesaratnam et al. 20 reported the rst use of a VR headset in assessing ocular misalignment and demonstrated its feasibility as the dissociative test for strabismus. ...
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Purpose: To study the usefulness of virtual reality (VR) based training for diagnosing strabismus Methods: Fourteen ophthalmology residents performed at least 30 VR training sessions to diagnose esotropia and exotropia. Examinations of real patients with esotropia or exotropia before and after the VR training were video-recorded and presented to a strabismus expert to assess accuracy and performance scores for measuring the deviation angle and diagnosing strabismus with anonymization. A feedback survey regarding the usefulness and ease of use of the VR application was conducted for participants. Results: The mean age of 14 ophthalmology residents, including 10 men and 4 women, was 29.7 years. Before VR training, participants showed a mean accuracy score of 14.50 ± 5.45 and performance score of 9.64 ± 4.67 for measuring the deviation angle and diagnosing strabismus in real patients with strabismus. After VR training, they showed a significantly improved accuracy score of 22.14 ± 4.37 (p = 0.012) and performance score of 15.50 ± 1.99 (p = 0.011). According to the survey, most participants agreed on the usefulness of VR application. Conclusions: This study suggests that VR based training improves ophthalmology residents’ clinical diagnostic skills for strabismus in a short period.
... Recently, there has been an explosion in the use of VR for an alternative rehabilitation for Amblyopia [18,13,2,3,22,8,5,21,15]. Our comprehensive study on VR and Amblyopia, as well as others' studies, use the binocular characteristic of VR Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for proft or commercial advantage and that copies bear this notice and the full citation on the frst page. ...
Conference Paper
Amblyopia, or "lazy eye" is the world's most common neurological eye disorder. Yet, very little has been done looking into how to make virtual reality (VR) more usable for people with Amblyopia. Furthermore, a trend of using VR for Amblyopia therapy has arisen, making such a study more essential than ever. Our study asks our user base of people with Amblyopia questions through two surveys, verbal feedback, and interviews about their experience with our VR video game Amblyopia therapy. We found patterns encoded in this information, which we use to create preliminary hypotheses for making VR experiences as usable as possible for people with Amblyopia.
... 14-16 PEP pixels can be measured by the computer-controlled perceptual examination evaluation system under a dichoptic vision condition. [14][15][16] The previous studies have shown that the sensory eye balance is abnormal in patients with amblyopia, anisometropia, and strabismus. 14 In our study, we quantitatively assessed the sensory eye dominance of surgically corrected X(T) with normal apparent eye position. ...
Article
The aim of this study was to investigate perceptual eye position (PEP) and to evaluate the effect of dichoptic visual perceptual training in postoperative intermittent exotropia [X(T)]. We enrolled 30 non-strabismus children (control group) and 54 postoperative X(T) children [divided into training group (33 patients) and non-training group (21 patients)]. All subjects received measurements of PEP, and the postoperative X(T) children were measured both in the third postoperative day and the third postoperative month. All patients in training group received 3-month dichoptic visual perceptual training based on a unique virtual reality platform. The results showed that the postoperative X(T) children with normal eye position still had an abnormal PEP. After a period of visual perceptual training, the PEP pixels in postoperative children dramatically decreased. The results revealed that PEP could evaluate fixation disparity and binocular visual function perceptively and precisely, and the dichoptic visual perceptive training may rebuild binocular visual function.
... In this study, the subjects were trained with a computer terminal based on an augmented virtual reality platform without any invasive stimulation, which was much safer than rtACS or other trans-corneal electrical stimulation. And it had been successfully displayed in children with intermittent exotropia and normal population without eye diseases [35,36]. ...
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Background To evaluate the efficacy of transient vision restoration training (tVRT) with an augmented virtual reality platform in glaucoma patients. Design A self-control, prospective study. Methods This study recruited subjects with glaucoma. All participants were treated with tVRT which based on an augmented virtual reality platform for 20 minutes. The intraocular pressure (IOP), the best-corrected visual acuity (BCVA), global mean defect (MD) values, global indices mean sensitivity (MS) were evaluated and compared before and after treatment. Results While the IOP and BCVA after tVRT did not change obviously compared to baseline. However, the global MD significantly reduced, consistently the global MS changed better in the treated patients. Conclusions The glaucomatous optic neuropathy remains potentially neuroplasticity. And the training based on an augmented virtual reality platform may have a positive impact on vision restoration.
... Convert the correlation coefficient into a standardized mean difference (SMD) [15,16]. ...
Article
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At present, the main treatment for strabismus is still surgical treatment, but there is no unified standard for the evaluation of the timing of surgery. This study mainly explores the clinical effects of using meta-analysis of intelligent image sensors combined with visual training to treat children with intermittent exotropia. Cochrane systematic reviews collect, evaluate, and synthesize an increasing number of original clinical research results to obtain the comprehensive effect of relevant interventions, so as to provide real and reliable evidence for health decision-making and clinical practice. It uses scientific, clear, and reproducible research methods to reduce the influence of biased factors, so it is different from traditional reviews. Cochrane systematic reviews are especially suitable for certain interventions when the pros and cons of interventions are difficult to determine based on the results of a single clinical study or when there are large differences in the clinical application process. Poor quality systematic reviews can mislead policymakers and clinicians. In the meta-analysis, the Cochrane systematic evaluation method of evidence-based medicine was used to comprehensively search the published literature research on the treatment of intermittent exotropia with vision training. Using the Cochrane system evaluation method, computer search of CENTRAL, MEDLINE, Embase, Chinese Biomedical Literature Database, Chinese Journal Full-text Database, manual retrieval of relevant conference documents, and inclusion of all clinical trial documents of visual training in children with intermittent exotropia was conducted. Patients with intermittent exotropia were selected, simultaneous vision, fusion function, and far stereo vision with the same vision machine were measured, and near stereo vision with a stereo vision chart was measured. The number of simultaneous vision, fusion function, and distance and near stereo vision “with” and “without” cases were recorded for all patients, and the relationship with age of onset, type of strabismus, degree of strabismus, and degree of control was counted. Among them, 91 patients who underwent strabismus correction surgery were followed up for at least 6 months with correct eye position. The presence or absence of simultaneous vision, fusion function, far stereo vision, and near stereo vision were recorded and compared with preoperative. The number of recovery and nonrecovery cases was recorded, and the relationship between the age of operation, the type of strabismus, the degree of strabismus, and the degree of control was counted. It was statistically analyzed by SPSS22.0. The results of the meta-analysis showed that in terms of the effective rate of fundus lesions, the visual training group was better than the nontraining group, and the difference between the two groups was statistically significant (RR = 1.32, 95% CI: (1.25, 1.40), P < 0.0001). This study provides guidance for the early rehabilitation of children with intermittent exotropia.
... VR has the potential to replace the Synoptophore (or Major Amblyoscope), as the standard instrument for the assessment and treatment of ocular motility disorders. VR has been used successfully in the treatment of mechanical strabismus and amblyopia [22,[31][32][33][34]. The recent incorporation of eye-tracking technology to VR can potentially allow the measurement of deviation angles objectively, as a preliminary study suggests [31]. ...
Article
Full-text available
The purpose of this study was (1) to implement a test for binocular imbalance in a Virtual Reality headset, (2) to assess its testability, reliability and outcomes in a population of clinical patients and (3) to evaluate the relationships of interocular acuity difference, stereoacuity and binocular imbalance to amblyogenic risk factors. 100 volunteers (6 to 70 years old, mean 21.2 ± 16.2), 21 with no amblyogenic risk factors and 79 with amblyopia or a history of amblyopia participated. Participants were classified by amblyogenic risk factor (24 anisometropic, 25 strabismic and 30 mixed) and, for those with strabismus, also by refractive response (16 accommodative and 39 non-accommodative). We characterized our sample using three variables, called the 'triplet' henceforth: interocular acuity difference, stereoacuity and imbalance factor. Binocular imbalance showed high test-retest reliability (no significant difference between test and retest in a subgroup, n = 20, p = 0.831); was correlated with Worth 4 dots test (r = 0.538, p
... Meanwhile, the visual perception examination and treatment system platform based on neurophysiological theories enriches detection methods for binocular function impaired and provides a basis for accurate diagnosis and treatment. In this study, we adopted a dynamic stereoscopic biological model based on the MATLAB algorithm designed by the National Engineering Research Center for Healthcare Devices, which can help us to examine stereopsis in multiple dimensions [10,11]. ...
Article
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Purpose: The purpose of this study is to test binocular visual function after femtosecond laser small incision lenticule extraction (SMILE) for high myopia. The traditional Titmus stereotest and dynamic stereotest based on the visual perception biological model were used for comparative analysis. Methods: A total of 43 patients were enrolled in this prospective study. At Week 1, Month 1, and Month 3 after surgery, the Titmus stereotest and dynamic stereotest generated by MATLAB were conducted. Dynamic stereopsis consists of randomly flickering Gabor spots and is divided into two models of high energy and low energy according to flicker frequency. Results: The preoperative manifest refraction spherical equivalent was -7.21 ± 0.70 D. The preoperative anisometropia was 0.52 ± 0.54D. The quartiles of static stereoacuity in preoperation and 3 follow-ups were as follows: 50.00 (25.00, 100.00) in preoperation, 63.00 (40.00, 63.00) at Week 1, 40.00 (32.00, 63.00) at Month 1, and 40.00 (25.00, 50.00) at Month 3. Static stereopsis improved at Month 1 and Month 3 compared with preoperation and Week 1 (P < 0.05). There were statistically significant differences in high energy dynamic stereopsis at Week 1 and Month 1 compared to preoperation (P < 0.05). In addition, significant differences in low energy dynamic stereopsis were detected between Month 1 and preoperation and also at Month 3 compared to Month 1 (P < 0.05). Conclusion: Most high myopia patients have a dynamic stereopsis deficiency before refractive correction. SMILE surgery can improve both static and dynamic stereopsis early in the postoperation period. However, in the long term, there is no significant difference or even a decrease in dynamic stereopsis.
... Studies which previously used a VR platform revealed that this approach is successful in stereopsis improving in young and adult patients with different binocular vision disorders. The first study which used a VR platform treated patients with exotropia [10]. They revealed improvement of stereopsis (and also eye alignment) of all 25 IXT patients after 6 months of training. ...
Article
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Background: Impaired stereopsis very often limits career options for patients with binocular vision disorders. Eyesight requirements for some occupations like police officers and firefighters usually include perfect visual acuity. In Po- land, candidates for these professions must also demonstrate perfect stereop- sis. The presented case study aims to demonstrate that vision therapy (VT1) mixed with new technologies may be an effective treatment for young adults who do not meet the chosen occupation's visual requirements. Case report: A case of a young man diagnosed with intermittent exotropia and poor stereopsis is discussed. Poor stereopsis did not allow him to pass the oph- thalmological qualification tests to the fire academy. Vision therapy was imple- mented to improve stereopsis. The case report presents the patient’s treatment implemented within 4 years. The patient started with prismatic correction, then received the office-based VT with home reinforcement. The improvement in fusional vergence and the control of deviation was observed. Nevertheless, the patient was still stereo-deficient. 3 years later, Binocular Vision Therapy in Vir- tual Reality (BVTVR2) was recommended. The patient received home-based therapy for 16 weeks (60 minutes per day), which has resulted in significant improvement of stereopsis. As a result, he finally met the visual requirements to become a firefighter. Conclusion: BVTVR appears to be a promising rehabilitation method for pa- tients with poor stereopsis. Three-dimensional anti-suppression therapy and dynamic, real-life stereopsis training seem to be a more effective treatment of poor stereopsis compared to standard VT techniques. Key words: intermittent exotropia, stereopsis, strabismus, virtual reality, vision therapy
... In recent years, virtual reality (VR) and augmented reality (AR) simulation training have also been utilized, focusing on various medical fields. Advancements in VR represent some of the newest modalities being integrated into ophthalmologic practice and resident education [1][2][3] . The importance of incorporating simulation in the education of the residents and skills assessment is increasingly emphasized 4 . ...
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To study the usefulness of virtual reality (VR)-based training for diagnosing strabismus. Fourteen residents in ophthalmology performed at least 30 VR training sessions to diagnose esotropia and exotropia. Examinations of real patients with esotropia or exotropia before and after the VR training were video-recorded and presented to a strabismus expert to assess accuracy and performance scores for measuring the deviation angle and diagnosing strabismus with anonymization. A feedback survey regarding the usefulness and ease of use of the VR application was conducted for participants. The mean age of the 14 ophthalmology residents (10 men and 4 women), was 29.7 years. Before VR training, participants showed a mean accuracy score of 14.50 ± 5.45 and a performance score of 9.64 ± 4.67 for measuring the deviation angle and diagnosing strabismus in real patients with strabismus. After VR training, they showed a significantly improved accuracy score of 22.14 ± 4.37 (p = 0.012) and a performance score of 15.50 ± 1.99 (p = 0.011). According to the survey, most participants agreed on the usefulness of VR applications. This study suggests that VR-based training improved ophthalmology residents’ clinical diagnostic skills for strabismus in a short period.
Chapter
This study investigates how therapists are able to adopt a virtual reality toolset for rehabilitation of patients with acquired brain injury. This was investigated by conducting a case study where the therapists and their interactions with the system as well as with the patients were in focus. A tracked tablet gives the therapist a virtual camera and control over the virtual environment. Video recordings, participant observers and field notes were the main sources for data used in an interaction analysis. Results reveal emergent behaviour and resourcefulness by the therapists in utilizing the virtual tools in combination with their conventional approaches to rehabilitation.
Preprint
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Stereopsis is a valuable feature of human visual perception, which may be impaired or absent in amblyopia and/or strabismus but can be improved through perceptual learning (PL) and videogames. The development of consumer virtual reality (VR) may provide a useful tool for improving stereovision. We report a proof of concept study, especially useful for strabismic patients and/or those with reduced or null stereoacuity. Our novel VR PL strategy is based on a principled approach which included aligning and balancing the perceptual input to the two eyes, dichoptic tasks, exposure to large disparities, scaffolding depth cues and perception for action. We recruited ten adults with normal vision and ten with binocular impairments. Participants played two novel PL games (DartBoard and Halloween) using a VR-HMD. Each game consisted of three depth cue scaffolding conditions, starting with non-binocular and binocular cues to depth and ending with only binocular disparity. All stereo-anomalous participants improved in the game and most (9/10) showed transfer to clinical and psychophysical stereoacuity tests (mean stereoacuity changed from 569 to 296 arc seconds, p<0.0001). Stereo-normal participants also showed in-game improvement, which transferred to psychophysical tests (mean stereoacuity changed from 23 to a ceiling value of 20 arc seconds, p=0.001). We conclude that a VR PL approach based on depth cue scaffolding may provide a useful method for improving stereoacuity, and the in-game performance metrics may provide useful insights into principles for effective treatment of stereo anomalies.
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Introduction: Virtual reality (VR) gameplay is popular with a range of games and educational resources available. However, it puts high demands on the visual system. Current evidence shows conflicting impacts on visual parameters. Therefore, this study explores the changes to vision following VR gameplay. Methods: The study was conducted at the School of Health Sciences, University of Liverpool. All participants had binocular vision with good visual acuity and no manifest strabismus. Participants were assessed before and after playing 15 minutes of the VR game Beat Saber, which incorporated convergence and divergence movements. Clinical assessments including near point of convergence (NPC) and near point of accommodation (NPA) using the RAF rule; accommodative convergence to accommodation (AC/A) ratio; motor fusion using the prism fusion range (at 33cm), accommodation facility using +2.00/-2.00DS flipper lenses, and stereoacuity using the Frisby stereo test were assessed before and after playing. Results: Seventy-eight participants (19-25 years old) were included in the study, with 16 males and 41 females respectively. The breakpoint of convergence reduced by 0.5 cm (p = 0.001). The binocular accommodative facility improved by 2 cycles per minute (cpm); p = 0.004. The mean, near horizontal prism fusion range (PFR) base break and recovery points both worsened by of 5.0 dioptres (p = 0.003), whereas the mean near horizontal PFR base in recovery point improved by of 4.0 dioptres (p = 0.003). Discussion: The study validated previous findings as VR gameplay over-exercised and fatigued convergence muscles, but to a small degree. The VR experience improved the participants' ability to change focus quickly and improve accommodation, as well as the divergence function of the eye. However, as the participants were retested directly after the VR gameplay, the findings were limited to short term effects on vision.
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Stereopsis is a valuable feature of human visual perception, which may be impaired or absent in amblyopia and/or strabismus but can be improved through perceptual learning (PL) and videogames. The development of consumer virtual reality (VR) may provide a useful tool for improving stereovision. We report a proof of concept study, especially useful for strabismic patients and/or those with reduced or null stereoacuity. Our novel VR PL strategy is based on a principled approach which included aligning and balancing the perceptual input to the two eyes, dichoptic tasks, exposure to large disparities, scaffolding depth cues and perception for action. We recruited ten adults with normal vision and ten with binocular impairments. Participants played two novel PL games (DartBoard and Halloween) using a VR-HMD. Each game consisted of three depth cue scaffolding conditions, starting with non-binocular and binocular cues to depth and ending with only binocular disparity. All stereo-anomalous participants improved in the game and most (9/10) showed transfer to clinical and psychophysical stereoacuity tests (mean stereoacuity changed from 569 to 296 arc seconds, P < 0.0001). Stereo-normal participants also showed in-game improvement, which transferred to psychophysical tests (mean stereoacuity changed from 23 to a ceiling value of 20 arc seconds, P = 0.001). We conclude that a VR PL approach based on depth cue scaffolding may provide a useful method for improving stereoacuity, and the in-game performance metrics may provide useful insights into principles for effective treatment of stereo anomalies. This study was registered as a clinical trial on 04/05/2010 with the identifier NCT01115283 at ClinicalTrials.gov.
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The clinical characteristics and surgical outcomes in a large sample of patients with intermittent exotropia (IXT) as well as an analysis of risk factors associated with surgical failures are presented in this article. Data from IXT patients who received surgical management at the Eye Hospital, in the Zhongshan Ophthalmic Center, of Sun Yat-Sen University, China from January 2009 to December 2013 were reviewed retrospectively. Included within this analysis were data from pre- and postoperative ocular motility, primary alignment, and binocular vision. A total of 1228 patients with IXT were reviewed. Males (50.4%) and females (49.6%) were nearly equally represented in this sample. Thirty-two patients (2.6%) had a family history of strabismus. The mean age at onset was 6.77 ± 6.43 years (range 7 months –48.5 years), mean duration at presentation was 7.35 ± 6.68 years (range 6 months–47 years), and mean age at surgery was 13.7 ± 8.8 years (range 3–49 years). The mean refractive error was −0.84 ± 2.69 diopter in the right eye and −0.72 ± 2.58 diopter in the left eye. Amblyopia (4.2%), oblique muscle dysfunction (7.0%), and dissociated vertical deviation (4.7%) were also present in these patients. The most common subtype of IXT was the basic type (88.1%). Orthophoria was observed in 80.5% of patients and the ratios of surgical undercorrection and overcorrection were 14.7% and 4.8%, respectively, as determined with a mean follow-up time of 7.8 ± 3.7 months. When combining ocular alignment with binocular vision as the success criteria, the success rate decreased to 35.6%. Multivariate risk factor analysis showed that only the loss of stereoacuity (P = 0.002) was associated with a poor outcome. There were no differences in the long-term results between bilateral lateral rectus recession and unilateral lateral rectus recession with medial rectus resection. Most IXT patients displayed normal vision, with few having positive family histories, amblyopia, oblique muscle dysfunction, and dissociated vertical deviation. The most common subtype of IXT was the basic type. Long-term surgical results were less favorable when sensory status was included in the criteria for success. Patients with stereoacuity loss were at an increased risk for poor outcomes.
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Memory is believed to occur in the human brain as a result of two types of synaptic plasticity: short-term plasticity (STP) and long-term potentiation (LTP; refs 1-4). In neuromorphic engineering, emulation of known neural behaviour has proven to be difficult to implement in software because of the highly complex interconnected nature of thought processes. Here we report the discovery of a Ag(2)S inorganic synapse, which emulates the synaptic functions of both STP and LTP characteristics through the use of input pulse repetition time. The structure known as an atomic switch, operating at critical voltages, stores information as STP with a spontaneous decay of conductance level in response to intermittent input stimuli, whereas frequent stimulation results in a transition to LTP. The Ag(2)S inorganic synapse has interesting characteristics with analogies to an individual biological synapse, and achieves dynamic memorization in a single device without the need of external preprogramming. A psychological model related to the process of memorizing and forgetting is also demonstrated using the inorganic synapses. Our Ag(2)S element indicates a breakthrough in mimicking synaptic behaviour essential for the further creation of artificial neural systems that emulate characteristics of human memory.
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Objective: To investigate the perceptual eye position and gaze stability of the children with normal visual acuity under dichoptic vision condition.
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Stereopsis, the process leading to the sensation of depth from retinal disparity, is compromised or absent in strabismus and/or amblypia. Here we provide the first evidence for the recovery of stereopsis in human adults through perceptual learning - the repetitive practice of a demanding visual task with a feedback. Three strabismic adult observers (23-28 year old) without stereopsis but with normal visual acuity participated in the training. Before stereo training, the three observers failed the Randot circle test (≤ 400 arcsec), and also failed to detect a large binocular disparity (≤ 1320 arcsec) in stereoscopic sinewave gratings. Training trials began with a dichoptic cross and a binocular surrounding frame. By decreasing the contrast of the dominant eye's frame until both frames were visible, and adjusting the vertical and horizontal positions of the two frames separately, observers were able to achieve binocular fusion and alignment. Once fusion was achieved, a pair of sinewave gratings, one above the other with identical contrast and spatial frequency, was presented to the two eyes stereoscopically. The lower grating was presented in the same plane as the surround (zero disparity), and the upper grating was presented with a binocular disparity. The observer's task was to judge the relative depth of the top grating (i.e., closer or farther than the bottom grating). Feedback was provided after each trial. Following the training (thousands of trials), all three observers recovered stereopsis, achieving 40-140 arcsec stereoacuity with the Randot circle test, and were able to detect disparities of 70-280 arcsec with stereoscopic sinewave gratings which were jittered in horizontal position to avoid monocular cues. However, even after recovery of local stereopsis, our observers were unable to detect depth in random dot stereograms. We conclude that perceptual learning may be a useful clinical tool for treating stereoblindness.
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Objective: To determine the age- and race-specific prevalence of amblyopia in Asian and non-Hispanic white children aged 30 to 72 months and of strabismus in children aged 6 to 72 months. Design: Cross-sectional survey. Participants: A population-based, multiethnic sample of children aged 6 to 72 months was identified in Los Angeles and Riverside counties in California to evaluate the prevalence of ocular conditions. Methods: A comprehensive eye examination and in-clinic interview were conducted with 80% of eligible children. The examination included evaluation of ocular alignment, refractive error, and ocular structures in children aged 6 to 72 months, as well as a determination of optotype visual acuity (VA) in children aged 30 to 72 months. Main outcome measures: The proportion of 6- to 72-month-old participants with strabismus and 30- to 72-month-olds with optotype VA deficits and amblyopia risk factors consistent with study definitions of amblyopia. Results: Strabismus was found in 3.55% (95% confidence interval [CI], 2.68-4.60) of Asian children and 3.24% (95% CI, 2.40-4.26) of non-Hispanic white children, with a higher prevalence with each subsequent older age category from 6 to 72 months in both racial/ethnic groups (P=0.0003 and 0.02, respectively). Amblyopia was detected in 1.81% (95% CI, 1.06-2.89) of Asian and non-Hispanic white children; the prevalence of amblyopia was higher for each subsequent older age category among non-Hispanic white children (P=0.01) but showed no significant trend among Asian children (P=0.30). Conclusions: The prevalence of strabismus was similar in Asian and non-Hispanic white children and was found to be higher among older children from 6 to 72 months. The prevalence of amblyopia was the same in Asian and non-Hispanic white children; prevalence seemed to be higher among older non-Hispanic white children but was relatively stable by age in Asian children. These findings may help clinicians to better understand the patterns of strabismus and amblyopia and potentially inform planning for preschool vision screening programs. Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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Background: The clinical management of intermittent exotropia has been discussed extensively in the literature, yet there remains a lack of clarity regarding indications for intervention, the most effective form of treatment and whether or not there is an optimal time in the evolution of the disease at which any treatment should be carried out. Objectives: The objective of this review was to analyse the effects of various surgical and non-surgical treatments in randomised trials of participants with intermittent exotropia, and to report intervention criteria and determine the significance of factors such as age with respect to outcome. Search methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library, Issue 4, 2012), MEDLINE (January 1966 to May 2012), EMBASE (January 1980 to May 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to May 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 4 May 2012. We are no longer searching the UK Clinical Trials Gateway (UKCTG) for this review. We manually searched the British Orthoptic Journal up to 2002, and the proceedings of the European Strabismological Association (ESA), International Strabismological Association (ISA) and American Academy of Paediatric Ophthalmology and Strabismus meeting (AAPOS) up to 2001. We contacted researchers who are active in the field for information about further published or unpublished studies. Selection criteria: We included randomised controlled trials of any surgical or non-surgical treatment for intermittent exotropia. Data collection and analysis: Each review author independently assessed study abstracts identified from the electronic and manual searches. Author analysis was then compared and full papers for appropriate studies were obtained. Main results: We found one randomised trial that was eligible for inclusion. This trial showed that unilateral surgery was more effective than bilateral surgery for correcting the basic type of intermittent exotropia. Authors' conclusions: The available literature consists mainly of retrospective case reviews, which are difficult to reliably interpret and analyse. The one randomised trial included found unilateral surgery more effective than bilateral surgery for basic intermittent exotropia. However, across all identified studies, measures of severity and thus criteria for intervention are poorly validated, and there appear to be no reliable natural history data. There is therefore a pressing need for improved measures of severity, a better understanding of the natural history and carefully planned clinical trials of treatment to improve the evidence base for the management of this condition.
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Adults with amblyopia, a common visual cortex disorder caused primarily by binocular disruption during an early critical period, do not respond to conventional therapy involving occlusion of one eye [1]. But it is now clear that the adult human visual cortex has a significant degree of plasticity [2], suggesting that something must be actively preventing the adult brain from learning to see through the amblyopic eye. One possibility is an inhibitory signal from the contralateral eye that suppresses cortical inputs from the amblyopic eye [3,4]. Such a gating mechanism could explain the apparent lack of plasticity within the adult amblyopic visual cortex [5,6]. Here we provide direct evidence that alleviating suppression of the amblyopic eye through dichoptic stimulus presentation induces greater levels of plasticity than forced use of the amblyopic eye alone. This indicates that suppression is a key gating mechanism that prevents the amblyopic brain from learning to see.
Article
Purpose: To determine the prevalence and causes of decreased visual acuity (VA). Design: Population-based cross-sectional study. Participants: Multi-ethnic sample of children 30 to 72 months of age identified in Los Angeles. Methods: All eligible children underwent a comprehensive ophthalmic evaluation including monocular VA testing, cover testing, cycloplegic autorefraction, fundus evaluation, and VA retesting with refractive correction. Decreased VA was defined as presenting or best-measured VA worse than 20/50 in children 30 to 47 months of age and worse than 20/40 for children 48 months of age and older. The prevalence and causes of decreased VA were determined, for both presenting and best-measured VA, in the better-seeing and the worse-seeing eyes. Main outcome measures: Prevalence and causes of decreased vision. Results: Presenting VA was assessed in 1840 children and best-measured VA was assessed in 1886 children. Presenting VA was decreased in the worse eye of 4.2% of Asian children and of 3.6% of non-Hispanic white (NHW) children. Close to one-fourth of these cases had no identifiable cause, and 81% of these resolved on retesting. Decreased presenting VA in the worse eye with an identifiable ophthalmic cause was present in 3.4% of Asian children and in 2.6% of NHW children. Decreased presenting VA attributable to simple refractive error (myopia ≥ 0.5 diopters [D]; hyperopia ≥ 3.0 D; astigmatism ≥ 2.0 D or ≥ 1.5 D for children older than 36 months) was present in the worse eye of 2.3% of Asian children and of 1.4% of NHW children and in the better eye of 0.5% of Asian children and of 0.3% of NHW children. Decreased best-measured VA attributable to a cause was present in the worse eye of 1.2% of both Asian children and NHW children and in the better eye of 0.2% of Asian and of 0.3% of NHW children. Amblyopia related to refractive error was the most common cause, and was 10 times as common as ocular disease. Severe visual impairment was rare. Conclusions: Seventy percent of all decreased VA in Asian and NHW preschool children and more than 90% of decreased VA with an identifiable cause is related to refractive error--either uncorrected refractive error or amblyopia resulting from refractive error. Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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Purpose: This study considered whether vergence drives accommodation or accommodation drives vergence during the control of distance exotropia for near fixation. High accommodative convergence to accommodation (AC/A) ratios are often used to explain this control, but the role of convergence to drive accommodation (the CA/C relationship) is rarely considered. Atypical CA/C characteristics could equally, or better, explain common clinical findings. Methods: Nineteen distance exotropes, aged 4–11 years, were compared while controlling their deviation with 27 non-exotropic controls aged 5–9 years. Simultaneous vergence and accommodation responses were measured to a range of targets incorporating different combinations of blur, disparity and looming cues at four fixation distances between 2 m and 33 cm. Stimulus and response AC/A and CA/C ratios were calculated. Results: Accommodation responses for near targets (p = 0.017) and response gains (p = 0.026) were greater in the exotropes than in the controls. Despite higher clinical stimulus AC/A ratios, the distance exotropes showed lower laboratory response AC/A ratios (p = 0.02), but significantly higher CA/C ratios (p = 0.02). All the exotropes, whether the angle changed most with lenses (‘controlled by accommodation’) or on occlusion (‘controlled by fusion’), used binocular disparity not blur as their main cue to target distance. Conclusions: Increased vergence demand to control intermittent distance exotropia for near also drives significantly more accommodation. Minus lens therapy is more likely to act by correcting overaccommodation driven by controlling convergence, rather than by inducing blur-driven vergence. The use of convergence as a major drive to accommodation explains many clinical characteristics of distance exotropia, including apparently high near stimulus AC/A ratios.
Article
To conduct a comparison of the long-term surgical outcomes of bilateral lateral rectus recession (BLR) vs unilateral lateral rectus recession-medial rectus resection (RR) in treatment of intermittent exotropia. Nonrandomized, retrospective case series. Consecutive patients who underwent BLR or RR for treatment of intermittent exotropia between 2002 and 2006 and had ≥2 years' follow-up were recruited. Surgical outcomes were grouped according to postoperative angle of deviation as overcorrection (esophoria/tropia >5 Δ), success (esophoria/tropia ≤5 Δ to exophoria/tropia ≤10 Δ), or undercorrection/recurrence (exophoria/tropia >10 Δ), and were compared between the BLR group and the RR group at postoperative 1 day, 1 month, 6 months, 1 year, and 2 years, and at the final examination. Of 128 patients, 55 underwent BLR and 73 underwent RR. The mean follow-up period was 44.2 months in the BLR group and 47.8 months in the RR group. At 1 day, 1 month, 6 months, 1 year, and 2 years after surgery, surgical outcomes in each group were not different (P > .05) However, the final outcome at a mean of 3.8 years was significantly different between the groups, demonstrating a higher success rate in the BLR group than in the RR group (58.2% vs 27.4%, P < .01). Cumulative probability of survival from recurrence was higher in the BLR group than in the RR group (P = .01, log-rank test). Recurrences were most common within 6 months from surgery; however, after that, recurrences occurred continuously in the RR group and rarely in the BLR group. Surgical outcomes by 2 years after surgery for intermittent exotropia were not different between the BLR and RR groups. However, final outcomes were better in the BLR group than in the RR group. This may be caused by the difference of recurrence rate over time: continuous recurrence of exotropia occurred in the RR group, while recurrence was low in the BLR group after postoperative 6 months.
Article
Citation information: Serrano-Pedraza I, Clarke MP & Read JCA. Single vision during ocular deviation in intermittent exotropia. Ophthalmic Physiol Opt 2011, 31, 45–55. Intermittent exotropia is a common oculomotor anomaly where one eye intermittently deviates outwards. Patients with this type of strabismus are often not aware of the exodeviation and do not usually experience diplopia. In this review, we discuss what is known about the cortical mechanisms which achieve single vision during exodeviation in this condition, and highlight some outstanding questions.
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Working memory (WM) capacity predicts performance in a wide range of cognitive tasks. Although WM capacity has been viewed as a constant trait, recent studies suggest that it can be improved by adaptive and extended training. This training is associated with changes in brain activity in frontal and parietal cortex and basal ganglia, as well as changes in dopamine receptor density. Transfer of the training effects to non-trained WM tasks is consistent with the notion of training-induced plasticity in a common neural network for WM. The observed training effects suggest that WM training could be used as a remediating intervention for individuals for whom low WM capacity is a limiting factor for academic performance or in everyday life.
Article
• To study the long-range results of surgically treated intermittent exotropia, 100 consecutive patients have been followed up for an average of 6.1 years. In all cases, the initial procedure was bilateral recession of the lateral rectus muscles. The overall functional cure rate was 78%. To accomplish this result, 27 patients were operated on a second time, 21 for undercorrection and six for overcorrection. A number of patients cooperated very poorly or were lost to follow-up while still under treatment. Had these patients been eliminated from the series, the cure rate would have been greater than 90%. In this study, bilateral recession of the lateral rectus muscles corrected the distant measurement more than the near measurement only with the divergence excess type of deviation. Also, this procedure was not notably more effective with divergence excess than with basic-type intermittent exotropia.
Article
There appear to be two modes of stereoscopic processing: a conventional linear operation that is dependent on correspondence between local luminance components in the two eyes' views, and a non-linear or second-order processing mode. This second mode may use disparity information provided by particular 'non-Fourier' features of the stimulus such as the contrast envelope. Preliminary results suggest that people who fail standard clinical stereotests are able to extract non-linear disparity information from Gabor stimuli [McColl & Mitchell, 1998. Vision Research, 38, 1889-1900]. Here we evaluate the status of the non-linear mechanism in such individuals by using two types of contrast enveloped stimuli, namely random line and Gabor micropatterns, in a task that requires near/far depth judgements [Ziegler & Hess, 1999. Vision Research, 39, 1491-1507]. Although our sample was small, three of our four subjects who had performed poorly on at least one standard clinical test of stereopsis could perform the task, as well as one 'stereoblind' subject who had failed all four standard clinical tests. The overall results suggest that individuals with stereoanomalies show a diversity of deficits, but some nevertheless can see depth using 'non-linear' mechanisms.
Article
1. 1. Records for 465 patients who had had surgery for an exodeviation were examined. Discarding those with inadequate follow-up, large vertical deviations, obvious paresis and secondary exodeviations, 200 records were left. These patients were classified into the distinct clinical entities of basic exodeviation, divergence excess and convergence insufficiency and were further subdivided into constant and intermittent deviations. 2. 2. The result of operations in these 200 patients with primary exodeviations are analyzed with regard to the change in deviation and the binocular result achieved. There was a follow-up of six months to 14 years with an average of 31.1 months. 3. 3. The characteristics of the patients as to sex, family history, age at onset, visual acuity and refraction are given. 4. 4. The choice of operation was determined by the type and size of the deviation and the behavior of the versions. In general, recession-resection operations were favored in basic exodeviations, bilateral recession in the divergence excess type, and recession-resection or bimedial resections in the convergence insufficiency type. Especially in the recession-resection operation, the amounts were so chosen as to perform a resection supported by a recession, or vice versa. In large deviations it was preferred to do two-step operations which tend to be symmetrizing. 5. 5. The final result of the operations was that the deviation in this group was reduced to 0 in 10 percent, to less than 10 Δ in 50 percent, and to less than 20 Δ in 82 percent. 6. 6. The deviation was transformed in 84 (or 42 percent) of the patients into an heterophoria in distance fixation and in 101 (or 50 percent) in near fixation. Binocular responses obtained instrumentally were more favorable. The binocular status existing preoperatively was no factor in our choice of operation.
Article
The neural mechanisms of stereoscopic 3D shape perception have only recently been investigated. Here we review the two cortical regions in which these mechanisms have been studied so far in macaques: a small subpart of inferotemporal cortex called TEs, and the caudal intraparietal (CIP) region. Neurons in TEs respond selectively to the orientation and curvature in depth of stereoscopic surfaces and this region provides a detailed 3D shape description of surface boundaries and surface content. This description is evoked only by binocular stimuli in which subjects see depth and it does not vary if depth is specified by different cues. Neurons in CIP are a selective for orientation in depth of surfaces and elongated objects, and their responses are also unaffected by changes in depth cues. Thus, stereoscopic 3D shape is processed in both the dorsal, occipito-parietal and the ventral, occipito-temporal streams.
Intermittent exotropia and stereopsis
  • W Lu
Lu W. Intermittent exotropia and stereopsis. Chinese Journal of Strabismus and Pediatric Ophthalmology 1999: 11-12. (In Chinese.)
Depth percepts from large disparities: individuals with strabismus outperform a visually normal control group
  • J R Harris
  • L M Wilcox
  • A Moroz-Harris
Harris JR, Wilcox LM, Moroz-Harris A, et al. Depth percepts from large disparities: individuals with strabismus outperform a visually normal control group. Investigative Ophthalmology and Visual Science 2000; 41:s813.
Effects of under correction and full correction of myopia on slowing the progression of myopia in school-aged children: a systematic review
  • S Y Li
  • S M Li
  • S S Wu
Li SY, Li SM, Wu SS, et al. Effects of under correction and full correction of myopia on slowing the progression of myopia in school-aged children: a systematic review.
Address correspondence to: Dr. Jin Zeng Department of Ophthalmology Guangdong Eye Institute Guangdong General Hospital Guangdong Academy of Medical Sciences No
  • Chinese Journal Of
  • Optometry Ophthalmology
  • Visual
Chinese Journal of Optometry Ophthalmology and Visual Science 2011; 13:223-226. Address correspondence to: Dr. Jin Zeng Department of Ophthalmology Guangdong Eye Institute Guangdong General Hospital Guangdong Academy of Medical Sciences No. 106 ZhongshanEr Road Guangzhou 510080