Peripheral Binocular Imbalance in Anisometropic and Strabismic Amblyopia.

Purpose: Individuals with amblyopia experience central vision deficits, including loss of visual acuity, binocular vision, and stereopsis. In this study, we examine the differences in peripheral binocular imbalance in children with anisometropic amblyopia, strabismic amblyopia, and typical binocular vision to determine if there are systematic patterns of deficits across the visual field. Methods: This prospective cohort study recruited 12 participants with anisometropic amblyopia, 10 with strabismic amblyopia, and 10 typically sighted controls (age range, 5-18 years). Binocular imbalance was tested at 0°, 4°, and 8° eccentricities (4 angular locations each) using band-pass filtered Auckland optotypes (5 cycles per optotype) dichoptically presented with differing contrast to each eye. The interocular contrast ratio was adjusted until the participant reported each optotype with equal frequency. Results: Participants with anisometropic and strabismic amblyopia had a more balanced contrast ratio, or decreased binocular imbalance, at 4° and 8° eccentricities as compared with central vision. Participants with strabismic amblyopia had significantly more binocular imbalance in the periphery as compared with individuals with anisometropic amblyopia or controls. A linear mixed effects model showed a main effect for strabismic amblyopia and eccentricity on binocular imbalance across the visual field. Conclusions: There is evidence of decreased binocularity deficits, or interocular suppression, in the periphery in anisometropic and strabismic amblyopia as compared with controls. Notably, those with strabismic amblyopia exhibited more significant peripheral binocular imbalance. These variations in binocularity across the visual field among different amblyopia subtypes may necessitate tailored approaches for dichoptic treatment.

Application of Absorbable Suture in Strabismus Correction and Nursing Management Advantage of Watson Care Theory in Perioperative Period.

Objectives: The article is aimed at investigating the suture effect of absorbable suture in strabismus correction and the advantage of Watson care theory. Methods: 148 children with strabismus were enrolled in this study and divided into two groups. The control group received routine nursing, and on this basis, the observation group was given Watson care theory nursing and eye muscle suture with absorbable sutures. The degree of cooperation (induction compliance checklist (ICC) score), negative emotion (modified Yale preoperative anxiety scale (m-YAPS) score), pain (face pain scale (FPS) score), quality of nursing management, parents' satisfaction, clinical efficacy, and adverse reactions were compared. Results: After nursing and surgical treatment, all children's strabismus symptoms were improved, and the improvement of strabismus and visual function in the observation group was more obvious. Watson care nursing can effectively improve the nursing management quality, parents' satisfaction, children's negative emotions, and treatment compliance. Conclusions: As a result, Watson care theory nursing is of great significance for improving the relationship between nurses and patients and building a harmonious hospital.

Altered functional connectivity of primary visual cortex in adults with strabismus and amblyopia: a resting-state fMRI study.

Functional connectivity of the primary visual cortex was explored with resting functional magnetic resonance imaging among adults with strabismus and amblyopia and healthy controls. We used the two-sample test and receiver operating characteristic curves to investigate the differences in mean functional connectivity values between the groups with strabismus and amblyopia and healthy controls. Compared with healthy controls, functional connectivity values in the left Brodmann areas 17, including bilateral lingual/angular gyri, were reduced in groups with strabismus and amblyopia. Moreover, functional connectivity values in the right Brodmann area 17, including left cuneus, right inferior occipital gyrus, and left inferior parietal lobule, were reduced in adults with strabismus and amblyopia. Our findings indicate that functional connectivity abnormalities exist between the primary visual cortex and other regions. This may be the basis of the pathological mechanism of visual dysfunction and stereovision disorders in adults with strabismus and amblyopia.

Gray matter volume alterations in patients with strabismus and amblyopia: voxel-based morphometry study.

This study proposes the use of the voxel-based morphometry (VBM) technique to investigate structural alterations of the cerebral cortex in patients with strabismus and amblyopia (SA). Sixteen patients with SA and sixteen healthy controls (HCs) underwent magnetic resonance imaging. Original whole brain images were analyzed using the VBM method. Pearson correlation analysis was performed to evaluate the relationship between mean gray matter volume (GMV) and clinical manifestations. Receiver operating characteristic (ROC) curve analysis was applied to classify the mean GMV values of the SA group and HCs. Compared with the HCs, GMV values in the SA group showed a significant difference in the right superior temporal gyrus, posterior and anterior lobes of the cerebellum, bilateral parahippocampal gyrus, and left anterior cingulate cortex. The mean GMV value in the right superior temporal gyrus, posterior and anterior lobes of the cerebellum, and bilateral parahippocampal gyrus were negatively correlated with the angle of strabismus. The ROC curve analysis of each cerebral region confirmed the accuracy of the area under the curve. Patients with SA have reduced GMV values in some brain regions. These findings might help to reveal the potential pathogenesis of SA and its relationship with the atrophy of specific regions of the brain.

Measuring functional connectivity in patients with strabismus using stationary functional magnetic resonance imaging: a resting-state network study.

BACKGROUND: Strabismus (STR) is a common eye disease characterized by abnormal eye movements and stereo vision. Neuroimaging studies have revealed that STR patients have impaired functional connectivity (FC) in the visual cortex and sensorimotor cortex. PURPOSE: To investigate alterations in FC and connections within and between subnetworks of the visual network (VN), sensorimotor network (SMN), and default mode network (DMN) in patients with STR. MATERIAL AND METHODS: A total of 32 patients with STR (24 men, 8 women) and 32 age- and sex-matched healthy controls (HCs) (24 men, 8 women) were recruited. Participants underwent resting-state functional magnetic resonance imaging scans. The resting-state network (RSN) was examined by independent component analysis, and differences in RSN FC between STR and HC groups were evaluated with the t test. Functional network connectivity (FNC) analysis was performed for the three RSNs. RESULTS: Compared to the HC group, the STR group showed increased FC in the VN and SMN (voxel-level P < 0.01; two-tailed Gaussian random field correction; cluster-level P < 0.05). There were no significant alterations in DMN FC between the two groups. FNC analysis of connections in the RSN revealed that one of the three connections in the VN was reduced, but no connectivity changes were observed in the SMN or DMN. FNC analysis of the connection between two RSNs showed that two had increased and one had a decreased connection value. CONCLUSION: The VN, SMN, and DMN are reorganized in patients with STR compared to HCs, providing novel insight into the neural substrates of STR.

Adjustable Sutures in the Treatment of Strabismus: A Report by the American Academy of Ophthalmology.

PURPOSE: To review the scientific literature that evaluates the effectiveness of adjustable sutures in the management of strabismus for adult and pediatric patients. METHODS: Literature searches were performed in the PubMed database through April 2021 with no date limitations and were restricted to publications in English. The searches identified 551 relevant citations, of which 55 were reviewed in full text. Of these, 17 articles met the inclusion criteria and were assigned a level of evidence rating by the panel methodologist. The search included all randomized controlled studies regardless of study size and cohort studies of 100 or more patients comparing the adjustable versus nonadjustable suture technique, with a focus on motor alignment outcomes or reoperation rates. RESULTS: The literature search yielded no level I studies. Of the 17 articles that met the inclusion criteria, 11 were rated level II and 6 were rated level III. Among the 12 studies that focused on motor alignment outcomes, 4 small randomized clinical trials (RCTs) did not find a statistically significant difference between groups, although they were powered to detect only very large differences. Seven of 8 nonrandomized studies found a statistically significant difference in motor alignment success in favor of the adjustable suture technique, both overall and in certain subgroups of patients. Successful motor alignment was seen in both exotropia (in 3 studies that were not limited to children) and esotropia (in 1 study of adults and 2 of children). The majority of included studies that reported on reoperation rates found the rates to be lower in patients who underwent strabismus surgery with adjustable sutures, but this finding was not uniformly demonstrated. CONCLUSIONS: Although there are no level I studies evaluating the effectiveness of adjustable sutures for strabismus surgery, the majority of nonrandomized studies that met the inclusion criteria for this assessment reported an advantage of the adjustable suture technique over the nonadjustable technique with respect to motor alignment outcomes. This finding was not uniformly demonstrated among all studies reviewed and warrants further investigation in the development and analysis of adjustable suture techniques.

Morphological change of the posterior pole following the horizontal strabismus surgery with swept source optical coherence tomography.

Extraocular muscle movement during strabismus surgery causes changes in eyeball shape. Because extraocular muscle insertion is in front of the equator, it is thought that changes due to strabismus surgery mainly occur in the anterior segment. However, changes in the posterior segment of eye may also occur, which may also result in changes in refractive error after strabismus surgery. Using a 3-dimensional reconstruction technique (en face imaging) of the swept source optical coherence tomography, we determined and quantitatively measured the posterior polar change. The deepest interface between Bruch's membrane and the choroid could be identified as the deepest point of the eyeball (DPE), and the location of the DPE relative to the optic disc and the fovea was measured. After lateral rectus muscle recession, the DPE moved away from the fovea, but after medial rectus muscle recession, the DPE moved toward the fovea. The amount of DPE movement differed by age and preoperative refractive error. Our findings suggest that the positional shift of the rectus muscle in horizontal strabismus surgery causes a structural change in the posterior segment of the eye, and the postoperative refractive changes may be related to this shift.

Unreferenced spatial localization under monocular and dichoptic viewing conditions.

Knowledge of eye position in the brain is critical for localization of objects in space. To investigate the accuracy and precision of eye position feedback in an unreferenced environment, subjects with normal ocular alignment attempted to localize briefly presented targets during monocular and dichoptic viewing. In the task, subjects' used a computer mouse to position a response disk at the remembered location of the target. Under dichoptic viewing (with red (right eye)-green (left eye) glasses), target and response disks were presented to the same or alternate eyes, leading to four conditions [green target-green response cue (LL), green-red (LR), red-green (RL), and red-red (RR)]. Time interval between target and response disks was varied and localization errors were the difference between the estimated and real positions of the target disk. Overall, the precision of spatial localization (variance across trials) became progressively worse with time. Under dichoptic viewing, localization errors were significantly greater for alternate-eye trials as compared to same-eye trials and were correlated to the average phoria of each subject. Our data suggests that during binocular dissociation, spatial localization may be achieved by combining a reliable versional efference copy signal with a proprioceptive signal that is unreliable perhaps because it is from the wrong eye or is too noisy.

Interocular suppression in primary visual cortex in strabismus: impact of staggering the presentation of stimuli to the eyes.

Diplopia (double vision) in strabismus is prevented by suppression of the image emanating from one eye. In a recent study conducted in two macaques raised with exotropia (an outward ocular deviation) but having normal acuity in each eye, simultaneous display of stimuli to each eye did not induce suppression in V1 neurons. Puzzled by this negative result, we have modified our protocol to display stimuli in a staggered sequence, rather than simultaneously. Additional recordings were made in the same two macaques, following two paradigms. In trial type 1, the receptive field in one eye was stimulated with a sine-wave grating while the other eye was occluded. After 5 s, the occluder was removed and the neuron was stimulated for another 5 s. The effect of uncovering the eye, which potentially exposed the animal to diplopia, was quantified by the peripheral retinal interaction index (PRII). In trial type 2, the receptive field in the fixating eye was stimulated with a grating during binocular viewing. After 5 s, a second grating appeared in the receptive field of the nonfixating eye. The impact of the second grating, which had the potential to generate visual confusion, was quantified by the receptive field interaction index (RFII). For 82 units, the mean PRII was 0.48 ± 0.05 (0.50 = no suppression) and the mean RFII was 0.46 ± 0.08 (0.50 = no suppression). These values suggest mild suppression, but the modest decline in spike rate registered during the second epoch of visual stimulation might have been due to neuronal adaptation, rather than interocular suppression. In a few instances neurons showed unequivocal suppression, but overall, these recordings did not support the contention that staggered stimulus presentation is more effective than simultaneous stimulus presentation at evoking interocular suppression in V1 neurons.NEW & NOTEWORTHY In strabismus, double vision is prevented by interocular suppression. It has been reported that inhibition of neuronal firing in the primary visual cortex occurs only when stimuli are presented sequentially, rather than simultaneously. However, these recordings in alert macaques raised with exotropia showed, with rare exceptions, little evidence to support the concept that staggered stimulus presentation is more effective at inducing interocular suppression of V1 neurons.

Excitatory Contribution to Binocular Interactions in Human Visual Cortex Is Reduced in Strabismic Amblyopia.

Binocular summation in strabismic amblyopia is typically reported as being absent or greatly reduced in behavioral studies and is thought to be because of a preferential loss of excitatory interactions between the eyes. Here, we studied how excitatory and suppressive interactions contribute to binocular contrast interactions along the visual cortical hierarchy of humans with strabismic and anisometropic amblyopia in both sexes, using source-imaged steady-state visual evoked potentials (SSVEP) over a wide range of relative contrast between the two eyes. Dichoptic parallel grating stimuli modulated at unique temporal frequencies in each eye allowed us to quantify spectral response components associated with monocular inputs (self-terms) and the response components because of interaction of the inputs of the two eyes [intermodulation (IM) terms]. Although anisometropic amblyopes revealed a similar pattern of responses to normal-vision observers, strabismic amblyopes exhibited substantially reduced IM responses across cortical regions of interest (V1, V3a, hV4, hMT+ and lateral occipital cortex), indicating reduced interocular interactions in visual cortex. A contrast gain control model that simultaneously fits self- and IM-term responses within each cortical area revealed different patterns of binocular interactions between individuals with normal and disrupted binocularity. Our model fits show that in strabismic amblyopia, the excitatory contribution to binocular interactions is significantly reduced in both V1 and extra-striate cortex, whereas suppressive contributions remain intact. Our results provide robust electrophysiological evidence supporting the view that disruption of binocular interactions in strabismus or amblyopia is because of preferential loss of excitatory interactions between the eyes.SIGNIFICANCE STATEMENT We studied how excitatory and suppressive interactions contribute to binocular contrast interactions along the visual cortical hierarchy of humans with normal and amblyopic vision, using source-imaged SSVEP and frequency-domain analysis of dichoptic stimuli over a wide range of relative contrast between the two eyes. A dichoptic contrast gain control model was used to characterize these interactions in amblyopia and provided a quantitative comparison to normal vision. Our model fits revealed different patterns of binocular interactions between normal and amblyopic vision. Strabismic amblyopia significantly reduced excitatory contributions to binocular interactions, whereas suppressive contributions remained intact. Our results provide robust evidence supporting the view that the preferential loss of excitatory interactions disrupts binocular interactions in strabismic amblyopia.

Remote Pediatric Ophthalmology and Adult Strabismus during the COVID-19 Pandemic.

BACKGROUND: The coronavirus (COVID-19) global pandemic has been a poignant reminder of the value of telehealth services to deliver care, especially as a means of reducing the risk of infectious disease transmission caused by close personal contact, decreasing unnecessary travel for medical consultations, and limiting the number of individuals in waiting rooms. The role of telehealth in ophthalmology has historically been limited to store-and-forwarding of images, much like what is used in radiology. PATIENTS AND METHODS: Remote evaluation using two-way audio-video communications over the initial 10-week period of clinic shutdowns. Visual acuity (VA) measurement was attempted using a printed single surrounded HOTV or Snellen chart. The VA measurement of fellow eyes was compared to the prior in person clinical visit. External and strabismus examinations were also conducted. RESULTS: Fifty-eight patients were evaluated with a mean age 12.5 years (range 5 months to 82 years). Twenty of 58 (34%) were younger than 5 years of age. Reasons for evaluation were strabismus in 26 patients (45%), refractive error in 25 (43%), and amblyopia in 10 patients (19%). Recognition visual acuity was obtained in 69% (40 of 58), including every patient older than 5 years of age. Nine children from 2 to 5 years of age (mean 3 years) were unable to perform HOTV VA testing. Of nine children unable to do complete VA testing, five had been premature and seven had developmental delay. There was a mean bias of -0.12 logMAR in favor of the prior in office test in the right eyes of 21 non-amblyopic patients. The 95% limits of agreement between the in-person visit and the subsequent telehealth video visit logMAR VA were +0.20 logMAR upper limit, -0.44 logMAR lower limit. CONCLUSIONS: Telehealth video visits provided basic ophthalmic information in patients who are physically incapable to come to the office, leading to improved triage. Vision could be tested remotely in young children, but we found substantial variability in the measurement of clinically normal eyes. Improvements in the reliability of at-home visual acuity testing are needed.

Convergence Insufficiency Neuro-Mechanism Adult Population Study: Phoria Adaptation Results.

Purpose: The purpose of this study was to compare changes in phoria adaptation between young adult binocularly normal controls (BNCs) and participants with symptomatic convergence insufficiency (CI), who were randomized to either office-based vergence accommodative therapy (OBVAT) or office-based placebo therapy (OBPT). Methods: In the double-masked randomized clinical trial, 50 BNC and 50 CI participants were randomized to the following therapeutic interventions: OBVAT or OBPT with home reinforcement for 12 one-hour office sessions. A 6∆ base-out and 6∆ base-in phoria adaptation experiment at near (40 cm) was conducted using the flashed Maddox rod technique at baseline and at outcome. Measurements included the rate and the magnitude of phoria adaptation. Results: At baseline, BNC and CI participants had significantly different rates and magnitudes of base-in and base-out phoria adaptation (P < 0.001). When comparing the outcome to baseline measurements, significant main effect differences in longitudinal measurements were observed for the magnitude and the rate of phoria adaptation for both base-out and base-in experiments (P < 0.05). For the magnitude and rate of phoria adaptation, post hoc analyses using paired t-tests revealed that the CI group administered the OBVAT intervention exhibited a significant increase in the magnitude and rate of phoria adaptation compared to baseline for both base-in and base-out phoria adaptation (P < 0.01) but not for those administered OBPT. Conclusions: Phoria adaptation is significantly different at baseline between those with normal binocular vision and symptomatic CI participants. OBVAT significantly improves the rate and magnitude of both base-out and base-in phoria adaptation at near compared to OBPT. Results have clinical implications for new therapeutic interventions.

Alternations of interhemispheric functional connectivity in children with strabismus and amblyopia: a resting-state fMRI study.

Previous neuroimaging studies demonstrated that patients with strabismus or amblyopia can show significant functional and anatomical changes in the brain, but alterations of interhemispheric functional connectivity (FC) have not been well studied in this population. The current study analyzed whole-brain changes of interhemispheric FC in children with strabismus and amblyopia (CSA) using voxel-mirrored homotopic connectivity (VMHC).A total of 24 CSA (16 males and 8 females) and 24 normal controls (NCs) consisting of 16 and 8 age-, sex, and education-matched males and females, respectively, underwent functional magnetic resonance imaging (fMRI) scans in the resting state. According to Gaussian random field theory, changes in the resting state FC (rsFC) between hemispheres were evaluated using the VMHC method. The relationships between mean VMHC values in multiple brain regions and behavioral performance were evaluated by Pearson correlation analysis. In contrast to NCs, the CSA group showed significantly decreased VMHC values in the bilateral cerebellum, bilateral frontal superior orbital (frontal sup orb), bilateral temporal inferior(temporal inf),and bilateral frontal superior(frontal sup). CSA have abnormal interhemispheric FC in many brain regions, which may reflect dysfunction of eye movements and visual fusion. These findings might provide insight into the underlying pathogenetic mechanisms of CSA.

Is Fixation Preference a Potential Indicator of Macular Function in Children?

Objectives: Fixation preference testing is widely used to detect amblyopia, particularly in preverbal children. Pattern electroretinogram (pERG) is an electrophysiological test which is a sensitive indicator of macular function. The aim of this study was to investigate the relationship between fixation preference and macular function on pERG in children with strabismus. Materials and Methods: The study included 11 children with strabismus. All underwent ophthalmological examination including fixation preference by binocular fixation pattern test, best corrected visual acuity (BCVA) assessment, and pERG. Results: The mean age of the patients was 10.09±1.18 years. All patients had unilateral fixation. The mean BCVA was 0.85±0.17 in preferred and 0.48±0.19 in non-preferred eyes (p=0.003). The mean p50 amplitude was 6.07±2.06 µV in preferred and 5.29±2.20 µV in non-preferred eyes (p=0.203), and the mean N95 amplitude was 8.27±2.86 µV and 8.03±3.24 µV respectively (p=0.594). BCVA was correlated with p50 and N95 amplitudes in the non-preferred eyes (p=0.023 and p=0.014). Interocular BCVA difference was correlated with interocular P50 amplitude difference (r=0.688, p=0.019). Conclusion: Although amblyopia is typically considered a cortical phenomenon, future larger studies are needed to investigate the relationship between fixation preference and macular electrophysiological function.

Botulinum Toxin Injection for the Treatment of Strabismus: A Report by the American Academy of Ophthalmology.

PURPOSE: To review the available evidence comparing the effectiveness of extraocular muscle botulinum toxin type A (BTXA) injection with eye muscle surgery for restoring ocular alignment in children and adults with nonparalytic, nonrestrictive horizontal strabismus. METHODS: Literature searches in the PubMed Cochrane Library, and clinical trial databases with no date restrictions, but limited to articles published in English, were conducted last on January 10, 2021. The searches yielded 515 citations, 40 of which were reviewed in full text by the first author. Fourteen articles met the criteria for inclusion (randomized or nonrandomized comparative studies, or case series with a minimum 50 patients; evaluating extraocular muscle BTXA injection for initial or repeat treatment of horizontal, nonparalytic, nonrestrictive strabismus; with at least 6 months of follow-up) and were graded by a methodologist. RESULTS: The 14 included studies consisted of 2 randomized clinical trials, 3 nonrandomized comparative studies, and 9 case series. All 5 comparative studies were graded level II evidence, and the 9 case series were graded level III evidence. Successful motor outcomes after BTXA injection were relatively consistent across 4 of the 5 comparative studies at 60%, when adjustment was made for differential selection bias in 1 of the studies. In the 4 studies, successful motor outcomes after surgery ranged from 66% to 77% with a mean follow-up of 23 to 75 months, and the outcomes were not significantly different from those after BTXA injection. In the fifth level II study, success was significantly higher with BTXA injection than with surgery (94% vs. 72%). The level III BTXA case series demonstrated higher motor success rates of 87% to 89% when children were treated in 2 muscles at a time; rates were lower in adults treated with single-muscle BTXA injection. CONCLUSIONS: Extraocular muscle injection of BTXA achieves a high rate of successful motor alignment, comparable with that achieved after eye muscle surgery for nonparalytic, nonrestrictive horizontal strabismus. Good alignment may require multiple BTXA injections, and it is not yet clear whether sensory outcomes are equivalent for BTXA injections versus eye muscle surgery in young children.

Near-point Findings in Children with Autism Spectrum Disorder and in Typical Peers.

SIGNIFICANCE: Clinicians can better diagnose and manage vision problems of autism spectrum disorder (ASD) children by establishing a standard of care for this population. Results also reinforce the importance of a comprehensive binocular vision evaluation in all patients with ASD. PURPOSE: The purposes of this study were to compare near-point and ocular motility test findings in ASD children and typically developing (TD) peers and to compare findings among ASD children by level of verbal communication. METHODS: Sixty-one children and adolescents (ASD, 34; TD, 27) aged 9 to 17 years completed an eye examination protocol including tests of distance and near phoria, near point of convergence, near fusional convergence and divergence, accommodative response, and Northeastern State University College of Optometry oculomotor testing. Testing was completed through refractive correction. Parents of ASD children provided information regarding subjects' verbal communication level (nonverbal, uses short words, verbal). RESULTS: Distance phoria did not differ significantly between groups. Near phoria of ASD subjects was more exophoric (difference, 2.8 prism diopters). Mean near point of convergence break and recovery were 7.0 and 8.02 cm, respectively, in ASD subjects and 2.19 and 3.99 cm in TD subjects. Near fusional divergence and convergence showed no significant difference. Autism spectrum disorder subjects had significantly poorer stereoacuity (P < .0001) and, on Northeastern State University College of Optometry Oculomotor Testing, reduced fixation, poorer accuracy and stamina/ability, and increased head and body movement. Monocular estimation method retinoscopy results did not differ significantly between ASD and TD subjects. No significant differences in phoria, near point of convergence, and near fusional divergence or convergence were observed between ASD subgroups (nonverbal, uses short words, verbal). CONCLUSIONS: Autism spectrum disorder children are more likely to show receded near point of convergence, poor fixation, inaccurate saccades, erratic pursuits, and exophoric posture. These differences occur, regardless of reported verbal communication level.

Multiple Short Daily Periods of Normal Binocular Vision Preserve Stereopsis in Strabismus.

Purpose: Infantile strabismus impedes the development of stereopsis. In optically strabismic monkeys, 2 continuous hours of normal binocular vision per day has been shown to preserve near-normal stereopsis. In this study, we investigated whether, as in learning, multiple shorter periods of intervention would further boost performance. Methods: To simulate infantile esotropia, infant monkeys were reared with 30 prism diopters base-in starting at 4 weeks of age. Daily periods of normal binocular vision were provided by replacing prisms with plano lenses. Altogether, 14 monkeys were prism reared: 2 with continuous prism, 2 with 2 continuous hours of normal binocular vision per day, 6 with 2 noncontinuous hours, and 4 with 1 noncontinuous hour of binocular vision each day. Seven normally reared monkeys provided control data. Behavioral methods were employed to measure spatial contrast sensitivity, eye alignment, and stereopsis. Results: One monkey reared with continuous prism had poor stereopsis, and the other had no stereopsis. Ten of the 12 monkeys reared with periods of normal binocular vision had stereopsis, and those with longer and more continuous periods of binocular vision had stereopsis approaching that of normally reared monkeys. Conclusions: During early development, multiple short periods of binocular vision were effective in preserving clinically significant stereopsis in monkeys. These results suggest that by providing relatively short multiple daily intervention periods, stereopsis may be preserved in strabismic human children.

Ocular motility changes and diplopia in sutured versus unsutured implantation of the Baerveldt glaucoma device.

PURPOSE: To investigate the effect of two surgical techniques in primary Baerveldt glaucoma implant (BGI) surgery, that is the sutured technique and the unsutured (free) plate technique, on the ocular motility and prevalence of diplopia. We hypothesize that the free plate technique results in a lower diplopia prevalence. METHODS: We performed a prospective study of patients who underwent BGI surgery with the free plate technique and compared them with patients from a previous study who had undergone BGI surgery with the sutured technique. Their ductions, ocular alignment and fusion range and the prevalence of diplopia were measured before surgery and at 3 months, 6 months and 1 year postoperatively. RESULTS: We analysed 57 free plate and 51 sutured plate patients. One year postoperatively, we found no statistically significant difference in the prevalence of diplopia between the two techniques. All duction changes between baseline and 1-year follow-up were restrictions and occurred statistically significantly more frequently in the free plate than in the sutured plate group (p = 0.03; 60% versus 34%). About the ocular alignment, in the horizontal direction, a change in exodirection was more common in both groups, while in the vertical direction, a hyperdeviation of the operated eye was more common. The vertical ocular alignment change was smaller in the free plate group than in the sutured plate group (p = 0.04 at near and p = 0.02 at distance). CONCLUSIONS: One year postoperatively, the prevalence of diplopia was not significantly different between patients with the sutured plate and patients with the free plate technique. Both surgical techniques induce diplopia and changes in ocular motility and/or in ocular alignment.

Primary and secondary superior rectus recessions to correct vertical deviations in Graves' orbitopathy patients.

PURPOSE: Patients with vertical strabismus and consecutive diplopia due to Graves' orbitopathy (GO) might need recession of the rectus superior muscle. The aim of this retrospective analysis is to provide dose-effect values and motility analysis for these patients. METHODS: Dose-effect relations (deviation reduction in primary position per amount of recession in mm), monocular excursions and size of the field of binocular single vision (BSV) were evaluated in three different groups of patients. Group 1 (n = 33) patients with primary fibrosis of superior rectus muscle undergoing recession of the ipsilateral rectus superior, Group 2 (n = 14) superior rectus muscle recession after recession of inferior rectus on the contralateral eye and Group 3 (n = 15) simultaneous ipsilateral superior rectus recession and contralateral inferior rectus muscle recession. Surgery was performed using the dose-effect for inferior rectus recession of 4 prism dioptre (PD,Δ ) reduction/per mm recession and the intraoperative traction test. RESULTS: Restoration of BSV in the central 20° of gaze could be reached in 88%, 79% and 67% of patients in the three groups, respectively. Restoration of BSV in downgaze (up to 30°) was a little less successful, 79%, 57% and 53%, respectively. The median dose-effect was 3.2Δ reduction/mm recession in Group 1 (Spearman correlation r = 0.75, p < 0.0001) and 3.3Δ /mm in Group 2 (n.s.) and 4Δ /mm in Group 3 (r = 0.67, p = 0.016). The basis for the improvement was the symmetrization of ductions. CONCLUSION: If superior rectus recession is necessary in GO, higher dosing around 3Δ reduction/per mm recession should be applied. In case of large deviations, combined vertical surgery (inferior rectus and superior rectus contralateral) is required and reasonable (low cyclotorsion). Single-step or two-step procedures lead to similar results.

Comparativa del control postural entre niños estrábicos y no estrábicos / Comparison of postural control between strabismic and non-strabismic children

OBJETIVO: Comparar el control postural de niños estrábicos frente a niños sin estrabismo. MATERIAL Y MÉTODOS: Cohortes transversales. Se incluyeron un total de 171 niños: 73 niños con endotropia, 24 con exotropia y 74 controles. El control postural fue explorado mediante una plataforma dinamométrica en bipedestación, en varias condiciones: ojos abiertos y cerrados, fijación de mirada cercana y lejana; y sobre suelo duro y gomaespuma. Se estudiaron como variables: el área, la velocidad media, las longitudes en el eje X e Y del desplazamiento del centro de presión. RESULTADOS: Los niños con endotropia y exotropia presentaron valores de velocidad media, longitud X e Y significativamente mayores frente a los controles en el examen de ojos abiertos, distancia de fijación lejana y sobre suelo de gomaespuma; con ojos abiertos, sobre suelo duro y distancia lejana, los valores de las exotropias fueron mayores que los de endotropias y controles. Con ojos cerrados, no hubo diferencias entre los 3 grupos en todas condiciones de exploración descritas, pero sus valores empeoraban frente a sus respectivos con ojos abiertos. CONCLUSIONES: Los niños estrábicos presentaron un peor control postural que los niños no estrábicos. Todos los niños se mostraron más inestables con ojos cerrados frente a con ojos abiertos lo que demuestra que, tanto para estrábicos como no estrábicos, la visión tiene un papel relevante en la estabilidad postural

OBJECTIVE: To compare the postural control of children with strabismus versus non-strabismus children. MATERIAL AND METHODS: Cross-sectional cohort study with a total of 171 children, including 73 children with esotropia, 24 with exotropia, and 74 controls. Postural control was determined using a dynamometric platform in a standing position in various conditions: eyes open and eyes closed, near and gaze fixation, and with and without foam pad. The studied variables were the area, the mean speed, and the lengths in the X and Y axis of the centre of pressure displacement. RESULTS: Children with esotropia and exotropia had significantly higher mean values (speed, lengths of X and Y) compared to controls. In the open-eye, far distance fixation, and on foam pad, as well as under exam conditions; with eyes open, without foam pad, and far distance fixation, the exotropia values were higher than those of endotropia and controls. With eyes closed, there were no differences between the 3 groups under the described examination conditions, but their values were worse compared to their respective ones with eyes open. CONCLUSIONS: The children with strabismus had a worse postural control than the non-strabismus ones. All of the them appeared to be more unstable with eyes closed than with eyes open, which demonstrates that vision plays an important relevant role in postural stability in both strabismus and non-strabismus children