Binocular Convergence Research Articles

Predicting Subjective Discomfort Associated with Lens Distortion in VR Headsets During Vestibulo-Ocular Response to VR Scenes.

With advances in Virtual Reality (VR) technology, user expectation for a near-perfect experience is also increasing. The push for a wider field-of-view can increase the challenges of correcting lens distortion. Past studies on imperfect VR experiences have focused on motion sickness provoked by vection-inducing VR stimuli and discomfort due to mismatches in accommodation and binocular convergence. Disorientation and discomfort due to unintended optical flow induced by lens distortion, referred to as dynamic distortion (DD), has, to date, received little attention. This study examines and models the effects of DD during head rotations with various fixed gazes stabilized by vestibulo-ocular reflex (VOR). Increases in DD levels comparable to lens parameters from poorly designed commercial VR lenses significantly increase discomfort scores of viewers in relation to disorientation, dizziness, and eye strain. Cross-validated results indicate that the model is able to predict significant differences in subjective scores resulting from different commercial VR lenses and these predictions correlated with empirical data. The present work provides new insights to understand symptoms of discomfort in VR during user interactions with static world-locked / space-stabilized scenes and contributes to the design of discomfort-free VR headset lenses.

The impacts of lens and stereo camera separation on perceived slant in Virtual Reality head-mounted displays.

Stereoscopic AR and VR headsets have displays and lenses that are either fixed or adjustable to match a limited range of user inter-pupillary distances (IPDs). Projective geometry predicts a misperception of depth when either the displays or virtual cameras used to render images are misaligned with the eyes. However, misalignment between the eyes and lenses might also affect binocular convergence, which could further distort perceived depth. This possibility has been largely ignored in previous studies. Here, we evaluated this phenomenon in a VR headset in which the inter-lens and inter-axial camera separations are coupled and adjustable. In a baseline condition, both were matched to observers' IPDs. In two other conditions, the inter-lens and inter-axial camera separations were set to the maximum and minimum allowed by the headset. In each condition, observers were instructed to adjust a fold created by two intersecting, textured surfaces until it appeared to have an angle of 90°. The task was performed at three randomly interleaved viewing distances, monocularly and binocularly. In the monocular condition, observers underestimated the fold angle and there was no effect of viewing distance on their settings. In the binocular conditions, we found that when the lens and camera separation were less than the viewer's IPD, they exhibited compression of perceived slant relative to baseline. The reverse pattern was seen when the lens and camera separation were larger than the viewer's IPD. These results were well explained by a geometric model that considers shifts in convergence due to lens and display misalignment with the eyes, as well as the relative contribution of monocular cues.

Influence of concussion history and age of first concussion on visio-vestibular function

ObjectivesTo assess if abnormalities on visio-vestibular examination (VVE) are associated with concussion history (first vs. repeat) or age of first concussion in acutely concussed adolescents. DesignCross-sectional. MethodsData were queried from the Children's Hospital of Philadelphia Minds Matter concussion registry. Patients aged 14–18 years old presenting for their initial visit to the specialty care concussion program within 28 days of injury were included. Demographics, including age, sex, concussion history, and age of first concussion, were collected before the exam. The VVE consisted of 9 subtests: smooth pursuit, horizontal/vertical saccades and vestibulo-ocular reflex (VOR), binocular convergence, left/right monocular accommodation, and complex tandem gait. Primary outcomes included VVE subtests (normal/abnormal), and total VVE score (abnormal = 2+ abnormal subtests). ResultsAmong 1051 patients included (female = 604(57.5 %); age = 15.6 ± 1.2; median lifetime concussions = 1 [IQR = 1,3]), 518 had repeat concussion. Controlling for age and sex, first vs. repeat concussion was not associated with any VVE subtest or total score (Total VVE Score RR = 1.35, 99.5%CI = 0.70,2.61). Of those with repeat concussion, 190 had valid age of first concussion data. Controlling for age, sex, and number of lifetime concussions, age of first concussion was not significantly associated with any VVE subtest or total score (Total VVE Score RR = 1.11, 99.5%CI = 0.78,1.57). ConclusionsAdolescents with concussion history present with similar visio-vestibular function to those with no concussion history. Additionally, clinical effects of early age of first concussion may not be evident in children. This study provides foundational data regarding potential cumulative effects of concussion in younger athletes.

The Effect of A Home Exercise Program on Visio-Vestibular Function in Concussed Pediatric Patients

Background:A home exercise program (HEP) can provide an equitable and cost-effective method for therapy targeted towards visio-vestibular deficits that are common following concussion. It is unclear if pediatric patients prescribed a HEP demonstrate improved visio-vestibular function.Purpose:To explore if a HEP affects visio-vestibular function in concussed pediatric patients.Methods:This observational study included 1,041 patients (614 female(59.0%); age=14.0±2.5 years) reporting to a specialty care concussion center for an initial visit within 28 days of injury and a first follow-up visit within 60 days of injury. All patients completed a Visio-Vestibular Examination (VVE) at both time points, which consisted of 9 maneuvers: smooth pursuit, horizontal/vertical saccades and gaze stability, binocular convergence, left/right monocular accommodation, and complex tandem gait. Patients were given a HEP at initial visit which consisted of exercises, including saccades, gaze stability, convergence, and balance, and instructed to complete these exercises 1-2 times daily. At follow-up, patients were asked to report their progress with the HEP, which was categorized as 1) has not done the HEP, 2) is currently doing the HEP, or 3) has completed the HEP. Primary outcomes included HEP status at first follow-up, VVE subtests (normal/abnormal), and total VVE (abnormal=2+ abnormal subtests). Separate chi-square tests with Bonferroni corrections were used to determine if the proportion of abnormal VVE outcomes was associated with HEP status (α=0.017 a priori).Results:At initial visit, 812 (77.6%) patients presented with abnormal total VVE. The proportion of abnormal subtests at initial visit ranged from 16.0% (right monocular accommodation) to 77.4% (horizontal gaze stability). At first follow-up, the proportion of abnormal total VVE did not differ among patients reporting not doing the HEP (101(62.0%)), patients currently doing the HEP (516(69.0%)), and patients who had completed the HEP (51(69.0%)). However among VVE subtests, a lower proportion of patients who completed the HEP presented with abnormal smooth pursuit (7.5%), horizontal (3.8%) and vertical (3.8%) saccades, and complex tandem gait (0%) relative to patients who were currently doing the HEP (P≤0.003) and to patients not doing the HEP (P≤0.01).Conclusions:Our findings indicate that patients who completed the HEP presented with better aspects of visio-vestibular function (smooth pursuit, saccades, and complex tandem gait) relative to those who did not start or were currently doing the HEP. This suggests that a HEP may be effective in reducing visio-vestibular dysfunction following concussion. Additional research investigating cost-effective concussion management tools is needed to improve patient outcomes.

Variations in intraocular pressure and visual parameters before and after using mobile virtual reality glasses and their effects on the eyes

We examined the effects of using mobile devices with immersive virtual reality for a short period on the physiological parameters of both eyes. The average age of the 50 participants (23 men and 27 women) was 17.72 ± 1.48 years, and refractive error ranged from 0 D to − 5.00 D. All the participants wore + 3.00 D glasses and underwent a 5-min relaxation adjustment through the atomization method. The participants wore immersive virtual reality (VR) glasses to watch a movie on a roller coaster for 10 min. Their relevant physiological parameters of the eyes were measured both before and after using VR glasses. Compared with before VR use, no significant difference (P > 0.05) was observed in the near-horizontal vergence and refractive error but a significant difference (P < 0.05) was observed in the amplitude of accommodation, intraocular pressure, divergence/convergence, and stereopsis after VR use. The corneal elastic coefficient was > 0.2 MPa, and we used Friedenwald’s eye rigidity relationship to obtain the K value (0.065–0.09). Approximately 10% of the participants experienced cybersickness symptoms such as nausea and dizziness. The use of VR to watch three-dimensional movies reduced intraocular pressure, which may help prevent or treat glaucoma. Moreover, the binocular convergence was higher when viewing near-field objects in VR than in the real world. Therefore, individuals with convergence excess may experience symptoms. Binocular parallax is the most likely cause of cybersickness symptoms. Thus, mobile VR devices with higher quality and comfort are necessary.

The Effect of a Home Exercise Program on Visio-Vestibular Function in Concussed Pediatric Patients

To explore if a home exercise program (HEP) affects visio-vestibular function in concussed pediatric patients. A HEP can provide an equitable and cost-effective method for therapy targeted towards visio-vestibular deficits that are common following concussion. It is unclear if pediatric patients prescribed a HEP demonstrate improved visio-vestibular function. This observational study included 1,041 patients (59% female; age = 14.0 ± 2.5 years) reporting to a specialty care concussion center for an initial visit ≤28 days post-injury and follow-up ≤60 days post-injury. All patients completed a Visio-Vestibular Examination (VVE) at both timepoints consisting of 9 subtests: smooth pursuit, horizontal/vertical saccades and gaze stability, binocular convergence, left/right monocular accommodation, and complex tandem gait. Patients were prescribed a HEP (1-2 times/day) at initial visit consisting of exercises addressing visio-vestibular deficits. At follow-up, patients reported their progress: (1) has not done the HEP, (2) is currently doing the HEP, or (3) has completed the HEP. Primary outcomes included HEP progress, VVE subtests (normal/abnormal), and total VVE (abnormal = 2 + abnormal subtests). Chi-square tests with Bonferroni corrections were used to determine if abnormal VVE outcomes were associated with HEP status. At initial visit, 81 2(77.6%) patients presented with abnormal total VVE. At follow-up, the proportion of abnormal total VVE did not differ among patients not doing the HEP (101 [62.0%]), patients currently doing the HEP (516 [69.0%]), and patients who had completed the HEP (51 [69.0%]). However among VVE subtests, a lower proportion who completed the HEP presented with abnormal smooth pursuit (7.5%), horizontal (3.8%) and vertical (3.8%) saccades, and complex tandem gait (0%) relative to patients currently doing the HEP (p = 0.003) and patients not doing the HEP (p = 0.01). Our findings indicate that patients who completed the HEP presented with improved elements of visio-vestibular function relative to those who did not start or were currently doing the HEP.

Pre- and post-season visio-vestibular function in healthy adolescent athletes

ABSTRACT Objective To evaluate pre – to post-season differences in individual subtests of the Visio-Vestibular Examination (VVE) in healthy middle and high school athletes. Methods This prospective cohort study recruited participants from a private suburban United States secondary school. Participants completed a demographic questionnaire prior to the start of their season. A proxy for head impact exposure was estimated by incorporating previously published head impact frequencies by team and sport. The VVE was completed pre – and post-season and consisted of 9 subtests: smooth pursuit, horizontal/vertical saccades and gaze stability, binocular convergence, left/right monocular accommodation, and complex tandem gait. Generalized estimating equations were employed to assess the relative risk of an abnormal VVE outcome based on testing session (pre – vs. post-season). Results Participants included middle and high school athletes (n = 115; female = 59 (51.3%); median age at first assessment = 14.9 years, [IQR = 13.6, 16.0]) during 2017/18 – 2019/20 school years. During pre-season testing, accommodation (10.0%) and complex tandem gait (9.2%) had the largest proportion of abnormal outcomes, while smooth pursuits (10.6%) and convergence (9.5%) had the largest proportion of abnormal outcomes post-season. When assessing the effect of testing session on the relative risk of any abnormal VVE subtest, there were no significant findings (P ≥ 0.25). Additionally, there were no significant effects of testing session when adjusting for estimated head impact exposure for any VVE subtest (P ≥ 0.25). Conclusions Visio-vestibular function as measured by the VVE does not change from pre – to post-season in otherwise healthy adolescent athletes. Our findings suggest that the VVE may be stable and robust to typical neurodevelopment occurring in this dynamic age group and help inform post-injury interpretation of visio-vestibular impairments.

Binocular accommodative response with extended depth of focus under controlled convergences.

Vergence and accommodation can be mismatched under virtual reality viewing conditions, and this mismatch has been thought to be one of the main causes of visual discomfort. The goal of this study was to investigate how optical conditions of the eyes affect accommodative responses to different convergence. Specifically, we hypothesized that extending the depth of focus (DoF) could weaken the control of the screen on accommodation, so that accommodation could be induced by convergence. To test this hypothesis, we extended the DoF using Zernike spherical aberrations (fourth and sixth orders) induced by a binocular adaptive optics (AO) vision simulator. Nine normal subjects between the ages of 21 and 34 (26 ± 5) years were recruited. Three optical conditions were generated: AO condition (aberration-free), monovision condition, and extended depth of focus (EDoF) condition. Binocular accommodative responses, along with binocular visual acuity and stereoacuity, were measured under all three optical conditions with varied binocular vergence levels. At 3 diopters of binocular convergence, the EDoF condition was the most efficient in inducing excessive accommodative response compared with the monovision condition and the AO condition. Visual acuity was impaired with EDoF as compared with the other two conditions. The average stereoscopic thresholds (at 0 vergence) under the EDoF condition were degraded compared with the AO condition but were superior to those of the monovision condition. Therefore, despite some compromise to visual performance, extending the DoF could allow for a more natural vergence–accommodation relationship, providing the potential for alleviating the vergence–accommodation conflict and associated visual fatigue symptoms in virtual reality.

Pre- And Post-season Visio-vestibular Function In Healthy Adolescent Athletes

PURPOSE: To examine pre- to post-season differences in visio-vestibular examination (VVE) outcomes in healthy adolescent athletes. METHODS AND STUDY DESIGN: This prospective observational study recruited male and female middle and high school athletes. Participants completed a demographic questionnaire prior to the start of their season. Head impact group was determined by factoring previously published head impact frequencies by team, sport, and sport level. The VVE was completed pre- and post-season and includes: smooth pursuits, horizontal/vertical saccades and gaze stability, binocular convergence, left/right monocular accommodation, and complex tandem gait. We used generalized estimating equations adjusting for head impact group to determine changes in VVE outcomes from pre- to post-season. RESULTS: A total of 115 middle and high school subjects (female: 59(51.3%); median age at first assessment = 14.9 years (IQR: 13.6, 16.0)) and 170 subject-seasons were included in our analysis. During pre-season testing, accommodation (10.0%) and complex tandem gait (9.2%) had the largest proportion of abnormal testing, while smooth pursuit (10.6%) and convergence (9.5%) had the largest proportion of abnormal testing at post-season. When assessing the effect of testing session (pre-season vs. post-season) on the relative risk of any abnormal VVE subtest, there were no significant findings (P > 0.05). Additionally, there were no significant effects of testing session when adjusting for head impact group for any VVE subtest (P > 0.05). CONCLUSIONS: Visio-vestibular function as measured by the VVE does not change from pre- to post-season in otherwise healthy pediatric athletes. Our findings suggest that the VVE may be a stable clinical measure of visual and oculomotor function and robust to typical neurodevelopment occurring in this dynamic age group. Additionally, our findings indicate that the VVE may be robust to sport participation and thus allow for flexibility in the timing of baseline test administration. This study provides formative data that may better inform post-injury interpretation of visio-vestibular deficits and provides insight into the clinical meaningfulness of lack of short-term changes in visio-vestibular function in adolescent athletes.

Reliability of the visio-vestibular examination for concussion among providers in a pediatric emergency department

BackgroundVisio-vestibular examination (VVE) deficits are common following pediatric concussion. Guidelines recommend assessing these deficits on all potentially concussed youth given their diagnostic and prognostic value, however test psychometrics of the VVE in the emergency department (ED) setting are unknown. Our objective was to determine the inter-rater (IRR) and test-retest reliability (TRR) of the VVE in a pediatric ED. MethodsWe enrolled 155 patients (112 IRR; 43 TRR) age 6–18 years with head injury presenting to the ED of a tertiary care children's hospital. Exams were performed by a group of 65 attending/fellow physicians, pediatricians, and advanced practice providers. The VVE consisted of 9 maneuvers (smooth pursuits, horizontal/vertical saccades and gaze stability, binocular convergence, left/right monocular accommodation, complex tandem gait). Cohen's kappa was calculated for IRR and TRR for each element. ResultsFor IRR, 5/9 kappas (saccades, gaze stability, monocular accommodation) were in the moderate agreement range (0.40 to 0.60); remaining kappas showed fair agreement. For TRR, 6/9 maneuvers (saccades, horizontal gaze stability, monocular accommodation, tandem gait) showed substantial agreement (0.60 to 0.80). Kappas of 7/9 elements for subjects age 15–18 showed improved IRR and TRR. ConclusionsThe individual elements of the VVE show fair to moderate agreement between providers and moderate to substantial agreement among the same provider in the ED setting. These findings suggest a role in the VVE in evaluating concussion acutely, particularly given its previously demonstrated ability to assist in risk stratification of concussed youth and the importance of early diagnosis for improved outcomes.

Normal Topography and Binocularity of the Superior Colliculus in Strabismus.

In subjects with alternating strabismus, either eye can be used to saccade to visual targets. The brain must calculate the correct vector for each saccade, which will depend on the eye chosen to make it. The superior colliculus, a major midbrain center for saccade generation, was examined to determine whether the maps serving each eye were shifted to compensate for strabismus. Alternating exotropia was induced in two male macaques at age 1 month by sectioning the tendons of the medial recti. Once the animals grew to maturity, they were trained to fixate targets with either eye. Receptive fields were mapped in the superior colliculus using a sparse noise stimulus while the monkeys alternated fixation. For some neurons, sparse noise was presented dichoptically to probe for anomalous retinal correspondence. After recordings, microstimulation was applied to compare sensory and motor maps. The data showed that receptive fields were offset in position by the ocular deviation, but otherwise remained aligned. In one animal, the left eye's coordinates were rotated ∼20° clockwise with respect to those of the right eye. This was explained by a corresponding cyclorotation of the ocular fundi, which produced an A-pattern deviation. Microstimulation drove the eyes accurately to the site of receptive fields, as in normal animals. Single-cell recordings uncovered no evidence for anomalous retinal correspondence. Despite strabismus, neurons remained responsive to stimulation of either eye. Misalignment of the eyes early in life does not alter the organization of topographic maps or disrupt binocular convergence in the superior colliculus.SIGNIFICANCE STATEMENT Patients with strabismus are able to make rapid eye movements, known as saccades, toward visual targets almost as gracefully as subjects with normal binocular alignment. They can even exercise the option of using the right eye or the left eye. It is unknown how the brain measures the degree of ocular misalignment and uses it to compute the appropriate saccade for either eye. The obvious place to investigate is the superior colliculus, a midbrain oculomotor center responsible for the generation of saccades. Here, we report the first experiments in the superior colliculus of awake primates with strabismus using a combination of single-cell recordings and microstimulation to explore the organization of its topographic maps.

Binocular Vision in Chronic Fatigue Syndrome

Introduction and PurposeTo compare binocular vision measurements between Chronic Fatigue Syndrome (CFS) patients and healthy controls.MethodsForty-one CFS patients referred by the Reference Centre for Chronic Fatigue Syndrome of the Antwerp University Hospital and forty-one healthy volunteers, matched for age and gender, underwent a complete orthoptic examination. Data of visual acuity, eye position, fusion amplitude, stereopsis, ocular motility, convergence, and accommodation were compared between both groups.ResultsPatients with CFS showed highly significant smaller fusion amplitudes (P < 0.001), reduced convergence capacity (P < 0.001), and a smaller accommodation range (P < 0.001) compared to the control group.ConclusionIn patients with CFS binocular vision, convergence and accommodation should be routinely examined. CFS patients will benefit from reading glasses either with or without prism correction in an earlier stage compared to their healthy peers. Convergence exercises may be beneficial for CFS patients, despite the fact that they might be very tiring. Further research will be necessary to draw conclusions about the efficacy of treatment, especially regarding convergence exercises. To our knowledge, this is the first prospective study evaluating binocular vision in CFS patients.

Vision Diagnoses Are Common After Concussion in Adolescents.

To determine the prevalence of vision diagnoses after concussion in adolescents. Cross-sectional study from July 1, 2013 to February 28, 2014, of patients aged 11 to 17 years with concussion evaluated in a comprehensive concussion program. A total of 100 adolescents were examined, with a mean age of 14.5 years. Overall, 69% had one or more of the following vision diagnoses: accommodative disorders (51%), convergence insufficiency (49%), and saccadic dysfunction (29%). In all, 46% of patients had more than one vision diagnosis. A high prevalence of vision diagnoses (accommodative, binocular convergence, and saccadic eye movement disorders) was found in this sample of adolescents with concussion, with some manifesting more than one vision diagnosis. These data indicate that a comprehensive visual examination may be helpful in the evaluation of a subset of adolescents with concussion. Academic accommodations for students with concussion returning to the classroom setting should account for these vision diagnoses.

Synaptic correlates of binocular convergence: just a coincidence?

A longstanding goal in neuroscience is to identify and understand synaptic mechanisms underlying the formation of neural circuits that perform sensory computations. Maturation of these circuits proceeds through developmental milestones like the critical period (CP), a time when sensory systems are

Strabismus Disrupts Binocular Synaptic Integration in Primary Visual Cortex

Visual disruption early in development dramatically changes how primary visual cortex neurons integrate binocular inputs. The disruption is paradigmatic for investigating the synaptic basis of long-term changes in cortical function, because the primary visual cortex is the site of binocular convergence. The underlying alterations in circuitry by visual disruption remain poorly understood. Here we compare membrane potential responses, observed via whole-cell recordings in vivo, of primary visual cortex neurons in normal adult cats with those of cats in which strabismus was induced before the developmental critical period. In strabismic cats, we observed a dramatic shift in the ocular dominance distribution of simple cells, the first stage of visual cortical processing, toward responding to one eye instead of both, but not in complex cells, which receive inputs from simple cells. Both simple and complex cells no longer conveyed the binocular information needed for depth perception based on binocular cues. There was concomitant binocular suppression such that responses were weaker with binocular than with monocular stimulation. Our estimates of the excitatory and inhibitory input to single neurons indicate binocular suppression that was not evident in synaptic excitation, but arose de novo because of synaptic inhibition. Further constraints on circuit models of plasticity result from indications that the ratio of excitation to inhibition evoked by monocular stimulation decreased mainly for nonpreferred eye stimulation. Although we documented changes in synaptic input throughout primary visual cortex, a circuit model with plasticity at only thalamocortical synapses is sufficient to account for our observations.

Retinal image quality during accommodation

We asked if retinal image quality is maximum during accommodation, or sub-optimal due to accommodative error, when subjects perform an acuity task. Subjects viewed a monochromatic (552nm), high-contrast letter target placed at various viewing distances. Wavefront aberrations of the accommodating eye were measured near the endpoint of an acuity staircase paradigm. Refractive state, defined as the optimum target vergence for maximising retinal image quality, was computed by through-focus wavefront analysis to find the power of the virtual correcting lens that maximizes visual Strehl ratio. Despite changes in ocular aberrations and pupil size during binocular viewing, retinal image quality and visual acuity typically remain high for all target vergences. When accommodative errors lead to sub-optimal retinal image quality, acuity and measured image quality both decline. However, the effect of accommodation errors of on visual acuity are mitigated by pupillary constriction associated with accommodation and binocular convergence and also to binocular summation of dissimilar retinal image blur. Under monocular viewing conditions some subjects displayed significant accommodative lag that reduced visual performance, an effect that was exacerbated by pharmacological dilation of the pupil. Spurious measurement of accommodative error can be avoided when the image quality metric used to determine refractive state is compatible with the focusing criteria used by the visual system to control accommodation. Real focusing errors of the accommodating eye do not necessarily produce a reliably measurable loss of image quality or clinically significant loss of visual performance, probably because of increased depth-of-focus due to pupil constriction. When retinal image quality is close to maximum achievable (given the eye's higher-order aberrations), acuity is also near maximum. A combination of accommodative lag, reduced image quality, and reduced visual function may be a useful sign for diagnosing functionally-significant accommodative errors indicating the need for therapeutic intervention.

Experience-Dependent and Independent Binocular Correspondence of Receptive Field Subregions in Mouse Visual Cortex

The convergence of eye-specific thalamic inputs to visual cortical neurons forms the basis of binocular vision. Inputs from the same eye that signal light increment (On) and decrement (Off) are spatially segregated into subregions, giving rise to cortical receptive fields (RFs) that are selective for stimulus orientation. Here we map RFs of binocular neurons in the mouse primary visual cortex using spike-triggered average. We find that subregions of the same sign (On-On and Off-Off) preferentially overlap between the 2 monocular RFs, leading to binocularly matched orientation tuning. We further demonstrate that such subregion correspondence and the consequent matching of RF orientation are disrupted in mice reared in darkness during development. Surprisingly, despite the lack of all postnatal visual experience, a substantial degree of subregion correspondence still remains. In addition, dark-reared mice show normal monocular RF structures and binocular overlap. These results thus reveal the specific roles of experience-dependent and -independent processes in binocular convergence and refinement of On and Off inputs onto single cortical neurons.

Accommodation and Convergence in 10-Year-Old Prematurely Born and Full-Term Children—A Population-Based Study

Purpose: To examine the accommodative amplitude and convergence in 10-year-old prematurely born children previously screened for retinopathy of prematurity (ROP) and to compare with full-term controls of the same age.Methods: Two-hundred and thirteen prematurely born and 217 children born at term were included. Accommodative amplitude and near-point convergence were assessed, together with best-corrected visual acuity (VA). A questionnaire was answered regarding possible problems at school.Results: Binocular accommodation (P = 0.03) and convergence (P = 0.003) were significantly poorer in prematurely born children. Accommodation was correlated to neurological findings in the preterm group, but not to the degree of prematurity or stage of ROP. Regarding convergence there were no correlations to neurology, stage of ROP, or degree of prematurity. For neither accommodation nor convergence were any correlations with distance and near VA found. Preterm children had a higher prevalence of school problems, and there was an association with poor accommodation.Conclusions: Prematurely born children had poorer accommodation and convergence than full-term children, but no association with near VA was found. The reduction of accommodative amplitude and convergence was small and was probably of little clinical significance. However, it may have additional effects on other ophthalmological problems and school problems in the preterm group.

Diplopia and Enophthalmos in Blowout Fractures

The aim of this study was to compare the changes of diplopia and enophthalmos in patients with blowout fractures. Three hundred sixty-two patients who presented with blowout fractures between March 2006 and February 2011 were analyzed. The sequential time changes of diplopia and enophthalmos were measured in the operated group and the observed group according to (1) the duration of preoperative observation (early: within 7 days, late: 8-14 days, delayed: >15 days); (2) the defect size (minimal: <1 cm(2), small: 1.1-2.0 cm, medium: 2.1-3.0 cm(2), large: >3.0 cm(2)); and (3) the age of the patients (<20, 21-40, 41-60, >61 years).Among the 362 patients, 242 (66.9%) had an operation, and 120 (33.1%) did not. The duration of preoperative observation did not affect the postoperative diplopia or enophthalmos. There were significant differences of enophthalmos among the operated groups with a different defect size at the preoperative period (P = 0.036 [Pearson χ(2)]). There were significant differences of diplopia among the operated groups with different defect sizes at the 6 months' follow-up period (P = 0.014 [Pearson χ(2)]). The diplopia in the older age group (>60 years) was significantly greater than that of the other 3 groups at 6 months (P = 0.023) and at 12 months (P = 0.023, [Pearson χ(2)]).We think surgery should be delayed until the swelling is decreased unless the medial rectus muscle is incarcerated. We also think that the defect size is not an important factor for whether to perform surgery. We think that the reason for the greater diplopia in the older age group is that the adaptation of binocular convergence is decreased in the older age group.

Experimental Investigations of Pupil Accommodation Factors

PURPOSE. The contraction and dilation of the iris muscle that controls the amount of light entering the retina causes pupil accommodation. In this study, experiments were performed and two of the three factors that influence pupil accommodation were analyzed: lighting conditions and depth fixations. The psychological benefits were not examined, because they could not be quantified. METHODS. A head-wearable eyeglasses-based, eye-capturing device was designed to measure pupil size. It included a near-infrared (NIR) camera and an NIR light-emitting diode. Twenty-four subjects watched two-dimensional (2D) and three-dimensional (3D) stereoscopic videos of the same content, and the changes in pupil size were measured by using the eye-capturing device and image-processing methods: RESULTS. The pupil size changed with the intensity of the videos and the disparities between the left and right images of a 3D stereoscopic video. There was correlation between the pupil size and average intensity. The pupil diameter could be estimated as being contracted from approximately 5.96 to 4.25 mm as the intensity varied from 0 to 255. Further, from the changes in the depth fixation for the pupil accommodation, it was confirmed that the depth fixation also affected accommodation of pupil size. CONCLUSIONS. It was confirmed that the lighting condition was an even more significant factor in pupil accommodation than was depth fixation (significance ratio: approximately 3.2:1) when watching 3D stereoscopic video. Pupil accommodation was more affected by depth fixation in the real world than was the binocular convergence in the 3D stereoscopic display.