Changes In Vergence Research Articles

Postoperative Changes of Fusional Vergence in Children Intermittent Exotropia

: This study aimed to evaluate changes in fusional vergence after strabismus surgery and to explore predictive parameters and the impact of fusional vergence on surgical outcomes. All patients diagnosed with intermittent exotropia (IXT) between March 2015 and October 2017 were included. Orthoptic assessments, including visual acuity, cover test, and mean fusional vergence (breakage/recovery, both negative and positive), were measured using a synoptophore. Subjects with symptomatic exotropia who underwent strabismus surgery were included. The primary outcome measure was the surgical success (SS) rate at a 6-month follow-up, with adverse effects such as over-correction and under-correction also evaluated. Data were analyzed using SPSS version 20.0. Surgical success was achieved in 62 patients (75.61%) at the 6-month follow-up. The postoperative fusional divergence breakpoints for the SS group and the surgical failure (SF) group were -7.52 ± 4.14 degrees and -10.00 ± 5.96 degrees (P = 0.040), respectively. The postoperative fusional convergence breakpoints for the SS group and the SF group were 10.03 ± 4.36 degrees and 4.65 ± 7.27 degrees (P < 0.001), respectively. The postoperative amplitude of fusional divergence was higher in the SS group compared to the SF group (P = 0.008). There was a significant difference in the duration of deviation (2.08 ± 0.84 vs. 4.23 ± 1.36, P < 0.001) between the groups, suggesting that the success rate of surgery is affected by the cumulative disease duration. Subjective deviation (-8.00 vs. -11.00, P = 0.049) and the amplitude of fusional divergence (6.52 ± 4.10 vs. 4.80 ± 2.59, P = 0.032) were also significantly different between the SS and SF groups. Postoperative breakpoints of fusional divergence and convergence, as well as the amplitude, were distinct between the SS and SF groups. Duration of deviation, angle of deviation, and subjective deviation were independent factors for (SS). Subjective deviation exhibited a predictive index for (SS) and may also reflect the severity of strabismus.

Evaluation of convergence, accommodation and fusional vergence in pre-presbyopes with asthenopia

Background: Pre-presbyopes may suffer from ocular symptoms such as asthenopia of near work.Aim: This study aimed to evaluate near points of convergence, amplitudes of accommodation, and fusional vergence among pre-presbyopes with asthenopia symptoms.Setting: The study was conducted at El-Walidain Eye Hospital, Khartoum, Sudan in 2022.Methods: The study was a hospital-based prospective, including 107 pre-presbyopes aged 35–40 years who complained of asthenopia symptoms. Clinical examinations included an assessment of amplitude of accommodation, near point of convergence and fusional vergence.Results: The findings showed receded in near points of convergence and a decrease in the accommodation was highly significantly associated with increased age among emerging presbyopes with asthenopia symptoms (p = 0.0001). Conversely, positive and negative fusional vergence amplitudes were not significantly correlated with age with p = 0.109 and p = 0.355, respectively. Positive and negative fusional amplitudes were not significantly different between males and females (p ˃ 0.05). Esophoria was more common in pre-presbyopia 62 (57.4%) and exophoria 45 (43.6) with p = 0.503.Conclusion: The pre-presbyopes presented with low accommodation amplitude and receded near point of convergence, but without significant changes in positive and negative fusional vergence amplitudes.Contribution: This study added by demonstrating how early presbyopia altered accommodation amplitude and near point of convergence significantly while having no significant impact on amplitudes of positive and negative fusional vergence.

The Effect of Heterophoria on the Size of Distance and Near Fusion Vergence.

To demonstrate changes in distance and near fusional vergence measured with prism bars, while compensating for present heterophoria using current ametropia correction. In addition, to determine the differences in values of the AC/A ratio determined by the heterophoric (calculation) and gradient methods. The basic sample includes 19 subjects with a mean age of 21.5 ±3.0 years (min. 18, max. 27). We used the Von Graefe technique for examination of distance and near phoria, and prism bars for examination of fusion vergences measured in prism diopters. We divided the basic cohort into six research sets according to the size of distance and near heterophoria. This was a cohort of patients with distance (D OR) and near orthophoria (N OR), a cohort of patients with distance (D EX) and near exophoria (N EX) and a set of patients with distance (D ES) and near esophoria (N ES). In the case of both groups with exophoria (distance, near) we found a statistically significant result only for negative fusion vergence (NFV). There was a statistically significant increase in NFV in the sample with distance and near exophoria (D EX, p = 0.01 and B EX, p = 0.02, respectively). In our study, we also demonstrated a statistically significant difference (p < 0.001) in the values of the AC/A ratio measured by the gradient and heterophoric methods. The values determined by the gradient method are lower (3.0 ±1.1 pD/D versus 5.8 ±0.9 pD/D) than by the heterophoric method. By comparing fusion vergence values in patients with exophoria and orthophoria, we demonstrated that in the presence of distance or near exophoria there is an increase in ipsilateral fusion vergence. In the case of an increase in ipsilateral fusion vergence, the finding was statistically significant both distance and near (p = 0.01 and p = 0.02, respectively). By contrast, we were unable to prove this fact in the group of patients with esophoria. In our study, we also demonstrated a statistically significant difference (p < 0.001) in the values of the AC/A ratio measured by the gradient and heterophoric methods. The values determined by the gradient method are lower (3.0 ±1.1 pD/D versus 5.8 ±0.9 pD/D) than by the heterophoric method.

The Effect of Over Minus Prescription on Negative and Positive Fusional Vergence and Amplitude of Accommodation After Watching Video at Six Meters

Background The purpose of the study was to compare the effects of a -1.00 Dioptre Sphere over minus prescription on negative fusional vergence and positive fusional vergence as well as the amplitude of accommodation in myopic individuals after watching a video at 6 meters.Aim To assess the effect of over-minus lens on the amplitude of accommodation and fusional vergence pre and post-video watching.Methods The study included 30 participants aged between 18 to 25 years who did not have any systemic or ocular-related issues. During the study the participants were given an over-correction of -1.00DS over their existing spectacle correction. They were then instructed to watch a video at a distance of 6 meters for 15 minutes. The amplitude of accommodation as well as negative and positive fusional vergence were measured before and after the 15-minute video-watching session.Results The study results indicate that there was a statistically significant change in the amplitude of accommodation in the right eye when using an over-correction of -1.00DS. However there was no statistically significant change in the fusional vergence with the minus over-correction.Conclusion It is possible that the reduction in the accommodation system observed in the study was caused by wearing the divergence lens which placed the image behind the retina resulting in retinal blur. Prolonged wear of over-minus lenses could also lead to visual fatigue which can disrupt the eye-focusing system. Therefore while prescribing a corrective lens it should be monitored carefully.

Accommodative Facility and Vergence Facility after Mobile Gaming

Aim: This study aimed to access the changes of accommodation and vergence before and after mobile gaming. Settings and Design: This was a comparative study conducted in the outpatient department of ophthalmology. Accommodative facility and vergence facility were measured using flippers. Methods and Materials: A comparative study was conducted on 50 healthy subjects, in both males and females, with age groups ranging between 18 and 30 years. This study has been approved by the IRB Committee; 25 young emmetropic patients and 25 young myopic patients were included. The comparison of accommodative facility and vergence facility before and after mobile gaming for 1 h was measured to determine the level of changes in accommodation and vergence. All patients were undergone comprehensive ophthalmic examination including vision, subjective/objective refraction, anterior segment examination, and accommodative and vergence facilities measured using accommodative and vergence flippers. Results: The mean and standard deviation value significantly increase before and after mobile gaming in the right eye, left eye, and both eyes in case of accommodation facility, and there is a decrease in the mean and standard deviation value in case of vergence facility in both eyes before and after mobile gaming. Conclusion: The mean and standard deviation value significantly increase before and after mobile gaming in the right eye, left eye, and both eyes in case of accommodative facility, and there is a decrease in the mean and standard deviation value in case of vergence facility in both eyes before and after mobile gaming.

Effects of Wearing a Swimming Cap and Goggles on Phoria and Fusional Vergence

This study evaluated changes in phoria and negative (NFV) and positive fusional vergence (PFV) when wearing a cap and/or goggles. Thirty-five healthy university students aged 20–25 years participated in the study. All participants were examined for phoria, NFV, and PFV at distance and near. A rotary prism was used before and after wearing a cap, goggles, and both a cap and goggles. The frequency of overall average change in phoria, NFV, and PFV after wearing swimming equipment compared with non-wearing ranged from one-third to four-fifths. The order of frequency in change was wearing of goggles and a cap, goggles alone, and a cap alone. The frequency of a prism prescription, determined by the relationship between phoria and vergence, was similar or higher for wearing than for non-wearing and higher at near than at distance. The effect on change in phoria and fusional vergence was greater when wearing both a cap and goggles than when wearing either alone. These findings demonstrate that wearing both swimming cap and goggles that contact or attach around the eyes influence phoria and fusional vergence by inducing pressure or pulling. These changes may contribute to the discomfort associated with the wearing of swimming equipment.

Accommodation and vergence function in children using atropine combined with orthokeratology

PurposeThis study aimed to evaluate binocular vision in terms of vergence and accommodative measurements in children treated with 0.01% atropine combined with orthokeratology (OK). MethodsThis was a prospective and randomized controlled clinical trial involving participants aged 8 to 12 years, with a spherical equivalent (SE) ranging from − 1.00 to − 6.00D. Participants were randomly divided into four groups: 1) a combination group using 0.01% atropine solution and OK lens; 2) an OK group using placebo solution and OK lens; 3) an atropine group using 0.01% atropine solution and wearing spectacles; and 4) a control group using placebo solution and wearing spectacles. Binocular vision was determined at baseline and at 3-month visits, with evaluations including horizontal phoria, fusional vergence, the accommodative convergence/accommodation (AC/A) ratio, accommodative lag, and accommodative amplitude (AA). The Wilcoxon signed-rank test was used to compare the changes in binocular vision in each group, and the Kruskal–Wallis test was used for comparisons of four groups. ResultsSixty-two participants completed the study. There was no significant difference in baseline refraction, accommodation or vergence measurements among the groups (all P > 0.05). Three months later, the accommodative lag significantly decreased in the OK group (P = 0.002) but remained unchanged in the other three groups (all P > 0.05). In addition, binocular accommodative facilities and positive relative accommodations increased in the combination and OK groups (both P < 0.05) but remained unchanged in the atropine and control groups (both P > 0.05). Only the participants with esophoria in the OK group had a significant decrease in esophoria (P = 0.008). Moreover, the changes in fusional vergence and AC/A did not significantly differ between the four groups (all P > 0.05). ConclusionAccommodative measurements changed similarly in the groups treated with OK. Changes in vergence measurements after treatment with 0.01% atropine were not significant.

Accommodative Facility and Vergence Facility after Mobile Gaming

Aim: This study aimed to access the changes of accommodation and vergence before and after mobile gaming. Settings and Design: This was a comparative study conducted in the outpatient department of ophthalmology. Accommodative facility and vergence facility were measured using flippers. Methods and Materials: A comparative study was conducted on 50 healthy subjects, in both males and females, with age groups ranging between 18 and 30 years. This study has been approved by the IRB Committee; 25 young emmetropic patients and 25 young myopic patients were included. The comparison of accommodative facility and vergence facility before and after mobile gaming for 1 h was measured to determine the level of changes in accommodation and vergence. All patients were undergone comprehensive ophthalmic examination including vision, subjective/objective refraction, anterior segment examination, and accommodative and vergence facilities measured using accommodative and vergence flippers. Results: The mean and standard deviation value significantly increase before and after mobile gaming in the right eye, left eye, and both eyes in case of accommodation facility, and there is a decrease in the mean and standard deviation value in case of vergence facility in both eyes before and after mobile gaming. Conclusion: The mean and standard deviation value significantly increase before and after mobile gaming in the right eye, left eye, and both eyes in case of accommodative facility, and there is a decrease in the mean and standard deviation value in case of vergence facility in both eyes before and after mobile gaming.

Structural geometry and evolution of the Carter-Knox structure, Anadarko Basin, Oklahoma

The Carter-Knox field is located on a northwest-southeast–trending faulted anticline in the southeastern part of the Anadarko Basin. Three-dimensional seismic and well data were used to develop a model for the geometry and evolution of the structure. The Carter-Knox structure formed during contractional deformation associated with the Wichita basement uplift in the Pennsylvanian. It is characterized by different structural styles in two main structural units. The lower unit, which includes the Cambrian Arbuckle Group to Mississippian Sycamore Limestone, is folded into a broad anticline associated with one or more frontal faults and back thrusts, with a change in vergence along trend. The upper unit, which includes the Upper Mississippian Springer shale to the Morrowan Primrose and the overlying Pennsylvanian growth units, is marked by a tight faulted detachment fold with a steep front limb, associated with multiple thrust faults that detach within the Springer shale. Kinematic reconstruction shows differential shortening between the two main structural packages. The evolution of the structure was episodic, resulting in two major angular unconformities within the Pennsylvanian. A major Permian unconformity truncates the structure. The southwestern flank of the structure was rotated along an active flexural hinge in the basement because of sedimentary loading, resulting in thickening of growth units on this flank. The Carter-Knox structure is an analogue for other thin-skinned structures in the Anadarko Basin and illustrates the impact of the thick-skinned Wichita uplift on the thin-skinned fold-thrust structures in the basin.

Does Vergence Affect Perceived Size?

Since Kepler (1604) and Descartes (1637), it has been suggested that ‘vergence’ (the angular rotation of the eyes) plays a key role in size constancy. However, this has never been tested divorced from confounding cues such as changes in the retinal image. In our experiment, participants viewed a target which grew or shrank in size over 5 s. At the same time, the fixation distance specified by vergence was reduced from 50 to 25 cm. The question was whether this change in vergence affected the participants’ judgements of whether the target grew or shrank in size? We found no evidence of any effect, and therefore no evidence that eye movements affect perceived size. If this is correct, then our finding has three implications. First, perceived size is much more reliant on cognitive influences than previously thought. This is consistent with the argument that visual scale is purely cognitive in nature (Linton, 2017; 2018). Second, it leads us to question whether the vergence modulation of V1 contributes to size constancy. Third, given the interaction between vergence, proprioception, and the retinal image in the Taylor illusion, it leads us to ask whether this cognitive approach could also be applied to multisensory integration.

The Cabo Frio Thrust: A folded suture zone, Ribeira belt, SE Brazil

Kinematic evolution of thrust systems in which vergence changes along strike result in divergent interpretations regarding the subduction polarity. The Ribeira belt, located in southeastern Brazil, resulted from progressive amalgamation of several terranes against the southeastern margin of the São Francisco Craton (SFC) between ca. 620 and 580 Ma. This study brings new structural analysis of the Cabo Frio Thrust (CFT) located in the Ribeira belt, that displays strike variations and apparently double thrusting vergence, generating current debate on subduction vergence for the region. Four major stages of deformation (Dn-1, D1cf, D2cf and D3cf) have been identified in the southwestern segment of the CFT. The Dn-1 affected only the metasedimentary rocks of the Oriental Terrane previously the collision. The D1 phase is associated with the thrusting of orthogneisses of the Cabo Frio Terrane onto the metasedimentary rocks of the Oriental Terrane, with the development of a penetrative S1 foliation and L1 stretching lineation. The D2 deformation phase produced a recumbent synform in the early/syn-D2 stages that overturned the CFT. This resulted in F2 isoclinal folds and S2 axial plane schistosity with F2 axis plunges towards W-SW, parallel to the L1 stretching and L2 intersection lineations. During the late-D2 stage, the recumbent F2 fold was sheared and refolded, leading to horizontal rotation of linear and planar elements, changing the CFT strike from W-SW to N–S. A series of irregular upright folds were developed in the D3 deformation phase. The double vergence and strike variations of the CFT are a result of the major F2 fold geometry, influenced by the granitic batholith (Tinguí Complex) that acted as an indenter during continuous crustal shortening towards northwest.

Changes in vergence and accommodation parameters after smartphone use in healthy adults.

Purpose:To assess pre and post vergence and accommodation parameters after monitored reading on a smartphone device.Methods:This prospective comparative study was performed in a tertiary eye care center for a duration of 6 months (December 2017 – May 2018). A total of 47 healthy emmetropic subjects of age group ranging from 18-30 years were recruited for the study. Participants underwent an initial visual screening protocol, followed by accommodation and vergence parameters assessment. The subjects were given reading text of optotype N6 at 40cm working distance for 30 minutes in a smart phone device. Pre and post measurements were documented.Results:Among 47 subjects there were 17 male and 30 females with mean age group of 21.2+2.06 years. There was a statistically significant worsening of accommodative components (negative & positive relative accommodation, lag of accommodation). In vergence parameters, a statistically significant deterioration of negative (12.8 + 1.65 to 12.38 + 1.93 PD) and positive fusional vergence (15.48 + 1.53 to 16.08 +1.61 PD) was observed. The mean vergence facility also showed a statistically significant change in pre and post task measurements (13.51 + 1.64 to 10.71 + 1.91 cpm (cycles per minute)).Conclusion:The current study investigated that perusing text with a smart phone for 30 minutes shows significant effect on accommodative and vergence components for near task, with greater impact on vergence parameters. Drawn out exposure to digital screens at near, may bring about visual quality dysfunction.

Comparisons of Proximal Vergence Measures

Proximal vergence is defined as a vergence eye movement subtype driven by an "awareness of nearness". The purpose of this experiment was to compare values of proximal vergence calculated with and without measures of accommodation to assess the clinical utility of each measurement method. Thirteen participants between the ages of 22 and 37 (mean = 28.5 ± 4.5 years) were enrolled. The distance and near heterophoria were measured using the Modified Thorington technique. The near heterophoria was measured under three randomized viewing conditions (no lenses, +1.00D lenses, +2.50D lenses). Refractive error was measured with an autorefractor. Proximal vergence was calculated as the difference in calculated (far-near) and gradient (+1.00) stimulus AC/A ratios (stimulus AC/A differencing method), the difference in calculated and gradient response AC/A ratios (response AC/A differencing method), and the change in vergence from distance to near with the +2.50D lenses (uncorrected +2.50D method). This latter value was also corrected for any active accommodation with +2.50D lenses (corrected +2.50D method). The mean proximal vergence values (Δ) were 7.82 ± 5.98 (stimulus AC/A differencing method), 8.29 ± 3.30 (response AC/A differencing method), 6.23 ± 3.52 (uncorrected +2.50D method), and 5.13 ± 2.98 (corrected +2.50D method). The only comparison that showed both a significant correlation (p<0.05) and a non-significant difference from the paired t-test (p>0.05) was that between the stimulus AC/A differencing method and the uncorrected +2.50D method. When response accommodation was accounted for, differences occurred in the mean proximal values obtained with the various methods. The means of the methods most likely to be used clinically (stimulus AC/A differencing method and uncorrected +2.50D method) were similar, although some individuals demonstrated significant differences between these methods.

History and Future Directions of Vision Testing in Head Trauma.

Concussion leads to neurophysiologic changes that may result in visual symptoms and changes in ocular motor function. Vision-based testing is used increasingly to improve detection and assess head injury. This review will focus on the historical aspects and emerging data for vision tests, emphasizing rapid automatized naming (RAN) tasks and objective recording techniques, including video-oculography (VOG), as applied to the evaluation of mild traumatic brain injury. Searches on PubMed were performed using combinations of the following key words: "concussion," "mild traumatic brain injury," "rapid automatized naming," "King-Devick," "mobile universal lexicon evaluation system," "video-oculography," and "eye-tracking." Additional information was referenced from web sites of vendors of commercial eye-tracking systems and services. Tests of rapid number, picture, or symbol naming, termed RAN tasks, have been used in neuropsychological studies since the early 20th century. The visual system contains widely distributed networks that are readily assessed by a variety of functionally distinct RAN tasks. The King-Devick test, a rapid number naming assessment, and several picture-naming tests, such as the Mobile Universal Lexicon Evaluation System (MULES) and the modified Snodgrass and Vanderwart image set, show capacity to identify athletes with concussion. VOG has gained widespread use in eye- and gaze-tracking studies of head trauma from which objective data have shown increased saccadic latencies, saccadic dysmetria, errors in predictive target tracking, and changes in vergence in concussed subjects. Performance impairments on RAN tasks and on tasks recorded with VOG are likely related to ocular motor dysfunction and to changes in cognition, specifically to attention, memory, and executive functioning. As research studies on ocular motor function after concussion have expanded, so too have commercialized eye-tracking systems and assessments. However, these commercial services are still investigational and all vision-based markers of concussion require further validation. RAN tasks and VOG assessments provide objective measures of ocular motor function. Changes in ocular motor performance after concussion reflect generalized neurophysiologic changes affecting a variety of cognitive processes. Although these tests are increasingly used in head injury assessments, further study is needed to validate them as adjunctive diagnostic aids and assessments of recovery.

Experimental Study of Refraction Effects of Nominally Plano Ophthalmic Prisms and Magnifying Lenses.

Nominally plano ophthalmic prisms give autorefraction results similar to those predicted on the basis of how effective powers change with pantoscopic tilt, and magnifying lenses give autorefraction results similar to those predicted on the basis of vergence changes. Without appreciation of the optics involved, these effects might wrongly be considered artifacts. The purpose of this study was to investigate the interactions of autorefractors with lenses and prisms. There were 15 adult participants across three experiments, with a range of ages and refractions. In experiments 1 and 2, participants wore frames containing base-up and base-down nominally plano prisms. In experiment 3, participants wore a lens that produced either 6.3% magnification or 5.9% minification, depending on which surface faced the eye. Autorefracting instruments with different operating principles were used: Shin-Nippon SRW5000 autorefractor, Grand Seiko 5100K autorefractor, Hoya AR-530 autorefractor, a Complete Ophthalmic Analysis System-High Definition wavefront sensor, and Tomey FC-800 autorefractor. A theory on the likely effects of magnifying lenses was presented. For ophthalmic prisms, refractions showed results similar to those predicted on the basis of how effective prism powers change with pantoscopic tilt. As tilt increased, base-up prism gave more positive mean refractions and more negative horizontal/vertical astigmatism and vice versa for base-down prisms. In the presence of 10° tilt, 8Δ base-up prisms and 8Δ base-down prisms had different effects by a mean of 0.36 diopters. Magnifying lenses affected refractions similar to those predicted on the basis of vergence changes, with 6% magnification and minification producing mean changes of -11 and +8%, respectively, in absolute mean refraction. There was no strong evidence that different instruments had different effects. The results have implications for studies in which prisms and lenses are placed in the front eyes, such as accommodation studies using thick lenses close to the eyes to stimulate accommodation rather than by changing object distance.

Assessment of vision in concussion.

To review emerging vision-based assessments in the evaluation of concussion. Involvement of the visual pathways is common following concussion, the mildest form of traumatic brain injury. The visual system contains widely distributed networks that are prone to neurophysiologic changes after a concussion, resulting in visual symptoms and ocular motor dysfunction. Vision-based testing is increasingly used to improve detection and assess head injury. Several rapid automatized naming (RAN) tasks, such as the King-Devick test and the Mobile Universal Lexicon Evaluation System, show capacity to identify athletes with concussion. Video-oculography (VOG) has gained widespread use in eye-tracking and gaze-tracking studies of head trauma from which objective data have shown increased saccadic latencies, saccadic dysmetria, errors in predictive target tracking, and changes in vergence in concussed individuals. RAN tasks demonstrate promise as rapid screening tools for concussion. Further investigation will involve assessment of the role for age, characterization of learning effects over repeated measurements, and identification of optimal thresholds for clinically significant performance decrements. Various RAN tasks are likely to be functionally distinct, engaging different neural networks according to the demands of each task. Measures of saccades, smooth pursuit eye-movements, the vestibulo-ocular reflex and, more recently, disparity vergence are candidate vision-based markers for concussion. Work to adopt these assessments to the sideline or clinical environments is ongoing.

Beyond Feeling Sick: The Visual and Cognitive Aftereffects of Virtual Reality

Despite continued improvements in virtual reality (VR) technologies, many people still experience adverse symptoms from using head-mounted displays (HMDs). Typically, these symptoms are monitored through self-report measures, such as the Simulator Sickness Questionnaire (SSQ); however, by only using subjective measures many symptoms may be overlooked. In an application-based study, we investigated visual and cognitive aftereffects of using HMDs and their relationship to the reporting of sickness on the SSQ. Visual (accommodation and vergence) and cognitive (reaction time and rapid visual processing) assessments were employed before and after participants engaged in a 30-minute VR table tennis game (VR group, n = 27) or went about their daily activities (control group, n = 28). The data showed changes in accommodation but no concurrent changes in vergence, which likely stems from decoupling accommodation and vergence in VR. Furthermore, larger changes in accommodation were linked to more severe sickness symptoms suggesting that decoupling accommodation and vergence could be more adverse than previously thought. The VR group also had slower decision (cognitive) times, but movement times were unaffected. These findings go beyond the typical self-reporting of sickness in VR studies. Moreover, we demonstrate that even in a high-quality commercial virtual environment, users may experience visual and cognitive aftereffects that may negatively influence their experience with subsequent activities in the real world. Developing an understanding of how VR aftereffects may influence later activities could help to minimise the risk of using HMDs for various applications and may be valuable to obtain a better understanding of user issues and VR safety.

Multisectorial changes in the ciliary muscle during accommodation measured with high-resolution optical coherence tomography.

To measure changes in the anterior ciliary muscle during accommodation at the nasal, superior, temporal, and inferior sectors by means of an anterior chamber optical coherence tomographer, and correlate them with vergence changes. Twenty-four subjects with healthy, phakic eyes, whose mean age was 27.1 ± 8.9 years, underwent measurement with an anterior chamber optical coherence tomographer. The anterior ciliary muscle was measured at the nasal, temporal, superior, and inferior sectors for 0, -1, -2, and -3 D of vergence. A linear model was used to assess the correlation of each eye parameter with the accommodative demand. The anterior ciliary muscle area significantly increased with accommodation for each sector, with a maximum increase of about 30% for the nasal-temporal sectors and about 25% for the inferior-temporal sectors. The linear model showed a tendency toward a positive relationship between change in the ciliary muscle area of each sector and vergence. The anterior ciliary muscle area tends to increase with accommodation, although the increase has been shown to be symmetric between the pair sectors superior-nasal and inferior-temporal. These results may help to increase understanding of accommodation biometry and biomechanics.

Response of supraoculomotor area neurons during combined saccade-vergence movements.

Combined saccade-vergence movements allow humans and other primates to align their eyes with objects of interest in three-dimensions. In the absence of saccades, vergence movements are typically slow, symmetrical movements of the two eyes in opposite directions. However, combined saccade-vergence movements produce vergence velocities that exceed values observed during vergence alone. This phenomenon is often called "vergence enhancement", or "saccade-facilitated vergence," though it is important to consider that rapid vergence changes, known as "vergence transients," are also observed during conjugate saccades. We developed a visual target array that allows monkeys to make saccades in all directions between targets spaced at distances that correspond to ~1° intervals of vergence angle relative to the monkey. We recorded the activity of vergence-sensitive neurons in the supra-oculomotor area (SOA), located dorsal and lateral to the oculomotor nucleus while monkeys made saccades with vergence amplitudes ranging from 0 to 10°. The primary focus of this study was to test the hypothesis that neurons in the SOA fire a high frequency burst of spikes during saccades that could generate the enhanced vergence. We found that individual neurons encode vergence velocity during both saccadic and non-saccadic vergence, yet firing rates were insufficient to produce the observed enhancement of vergence velocity. Our results are consistent with the hypothesis that slow vergence changes are encoded by the SOA while fast vergence movements require an additional contribution from the saccadic system. NEW & NOTEWORTHY Research into combined saccade-vergence movements has so far focused on exploring the saccadic neural circuitry, leading to diverging hypotheses regarding the role of the vergence system in this behavior. In this study, we report the first quantitative analysis of the discharge of individual neurons that encode vergence velocity in the monkey brain stem during combined saccade-vergence movements.

Changes in stimulus and response AC/A ratio with vision therapy in Convergence Insufficiency

PurposeTo evaluate the changes in the stimulus and response Accommodative Convergence to Accommodation (AC/A) ratio following vision therapy (VT) in Convergence Insufficiency (CI). MethodsStimulus and response AC/A ratio were measured on twenty five CI participants, pre and post 10 sessions of VT. Stimulus AC/A ratio was measured using the gradient method and response AC/A ratio was calculated using modified Thorington technique with accommodative responses measured using WAM-5500 open-field autorefractor. The gradient stimulus and response AC/A cross-link ratios were compared with thirty age matched controls. ResultsMean age of the CI and control participants were 23.3±5.2 years and 22.7±4.2 years, respectively. The mean stimulus and response AC/A ratio for CI pre therapy was 2.2±0.72 and 6.3±2.0 PD/D that changed to 4.2±0.9 and 8.28±3.31 PD/D respectively post vision therapy and these changes were statistically significant (paired t-test; p<0.001). The mean stimulus and response AC/A ratio for controls was 3.1±0.81 and 8.95±2.5 PD/D respectively. ConclusionsStimulus and response AC/A ratio increased following VT, accompanied by clinically significant changes in vergence and accommodation parameters in subjects with convergence insufficiency. This represents the plasticity of the AC/A crosslink ratios that could be achieved with vision therapy in CI.