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PubMed2026

Near and distance vergence facility provides complementary clinical information in concussion-related convergence insufficiency.

PURPOSE: To compare near and distance vergence facility testing in adolescents and young adults with concussion-related convergence insufficiency and evaluate changes following office-based vergence/accommodative therapy (OBVAM). METHODS: This secondary analysis of the CONCUSS randomized clinical trial evaluated vergence facility at near (40 cm) and distance (4 m) using a 12Δ base out/3Δ base in prism flipper. Participants aged 11-25 years with concussion-related convergence insufficiency were randomized to immediate or 6 weeks delayed OBVAM. Vergence facility was assessed at baseline, outcome time 1 assessment (after 12 therapy sessions for the immediate group and 6 weeks of watchful waiting for the delayed group), and outcome time 2 assessment (after both groups completed 16 therapy sessions). Agreement between near and distance vergence facility classifications was evaluated, and treatment-related changes were compared between groups. RESULTS: Of the 106 enrolled participants, 102 completed all study visits. At baseline, the near and distance vergence facility classifications demonstrated substantial discordance. Among 101 participants with both measures available, 49 demonstrated reduced distance vergence facility despite normal near vergence facility, whereas only two showed the opposite pattern (Cohen's κ = 0.12; p < 0.0001). Vergence facility improved following therapy in both treatment groups, with larger early improvements in the immediate-treatment group. CONCLUSIONS: Near and distance vergence facility testing provided complementary rather than interchangeable clinical information in adolescents and young adults with concussion-related convergence insufficiency. Both measures improved following vergence/accommodative therapy, supporting consideration of both testing distances in clinical assessment.

Humans↗

PubMed2000

[Motor and sensory responses in fusion of vertical disparities in different convergence places].

UNLABELLED: To study motor and sensory responses in vertical fusion at different angles of horizontal vergence in normal humans. METHODS: The study included 12 normal subjects. A cross (+) extending 3.4 degrees x3.2 degrees was presented dichoptically. Vertical disparity was introduced by changing the vertical position of the cross in front of one eye. The disparity was incremented by 0.08 degrees every 8 s. Distance viewing was tested with 1 degrees of convergence demand, near vision with 6-15 degrees convergence demand. Eye movements were recorded using three-axis search coils. RESULTS: Vertical fusion capability was larger at near vision than at distance in 9 of 12 subjects. For the entire group, total vertical fusion capability (motor plus sensory response) differed between distance (mean 1.68 degrees ) and near (mean 2.39 degrees ). The motor component differed significantly between distance (mean 1.42 degrees ) and near (mean 2.13 degrees ). No difference in the sensory component was seen between distance (mean 0.26 degrees ) and near (mean 0.27 degrees ). CONCLUSIONS: Vertical fusion capability increases with convergence. This increase is mainly due to an increase of the motor response.

Accommodation, Ocular↗

PubMed2026

Microplastic aging drives convergence of the plastisphere microbiome and resistome toward agricultural soils.

The degree of microplastic (MP) aging varies substantially in agricultural soils; however, how this common aging gradient influences the plastisphere microbiome and resistome remains largely unknown. We therefore collected polyethylene MPs from long‑term mulched farmlands and classified them into low‑aged plastispheres (LAPs) and high‑aged plastispheres (HAPs). Bacterial community dissimilarity to soil decreased progressively from LAPs to HAPs, accompanied by broadening niche breadth, increasing bacterial diversity, and a shift toward more stochastic community assembly. The diversity and abundance of antibiotic resistance genes (ARGs) declined significantly along the aging gradient, with clinically relevant high-risk ARGs (e.g., vanR, ugd, and aac(6')-I) decreasing by 53.34-84.01%. Furthermore, the ARG hosts shifted from Actinomycetota in LAPs to Pseudomonadota in soils. Variance partitioning showed that the carbonyl index uniquely explained 57.03% of the variation in plastisphere ARG profile distance toward soil, identifying MP aging as the primary driver of resistome convergence. Collectively, these findings demonstrate that natural MP aging drives a progressive convergence of the plastisphere resistome toward that of the surrounding soil, indicating that aged MPs may pose a reduced risk of antibiotic resistance compared to newly formed MPs. This convergence underscores the need to incorporate plastic aging into future risk assessment frameworks for plastisphere-associated ARGs.

Soil Microbiology↗

PubMed1992

Development of accommodation and convergence in infancy.

Paraxial photorefraction was used to assess the development of accommodation and convergence in a large sample of infants under 1 year of age. The infants viewed small dolls placed at various distances (200-25 cm). The majority of infants at all ages demonstrated appropriate convergence for target distance, regardless of manifest refractive error. However, accommodation lagged behind convergence in development. Infants under 2 months tended to demonstrate either flat accommodation responses with a fixed plane of focus at around 30 cm, or accommodated appropriately for near targets, but failed to relax their accommodation sufficiently for the more distant targets. Thus, the focussing error increased with increasing target distance. Since the manifest refractive error was estimated by extrapolating the accommodation function to 0 diopters demand, these infants demonstrated spuriously myopic behavior. After 2 months, the majority of infants showing emmetropic behavior had accommodation responses that changed appropriately with target distance. However, infants with myopic or hyperopic manifest refractive errors displayed a variety of accommodative styles.

Accommodation, Ocular↗

PubMed2005

Unilateral recession-resection in children with exotropia of the convergence insufficiency type.

PURPOSE: The surgical success rates for intermittent exotropia of the convergence insufficiency type have been reported to be variable, and most were studied retrospectively in adults. The purpose of this study was to evaluate prospectively the long-term surgical results of unilateral lateral rectus (LR) muscle recession and medial rectus (MR) muscle resection in children with intermittent exotropia of the convergence insufficiency type. METHODS: A total of 14 children with intermittent exotropia greater at near than at distance by 10 prism diopters (PD) or more were included in this prospective study. The amounts of resection and recession were based on near and distance deviation, respectively. Minimum follow-up was 1 year (mean 26.6 months; range, 12-68 months) after surgery. The paired t-test was used to compare preoperative and postoperative measurements of the angle of deviation at distance and near, near-distance difference. RESULTS: Significant postoperative reduction was achieved in terms of mean distance exodeviation, from 22.5 PD to 9.1 PD (P=0.000), and mean near exodeviation from 33.8 PD to 13.6 PD (P=0.000). Mean near-distance difference reduced from 11.3 PD preoperatively to 4.6 PD postoperatively (P=0.000). Fresnel prism was used temporarily to treat postoperative esotropia in only one patient for postoperative 6 months. CONCLUSIONS: Unilateral surgery biased to MR strengthening more than LR weakening in children with intermittent exotropia of the convergence insufficiency type, was found to successfully reduce both distance and near deviation and to collapse near-distance differences with a low risk of long-term postoperative esotropia.

Child↗

PubMed1990

[The accommodation-convergence bar (A=C bar)].

The accommodation-convergence bar was developed as a simple measuring and exercise instrument. For the ophthalmologist, it is a convenient means of measuring accommodation and convergence in the office, while patients can use it for home convergence and fixation exercises which they can monitor themselves. The A = C bar has also been used experimentally to eliminate the functional central scotoma in dyslexic children.

Accommodation, Ocular↗

PubMed2001

Medial rectus resection(s) with adjustable suture for intermittent exotropia of the convergence insufficiency type.

BACKGROUND: The surgical results for intermittent exotropia of the convergence insufficiency type have been reported to be of varying success. The purpose of this study is to evaluate the surgical results of medial rectus muscle (MR) resection(s) with adjustable suture for this condition. METHODS: Twenty-one consecutive patients with intermittent exotropia of the convergence insufficiency type were included in this retrospective study. All patients had a history of prolonged difficulties at near work unrelieved by nonsurgical treatment. Unilateral or bilateral MR resection(s) were done with the adjustable suture, which was tied at the first postoperative day. The target angle was an esotropia of 10 to 20 PD at distance and an esotropia of 5 to 10 PD at near. Postoperatively Fresnel prisms were used temporarily in patients manifesting a consecutive esotropia with diplopia at distance. Postoperative follow-up period was between 6 months and 24 months with a mean of 9.1 months. RESULTS: MR resection(s) with the adjustable suture reduced the mean exodeviation at near from 25.7 to 3 PD. It also reduced the exodeviation at distance from 11.4 to -2 PD (esodeviation). The mean near-distance difference was collapsed from 14.3 PD preoperatively to 5 PD postoperatively. CONCLUSIONS: MR resection(s) with adjustable suture combined with intentional postoperative aggressive overcorrection and the use of Fresnel prisms is useful in intermittent exotropia of the convergence insufficiency type. The intentional overcorrection during the immediate postoperative period at distance and near is required to prevent long-term undercorrection.

Adolescent↗

PubMed2003

Preoperative prism adaptation in acquired esotropia with convergence excess.

PURPOSE: The prism adaptation test (PAT) is used preoperatively to determine the surgical target angle for acquired esotropia. We assessed the surgical outcomes for children with convergence-excess esotropia (near esotropia greater than distance esotropia by 10 prism diopters [PD] or more) whose target angle was based on the results of the PAT geared to the near deviation. METHODS: We reviewed the charts for all of one surgeon's patients who underwent the PAT for near convergence-excess esotropia and who were followed-up for at least 6 months after surgery. Patients who wore prisms were classified as PAT responders (esotropia <= 8 PD at distance and near with four-dot fusion at near) or nonresponders (exotropia at distance or lack of four 4-dot fusion at near). Responders underwent surgery for the adapted angle at near. The nonresponders who had exotropia at distance had surgery for an angle between the near and distance angles. Nonresponders with esotropia angles <= 8 PD at distance and near underwent surgery for the total near deviation. RESULTS: Fifty-four (83%) of the 65 children were PAT responders. Thirty-nine (72%) of the 54 responders and 6 (55%) of 11 nonresponders had excellent results (heterotropia <= 8 PD at distance and near with four-dot fusion at near). All 13 responders whose angles built with prism had excellent results. Among 61 patients who had an esotropia <= 8 PD at near with prisms preoperatively, only 4 (6.6%) developed overcorrections at distance by the latest follow-up examination; 3 were responders and 1 a nonresponder. CONCLUSIONS: PAT for the near deviation in children who have convergence-excess esotropia is a useful test in estimating the target angle for surgery. Responders whose angles built with prism had a particularly high success rate. Surgery geared to the near-adapted angle has a low risk of creating an overcorrection in the distance regardless of the response to PAT.

Adaptation, Physiological↗

PubMed1999

Convergence insufficiency in idiopathic Parkinson's disease responsive to levodopa.

We report a patient with pathologically proven idiopathic Parkinson's disease (IPD) who developed diplopia secondary to convergence insufficiency during his motor "off" periods. Diplopia resolved with onset of motor benefit from levodopa. Neuro-ophthalmologic examination demonstrated convergence insufficiency during motor "off" periods that was alleviated after onset of motor benefit from levodopa. This is the first reported case of convergence insufficiency in IPD responsive to levodopa.

Antiparkinson Agents↗

PubMed2026

An automated geometric modeling framework in GATE for the design and optimization of high-sensitivity converging-beam SPECT collimators.

Objective.The trade-off between detection sensitivity and spatial resolution is a fundamental challenge in designing organ-dedicated Single-photon emission computed tomography (SPECT) collimators. While converging-hole geometries offer a solution, their optimization is often hindered by the lack of flexible computational tools capable of modeling large-scale, non-parallel hole arrays. This study aims to develop an automated geometric modeling framework to facilitate the design and evaluation of complex converging- and diverging-hole collimators within standard Monte Carlo environments.Approach.We developed a specialized modeling framework by implementing custom C++ classes and a vector-based alignment algorithm within GATE. This platform enables automated, orientation-consistent construction of large-scale converging arrays not natively supported by standard implementations. A high-sensitivity pure cone-beam collimator (CBC) was designed using this framework. The evaluation used hot-rod, disc, and Jaszczak phantoms for physical characterization, while XCAT and dedicated brain models were employed for clinical tasks, including cardiac, brain perfusion, and DaTscan SPECT simulations.Main results.The CBC achieved a nearly fourfold sensitivity increase compared to a conventional low-energy high-resolution parallel-hole collimator at a 20 cm radius of rotation, while maintaining comparable spatial resolution. Despite a 52.3% field of view reduction, the CBC yielded a 2.2-fold noise reduction (CV: 11.7% vs 25.9%) and mitigated partial volume effects via geometric magnification. XCAT and brain phantom simulations confirmed enhanced anatomical definition and contrast recovery in cardiac, perfusion, and DaTscan tasks.Significance.This work provides an efficient computational tool for rapid design space exploration of advanced collimator geometries. The results demonstrate that the proposed CBC design offers a significant sensitivity advantage, making it highly suitable for high-performance, small-volume clinical applications such as brain and cardiac molecular imaging.

Tomography, Emission-Computed, Single-Photon↗

PubMed1987

Determining the convergence demand for a patient who reads at a close working distance.

Low vision practitioners frequently prescribe microscopic spectacles for reading. Although the lens power enables the patient to focus clearly, the convergence demand at the close working distance may make it difficult for the patient to achieve and sustain binocular vision. Base-in prism and lens decentration can reduce the convergence demand but even these methods are not always sufficient to achieve the goal of binocular vision. A means of calculating the convergence demand for a patient who is using microscopic spectacles of known parameters is presented as an aid to understanding the dynamics involved in achieving binocularity.

Convergence, Ocular↗

PubMed1988

Visual therapy results for convergence insufficiency: a literature review.

This paper is a review of the literature relative to treatment results for convergence insufficiency utilizing vision therapy training procedures. Vision therapy is shown to improve the nearpoint of convergence and fusional convergence and to ameliorate associated symptoms. The overall cure rate is 72%. Furthermore, the training results appear to persist for at least 2 years if the patients are initially cured and are independent of age until the late presbyopic years. Also, recent studies indicate the type of training procedures which yield the most effective training results.

Adolescent↗

PubMed1998

Normative values for the nearpoint of convergence of elementary schoolchildren.

BACKGROUND: Nearpoint of convergence (NPC) values of 8 to 10 cm are widely used to diagnose binocular dysfunctions such as convergence insufficiency. However, there are no published age-related normative values in the literature to substantiate these values. METHODS: Subjects were 297 schoolchildren in kindergarten, third grade, and sixth grade who had passed a school-based Modified Clinical Technique vision screening. Each child had the NPC break and recovery taken three times using a standardized protocol developed by the Convergence Insufficiency and Reading Study group. The examiners used an Astron International (ACR/21) Accommodative Rule with a movable column of 20/30 letters as the target. RESULTS: For each grade, the distribution of NPC break was right skewed, with a concentration of values between 1 and 6 cm. At least 85% of the subjects in each grade had an NPC break < or = 6 cm. NPC break values (mean +/- SD) were 3.3 +/- 2.6 cm for kindergartners, 4.1 +/- 2.4 cm for third graders, and 4.3 +/- 3.4 cm for sixth graders, and the means were found to be statistically different (analysis of variance, p = 0.031). NPC recoveries (mean +/- SD) for the three groups were 7.3 +/- 4.8 cm, 8.7 +/- 4.2 cm, and 7.2 +/- 3.9 cm, respectively, which were also significantly different (analysis of variance, p = 0.027). The recovery distributions were more symmetric and less skewed than those for break. For each grade level, there was a strong positive relationship between NPC recovery and NPC break, but the difference between NPC recovery and break had a low correlation with the NPC break. SUMMARY: Kindergartners had somewhat better NPC breaks than third or sixth graders, whereas no clear age trend was present for NPC recovery. A supporting study using a random sample of clinic patients (aged 10-12 years) suggests that patients with NPC breaks > 6 cm are more than twice as likely to be symptomatic than patients with NPC breaks < or = 6 cm. Based on these results and the NPC break distributions in this study, a clinical cutoff value of 6 cm is suggested for patients of elementary school age. A cutoff value in the 6- to 10-cm range is recommended for children of elementary school age in a screening context. The exact value within this range depends on the level of concern with identifying patients who have visual signs and symptoms associated with a receded NPC.

Accommodation, Ocular↗

PubMed2000

Stability analysis of two linear accommodation and convergence models.

PURPOSE: To perform time domain stability analysis on two widely accepted linear models of accommodation and convergence. METHODS: For each model, the governing differential equations were used to compute the system matrix. The system matrices were used to calculate the respective trace and determinant from which eigen-vectors and eigenvalues were quantified. These characteristic numbers fully identified and classified the fixed points of each model and, thus, their stability. RESULTS: Controller gains, time constants, and accommodation and convergence cross-links determined model stability. Accommodation and convergence cross-links have the greatest influence on stability. A model-specific transition between stabilities was identified as the product of these cross-links, AC.CA(CRITICAL). For each model, three types of fixed points are described and displayed graphically: stable node, line of nonisolated fixed points, and saddle. CONCLUSION: We demonstrated the stability analysis of a two-dimensional linear system, working only in the time domain. The benefit of time-domain stability analysis is that it can be extended to nonlinear systems when frequency domain analysis techniques fail. Given that we live in a fundamentally nonlinear world and that the use and application of computational models is extensive, this is a valuable and important tool.

Accommodation, Ocular↗

PubMed2002

Reliability of binocular vision measurements used in the classification of convergence insufficiency.

PURPOSE: To evaluate the reliability of binocular vision measurements used in the classification of convergence insufficiency. METHODS: Two examiners tested 20 fifth and sixth graders in a school setting who passed a screening of visual acuity, refraction, and binocularity. The tests, conducted using a standard protocol, consisted of von Graefe near heterophoria (NH), phorometric positive fusional vergence (PFV), nearpoint of convergence (NPC), and monocular pushup accommodative amplitude (AA). Each examiner measured each child three consecutive times for each test, on two separate occasions, spaced approximately 1 week apart. Intraexaminer and interexaminer agreement was assessed using intraclass correlation coefficients (ICC), the median absolute difference (MAD), and the coefficient of repeatability (COR). RESULTS: The within-session reliability of the NH (ICC: 0.95 to 0.99), NPC (ICC: 0.94 to 0.98), and AA (ICC: 0.88 to 0.95) were good, whereas the PFV was less reliable (ICC: 0.71 to 0.94). The intraexaminer reliability between sessions was good for the NPC (ICC: 0.92 and 0.89), less reliable for NH (ICC: 0.81 and 0.81) and AA (ICC: 0.89 and 0.69), and much less reliable for PFV break (ICC: 0.59 and 0.53). Typical between-session PFV differences (MAD) were between 3 and 4 delta, whereas the COR differences were as large as 12 delta. CONCLUSIONS: Three of the four measures (NH, NPC, and AA) often used in the classification of convergence insufficiency generally have good within-session and between-session reliability. The PFV break was found to have only fair reliability with clinically significant differences between sessions. The large potential test-retest differences found could complicate clinical decision-making in regards to diagnosis and treatment.

Accommodation, Ocular↗

PubMed2002

The effectiveness of pencil pushups treatment for convergence insufficiency: a pilot study.

PURPOSE: To study the effectiveness of pencil pushups treatment (PPT) for the treatment of convergence insufficiency in a clinical situation. METHODS: PPT was prescribed for use at home for 6 weeks for 25 subjects with convergence insufficiency. RESULTS: Twelve of the subjects returned for follow-up. Seven of 12 (58%) subjects showed a clinically significant improvement in nearpoint of convergence and positive fusional vergence, and 11 of 12 reported improvement in symptoms. Only one subject became asymptomatic. CONCLUSIONS: PPT resulted in some improvement in both objective findings and symptoms for some subjects. Compliance with the recommended home therapy protocol was poor.

Adolescent↗

PubMed1990

Dynamic interactions between accommodation and convergence.

Frequency-domain equations were derived for the current dual-interaction model of accommodation and convergence control, and its adaptive behavior was related to the system's parameters. Contrary to predictions based on the steady-state performance of the model [18], dynamic analysis showed that the AC/A is sensitive to the method of measurement and a procedure is established for its reliable determination. Additionally, the results provided theoretical support for the empirical finding that low AC/A and CA/C ratios are associated with high accommodative and convergence adaptation, respectively [15]. The derived equations should help future studies relate the physiological behavior of accommodative and convergence to specific model parameters.

Accommodation, Ocular↗

PubMed2026

Comparative Genomics Reveals Convergent Evolution Between Avivorous Bats (Ia io and Nyctalus aviator).

Investigating the genetic basis of dietary specialization can provide insights into the evolution of niche breadth. In this study, we employed comparative genomics to investigate the adaptive mechanisms enabling two bat species (Nyctalus aviator and Ia io) to shift from insectivory to seasonal bird consumption (avivorous bats). Our findings revealed adaptation related to immune response and lipid metabolism in avivorous bat species. Avivorous bats exhibit strong positive selection and convergent evolution in immune-related genes, which are under heightened selective pressure compared to those of non-avivorous bats. These species also display significantly fewer endogenous retroviral elements. These findings emphasized the significance of immune-driven adaptive evolution in avivory. Additionally, our results showed that the dietary evolution of avivorous bats is accompanied by convergent evolution associated with the lipid metabolism. Notably, CEPT1, the upstream gene required for the activation of the PPAR pathway, underwent positive selection and convergence, which may have affected lipid metabolism. These adaptations may enable avivorous bat species to face the challenge of immune response and nutrition during dietary niche expansion. These findings not only provide comprehensive insights into the adaptive evolution driving the unique diet of avivorous bats but also offered novel perspectives on the molecular mechanisms underlying ecological niche evolution in a dietary context.

Animals↗