Positive Fusional Vergence Research Articles

Binocular Vision and the Stroop Test.

Recent studies report a link between optometric results, learning disabilities, and problems in reading. This study examines the correlations between optometric tests of binocular vision, namely, of vergence and accommodation, reading speed, and cognitive executive functions as measured by the Stroop test. Fifty-one students (mean age, 20.43 ± 1.25 years) were given a complete eye examination. They then performed the reading test L'Alouette and the Stroop interference test at their usual reading distance. Criteria for selection were the absence of significant refractive uncorrected error, strabismus, amblyopia, color vision defects, and other neurologic findings. The results show a correlation between positive fusional vergences (PFVs) at near distance and the interference effect (IE) in the Stroop test: the higher the PFV value is, the less the IE. Furthermore, the subgroup of 11 students presenting convergence insufficiency, according to Scheiman and Wick criteria (2002), showed a significantly higher IE during the Stroop test than the other students (N = 18) who had normal binocular vision without symptoms at near. Importantly, there is no correlation between reading speed and PFV either for the entire sample or for the subgroups. These results suggest for the first time a link between convergence capacity and the interference score in the Stroop test. Such a link is attributable to the fact that vergence control and cognitive functions mobilize the same cortical areas, for example, parietofrontal areas. The results are in favor of our hypothesis that vergence is a vector of attentional and cognitive functions.

Independent development of refraction, accommodation and convergence over two years in primary school children

Abstract Purpose: To examine whether age-related changes in refraction covary with changes in parameters describing accommodation and convergence over time in a group of Danish school children. Methods: Two-hundred and seventy-eight unselected Danish school children (7.1-13.9 years) without manifest strabismus were studied at baseline and after two years. Each examination included measurement of distance visual acuity, unilateral cover test, non-cycloplegic autorefraction, monocular amplitude of accommodation, monocular accommodation facility, near phoria, near point of convergence, and positive and negative fusional vergence. The changes in the measured parameters were studied over time, followed by the testing for dependencies in the development of these parameters. Results: After two years there was a significant increase in distance visual acuity (p=0.04), monocular accommodation facility (p<0.001), near point exophoria (p=0.04), near point of convergence (p=0.01), and fusional range (p<0.001), a significant reduction in hyperopia (p=0.01) and monocular amplitude of accommodation (p<0.001), while the midpoint of the fusional range changed significantly towards convergence (p<0.001). The increase in near point of convergence correlated significantly with the decrease in monocular amplitude of accommodation (p<0.001) and the convergent shift in the midpoint of the fusional range was significantly correlated with a larger fusional range (p<0.001). The changes in all other parameters were independent. Conclusions: The development of refraction, accommodation, and convergence parameters in school children over two years are independent. This may be due to separate processes regulating development, and suggests that therapeutic intervention may be performed on each of the parameters individually without a derived effect on the other parameters.

조도변화가 시기능 성분에 미치는 영향

목적: 조도변화가 시기능에 미치는 영향을 알아보고자 하였다. 방법: 평균나이 <TEX>$23.93{\pm}1.59$</TEX>세 40명(남 21, 여 19)을 대상으로 시표면 조도를 5, 50, 200, 500 및 800 lx로 조정하여 각 조도 상태에서 조절력, 폭주근점, 원거리 및 근거리 사위, 원거리 및 근거리 융합버전스, 상대조절력, 조절래그를 측정하였다. 결과: 시표면의 조도가 감소함에 따라 조절력은 유의하게 감소하였고(p<0.05), 조절래그는 감소하였고, 폭주근점은 멀어졌으며, 수평사위는 내편위의 경향을 보였다. 음성융합버전스는 조도가 감소함에 따라 분리점과 회복점이 감소하는 경향을 보인 반면 양성융합버전스는 분리점이 증가하는 경향을 보였다. 음성 및 양성상대조절력의 경우 조도가 감소함에 따라 유의한(p<0.05) 감소를 보였다. 결론: 임상현장에서 시기능 검사는 환자의 생활환경 및 직업 등을 고려한 적절한 조도 수준에서 수행되어야 할 것으로 사료된다. Purpose: This study was performed in order to figure out the influence of illumination on visual function. Methods: 40 adults (male 21, female 19) of average age <TEX>$23.93{\pm}1.59$</TEX> years were participated in this study. The test chart surface illumination was adjusted to 5, 50, 200, 500 and 800 lx, and then amplitude of accommodation, near point of convergence, far and near distance phoria, far and near distance fusional vergence, relative accommodation, and accommodation lag were measured at each illumination condition. Results: As illumination intensity of test chart was reduced, amplitude of accommodation was significantly decreased (p<0.05), accommodation lag was also decreased, near point of convergence was receded, and horizontal phoria showed a tendency of esodeviation. In the case of negative fusional vergence, with reduction of illumination intensity, the break point and the recovery point were decreased but in the case of positive fusional vergence, the break point was increased. The negative and positive relative accommodation were significantly decreased (p<0.05) with reduction of illumination intensity. Conclusions: In clinical practice, visual functional test should be performed under condition of adequate illumination level through patient's living environment and job.

Frequency of Convergence and Accommodative Disorders in a Clinical Population of Mashhad, Iran

Purpose: To investigate the frequency of convergence and accommodation anomalies in an optometric clinical setting in Mashhad, Iran, and to determine tests with highest accuracy in diagnosing these anomalies.Methods: From 261 patients who came to the optometric clinics of Mashhad University of Medical Sciences during a month, 83 of them were included in the study based on the inclusion criteria. Near point of convergence (NPC), near and distance heterophoria, monocular and binocular accommodative facility (MAF and BAF, respectively), lag of accommodation, positive and negative fusional vergences (PFV and NFV, respectively), AC/A ratio, relative accommodation, and amplitude of accommodation (AA) were measured to diagnose the convergence and accommodation anomalies. The results were also compared between symptomatic and asymptomatic patients. The accuracy of these tests was explored using sensitivity (S), specificity (Sp), and positive and negative likelihood ratios (LR+, LR−).Results: Mean age of the patients was 21.3 ± 3.5 years and 14.5% of them had specific binocular and accommodative symptoms. Convergence and accommodative anomalies were found in 19.3% of the patients; accommodative excess (4.8%) and convergence insufficiency (3.6%) were the most common accommodative and convergence disorders, respectively. Symptomatic patients showed lower values for BAF (p = .003), MAF (p = .001), as well as AA (p = .001) compared with asymptomatic patients. Moreover, BAF (S = 75%, Sp = 62%) and MAF (S = 62%, Sp = 89%) were the most accurate tests for detecting accommodative and convergence disorders in terms of both sensitivity and specificity.Conclusions: Convergence and accommodative anomalies are the most common binocular disorders in optometric patients. Including tests of monocular and binocular accommodative facility in routine eye examinations as accurate tests to diagnose these anomalies requires further investigation.

Reduced vergence adaptation is associated with a prolonged output of convergence accommodation in convergence insufficiency.

Convergence insufficiency (CI) is a developmental visual anomaly defined clinically by a reduced near point of convergence, a reduced capacity to view through base-out prisms (fusional convergence); coupled with asthenopic symptoms typically blur and diplopia. Experimental studies show reduced vergence parameters and tonic adaptation. Based upon current models of accommodation and vergence, we hypothesize that the reduced vergence adaptation in CI leads to excessive amounts of convergence accommodation (CA). Eleven CI participants (mean age=17.4±2.3 years) were recruited with reduced capacity to view through increasing magnitudes of base out (BO) prisms (mean fusional convergence at 40 cm=12±0.9Δ). Testing followed our previous experimental design for (n=11) binocularly normal adults. Binocular fixation of a difference of Gaussian (DoG) target (0.2 cpd) elicited CA responses during vergence adaptation to a 12Δ BO. Vergence and CA responses were obtained at 3 min intervals over a 15 min period and time course were quantified using exponential decay functions. Results were compared to previously published data on eleven binocular normals. Eight participants completed the study. CI's showed significantly reduced magnitude of vergence adaptation (CI: 2.9Δ vs. normals: 6.6Δ; p=0.01) and CA reduction (CI=0.21 D, Normals=0.55 D; p=0.03). However, the decay time constants for adaptation and CA responses were not significantly different. CA changes were not confounded by changes in tonic accommodation (Change in TA=0.01±0.2D; p=0.8). The reduced magnitude of vergence adaptation found in CI patients resulting in higher levels of CA may potentially explain their clinical findings of reduced positive fusional vergence (PFV) and the common symptom of blur.

Improvement of Vergence Movements by Vision Therapy Decreases K-ARS Scores of Symptomatic ADHD Children

[Purpose] To determine whether the improvement of vergence movements by vision therapy can decrease the K-ARS scores of symptomatic ADHD children. [Methods] Eighty-one out of 1,123 children surveyed using the K-ARS, a parents’-reported questionnaire, led to 16 of these 81 children being showed scores of ≥19, and measurement of binocular function diagnosed as having convergence insufficiency. The 16 children were divided equally into a control group and a vision therapy group. [Results] After vision therapy for 12 weeks, near point convergence (4.38±0.69 cm) significantly neared compared to the near point convergence before vision therapy (11.50±2.28 cm), and both the break point (32.38±2.53 Δ) and recovery point (19.75±2.11 Δ) of near positive fusional vergence significantly improved compared to their values before vision therapy (15.88±2.64 Δ, 6.38±6.70 Δ, respectively). Near exophoria after vision therapy (7.81±2.00 Δ BI) significantly decreased compared to its value before vision therapy (12.00±1.16 Δ BI). The K-ARS scores referring to symptomatic ADHD significantly decreased after vision therapy (17.13±2.84) compared to before vision therapy (23.25±1.49). [Conclusions] Convergence insufficiency symptoms are closely related to symptoms screened for ADHD, and vision therapy to improve vergence movements is an effective method of decreasing the K-ARS scores.

Independence between age-related changes in refraction, accommodation and convergence in primary school children

The parameters which describe how refraction, accommodation and convergence develop during childhood are well understood, but the possible interdependencies between these agerelated changes are not known. Hence it is unknown whether refractive development is associated with development of accommodation and convergence. Four-hundred and fifty-two unselected 7-13 year old school children were subjected to autorefraction and unilateral cover test, and measurement of visual acuity, amplitude of accommodation, monocular accommodation facility, near phoria, near point of convergence, and positive and negative fusional vergence using subjective techniques. Linear regression was used to study the correlation of these parameters with age, followed by study of correlations between age-dependent parameters. There was a significant reduction in hyperopia (0.13 D/year, 95% CI [-0.20, -0.06]), a significant increase in the monocular accommodation facility (0:48 cpm/year, 95% CI [0.18, 0.79]), and a non-significant shift towards convergence of the midpoint of the fusional range (0.43 ΔD/year, 95% CI [0.12, 0.74]) with age. Age-dependent variables were not significantly correlated. Autorefraction was not correlated with any other variable. None of the other parameters showed any significant correlations with age. Age-related changes in refraction, monocular accommodation facility and midpoint of fusional range were independent. This indicates that the development of these parameters involves separate processes, and suggests that therapeutic intervention may be performed on these parameters individually without a derived effect on the other age-related parameters.

Relationship Between Clinical Signs and Symptoms of Convergence Insufficiency

The percentage of children who are symptomatic has been shown to increase with the number of signs of convergence insufficiency (CI). Our goal was to investigate whether there is a relationship between the severity of the clinical signs of CI and symptom level reported in children with a three-sign symptomatic CI. The Convergence Insufficiency Treatment Trial enrolled 221 children with symptomatic CI from ages 9 to 17 years. Inclusion criteria included the following three signs of CI: (1) exophoria at near at least 4Δ greater than at distance, (2) insufficient positive fusional vergence (PFV) at near, and (3) a receded near point of convergence (NPC) of 6 cm break or greater. The relationships between the severity of each sign of CI (mild, moderate, and severe) and the level of symptoms as measured by the Convergence Insufficiency Symptom Survey (CISS) at baseline were evaluated. Mean CISS scores were not significantly different between mild, moderate, and severe exophoria (p = 0.60), PFV blur (p = 0.99), Sheard's criterion (p = 0.89), or NPC break (p = 0.84). There was also no difference between the frequency of subjects scoring at mild, moderate, or severe levels on the CISS and the severity of each sign of CI. Correlations between individual clinical signs and the CISS score were very low and not statistically significant. Among symptomatic children with a CISS score of 16 or higher and three clinical signs of CI, there is no further association between the severity of the clinical signs and their level of symptoms.

Evaluation of ocular accommodation, convergence and fusional vergence changes during Ramadan

Introduction: There are a few researches regarding the effects of Islamic fasting on visual system. The aim of this study was to investigate the effects of Ramadan fasting on the amplitude of accommodation (AA), near point of convergence (NPC), positive and negative fusional vergences (PFV and NFV, respectively) in visually healthy fasters. Methods: AA, NPC, PFV and NFV at far (6m) and near (40cm) were measured in 30 male students. Nutritional habits in a week before each examination visit were assessed with the Food Frequency Questionnaire (FFQ). Results: Mean age and fasting average experience were 23.9 and 10 years, respectively. AA and NPC showed significant changes (p<0.05) during Ramadan; but there was no significant difference before and after Ramadan in these parameters. NFV blur, break and recovery points at far significantly reduced in Ramadan than before (p=0.003, p=0.005, p=0.003, respectively) with insignificant compensation after Ramadan. Results showed that there was no significant correlation between changes in diet pattern and AA, NPC and distant NFV variations (p<0.05). Conclusion: Some visual problems may be reported at far and near visual tasks during Ramadan; but most of the problems may be resolved after it. Some visual preparations may be needed for more effective visual activities during Ramadan; essentially for students with intensive visual tasks. Vision therapy may be suggested along with nutrient pattern improvement during Ramadan.

Visual Dysfunctions and Symptoms During the Subacute Stage of Blast-Induced Mild Traumatic Brain Injury

The purpose of the present study was to assess the occurrence of visual dysfunctions and associated symptoms in active duty warfighters during the subacute stage of blast-induced mild traumatic brain injury (mTBI). A comprehensive visual and oculomotor function evaluation was performed on 40 U.S. military personnel, 20 with blast-induced mTBI and 20 without. In addition, a comprehensive symptom questionnaire was used to assess the frequency of visual, vestibular, and neuropsychiatric-associated symptoms. The most common mTBI-induced visual dysfunctions were associated with near oculomotor deficits, particularly large exophoria, decreased fusion ranges, receded near point of convergence, defective pursuit and saccadic eye movements, decreased amplitude of accommodation, and monocular accommodative facility. These were associated with reduced reading speed and comprehension and an increased Convergence Insufficiency Symptom Survey score. Photosensitivity was a common visual dysfunction along with hearing, balance, and neuropsychiatric symptoms. The oculomotor testing for warfighters suspected of blast-induced mTBI should include, at a minimum, the assessment of near lateral and vertical phorias, positive fusional vergence, stereoacuity, near point of convergence, amplitude of accommodation, monocular accommodative facility, saccades, and pursuit eye movements. A reading test should be included in all routine exams as a functional assessment of the integration of oculomotor functions.

Factors associated with base‐in prism treatment outcomes for convergence insufficiency in symptomatic presbyopes

Purpose: The aim was to determine whether baseline measurements of binocular vision are associated with symptoms of convergence insufficiency (CI) both before and after CI treatment with base‐in prism in symptomatic presbyopes. We further determined the factors that predicted CI treatment outcomes.Methods: A total of 29 symptomatic CI subjects aged 45 to 68-years were examined and the following binocular vision measurements were obtained at the baseline: near heterophoria by cover test, associated phoria at near (AP), near point of convergence (NPC) and positive fusional vergence at near (PFV). Each subject wore each of two pairs of progressive addition spectacles for a three‐week period, one with prism and one with the same prescription but no prism. The wear order was randomised across subjects. Subjects completed the CI symptom survey (CISS) before and at the end of the three weeks, thus baseline, placebo and treatment CISS scores were tabulated. The reduction in symptoms (CISS score improvement) was calculated as the difference between the placebo and treatment CISS scores.Results: Neither baseline CISS score nor treatment CISS score had statistically significant correlations with any of the binocular vision measurements. CISS score improvement was statistically significantly associated with near heterophoria, AP and NPC break but not with PFV. CISS score improvement was significantly predicted by both near heterophoria and NPC break but not by AP and PFV. With other variables held constant, the CISS score improved by 1.57 for each additional prism dioptre of exophoria at near and by 0.81 for each additional centimetre that the NPC break was receded.Conclusion: There was no significant association between the CISS score with any of the baseline binocular vision measurements before or after prism treatment. Our findings suggest that a greater near heterophoria and/or more receded NPC before treatment are associated with more reduction in CI symptoms by prism treatment.

Improvement in Academic Behaviors After Successful Treatment of Convergence Insufficiency

To determine whether treatment of symptomatic convergence insufficiency (CI) has an effect on Academic Behavior Survey (ABS) scores. The ABS is a six-item survey developed by the Convergence Insufficiency Treatment Trial Group that quantifies the frequency of adverse school behaviors and parental concern about school performance on an ordinal scale from 0 (never) to 4 (always) with total scores ranging from 0 to 24. The ABS was administered at baseline and after 12 weeks of treatment to the parents of 218 children aged 9 to 17 years with symptomatic CI, who were enrolled in the Convergence Insufficiency Treatment Trial and randomized into (1) home-based pencil push-ups; (2) home-based computer vergence/accommodative therapy and pencil push-ups; (3) office-based vergence/accommodative therapy with home reinforcement; and (4) office-based placebo therapy with home reinforcement. Participants were classified as successful (n = 42), improved (n = 60), or non-responder (n = 116) at the completion of 12 weeks of treatment using a composite measure of the symptom score, nearpoint of convergence, and positive fusional vergence. Analysis of covariance methods were used to compare the mean change in ABS between response to treatment groups while controlling for the ABS score at baseline. The mean ABS score for the entire group at baseline was 12.85 (SD = 6.3). The mean ABS score decreased (improved) in those categorized as successful, improved, and non-responder by 4.0, 2.9, and 1.3 points, respectively. The improvement in the ABS score was significantly related to treatment outcome (p < 0.0001), with the ABS score being significantly lower (better) for children who were successful or improved after treatment as compared to children who were non-responders (p = 0.002 and 0.043, respectively). A successful or improved outcome after CI treatment was associated with a reduction in the frequency of adverse academic behaviors and parental concern associated with reading and school work as reported by parents.

Effectiveness of computerized oculomotor vision screening in a military population: Pilot study

The prevalence of oculomotor dysfunctions associated with blast-induced mild traumatic brain injury (mTBI) in warfighters has increased as a consequence of recent conflicts. This study evaluated the effectiveness of computerized oculomotor vision screening (COVS) in a military population. Oculomotor functions were assessed with COVS and by conventional methods in 20 U.S. military personnel with and 20 without mTBI. The validity of COVS was determined by Pearson correlation and Bland-Altman method or the kappa coefficient. The repeatability of the COVS was assessed with the coefficient of repeatability or the kappa coefficient. The results showed that COVS had high sensitivity and specificity for screening near oculomotor functions. Overall, the COVS showed excellent validity and repeatability for assessing near lateral and vertical phorias, Worth 4 Dot, and fixation, as well as pursuit and saccadic eye movements. Despite the strong Pearson correlation, the Bland-Altman analysis identified minor to moderate discrepancies for both positive and negative fusional vergence and their associated recovery as well as for the monocular accommodative facility measurements. This study demonstrated that non-eye-care professionals may be able to use the COVS as a tool to efficiently screen oculomotor functions in a military population with or without mTBI.

Treatment of symptomatic convergence insufficiency with a home-based computer orthoptic exercise program

To determine the efficacy of a home-based computer orthoptic program to treat symptomatic convergence insufficiency. A retrospective review of consecutive patients with symptomatic convergence insufficiency treated with a home-based computer orthoptic program was performed. Symptomatic convergence insufficiency was defined as: near point of convergence (NPC) >6 cm, decreased positive fusional vergence, exophoria at near at least 4(Δ) greater than at far, and documented complaints of asthenopia, diplopia, or headaches with reading or near work. The Computer Orthoptics CVS program was used for this study. Before beginning the computer orthoptic program, patients with an NPC >50 cm were given 4 base-in prisms and push-up exercises (NPC exercises with an accommodative target) for 2 weeks. A total of 42 patients were included. Mean treatment duration was 12.6 weeks; mean follow-up, 8.5 months. Of the 42 patients, 35 were treated with the home-based computer orthoptic program and push-up exercises; the remaining 7 only used the computer orthoptic program. Because of a remote NPC, 5 patients were given base-in Fresnel prism before starting treatment. Baseline mean NPC was 24.2 cm; posttreatment mean NPC improved to 5.6 cm: 39 patients (92.8%) achieved an NPC of ≤6 cm (p < 0.001). Positive fusional vergence improved in 39 patients (92.8%). Fourteen patients reduced their near exophoria by ≥5(Δ). A total of 27 patients (64.2%) reported resolution of symptoms after treatment. In our study, home-based computer orthoptic exercises reduced symptoms and improved NPC and fusional amplitudes. The computer orthoptic program is an effective option for treating symptomatic convergence insufficiency.

Non-surgical interventions for convergence insufficiency.

Convergence insufficiency is a common eye muscle co-ordination problem in which the eyes have a strong tendency to drift outward (exophoria) when reading or doing close work. Symptoms may include eye strain, headaches, double vision, print moving on the page, frequent loss of place when reading, inability to concentrate, and short attention span. To systematically assess and synthesize evidence from randomized controlled trials (RCTs) on the effectiveness of non-surgical interventions for convergence insufficiency. We searched The Cochrane Library, MEDLINE, EMBASE, Science Citation Index, the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) and ClinicalTrials.gov (www.clinicaltrials.gov ) on 7 October 2010. We manually searched reference lists and optometric journals. We included RCTs examining any form of non-surgical intervention against placebo, no treatment, sham treatment, or each other. Two authors independently assessed eligibility, risk of bias, and extracted data. We performed meta-analyses when appropriate. We included six trials (three in children, three in adults) with a total of 475 participants. We graded four trials at low risk of bias.Evidence from one trial (graded at low risk of bias) suggests that base-in prism reading glasses was no more effective than placebo reading glasses in improving clinical signs or symptoms in children.Evidence from one trial (graded at high risk of bias) suggests that base-in prism glasses using a progressive addition lens design was more effective than progressive addition lens alone in decreasing symptoms in adults. At three weeks of therapy, the mean difference in Convergence Insufficiency Symptoms Survey (CISS) score was -10.24 points (95% confidence interval (CI) -15.45 to -5.03).Evidence from two trials (graded at low risk of bias) suggests that outpatient (or office-based as used in the US) vision therapy/orthoptics was more effective than home-based convergence exercises (or pencil push-ups as used in the US) in children. At 12 weeks of therapy, the mean difference in change in near point of convergence, positive fusional vergence, and CISS score from baseline was 3.99 cm (95% CI 2.11 to 5.86), 13.13 diopters (95% CI 9.91 to 16.35), and 9.86 points (95% CI 6.70 to 13.02), respectively.In a young adult population, evidence from one trial (graded at low risk of bias) suggests outpatient vision therapy/orthoptics was more effective than home-based convergence exercises in improving positive fusional vergence at near (7.7 diopters, 95% CI 0.82 to 14.58), but not the other outcomes.Evidence from one trial (graded at low risk of bias) comparing four interventions, also suggests that outpatient vision therapy/orthoptics was more effective than home-based computer vision therapy/orthoptics in children. At 12 weeks, the mean difference in change in near point of convergence, positive fusional vergence, and CISS score from baseline was 2.90 cm (95% CI 0.96 to 4.84), 7.70 diopters (95% CI 3.94 to 11.46), and 8.80 points (95% CI 5.26 to 12.34), respectively. Evidence was less consistent for other pair-wise comparisons. Current research suggests that outpatient vision therapy/orthoptics is more effective than home-based convergence exercises or home-based computer vision therapy/orthoptics for children. In adult population, evidence of the effectiveness of various non-surgical interventions is less consistent.

Vision Therapy in Adults with Convergence Insufficiency: Clinical and Functional Magnetic Resonance Imaging Measures

This research quantified clinical measurements and functional neural changes associated with vision therapy in subjects with convergence insufficiency (CI). Convergence and divergence 4° step responses were compared between 13 control adult subjects with normal binocular vision and four CI adult subjects. All CI subjects participated in 18 h of vision therapy. Clinical parameters quantified throughout the therapy included: nearpoint of convergence, recovery point of convergence, positive fusional vergence at near, near dissociated phoria, and eye movements that were quantified using peak velocity. Neural correlates of the CI subjects were quantified with functional magnetic resonance imaging scans comparing random vs. predictable vergence movements using a block design before and after vision therapy. Images were quantified by measuring the spatial extent of activation and the average correlation within five regions of interests (ROI). The ROIs were the dorsolateral prefrontal cortex, a portion of the frontal lobe, part of the parietal lobe, the cerebellum, and the brain stem. All measurements were repeated 4 months to 1 year post-therapy in three of the CI subjects. Convergence average peak velocities to step stimuli were significantly slower (p = 0.016) in CI subjects compared with controls; however, significant differences in average peak velocities were not observed for divergence step responses (p = 0.30). The investigation of CI subjects participating in vision therapy showed that the nearpoint of convergence, recovery point of convergence, and near dissociated phoria significantly decreased. Furthermore, the positive fusional vergence, average peak velocity from 4° convergence steps, and the amount of functional activity within the frontal areas, cerebellum, and brain stem significantly increased. Several clinical and cortical parameters were significantly correlated. Convergence peak velocity was significantly slower in CI subjects compared with controls, which may result in asthenopic complaints reported by the CI subjects. Vision therapy was associated with and may have evoked clinical and cortical activity changes.

Contact lenses vs spectacles in myopes: is there any difference in accommodative and binocular function?

Theoretically, the accommodative and vergence demands are different between single-vision contact lenses and spectacle lenses. The aim of the present study was to determine whether these differences exist when these two correction methods are used in clinical practice. For this, different visual parameters that characterize the accommodative (accommodation amplitude, accommodative facility, and accommodative response) and binocular function (near and distance horizontal and vertical dissociated phorias, near and vertical associated phorias, near and distance negative and positive fusional vergence, vergence facility, near point of convergence, negative and positive relative accommodation, stimulus AC:A ratio and stereoacuity) were evaluated in a student population when their myopia was corrected with either spectacles or soft contact lenses (SCL). All parameters were measured on two separate occasions in 30 myopic habitual contact lens and spectacle wearers of mean age 19 ± 2.4years. Some parameters such as accommodation amplitude, accommodative response, and stimulus AC:A ratio were measured using two measurement methods which are commonly used in clinical practice. Three measurements were taken for each parameter and averaged. For the comparative statistical analysis, we used the Student's t-test (p value < 0.05). The following statistically significant differences were found with the use of SCL in comparison to spectacles: higher accommodative lags, higher negative relative accommodation, more esophoric near horizontal dissociated phoria, and lower negative fusional vergence in near vision. The results found in this study show a definite trend towards poorer accommodative and vergence function with the use of contact lenses in comparison to glasses. This downward trend, though not statistically significant in accommodative function (lower PRA values and less lens amplitude of accommodation) might suggest that temporal insufficiency in the accommodation process could be occurring while contact lenses are used, thereby possibly creating a lag in accommodation to reduce associated overconvergence. This would be manifested in more esophoric values being found in the vergence function. The higher accommodative lags found in this study with SCL could indicate that prolonged use of SCL in near tasks may provoke a continuous hyperopic retinal defocus, a risk factor for the onset and progression of myopia, as indicated in numerous studies.

Vision Therapy/Orthoptics for Symptomatic Convergence Insufficiency in Children: Treatment Kinetics

To evaluate the kinetics of change in symptoms and signs of convergence insufficiency (CI) during 12 weeks of treatment with commonly prescribed vision therapy/orthoptic treatment regimens. In a randomized clinical trial, 221 children aged 9 to 17 years with symptomatic CI were assigned to home-based pencil push-ups (HBPP), home-based computer vergence/accommodative therapy and pencil push-ups (HBCVAT+), office-based vergence/accommodative therapy with home reinforcement (OBVAT), or office-based placebo therapy with home reinforcement (OBPT). Symptoms and signs were measured after 4, 8, and 12 weeks of treatment. The outcome measures were the mean CI Symptom Survey (CISS), near point of convergence (NPC), positive fusional vergence (PFV), and proportions of patients who were classified as successful or improved based on a composite measure of CISS, NPC, and PFV. Only the OBVAT group showed significant improvements in symptoms between each visit (p < 0.001). Between weeks 8 and 12, all groups showed a significant improvement in symptoms. Between-group differences were apparent by week 8 (p = 0.037) with the fewest symptoms in the OBVAT group. For each group, the greatest improvements in NPC and PFV were achieved during the first 4 weeks. Differences between groups became apparent by week 4 (p < 0.001), with the greatest improvements in NPC and PFV in the OBVAT group. Only the OBVAT group continued to show significant improvements in PFV at weeks 8 and 12. The percentage of patients classified as "successful" or "improved" based on our composite measure increased in all groups at each visit. The rate of improvement is more rapid for clinical signs (NPC and PFV) than for symptoms in children undergoing treatment for CI. OBVAT results in a more rapid improvement in symptoms, NPC and PFV, and a greater percentage of patients reaching pre-determined criteria of success when compared with HBPP, HBCVAT+, or OBPT.

Effect of Vergence Adaptation and Positive Fusional Vergence Training on Oculomotor Parameters

Clinical studies have shown that positive fusional vergence (PFV) can be trained through a program of orthoptic exercises. Models of accommodation and vergence predict that training PFV would require a reduction in the convergence accommodation (CA) cross-link. Recent investigations have found that the CA/C ratio is not changed in a clinical population after orthoptics. We hypothesized that such orthoptic programs may instead act to reduce CA through changes in the relationship between fast and slow vergence components. METHODS.: Eleven visually normal subjects were tested. Phoria adaptation to a 12-Delta base-out (BO) wedge prism and the resulting CA responses were monitored every 3 min for 15 min to a DoG target at 0.4 m. These measures were repeated after 2 weeks of orthoptics. Phorias, stimulus accommodative convergence (AC)/A and CA/C ratios, and PFV amplitudes at near were also determined. Before the orthoptics program, these measures were repeated under "adapted" conditions. Phoria adaptation following prolonged viewing through the 12-Delta BO wedge prism was associated with a concomitant reduction in the CA. These changes were asymptotic over time with 95% of the change occurring within the first 3 to 6 min. After 2 week of orthoptics, the rates and magnitudes of both phoria adaptation and CA reduction increased significantly (p < 0.01). PFV at 40-cm limits showed increases with orthoptics and under vergence adaptation. CA/C and AC/A ratios were unchanged after orthoptics, but the former was reduced, and the latter increased under the vergence adapted condition. Orthoptics acts to change the time constant and magnitude of vergence adaptation to BO prisms, which leads to a concomitant reduction of CA over a similar time course. This process appears to underlie the increase in positive fusion limits. Although reductions in CA/C ratio occur under the vergence adapted state, this ratio is not directly changed with orthoptics.

Fusional Vergence Measures and Their Significance in Clinical Assessment

Purpose: The aims of this study have been to evaluate differences between ranges in eso or exo deviances and with varying target size.Methods: Evaluation of sensory status in compensated deviations included measures of fusional vergence (blur, break and recovery values) with randomization of target size and order of prism base. Angle of deviation measures were assessed for each case.Results: Twenty-two subjects, 7 esophoric and 15 exophoric, were recruited. Median prism fusional vergence range at near fixation was 25BO to 10BI (central target); 35BO to 12BI (peripheral target). At distance fixation median range was 16BO to 6BI (central); 25BO to 6BI (peripheral). Esophorics had a range shift towards the base out range. Exophorics had a shift towards the base in range.Conclusions: Smaller positive fusional vergence values were obtained with small compared with large target sizes. Additionally, esophoric subjects had a trend towards larger base out ranges while exophoric subjects had a trend towards larger base in ranges.