Fusional Convergence Amplitudes Research Articles

Effectiveness of Clinic-Based Vision Therapy for Non-Strabismic Binocular Vision Anomalies (NSBVA) Among Adults

Background: To assess the effectiveness of clinic-based vision therapy in adults with non-strabismic binocular vision anomalies. Methods: This retrospective study was conducted between January 2018 and December 2021 at a tertiary eye care center in Southern India. Elec-tronic medical records of adults aged 30 years and above diagnosed with non-strabismic binocular vision anomalies, and who underwent a mini-mum of five sessions of clinic-based vision therapy (VT), were reviewed. Clinical parameters of vergence and accommodation were analyzed pre and post-therapy. Results: A total of 44 participants meeting the inclusion criteria were included in the study, with a mean (SD) age of 36 (±6) years. The partic-ipants were categorized into two groups based on the completion of either five sessions (Group A) or ten sessions (Group B) of vision therapy (VT). The overall median (IQR) for near phoria was -4 (-8 to 0) PD, the near point of convergence break point was 8 (4 to 12) cm, fusional conver-gence amplitude for near was 25 (14 to 30) PD, and binocular accommo-dative facility and amplitude were 3 (0 to 6) cpm and 9 (7 to 10) D, respectively. Conclusion: Clinic-based vision therapy is efficacious in managing non-strabismic binocular vision anomalies in adult.

The Effects of Orthoptic Therapy on the Surgical Outcome in Children with Intermittent Exotropia: Randomised Controlled Clinical Trial

To assess the clinical effectiveness of orthoptic therapy in the postoperative stabilisation and rehabilitation of binocular function in children with intermittent exotropia (IXT) after surgery. This was a prospective, parallel, randomised controlled trial. A total of 136 IXT patients (aged from 7 to 17 years) who had been successfully corrected at 1 month after surgery were enrolled in this study, and 117 patients (58 controls) completed the 12-month follow-up visit. The primary outcome was established as the proportion of patients with suboptimal surgical outcomes, which were defined as: (1) exodeviation ≥10 prism diopters (PD) at distance or near using the simultaneous prism and cover test (SPCT), or (2) constant esotropia ≥6 PD at distance or near using SPCT, or (3) loss of 2 or more octaves of stereopsis from baseline. The secondary outcomes were the exodeviation at distance and near using the prism and alternate cover test (PACT), stereopsis, fusional exotropia control and convergence amplitude. The cumulative probability of suboptimal surgical outcome by 12 months was 20.5% (14/68) in the orthoptic therapy group and 42.6% (29/68) in the control group. There was a significant difference between these two groups (χ2 = 7.402, p = 0.007). Improvements in stereopsis, fusional exotropia control and fusional convergence amplitude were found in the orthoptic therapy group. A smaller exodrift was found in the orthoptic therapy group at near fixation (t = 2.26, p = 0.025). Early postoperative orthoptic therapy can effectively improve the surgical outcome as well as stereopsis and fusional amplitude.

Fusional Vergence Dysfunctions in Acute Acquired Concomitant Esotropia of Adulthood with Myopia

Introduction: Acute acquired concomitant esotropia (AACE) has been increasing dramatically in myopia. The aim of this study was to clarify whether fusional vergence dysfunctions exist in AACE with myopia and to explore the relationship between fusional vergence and myopia in AACE. Methods: This is a prospective clinical study. Adult AACE patients as well as controls (aged ≥18 years) both with myopia were prospectively recruited from October 2016 to August 2021. Refractive error and fusional divergence and convergence amplitude at distance were measured, as determined with a comprehensive refractor. The main outcome measures were the real value of the fusional divergence amplitude (calculated by subtracting the break point value from the angle of deviation) and the real value of the fusional convergence amplitude (calculated by subtracting the angle of deviation from the break point value). Two-sided p value of less than 0.05 was considered to indicate statistical significance. Results: Fusional vergence consisting of fusional divergence and fusional convergence in patients with AACE of adulthood was different from the controls (p < 0.001), with fusional convergence decreased and fusional divergence increased. In the linear regression analysis, spherical equivalents were significantly negatively correlated with fusional convergence (right eyes, p < 0.001; left eyes, p < 0.001) in patients with AACE of adulthood but not in controls. There was a significant difference in fusional convergence amplitude among different degrees of spherical equivalents (p < 0.001). Conclusions: Fusional vergence dysfunction exists in AACE of adulthood, which may be attributed to self-adaptation based on concomitant esotropia to maintain fusion in AACE. Fusional convergence was associated with degrees of myopia, implying the adaption would be weakened as the degree of myopia becomes serious.

Correlation of saccade amplitude during refusion with the fusional convergence amplitude in patients with intermittent exotropia

ABSTRACT In patients with intermittent exotropia (IXT), to investigate the correlation between fusional convergence amplitude and saccade during refusion, as well as the differences in saccade caused by suppression. We measured the fusional convergence amplitude using a synoptophore. Suppression was assessed in 15 patients with IXT (mean age 18.1 ± 11.0 yrs, range 8–54 yrs) having diplopia during exotropia. We performed the cover-uncover test and recorded the saccade during the shift from exotropia to binocular fixation using an eye-tracking system. We analyzed the correlation between the fusional convergence amplitude on the one hand and the saccade peak velocity (PV), the saccade amplitude, and the saccade amplitude of the fusion on the other. We also investigated the difference of those saccade variables between patients with and without suppression. In 15 patients with IXT, the median fusional convergence amplitude was 14 (range 0–60) °, and suppression was confirmed in 11 patients. When the cover was removed from the dominant eye, the fusional convergence amplitude showed a positive correlation with the saccade PV and the amplitude in non-dominant eye (r = 0.570, p = 0.042 and r = 0.669, p = 0.012, respectively). The mean saccade PV, the mean saccade amplitude and the mean saccade amplitude of the fusion were not significantly different with the presence or the absence of the suppression. The fusional convergence amplitude was correlated with saccade in patients with IXT. The saccade during refusion can thus be used to quantitatively evaluate sensory and/or motor fusion.

Can Clinical Measures of Postoperative Binocular Function Predict the Long-Term Stability of Postoperative Alignment in Intermittent Exotropia?

Purpose To evaluate whether clinical measures of postoperative binocular functions could predict the long-term stability of postoperative ocular alignment in children with intermittent exotropia. Methods A retrospective study was performed in thirty-nine children (median: 7 years) who have been surgically treated from intermittent exotropia without overcorrection (less than 10 prism diopters [pd] of exodeviation at 1 month postoperatively). Angles of deviation and binocular functions were measured preoperatively and at 1 month, 6 months, and the final follow-up visit (≥24 months) postoperatively. We examined the relationships between postoperative drift (change of ocular alignment) and binocular functions (sensory fusion, fusional convergence amplitude, and stereoacuity). Results The surgical success rate (esophoria/tropia ≤5 pd to exophoria/tropia ≤10 pd) dropped to 76.9% at 6 months after surgery and to 53.8% at individuals' last visit (mean: 37 months). The mean exodrift was 7.7 ± 9.2 pd from the postoperative month 1 to the final visit (p < 0.001) on distance fixation. Distance stereoacuity, central fusion, and fusional convergence amplitude significantly improved following surgery (p < 0.05). However, no significant correlation was found between their binocular functions measured at the beginning of each follow-up period and the postoperative drift (all p > 0.13). Conclusion Our findings suggest that the clinical measures of sensory fusion, fusional convergence amplitude, and stereoacuity cannot serve as a robust predictor for the long-term stability of postoperative ocular alignment in patients who underwent successful surgery without overcorrection at 1 month postoperatively.

Objective convergence insufficiency and fusional convergence amplitude measurements with an eye tracking based device

Convergence insufficiency (CI) is a common binocular vision disorder of substantial clinical significance which may cause asthenopia, diplopia, headaches, and blurred vision at near.

The Value of Fusional Convergence Amplitudes in Esodeviation Surgery Without Adjustable Sutures.

To explore the application of preoperative fusional convergence amplitudes in the selection of a target angle for non-adjustable suture strabismus surgery with deteriorated intermittent esotropia and diplopia. Thirty-one consecutive cases of presumed acquired non-accommodative, deteriorated intermittent esotropia managed surgically between 2005 and 2016 were reviewed retrospectively. For each individual, a target angle (deviation angle for which surgery was based) was selected preoperatively after analysis of fusional convergence amplitudes. Outcomes in patients selected for overcorrection at 6 meters (target angle > angle in primary position at 6 meters) were compared to those who had planned surgery based on a target angle that did not exceed their measured angle (target angle ≤ angle in primary position) at 6 meters. All 31 patients achieved binocular single vision in primary position at both near and 6 meters without prisms, orthoptic therapy, or additional surgery at 4 to 6 months postoperatively. Greater mean correction in the target angle > angle in primary position group compared to the target angle ≤ angle in primary position group was observed, but this difference was not statistically significant (P = .57). Among this diagnostically specific cohort with intermittent esotropia with symptomatic diplopia and measurable binocular single vision preoperatively, targeted surgery based on an analysis of preexisting fusional convergence amplitudes had an outcome that compared favorably to that of documented adjustable suture strabismus surgery. [J Pediatr Ophthalmol Strabismus. 2018;55(6):375-381.].

Role of fusional convergence amplitude in postoperative phoria maintenance in children with intermittent exotropia.

To examine the role of fusional convergence amplitude in postoperative phoria maintenance in childhood intermittent exotropia [X(T)]. The medical records of 29 children aged 15 years or younger (mean age, 10.8 ± 2.4 years) and treated with monocular recession-resection for X(T) were reviewed retrospectively. The patients' fusional convergence amplitude (break point/total amplitudes), physiologic diplopia, and phoria maintenance (presence/absence of phoria maintenance and ability to maintain phoria) were assessed. The presence of phoria maintenance was confirmed by a cover test, and the ability to maintain phoria was quantified using the Bagolini red filter bar. Correlations of the amplitude size with the presence and ability of phoria maintenance were investigated. A significant correlation was seen between fusional amplitude (break point/total) and ability to maintain phoria at near and at far (break point: P < .05 at near/P < .01 at far; total: P < .05 at near/far). Neither the break point amplitude nor the total amplitude significantly differed between the patients with phoria maintenance and those without it (break point: P = .71 at near, P = .29 at far; total: P = .98 at near, P = .85 at far). Phoria maintenance correlated with the suppression of physiologic diplopia during phoria (P < .01). The deviation angle did not significantly correlate with fusional amplitude either at near (P = .58) or at far (P = .27). In childhood X(T), fusional amplitude plays a role in enforcing the patient's ability to maintain phoria. However, sufficient fusional amplitude does not guarantee fully functioning fusion if suppression is present during phoria.

Long-term evolution of age-related distance esotropia

To evaluate the evolution of horizontal deviation and fusional amplitudes both at distance and at near in patients with age-related distance esotropia (ARDET). The medical records of consecutive patients diagnosed with ARDET between January 2008 and March 2016 were reviewed retrospectively. Patients with at least 60months' follow-up were eligible for inclusion. Horizontal deviation, fusional convergence amplitude, and fusional divergence amplitude both at distance and at near were compared. Of 131 cases reviewed, 31 patients were identified for inclusion. Median age at diagnosis was 73years. Median distance esodeviation was 6Δ esotropia at initial examination (range, 2Δ-12Δ esotropia) and 8Δ eostropia at final examination (range, 2Δ-25Δ esotropia). Median near deviation was orthophoria at initial examination (range, 10Δ exophoria to 8Δ esophoria) and 4Δ esophoria at final examination (range, 4Δ exophoria to 14Δ esophoria). Median fusional divergence amplitude at distance was 4Δ at initial and at final examinations. At near, median fusional divergence amplitude was 8Δ at initial and at final examinations. Median fusional convergence amplitude at distance was 14Δ at initial examination and 12Δ at final examination. At near, median fusional convergence amplitude was 26Δ at initial and at final examinations. Base-out prisms were prescribed in all patients. In 23 patients the prism correction gradually increased. Strabismus surgery was performed in 3 patients. Our patients with ARDET experienced a slight increase in distance esodeviation (P<0.001), whereas no significant change in fusional amplitudes was observed over time (P≥0.05).

Binocular vision and abnormal head posture in children when watching television.

To determine the association between the binocular vision and an abnormal head posture (AHP) when watching television (TV) in children 7-14y of age. Fifty normal children in the normal group and 52 children with an AHP when watching TV in the AHP group were tested for spherical equivalents, far and near fusional convergence (FC) and fusional divergence (FD) amplitudes, near point of convergence, far and near heterophoria, accommodative convergence/ accommodation ratio and stereoacuity. The values of these tests were compared between the two groups. The independent t test was applied at a confidence level of 95%. The far and near FC amplitudes and far FD amplitudes were lower in the AHP group (the far FC amplitudes: break point 13.6±5.4(Δ), recovery point 8.7±5.4(Δ). The near FC amplitudes: break point 14.5±7.3(Δ), recovery point 10.3±5.1(Δ). The far FD amplitudes: break point 3.9±2.7(Δ), recovery point 2.6±2.3(Δ)) compared with those in the normal group (the far FC amplitudes: break point 19.1±6.2(Δ), recovery point 12.4±4.5(Δ). The near FC amplitudes: break point 22.3±8.0(Δ), recovery point 16.1±5.7(Δ). The far FD amplitudes: break point 7.0±2.1(Δ), recovery point 4.6±1.9(Δ)). Other tests presented no statistically significant differences. An association between the reduced FC and FD amplitudes and the AHP in children when watching TV is proposed in the study. This kind of AHP is considered to be an anomalous manifestation which appears in a part of puerile patients of fusional vergence dysfunction.

Lyme Disease and Convergence Insufficiency: Is it a Near Fit?

Introduction and PurposeThe purpose of this study is to determine the prevalence of convergence insufficiency (CI) in patients who have been diagnosed with Lyme disease.Methods and ResultsThis study is a retrospective review of charts from 190 patients with confirmed Lyme disease. The diagnosis of CI is based on decreased fusional convergence amplitudes at near fixation. The number of patients with CI was reviewed as well as information on patient gender, age, and symptoms. Seventy percent of patients in this study were female. Ages ranged from 4 to 80 years old. Fifty-three percent of patients with Lyme disease had CI. Symptomatic patients were treated with orthoptic exercises or vision therapy.ConclusionsPatients diagnosed with Lyme disease seem to develop CI. Symptomatic CI associated with Lyme disease seems to respond well to conventional CI treatment.

Binocular function and patient satisfactionafter monovision induced by myopic photorefractive keratectomy

Purpose: To measure binocular function and patient satisfaction with monovisioninduced by photorefract ve keratectomy (PRK) in myopic presbyopic patients. Setting: Refractive Department; Cleveland Clinic; Cleveland, Ohio, USA. Methods: This study comprised 21 myopic presbyopic patients with monovisioninduced by PRK. Sixteen emmetropic patients who had PRK served as a control group. Monovision was induced by undercorrecting the nondominant eye by 1.25 diopters for near vision and correcting, the dominant eye with emmetropia for distance vision. Monocular and binocular uncorrected Snellen visual acuities at 20 feet and 13 inches, manifest refraction, ocular dominance, stereopsis at 20 feet and 13 inches, Monocular and binocular contrast sensitivities, Worth-4-Dot test at 20 feet and ⅓ of a meter, and fusional convergence amplitudes were examined in each patient. Results: In the monovision group at near and distance, 20 patients (95.3%) had binocular visual acuity of 20/25 or better. No patient in the monovision group used reading glasses postoperatively; 4 of 16 patients (25.0%) in the control group used such glasses. All patients maintained binocular fusion and stereo acuity ranging from 40 to 800 seconds of arc. Mean patient satisfaction was 86% (range 40% to 100%). In the control group, 12 patients (75.0%) had binocular distance visual acuity of 20/25 or better and 11 (68.8%) had binocular near visual, acuity of 20/25 or better. Conclusion: Monovision PRK patients had better near vision than control PRKpatients, with minimal compromise in stereo acuity and overall high patient satisfaction.

The Treatment of Convergence Insufficiency

Idiopathic convergence insufficiency is characterized by in-adequate fusional convergence, causing a variety of asthenopic symptoms which occur during the act of reading.Orthoptic therapy to increase fusional convergence amplitudes and enhance voluntary convergence is the primary treatment of convergence insufficiency. When unresponsive to orthoptic therapy, other treatment options include optical correction with base-in prisms or surgical intervention in cases associated with a near exophoria. Convergence-accommodative insufficiency and subnormal convergence associated with head trauma are entities that are symptomatically similar to classic convergence insufficiency, but do demonstrate the same response to orthoptic therapy.

NEGATIVE FUSIONAL CONVERGENCE

Cleveland, Ohio *Submitted for publication January 13, 1935. 1An Experimental Investigation of the Negative Fusional Convergence Amplitude. W. J. Tait. Am. Jour. of Optom. Vol. 11, No. 12, pp. 462–472. 1934.