Accommodative and binocular dysfunctions: prevalence in a randomised sample of university students

Kinematic Assessment of Fine Motor Skills in Children: Comparison of a Kinematic Approach and a Standardized Test

Deficits in fine motor skills have been reported in some children with neurodevelopmental disorders such as amblyopia or strabismus. Therefore, monitoring the development of motor skills and any potential improvement due to therapy is an important clinical goal. The aim of this study was to test the feasibility of performing a kinematic assessment within an optometric setting using inexpensive, portable, off-the-shelf equipment. The study also assessed whether kinematic data could enhance the information provided by a routine motor function screening test (the Movement Assessment Battery for Children, MABC). Using the MABC-2, upper limb dexterity was measured in a cohort of 47 typically developing children (7-15 years old), and the Leap motion capture system was used to record hand kinematics while children performed a bead-threading task. Two children with a history of amblyopia were also tested to explore the utility of a kinematic assessment in a clinical population. For the typically developing children, visual acuity and stereoacuity were within the normal range; however, the average standardized MABC-2 scores were lower than published norms. Comparing MABC-2 and kinematic measures in the two children with amblyopia revealed that both assessments provide convergent results and revealed deficits in fine motor control. In conclusion, kinematic assessment can augment standardized tests of fine motor skills in an optometric setting and may be useful for measuring visuomotor function and monitoring treatment outcomes in children with binocular vision anomalies.

Assessing the role of visual dysfunctions in the association between visual symptomatology and the use of digital devices

PURPOSE

To evaluate the association between visual symptoms and use of digital devices considering the presence of visual dysfunctions.

METHODS

An optometric examination was conducted in a clinical sample of 346 patients to diagnose any type of visual anomaly. Visual symptoms were collected using the validated SQVD questionnaire. A threshold of 6 hours per day was used to quantify the effects of digital device usage and patients were divided into two groups: under and above of 35 years old. A multivariate logistic regression was employed to investigate the association between digital device use and symptoms, with visual dysfunctions considered as a confounding variable. Crude and the adjusted odds ratio (OR) were calculated for each variable.

RESULTS

57.02 % of the subjects reported visual symptoms, and 65.02% exhibited some form of visual dysfunction. For patients under 35 years old, an association was found between having visual symptoms and digital device use (OR = 2.10, p = 0.01). However, after adjusting for visual dysfunctions, this association disappeared (OR = 1.44, p = 0.27) and the association was instead between symptoms and refractive dysfunction (OR = 6.52, p < 0.001), accommodative (OR = 10.47, p < 0.001), binocular (OR = 6.68, p < 0.001) and accommodative plus binocular dysfunctions (OR = 46.84, p < 0.001). Among patients over 35 years old, no association was found between symptoms and the use of digital devices (OR = 1.27, p = 0.49) but there was an association between symptoms and refractive dysfunction (OR = 3.54, p = 0.001).

CONCLUSIONS

Visual symptoms are not dependent on the duration of digital device use but rather on the presence of any type of visual dysfunction: refractive, accommodative and/or binocular one, which should be diagnosed.

Altered Large-Scale Resting-State Functional Network Connectivity in Convergence Insufficiency Young Adults Compared With Binocularly Normal Controls

Purpose

To investigate the underlying resting-state functional connectivity (RSFC) of symptomatic convergence insufficiency (CI) compared with binocularly normal controls (BNC) using functional magnetic resonance imaging (fMRI) under The Convergence Insufficiency Neuro‑mechanism Adult Population Study (NCT03593031).

Methods

A total of 101 participants were eligible for this study. After removing datasets with motion artifacts, 49 CI and 47 BNC resting-state functional magnetic resonance imaging datasets were analyzed. CI was diagnosed with the following signs: (1) receded near point of convergence of 6 cm or greater, (2) decreased positive fusional vergence of less than 15∆ or failing Sheard's criteria of twice the near phoria, (3) near phoria of at least 4∆ more exophoric compared with the distance phoria, and (4) symptoms using the Convergence Insufficiency Symptom Survey (score of ≥21). RSFC was assessed using a group-level independent components analysis and dual regression. A behavioral correlation analysis using linear regression method was performed between clinical measures and RSFC using the significant difference between the CI and BNC.

Results

On average, a decreased RSFC was observed within the frontoparietal network, default mode network and visual network in patients with CI, compared with the participants with BNC (P < 0.05, corrected for multiple comparisons). The default mode network RSFC strength was significantly correlated with the PFV, near point of convergence, and difference between the horizontal phoria at near compared with far (P < 0.05).

Conclusions

Results support altered RSFC in patients with CI compared with participants with BNC and suggest that these differences in underlying neurophysiology may in part be in connection with the differences in optometric visual function used to diagnose CI.

Accommodative disorders in non-presbyopic subjects with type 1 diabetes without retinopathy: A comparative, cross-sectional study

PURPOSE

The purpose of this study was to assess accommodative function in non-presbyopic individuals diagnosed with type 1 diabetes (T1D) without any signs of retinopathy, to determine the existence of possible accommodative disorders related to this disease, and to determine the influence of T1D duration and glycosylated haemoglobin values on accommodative function.

METHODS

This comparative, cross-sectional study included 60 participants between 11 and 39 years old, 30 with T1D and 30 controls, with no previous eye surgery, ocular disease or medication that could affect the results of the visual examination. Amplitude of accommodation (AA), negative and positive relative accommodation (NRA and PRA), accommodative response (AR) and accommodative facility (AF) were assessed using the tests that showed the highest repeatability. Participants were classified based on normative values into 'insufficiency, excess or normal results', and a diagnosis of accommodative disorders (accommodative insufficiency, accommodative infacility and accommodative excess) was made.

RESULTS

Participants with T1D had statistically significant lower AA and AF and higher NRA values than the controls. Furthermore, AA was significantly and inversely correlated with age and the duration of diabetes; however, AF and NRA were only correlated with disease duration. In the classification by accommodative variables, a higher percentage of 'insufficiency values' was observed in the T1D group (50%) than in the control group (6%; p < 0.001). In terms of accommodative disorders, accommodative infacility was the most prevalent (15%), followed by accommodative insufficiency (10%).

CONCLUSIONS

Our findings indicate that T1D affects most accommodative parameters, with accommodative insufficiency being associated with this disease.

Short-Term Effect of Spinal Manipulation on the Magnitude of Exophoria in Adults Who Are Asymptomatic: A Randomized Controlled Trial

OBJECTIVE

This study aimed to assess the immediate and short-term effects of cervical spinal manipulation (SM), compared with a placebo, on the magnitude of near and distance exophoria in adults with asymptomatic exophoria.

METHODS

In this single-blind, randomized controlled trial, individuals with a clinical diagnosis of horizontal exophoria confirmed with the prism alternating cover test (PACT) were allocated to a single intervention session using a high-velocity, low-amplitude cervical SM technique or a sham intervention (manual contact under the head). Outcomes were the magnitude of horizontal heterophoria, as a measure of binocular vision efficiency at near (40 cm) or distance (4 m) fixation, using the PACT. Evaluations were made at baseline, immediately after intervention, and at a 1-week follow-up.

RESULTS

From May to September 2021, 44 volunteers (23 women), with a mean age of 35 (SD = 9.5) years, were recruited and equally distributed into the study groups. All participants completed follow-up assessments, and no adverse events were reported. There was a significant time × group interaction for exophoria at near vision, but not at distance fixation. The SM group showed a significant decrease of near exophoria compared with the control group at the 1-week follow-up (mean difference = -1.09 prism diopters; 95% CI = -0.20 to -1.98 prism diopters).

CONCLUSION

The use of cervical SM therapy resulted in a significant reduction of the magnitude of horizontal exophoria at near vision (medium effect size), compared with the placebo, in young adults who are asymptomatic. However, these effects were not observed at distance fixation and should be considered cautiously due to the pre-post design with a single intervention session and the short-term follow-up.

IMPACT

The findings suggest short-term benefits of SM therapy can manage undiagnosed ocular convergence disorders, although changes were not clinically relevant.

Convergence insufficiency symptom survey: A tool to evaluate convergence excess in young adults

PURPOSE

To determine the effectiveness of the Convergence Insufficiency Symptom Survey (CISS) in evaluating visual symptoms in young adults with convergence excess (CE).

METHODS

A cross-sectional study was performed based on a population of optometry students. Comprehensive binocular vision tests including cover test, near point of convergence, fusional vergence and accommodative amplitude, were performed. Participants were categorised into three groups: normal binocular vision (NBV), CE and CE + accommodative insufficiency (AI) (i.e., CE + AI). The CISS was administered to each participant. An analysis of variance with Bonferroni correction was performed to compare clinical measures among the three groups. A receiver-operating characteristic (ROC) curve was constructed to evaluate the ability of CISS to differentiate CE from the NBV population.

RESULTS

A total of 181 participants were enrolled, including 96 in the NBV group, 66 in the CE group and 19 in the CE + AI group. A significant difference in CISS score was detected between the three groups (p < 0.001). Post-hoc tests showed significantly higher CISS scores in the CE group (16.7 ± 10.8) and the CE + AI group (19.7 ± 10.9) compared with the NBV group (12.2 ± 7.8) (p = 0.01 and p = 0.005, respectively), with no difference between the CE and the CE + AI groups (p = 0.52). The ROC curve showed the CISS poorly (but significantly) differentiated CE from NBV (area under the curve = 0.62, p = 0.01). The optimal cutoff value for a CISS score to differentiate CE was 16, with sensitivity and specificity of 52% and 72%, respectively.

CONCLUSIONS

Young adults with CE had significantly higher CISS scores than those with NBV. Although using the CISS solely for diagnosing CE is not recommended, it can be used to provide a measure of symptoms in individuals identified as having CE based on clinical measurements.

Feasibility of measuring fusional vergence amplitudes objectively

Two tests to measure fusional vergence amplitudes objectively were developed and validated against the two conventional clinical tests. Forty-nine adults participated in the study. Participants' negative (BI, base in) and positive (BO, base out) fusional vergence amplitudes at near were measured objectively in an haploscopic set-up by recording eye movements with an EyeLink 1000 Plus (SR Research). Stimulus disparity changed in steps or smoothly mimicking a prim bar and a Risley prism, respectively. Break and recovery points were determined offline using a custom Matlab algorithm for the analysis of eye movements. Fusional vergence amplitudes were also measured with two clinical tests using a Risley prism and a prism bar. A better agreement between tests was found for the measurement of BI than for BO fusional vergence amplitudes. The means ± SD of the differences between the BI break and recovery points measured with the two objective tests were -1.74 ± 3.35 PD and -1.97 ± 2.60 PD, respectively, which were comparable to those obtained for the subjective tests. For the BO break and recovery points, although the means of the differences between the two objective tests were small, high variability between subjects was found (0.31 ± 6.44 PD and -2.84 ± 7.01 PD, respectively). This study showed the feasibility to measure fusional vergence amplitudes objectively and overcome limitations of the conventional subjective tests. However, these tests cannot be used interchangeably due to their poor agreement.

Translation and validation of convergence insufficiency symptom survey to Italian: Psychometric results

PURPOSE

This study aimed to translate the Convergence Insufficiency Symptom Survey (CISS) into the Italian language and assess psychometric properties of the translated questionnaire (CISS_I).

METHODS

The CISS_I was arranged according to guidelines for a comprehensive multistep methodologic process for translating, adapting, and validating psychometric instruments in health care research. The CISS_I questionnaire was administered to 103 volunteers (21.8 ± 2.2 years), students in higher education, at two different times. A complete optometric evaluation was performed including subjective refraction, best corrected visual acuity, near point of convergence, prism fusional ranges to blur, diplopia and recovery, TNO stereo test and prism cover test for measurement of heterophoria.

RESULTS

The performance of the CISS_I in terms of validity showed some points of weakness. Sensitivity was 42%, specificity was 74%, positive predictive value was 27% and negative predictive value was 85%. The area under the ROC curve was 0.672. On the contrary, the results showed good internal consistency of the CISS_I (Cronbach's alpha - α=0.89) and good test-retest reliability (ICC = 0.92). Rasch analysis showed good model fit (all items, except one, with infit and outfit mean square between 0.7 and 1.3), good measurement precision (person separation = 2.66) and good targeting -0,81 logits but also some evidence of multidimensionality.

CONCLUSIONS

The CISS_I showed some point of weakness in terms of validity but also good psychometric properties and has been shown to be applicable to an Italian speaking population to quantify the visual discomfort associated with near vision in higher education students. The results show that high CISS_I score is not necessarily linked to convergence insufficiency, while low scores can exclude the presence of this anomaly. The CISS_I can help in interpreting and monitoring convergence insufficiency symptoms in already identified subjects, but it is not suitable for screening a general population of young adults.

Prevalence of convergence insufficiency among Spanish school children aged 6 to 14 years

CLINICAL RELEVANCE

Convergence insufficiency (CI) at an early age can lead to learning difficulties affecting school performance. The aim of this study was to examine the prevalence of CI in a non-clinical population of Spanish children using well defined clinical criteria and to determine whether sex is a risk factor.

METHODS

Visual acuity and binocular vision tests were performed in 628 children aged 6-14 years (mean age 9.6 ± 1.3 years) at three schools in the Madrid Community, Spain. To assess CI prevalence we used CITT (Convergence Insufficiency Treatment Trial) criteria. The three signs considered were: i) exophoria at least 4^∆ greater at near than at far; ii) near break point of convergence (NPC) ≥ 6 cm; and iii) reduced positive fusional vergence (PFV) at near (≤ 15^∆ base-out break or failed Sheard's criterion).

RESULTS

The CI prevalence detected was 5.30% (33 children). Proportions of children with one or two signs of CI were 23.76% (148 children) and 12.20% (76 children), respectively. No differences in these CI rates by sex were detected.

CONCLUSION

The clinically significant CI prevalence observed here suggests the need for more binocular vision screening programmes in school settings.

Convergence insufficiency: Review of clinical diagnostic signs

Convergence insufficiency (CI) is a common binocular vision (BV) disorder characterized by difficulty in maintaining motor fusion at near, which affects approximately 7.5 percent of the population. Diagnostic criteria for the disorder are inconsistent, ranging from one to many clinical signs. Methodology for clinical tests is inconsistent in measurement technique, visual targets, required repetitions, and normative values. This manuscript demonstrates the inconsistencies amongst published studies, and highlights the importance of consistent clinical diagnostic signs, measurement techniques, visual targets, and cut-off criteria. For each clinical sign, the recommended methodology for the procedure is described. Several studies do not take age into account when diagnosing CI in their cohorts. As such, the review emphasizes changes in diagnostic signs with age. This manuscript highlights the need for consistent and clear procedures and diagnostic criteria amongst clinicians and provides the basis for future studies in terms of diagnostic testing required for CI of varying age groups.

Accommodative and binocular vision dysfunctions in a Portuguese clinical population

BACKGROUND

Several studies have suggested that accommodative and non-strabismic binocular dysfunctions are commonly encountered in optometric practice. This study aims to verify whether these findings apply to a Portuguese clinical population.

METHODS

This study included consecutive nonpresbyopic subjects that came to two Portuguese optometric clinics over a period of six months. A complete visual exam was conducted and included the measurement of visual acuity (VA), refraction, near point of convergence (NPC), distance and near phoria, near and distance fusional vergences, amplitude of accommodation (AA), monocular accommodative facility (MAF), relative accommodation and lag of accommodation.

RESULTS

156 subjects with a mean age of 24.9 ± 5.3 years (from 18 to 35 years old) participated in the study. Of all subjects, 32 % presented binocular vision and/or accommodative disorders accompanied or not by refractive errors. Moreover, 21.1 % had accommodative disorders, and 10.9 % had a binocular vision dysfunction. Accommodative insufficiency (11.5 %) was the most prevalent disorder, followed by convergence insufficiency (7.1 %) and accommodative infacility (5. 8 %).

CONCLUSIONS

Clinicians should be aware that about one third of the optometric clinical population could have accommodative and/or non-strabismic binocular disorders. Accommodative insufficiency was the most prevalent dysfunction presented in the studied population, followed by accommodative infacility and convergence insufficiency.

Cataract surgery is not associated with post-operative binocular vision anomalies in age-related cataract patients

PURPOSE

To compare the binocular vision status of patients pre- and post-cataract surgery, and to investigate the risk factors for patients who develop binocular vision anomalies post-surgery.

METHODS

A prospective study of patients (≥50 years) who elected to undergo bilateral cataract surgery was implemented. A comprehensive binocular vision test battery including stereopsis, ocular alignment, fusional vergence, vergence facility, near point of convergence and the Convergence Insufficiency Symptom Survey (CISS) was administered before the first surgery and at the third visit after surgery on the second eye. A detailed diagnostic classification protocol was applied to identify the presence of binocular vision anomalies pre- and post-surgery.

RESULTS

Seventy-three participants were included at baseline, 24 (33%) of whom were diagnosed with non-strabismic binocular vision anomalies (NSBVA), mainly convergence insufficiency (18/73, 25%). Fifty-one participants completed the post-operative evaluation, 17 (33%) of whom had NSBVA pre-surgery and 13 (26%) post-surgery (p = 0.48). There were a number of conversions from NSBVA to normal binocular vision and vice versa. Logistic regression showed that the adjusted odds ratio of pre-existing NSBVA diagnosis for predicting the risk of post-operative NSBVA was 6.37 (p < 0.01). There were no significant changes in most binocular vision measures post-surgery, except for a significant improvement in the CISS score (p < 0.01, Cohen's d = 0.83).

CONCLUSIONS

Binocular vision anomalies, especially convergence insufficiency, are prevalent in the age-related cataract population. Cataract surgery does not appear to be a significant risk factor for the development of new binocular vision anomalies. A pre-existing binocular vision anomaly is the main risk factor for predicting a post-operative binocular vision anomaly in this population.

Characterizing Refractive Errors, Near Accommodative and Vergence Anomalies and Symptoms in an Optometry Clinic

Background:

Refractive, accommodative and vergence parameters and associated anomalies cause symptoms of asthenopia. Patients consult eye care practitioners mainly due to symptoms they experience. To enhance targeted treatments from various anomalies, it is relevant to study symptoms with associating anomalies.

Aim:

To determine the frequencies of refractive error, accommodative and vergence anomalies, and their associations with symptoms in sample of Black South Africans.

Method:

This prospective, cross-sectional study comprised consecutive participants aged 10–40 years who attended the author’s optometry practice in a Black population in South Africa. Visual acuity, refraction, accommodative and vergence tests were performed. Anomalies were classified as either single measure or syndromes based on the number of failed clinical signs.

Results:

Participants (n = 254) had mean age 22.6 ± 7.22 years. Ninety-four were male (37%) and 160 were female (63%). The frequencies of syndrome anomalies were accommodative insufficiency 17 [(6.6%) 95% CI 3.9–10.5%)], accommodative infacility 32 [(12.6%)] 8.7–17.3%] and convergence insufficiency 22 [(8.6%, 5.1–12.3%)]. Frequencies of coexisting anomalies were refractive error and accommodative 150 (60.0%), refractive error and vergence anomalies 136 (54.4%) and vergence and accommodative disorders 155 (62.0%). Most patients were symptomatic (70.9%). Headache was the most frequent symptom (41.1%).

Conclusion:

Accommodative anomalies were more frequent than refractive error and vergence anomalies. The high frequency of anomalies suggests a high uptake of optometric services for asthenopia. Accommodative anomalies were the most symptomatic. The study highlights the need for diagnosing visual symptoms and coexisting anomalies. Establishment of validated study protocols for all accommodative and vergence anomalies is recommended.

Preoperative binocular vision characteristics in the age-related cataract population

Background

This study is the first part of the “Binocular Vision Anomalies after Cataract Surgery” study that aimed to investigate the impact of cataract surgery on binocular vision status in adults with age-related cataract. This study aimed to investigate the preoperative binocular vision status of participants with age-related cataract.

Methods

Patients who elected to undergo bilateral cataract surgery (≥50 years of age) were recruited. Clinical measures of binocular vision including stereopsis, ocular alignment, fusional vergence, vergence facility, convergence amplitude and a symptom survey related to binocular vision anomalies were administered. A detailed classification protocol was established to identify the presence of binocular vision anomalies. The frequency of specific binocular vision anomalies and normative data of binocular vision measures were reported.

Results

A total of 73 subjects were evaluated. No strabismus was detected in the cohort. Non-strabismic binocular vision anomalies were detected in 24 subjects (32.9%), of whom 18 (24.7%) had convergence insufficiency, 3 (4.1%) had basic exophoria, 2 (2.7%) had convergence excess, and 1 (1.4%) had fusional vergence dysfunction. Decreased vergence facility and convergence amplitude were more common compared to the pre-presbyopes (P < 0.01).

Conclusion

Binocular vision problems, especially convergence insufficiency, are common in the adults with age-related cataract. The study results demonstrate that the lack of normative binocular vision data for the presbyopic population is a significant gap in the literature and suggest the need for a study of normative data for this population.

Trial registration

The study was registered at ClinicalTrials.gov (NCT03592615, USA).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02418-7.

Virtual reality-based vision therapy versus OBVAT in the treatment of convergence insufficiency, accommodative dysfunction: a pilot randomized controlled trial

Background

Virtual reality is being increasingly applied in vision therapy. However, the differences in effectiveness, optimal treatment cycle, and prognosis between virtual reality-based vision therapy and traditional therapies remain unknown. The purpose of this study was to compare the effectiveness of virtual reality-based vision therapy and office-based vergence/accommodative therapy in young adults with convergence insufficiency or accommodative dysfunction.

Methods

The patients were randomly assigned to either the virtual reality-based vision therapy group or the office-based vergence/accommodative therapy group. The vision therapy lasted 12 weeks (1 h/week) in both groups. Binocular visual functions (vergence and accommodation) were measured and a subjective questionnaire-based assessment was performed at baseline and after 6 and 12 weeks of therapy.

Results

In total, 33 patients with convergence insufficiency and 30 with accommodative dysfunction completed the study. After 12 weeks of treatment for convergence insufficiency, the Convergence Insufficiency Symptom Survey score (F_2,31 = 13.704, P < 0.001), near point of convergence (F_2,31 = 21.774, P < 0.001), positive fusional vergence (F_2,31 = 71.766, P < 0.001), and near horizontal phoria (F_2,31 = 16.482, P < 0.001) improved significantly in both groups. Moreover, the monocular accommodative amplitude (F_2,25 = 22.154, P < 0.001) and monocular accommodative facility (F_2,25 = 86.164, P < 0.001) improved significantly in both groups after 12 weeks of treatment. A statistically significant difference was observed in monocular accommodative facility (F_1,25 = 8.140, P = 0.009) between the two groups, but not in other vergence and accommodative functions (0.098 < P < 0.687).

Conclusion

Virtual reality-based vision therapy significantly improved binocular vision functions and symptoms in patients with convergence insufficiency and accommodative dysfunction, thereby suggesting its effectiveness as a new optional or additional treatment for young adults with these conditions.

Trial registration

This study was registered at the Chinese Clinical Trials Registry on 16/04/2019 (identifier: ChiCTR1900022556).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02393-z.

Validation of the Symptom Questionnaire for Visual Dysfunctions (SQVD): A Questionnaire to Evaluate Symptoms of any Type of Visual Dysfunctions

Purpose

To assess psychometric properties of the Symptom Questionnaire for Visual Dysfunctions (SQVD) questionnaire, including accuracy, validity, and reliability, in a clinical sample of patients having any type of visual dysfunction.

Methods

A clinical sample of 306 patients self-administered the SQVD. Rasch analysis was performed to analyze the functionality of the response categories, fit statistics, differential item functioning (DIF), person and item reliability, targeting, local dependency, unidimensionality, and transformation table. Accuracy was assessed by means of receiver operating characteristic (ROC) curves, using symptoms reported in each patient's clinical record as the gold standard for classifying patients with and without symptoms. The concurrent validity, known group validity, and test–retest reliability (repeatability, using the intraclass correlation coefficient [ICC]) were also examined.

Results

SQVD showed orderly category responses. The 14 items fit the Rasch model without significant DIF for gender, presbyopia, and dysfunctions. Person and item reliabilities were 0.81 and 0.85, respectively. Targeting was –1.49 logits. Yen's Q3 statistic showed no local dependency. SQVD was unidimensional (first contrast of the residual = 1.852 eigenvalue with a variance explained by measures of 52.23%). The area under the ROC curve was 0.836 (95% confidence interval [CI], 0.792–0.879) with a cutoff of ≥6 showing good accuracy (sensitivity = 0.759; specificity = 0.783). SQVD showed good concurrent and known group validity and high repeatability (ICC, 0.857; 95% CI, 0.710–0.933) when administered twice 1 week apart.

Conclusions

SQVD has shown good psychometric properties. It can be considered an accurate, valid, and reliable questionnaire to detect visual symptoms related to any type of refractive, accommodative, and binocular dysfunction.

Translational Relevance

SQVD may be used for diagnostic purposes, as it can accurately detect symptoms related to any sort of visual dysfunction. It may also be useful to monitor the treatment outcomes of these conditions.

Prevalence of binocular vision dysfunctions in professional football players

CLINICAL RELEVANCE

The extent of binocular vision dysfunction in elite soccer players needs to be determined as it may impact performance.

BACKGROUND

The purpose of the study was to investigate the prevalence of binocular vision dysfunctions in elite soccer players.

METHODS

One hundred and seven professional soccer players were evaluated. Refractive error was measured and the following binocular vision parameters were assessed: horizontal and vertical phoria for distance and near vision, the values of break and recovery for negative and positive fusional vergences at distance and near vision, vergence facility at distance and near vision, monocular accommodative facility at near vision, and near point of convergence (break and recovery points). All the athletes were men with a mean age of 24.4 ± 4.8 years.

RESULTS

No athlete was diagnosed with divergence excess, divergence insufficiency, or basic exophoria. About 13.0% of the athletes have binocular vision dysfunctions related to esophoria (0.9% with esophoria at near vision and 12.1% with esophoria at distance and near vision). About 10.3% have convergence insufficiency and 2.8% were diagnosed with fusional vergence dysfunction. The only accommodation-related parameter analysed was accommodative infacility, and 6.5% of the athletes had this dysfunction. Vertical phoria was present in 3.7% of the athletes. No statistically significant differences were found based on in athletes with respect to ethnicity, position occupied on the field, age, ametropia or laterality.

CONCLUSION

The overall prevalence of binocular vision dysfunction in elite soccer players was 36.4%. The most prevalent dysfunctions are related to the presence of esophoria (13.0%). The values found point out the need to include binocular vision assessment protocols in the visual assessment routine for athletes.

Associations between Binocular Vision Disorders and Contact Lens Dissatisfaction

SIGNIFICANCE

These data demonstrate that binocular vision disorders (BVDs) contribute to contact lens (CL) dissatisfaction independently of CL discomfort (CLD) in myopic, pre-presbyopic, adult, single-vision CL wearers.

PURPOSE

This study aimed to determine whether BVDs contribute to CL dissatisfaction and whether this contribution is independent of CLD.

METHODS

Participants attended one clinical visit while wearing their habitual CLs. Symptoms from CLD and BVDs were measured with the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8) and Convergence Insufficiency Syndrome Survey (CISS), respectively. A comprehensive binocular vision (BV) assessment was performed. The Ocular Surface Disease Index (OSDI) was used to measure CL dissatisfaction from CLD and BVDs based on reported correlations between the CLDEQ-8 and the CISS with the OSDI. Participants were categorized according to their CL comfort status (CLD [≥12 on CLDEQ-8] or non-CLD [<12 on CLDEQ-8]) and BV status (BVD or non-BVD).

RESULTS

Seventy-six participants completed the trial, and 19 (25%) were diagnosed with BVD. Those diagnosed with BVD scored higher than did those diagnosed with non-BVD for the OSDI (25.1 ± 12.7 vs. 10.7 ± 7.3, P < .001) and CISS (18.7 ± 7.7 vs. 11.9 ± 5.9, P = .001), but not the CLDEQ-8 (P = .25). Those categorized as having CLD scored higher than did those categorized as having non-CLD for the OSDI (19.0 ± 12.3 vs. 9.3 ± 5.9, P = .003) and CISS (16.1 ± 6.8 vs. 11.0 ± 6.2, P = .001). There were no significant interactions between BV status and CL comfort status for any questionnaire (P > .08).

CONCLUSIONS

Higher scores for OSDI in those with CLD or BVD indicate that both conditions contribute to CL dissatisfaction. Higher scores for the CISS in those with CLD suggest a degree of overlap for some BVD symptoms. Nonsignificant differences between BVD and non-BVD for the CLDEQ-8 suggest that BVDs contribute to CL dissatisfaction independently of CLD.

Convergence Insufficiency Neuro-Mechanism Adult Population Study: Phoria Adaptation Results

Purpose

The purpose of this study was to compare changes in phoria adaptation between young adult binocularly normal controls (BNCs) and participants with symptomatic convergence insufficiency (CI), who were randomized to either office-based vergence accommodative therapy (OBVAT) or office-based placebo therapy (OBPT).

Methods

In the double-masked randomized clinical trial, 50 BNC and 50 CI participants were randomized to the following therapeutic interventions: OBVAT or OBPT with home reinforcement for 12 one-hour office sessions. A 6∆ base-out and 6∆ base-in phoria adaptation experiment at near (40 cm) was conducted using the flashed Maddox rod technique at baseline and at outcome. Measurements included the rate and the magnitude of phoria adaptation.

Results

At baseline, BNC and CI participants had significantly different rates and magnitudes of base-in and base-out phoria adaptation (P < 0.001). When comparing the outcome to baseline measurements, significant main effect differences in longitudinal measurements were observed for the magnitude and the rate of phoria adaptation for both base-out and base-in experiments (P < 0.05). For the magnitude and rate of phoria adaptation, post hoc analyses using paired t-tests revealed that the CI group administered the OBVAT intervention exhibited a significant increase in the magnitude and rate of phoria adaptation compared to baseline for both base-in and base-out phoria adaptation (P < 0.01) but not for those administered OBPT.

Conclusions

Phoria adaptation is significantly different at baseline between those with normal binocular vision and symptomatic CI participants. OBVAT significantly improves the rate and magnitude of both base-out and base-in phoria adaptation at near compared to OBPT. Results have clinical implications for new therapeutic interventions.

Accommodative and convergence anomalies in patients with opioid use disorder

Clinical relevance: Considering the significant relationship between opioid abuse and some accommodative and convergence disorders, opioid use should be considered in the differential diagnosis and will directly affect the management plan.Background: To determine the prevalence of accommodative and convergence anomalies and their related factors in a population of male young adults with opioid use disorder (OUD).Methods: This cross-sectional study was conducted using a convenience sampling method in 2019. The study sample included male young adults with OUD who had been referred to a specialised drug-dependence rehabilitation centre in Mashhad, Iran. The diagnosis of OUD was made by a psychologist based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria. All patients underwent complete optometric examinations.Results: Eighty male young adults with OUD were included in this study. The mean age of participants was 30.5 ± 3.9 years (age range 19 to 35 years). The prevalence of accommodative and convergence disorders was 33.75% (95% CI: 23.55-45.19) and 25.00 (95% CI: 15.99-35.94), respectively. Accommodative insufficiency (22.5%, 95% CI: 13.91-33.21) had a higher prevalence than accommodative excess (3.75%, 95% CI: 0.78-10.57) and accommodative infacility (7.50%, 95% CI: 2.80-15.61). Convergence insufficiency (18.75%, 95% CI: 10.89-29.03) had a higher prevalence compared to convergence excess (3.75%, 95% CI: 0.78-10.57) and basic exophoria (2.50%, 95% CI: 0.30-8.74). According to the multiple logistic regression, a significant inverse relationship was observed between pupil size with accommodative insufficiency (OR = 0.45), accommodative infacility (OR = 0.67), and convergence insufficiency (OR = 0.55).Conclusion: The results of the present study showed a higher prevalence of some accommodative and convergence disorders in OUD patients compared to the prevalence reported in previous studies conducted on the normal populations with a similar age range.

Disparity vergence differences between typically occurring and concussion-related convergence insufficiency pediatric patients

This study sought to test the hypothesis that significant differences would be observed in clinical measures, symptoms, and objective assessments of vergence eye movements between children with typically developing convergence insufficiency (TYP-CI) and children with persistent post-concussion symptoms with convergence insufficiency (PPCS-CI). Data from age-matched binocularly normal controls (BNC) were used for comparison. Data from three groups of children 11 to 17 years of age are presented: BNC (N = 11), TYP-CI (N = 10), and PPCS-CI (N = 15). Clinical measures of vergence, accommodation, and symptom severity were collected. Symmetrical 4° disparity vergence eye movements were quantified with an eye tracker integrated into a head-mounted display (Oculus DK2). Peak velocity and final response amplitude of convergence and divergence eye movement responses were assessed. The mean near point of convergence (break) was more receded (worse), the amplitude of accommodation more deficient, and convergent and divergent peak velocities slower in the PPCS-CI group compared with the TYP-CI and BNC groups. These results suggest that PPCS-CI may be a different clinical entity than TYP-CI. Hence, more research is warranted to determine whether the therapeutic interventions that are effective for TYP-CI can also be used for PPCS-CI populations.

The Prevalence of Fusional Vergence Dysfunction in a Population in Iran

PURPOSE

To determine the prevalence of fusional vergence dysfunction (FVD) and its relationship with age, sex, and refractive errors in a population-based study.

METHODS

In this cross-sectional study, all residents of Mashhad, northeast of Iran, aged >1 year were subjected to random stratified cluster sampling. After selecting the participants, they all underwent complete optometric examinations including the measurement of visual acuity and refraction, assessment of binocular vision and accommodative status, and slit-lamp biomicroscopy.

RESULTS

Of 4453 invited individuals, 3132 participated in the study. After applying the exclusion criteria, statistical analysis was performed on the data of 1683 participants. The prevalence of FVD was 3.2% in all participants, 4.0% in men, and 2.9% in women (P = 0.234). The prevalence of FVD increased linearly with aging from 2.3% in the age group of 10-19 years to 5.4% in the age group of 40-49 years (P = 0.034). The prevalence of myopia, hyperopia, and emmetropia was 11.1%, 29.6%, and 59.3% in participants with FVD and 16.7%, 26.4%, and 57% in participants without FVD, respectively (P = 0.570). Multiple logistic regression analysis only showed a significant association between age and FVD (odds ratio =1.03 95% confidence interval: 1.02-1.05, P = 0.031).

CONCLUSION

The prevalence of FVD in this study was higher than most previous reports and increased significantly with aging. FVD had no significant association with sex and refractive errors.

Underlying neurological mechanisms associated with symptomatic convergence insufficiency

Convergence insufficiency (CI) is the most common binocular vision problem, associated with blurred/double vision, headaches, and sore eyes that are exacerbated when doing prolonged near work, such as reading. The Convergence Insufficiency Neuro-mechanism Adult Population Study (NCT03593031) investigates the mechanistic neural differences between 50 binocularly normal controls (BNC) and 50 symptomatic CI participants by examining the fast and slow fusional disparity vergence systems. The fast fusional system is preprogrammed and is assessed with convergence peak velocity. The slow fusional system optimizes vergence effort and is assessed by measuring the phoria adaptation magnitude and rate. For the fast fusional system, significant differences are observed between the BNC and CI groups for convergence peak velocity, final position amplitude, and functional imaging activity within the secondary visual cortex, right cuneus, and oculomotor vermis. For the slow fusional system, the phoria adaptation magnitude and rate, and the medial cuneus functional activity, are significantly different between the groups. Significant correlations are observed between vergence peak velocity and right cuneus functional activity (p = 0.002) and the rate of phoria adaptation and medial cuneus functional activity (p = 0.02). These results map the brain-behavior of vergence. Future therapeutic interventions may consider implementing procedures that increase cuneus activity for this debilitating disorder.

Effect of corneal refractive surgery on accommodative and binocular dysfunctions among civilian pilots in Southwest China

Background

To analyze whether corneal refractive surgery (CRS) is associated with the distribution of different accommodative dysfunctions (ADs) and binocular dysfunctions (BDs) in civilian pilots. A further aim was to analyze the percentages and visual symptoms associated with ADs and/or BDs in this population.

Methods

One hundred and eight civilian pilots who underwent CRS from January 2001 to July 2012 (age: 30.33 ± 4.60 years) were enrolled, the mean preoperative SE was − 1.51 ± 1.15 D (range: − 1.00- − 5.00 D). Ninety-nine emmetropic civilian pilots (age: 29.64 ± 3.77 years) who were age- and sex-matched to the CRS group were also enrolled. Refractive status, accommodative and binocular tests of each subject were performed. Visually related symptoms were quantified using the 19-item College of Optometrists in Vision Development Quality of Life (COVD-QOL) questionnaire. The 19 items were summed to obtain visual symptom scores that might indicate visual dysfunctions. The chi-square test was used to analyze differences in percentages of ADs and/or BDs between the CRS and emmetropic groups. The Mann-Whitney U test was used to compare visual symptom scores between pilots with ADs and/or BDs and pilots with normal binocular vision.

Results

No significant difference was observed between the CRS and emmetropic groups in the overall prevalence of ADs and BDs (15.7% and 15.2% in the CRS and emmetropic groups, respectively; P = 0.185). ADs were present in 4.63% and 3.03% of the CRS and emmetropic group, respectively. BDs were observed in 11.1% and 12.1% of the CRS and emmetropic group, respectively, yielding no significant differences between the groups in the prevalence of ADs or BDs (AD: P = 0.094; BD: P = 0.105). Pilots with ADs and/or BDs had significantly more visual symptoms than pilots with normal binocular vision (p < 0.001).

Conclusions

CRS for civilian pilots with low-moderate myopia might not impact binocular functions. ADs and/or BDs commonly occur in both emmetropia pilots and pilots who undergo CRS, and pilots with ADs and/or BDs are associated with increased symptoms. This study confirms the importance of a full assessment of binocular visual functions in detecting and remedying these dysfunctions in this specific population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-01855-0.

Delphi methodology for symptomatology associated with visual dysfunctions

To analyse what eyecare clinicians think about which symptoms are associated with refractive, accommodative and binocular dysfunctions, and which of them should be used in a questionnaire of visual symptomatology. A Delphi method was developed, using a coordinating group and a group of experts, and the process was conducted in three rounds. In the first round we compiled a list of 34 symptoms from the scientific literature and additional 10 suggested by the experts. These symptoms were categorized by each expert to the associated visual anomalies and working distance. In the second round, the relationship between each symptom and visual dysfunctions was analysed using a numeric scale. In the third round, the appearance or absence of the 44 symptoms in a questionnaire was assessed. Symptoms most frequently assigned by the experts to visual anomalies were related to near vision. Symptoms of blurred vision, difficulty focusing from one distance to another and close one eye obtained the highest mean score for refractive, accommodative and binocular disorders respectively. The experts were in agreement for 15 symptoms and in disagreement for 5 symptoms that should appear in a questionnaire. Delphi method has been used to identify the symptoms related to visual dysfunctions according to eyecare professionals and has allowed to arrive at appropriate symptoms to be asked for in a visual symptomatology questionnaire.

The Effect of Age on Binocular Vision Normative Values

PURPOSE

To establish a relationship between age and horizontal heterophoria, horizontal fusional vergence amplitudes, and vergence facility testing.

METHODS

The sample consisted of 112 patients with a mean age of 39.8 ± 14.97 years (range: 18 to 65 years) and was composed of 61 women (54.5%) and 51 men (45.5%). The non-presbyopic group included patients 18 to 39 years old (n = 49) and the presbyopic group included patients 41 to 65 years old (n = 63). Binocular vision was studied by heterophoria horizontal magnitude (prism diopters [PD]), horizontal fusional vergences amplitudes (PD), and vergence facility testing (cycles per minute [cpm]) and quantified with a combination of 3 PD base-in and 12 PD base-out prisms.

RESULTS

Significant differences were obtained in near heterophoria with compensation (exophoria increased by 3.74 PD, t = 2.12, P < .05), distance positive fusional vergence (PFV) recovery (decreased by 2.86 PD, t = 3.03, P < .01), near PFV blur (decreased by 3.13 PD, t = 1.98, P = .05), near PFV break (decreased by 4.45 PD, t = 2.75, P < .01), near PFV recovery (decreased by 4.69 PD, t = 3.30, P < .01), and vergence facility testing (decreased by 2.63 PD, t = 2.77, P < .01).

CONCLUSIONS

The results indicated an increase of exophoria, a decrease in near positive horizontal fusional vergences, and vergence facility was dependent on age; thus, the authors suggest that changes in the normal values should be considered for each age range. [J Pediatr Ophthalmol Strabismus. 2020;57(6):363-371.].

The Influence of COVID-19 Isolation on Physical Activity Habits and Its Relationship with Convergence Insufficiency

The purpose of this work is to evaluate the effects of confinement due to COVID-19 isolation on visual function, considering insufficient convergence as one of the possible effects of living the whole day in a reduced space. We pass a Convergence Insufficiency Symptom Survey (CISS) among 235 people to detect their habits before and after 25 confinement days. The data collection protocol consisted on a Google forms questionnaire included two parts: the first with current data (isolation period) and a second with pre-isolation period data. Differences between the pre-isolation and isolation period were calculated using the related paired T-tests. When statistically significant differences were found, the effect size was estimated using the Cohen’s d index (d). The reduction in physical activity levels during confinement were related to the increase in total number of minutes of screen consumption from 433.49 min to 623.97 min per day (d = 0.67; 44.01%). The CISS scores were increased by more than 43% during confinement. The increase in convergence insufficiency was 100% after the studied isolation period of 25 days. The 92.19% increase in television use during 25 days of confinement is not responsible for the increase in convergence insufficiency. However, due to the increase in the use of PCs in this period, there is a notable increase in convergence insufficiency. Therefore, we can conclude that not all increases in tasks with electronic devices are responsible for the increase in convergence insufficiency.

Ocular symptoms associated with digital device use in contact lens and non-contact lens groups

PURPOSE

Previous reports indicate that "eye fatigue" occurs in roughly 60 % of the adult population using digital devices and may negatively impact quality of life. However, the construct of eye fatigue remains poorly understood. The goal of this study was to quantify the relationship among symptoms most frequently associated with eye fatigue in those using digital devices.

METHODS

Six hundred and two soft contact lens (SCL) wearers and 127 non-contact lens (non-CL) wearers who reported using digital devices at least 4 hours per day completed a questionnaire assessing the frequency and severity of ten symptoms commonly associated with digital device-related eye fatigue. Subjective ratings were made separately for each symptom using unipolar, five-point Likert scales.

RESULTS

From the initial pool of respondents, 89 % of the SCL wearers reported experiencing eye fatigue more than once per month, while over 60 % reported more than once per week. Notably, eye fatigue frequency did not differ between the soft contact and non-contact lens groups. Although eye strain/pain, dryness, and tired eyes were the most frequently endorsed symptoms by both groups, only dryness and eye irritation were significant factors that discriminated the SCL from the non-CL wearers on the basis of frequency and severity. Principal component analysis indicated that eye strain/pain, soreness, tired eyes, and headaches may comprise a "primary sensations" factor, whereas burning, eye irritation, tearing and dryness comprise a "secondary or surface sensations" factor, and blurred/double vision and words move/float comprise a "visual sensations" factor. Confirmatory factor analysis (CFA) of frequency and severity ratings for SCL wearers yielded excellent fits (RMSEA = 0.046 and 0.050, respectively) with construct reliabilities ranging from 0.729 to 0.824.

CONCLUSION

Frequent and severe eye fatigue is highly prevalent among both soft contact lens and non-contact lens wearers. Those utilizing SCL do not experience symptoms at higher frequency or severity. Key descriptors of digital eye fatigue have been identified and may then be used to help identify and evaluate specific causative, palliative, or ameliorating factors.

Test-Retest Reliability of Functional Magnetic Resonance Imaging Activation for a Vergence Eye Movement Task

Vergence eye movements are the inward and outward rotation of the eyes responsible for binocular coordination. While studies have mapped and investigated the neural substrates of vergence, it is not well understood whether vergence eye movements evoke the blood oxygen level-dependent signal reliably in separate experimental visits. The test-retest reliability of stimulus-induced vergence eye movement tasks during a functional magnetic resonance imaging (fMRI) experiment is important for future randomized clinical trials (RCTs). In this study, we established region of interest (ROI) masks for the vergence neural circuit. Twenty-seven binocularly normal young adults participated in two functional imaging sessions measured on different days on the same 3T Siemens scanner. The fMRI experiments used a block design of sustained visual fixation and rest blocks interleaved between task blocks that stimulated eight or four vergence eye movements. The test-retest reliability of task-activation was assessed using the intraclass correlation coefficient (ICC), and that of spatial extent was assessed using the Dice coefficient. Functional activation during the vergence eye movement task of eight movements compared to rest was repeatable within the primary visual cortex (ICC = 0.8), parietal eye fields (ICC = 0.6), supplementary eye field (ICC = 0.5), frontal eye fields (ICC = 0.5), and oculomotor vermis (ICC = 0.6). The results demonstrate significant test-retest reliability in the ROIs of the vergence neural substrates for functional activation magnitude and spatial extent using the stimulus protocol of a task block stimulating eight vergence eye movements compared to sustained fixation. These ROIs can be used in future longitudinal RCTs to study patient populations with vergence dysfunctions.

Diurnal variations of amplitude of accommodation in different age groups

Clinical assessment of amplitude of accommodation (AA) involves measuring the ability of the eye to change its optical power and focus on near tasks/objects. AA gradually decreases with increasing age. However, details of age-related diurnal changes in AA are not well known. This study compared diurnal changes in AA in the adolescents, the twenties, and the forties age groups. Measurement of AA using the push-up method was performed in six sessions at two-hourly intervals for 154 subjects (48, 56, 50 subjects for the adolescents, twenties, and forties age groups, respectively); the first measurements were taken from 9:00–10:00 a.m. and the final measurements from 7:00–8:00 p.m. The mean AA was 14.67 D (highest: 16.15 D in the 3:00–4:00 p.m. session, lowest: 13.35 D in the 9:00–10:00 a.m. session) for the adolescent group; 11.13 D (highest: 11.69 D in the 3:00–4:00 p.m. session; lowest: 10.61 D in the 9:00–10:00 a.m. session) in the twenties group; and 5.53 D (highest: 5.80 D in the 1:00–2:00 p.m. session, lowest: 5.11 D in the 7:00–8:00 p.m. session) in the forties age group. The measured AA showed significant difference between sessions; however, diurnal variations were greater in the younger groups. The measured AA was low at the beginning of the day in the adolescents and twenties groups and low at the end of the day in the forties age group. All age groups showed a high AA during the afternoon hours of the day (1:00–4:00 p.m.). Since the difference between each session was larger in younger subjects, AA should be evaluated while taking the age-related diurnal variations into account.

Near Points of Convergence and Accommodation in a Population of University Students in Iran

Purpose

To determine the distribution of the near point of convergence (NPC) and near point of accommodation (NPA) in a young student population in Iran.

Methods

The subjects were selected using a cluster sampling method. All students underwent optometry tests, including visual acuity measurement, refraction, and cover test, as well as ophthalmic examinations. The NPC and NPA were measured using an accommodative target (near Snellen chart).

Results

Of 1,595 students, the data of 1,357 were analyzed. The mean NPC and NPA in the total sample were 7.25 cm (95% confidence interval [CI], 7.02 to 7.48) and 9.99 cm (95% CI, 9.69 to 10.29), respectively. Older age was associated with an increase in the NPC, which increased from 6.98 cm in 18-20 years olds to 9.51 cm in those over 30 years. The NPA was significantly associated with age and refractive errors in the multiple linear regression model, increasing from 9.92 cm in 18-20 years olds to 11.44 cm in those over 30 years ( P = 0.003). Hyperopic eyes had lower NPA than myopic and emmetropic eyes ( P = 0.001). In younger age groups, the mean accommodation amplitude was lower than the mean Hofstetter value. Moreover, with age, especially after 30 years, the mean values surpassed those determined using the Hofstetter formula.

Conclusion

The NPC values in this study were lower than those previously reported for identical age groups. The Hofstetter formula is not always an accurate predictor of the accommodation amplitude in the Iranian adult population.

Vergence and Accommodative Dysfunctions in Emmetropic and Myopic Chinese Young Adults

Purpose

To investigate the association between refractive error and common binocular vision and accommodative dysfunctions in Chinese adults and to report the percentage of these disorders in this sample population.

Methods

This was a single-site, prospective cross-sectional clinic-based study. A total of 415 Chinese participants aged between 21 and 38 years were grouped into 4 refractive error groups (emmetropia, low, moderate, and high myopia) based on the spherical equivalent power of noncycloplegic refraction. Baseline testing including binocular vision and accommodative testing was performed on all eligible participants. A multiple-sign classification system was used to analyze these data for the diagnosis of common nonstrabismic binocular vision and accommodative dysfunctions. Associations between the diagnosis and refractive error groupings were examined by the chi-square test for the linear trend.

Results

Associations with refractive error groupings were found for convergence insufficiency (p=0.008, r = −0.13) and divergence insufficiency (p=0.008, r = 0.131). The 3 most common dysfunctions in this sample population were basic exophoria (10.8%), convergence insufficiency (9.6%), and divergence insufficiency (7.0%). Approximately 40% of the sample population demonstrated at least one type of binocular vision dysfunction.

Conclusion

Convergence insufficiency and divergence insufficiency were associated with refractive error groupings. Binocular vision dysfunction was a common finding in this sample population.

Accommodative insufficiency in a student population in Iran

PURPOSE

To determine the prevalence of accommodative insufficiency (AI) and its relation with age, gender, and refractive errors in a college-age student population in Iran.

METHODS

The present study was conducted cross-sectionally in 2017. All students had optometric tests including measurement of visual acuity, objective and subjective refraction, as well as binocular vision and accommodative examinations. Amplitude of accommodation was measured with the Donders' push-up method using the Royal Air Force (RAF) rule. Monocular accommodative facility was measured with ±2.00diopter flipper lenses. The accommodative response was tested using dynamic retinoscopy with the monocular estimation method (MEM).

RESULTS

The prevalence of AI in the studied population was 4.07% (95% CI: 2.61-5.52). The rate was 6.04% (95% CI: 3.58-8.50) in females and 2.01% (95% CI: 0.53-3.48) in males, and logistic regression showed a significantly higher odds of AI in females (OR=3.14, 95% CI: 1.33-7.45, p-value=0.009). The prevalence of AI was 2.59% (95% CI: 0.55-7.56) in the 18-19-year-old age group and 4.08% (95% CI: 0.09-8.07) in the 24-25-year-old group (p-value=0.848). The prevalence of AI among emmetropic, myopic, and hyperopic individuals was 3.74% (95% CI: 1.88-5.61), 4.44% (95% CI: 2.07-6.81), and 5.26% (95% CI: 4.79-16.32), respectively (p-value=0.869). In the multiple regression model, only gender showed significant relationship with AI (Odds ratio=3.14, 95% CI: 1.33-7.45; p-values=0.009).

CONCLUSION

The prevalence of AI in the present study is lower than the most prevalence rates reported in previous studies. In the present study, gender and AI showed a strong association, such that AI prevalence was significantly higher in females than males.

Nonstrabismic binocular dysfunctions and cervical complaints: The possibility of a cross-dysfunction

The aim of this study is to establish a relationship between non-strabismic binocular dysfunction and neck pain. One hundred twelve participants underwent binocular vision assessment by evaluating horizontal heterophoria, horizontal and vertical fusional vergence ranges and vergence facility. The subjects were classified into two groups: binocular anomalies and normal binocular function. Neck complaints were measured with the Neck Disability Index, visual analogue scale, cervical range of motion, deep-flexor muscle activation score (AS) and performance index (PI). Our results showed that participants with low AS had significantly altered values of lateral phoria (near) (mean = -6.99 SD ± 6.96 PD) and PFV (near) blur (mean = 9.49 SD ± 5.45 PD) against those who presented normal AS (lateral phoria (near) mean = -3.64 SD ± 6.37 PD; PFV (near) blur mean = 12.84 SD ± 6.20 PD). In addition, participants with NFV (near) recovery outside the norm had a significantly lower right side-bending (mean = 35.63 SD ± 8.35 PD) than those within the standard (mean = 39.64 SD ± 9 PD). The subjects with binocular vision impairment showed a diminished response to the deep cervical musculature, with low AS and PI, as well as a tendency to suffer from cervicalgia of more than three months’ evolution and a lower range of motion.

Prefrontal Cortex Oxygenation Evoked by Convergence Load Under Conflicting Stimulus-to-Accommodation and Stimulus-to-Vergence Eye-Movements Measured by NIRS

Purpose: To extend our knowledge of the functional linkages between visual fatigue and regional cerebral prefrontal cortex (PFC) oxygenation, we measured time related hemodynamic changes over the right dorsolateral prefrontal cortex (dlPFC) during convergence load under conflicting stimulus-to-accommodation and stimulus-to-vergence eye movements with and without concurrent mental load.

Methods: Twenty healthy participants with a median age of 28 years (range: 18–44 years) fixated upon a vertical bar presented separately to the left and right eyes, using polarized filters, during four counterbalanced 10-min periods: (i) no accommodation/vergence conflict (Control, Ctrl); (ii) added convergence load and accommodation/vergence conflict (Conv); (iii) added cognitive load only (Cog) and; (iv) a combination of added cognitive and convergence load and accommodation/vergence conflict (Cc). Viewing distance was 65 cm. Non-invasive measurements of hemodynamic activity over the dlPFC were quantified by functional near-infrared spectroscopy (fNIRS). During the two-convergence load conditions, the horizontal disparity of the two bars varied dynamically from no disparity to a disparity set 20% below the individual threshold for diplopia. Cognitive load was induced by the n-back-2 test which required the subject to memorize and recall the changing colors of the horizontal bars and decide when a given color was the same as that occurring two colors previously. fNIRS data were averaged over 10-s windows centered at 0, 2, 4, 6, 8, and 10 min of each task, subtracted from a 20-s baseline window immediately preceding the visual task, and then represented as changes in oxygenated hemoglobin (ΔHbO₂)_, deoxygenated hemoglobin (ΔHHb) and total hemoglobin (ΔtHb).

Results: Linear mixed model analyses showed that hemodynamic activity was systematically influenced by time (p < 0.001). The group-averaged time-related level of change across the viewing conditions did not differ when compared with one another (p > 0.05). Larger convergence eye-movement responses under conflicting stimulus-to-accommodation, and stimulus-to-vergence over time, increased ΔHbO₂ and ΔtHb only in condition Cc and after 8 min of task time (p < 0.10 for min^-6 and min^-8: p < 0.05 for min^-10).

Discussion: Collectively, our data suggest that HbO₂, HHb, and tHb, recorded over the dlPFC with fNIRS, can be used to assay the degree to which supervisory oculomotor control processes are activated during visually deficient near work.

Symptomatic accommodative and binocular dysfunctions from the use of flat-panel displays

AIM

To determine the presence of symptomatic accommodative and non-strabismic binocular dysfunctions (A_NSBD) in a non-presbyopic population of video display unit (VDU) users with flat-panel displays.

METHODS

One hundred and one VDU users, aged between 20 to 34y, initially participated in the study. This study excluded contact-lens wearers and subjects who had undergone refractive surgery or had any systemic or ocular disease. First, subjects were asked about the type and nature of eye symptoms they experienced during VDU use. Then, a thorough eye examination excluded those subjects with a significant uncorrected refractive error or other problem, such as ocular motility disorders, vertical deviation, strabismus and eye diseases. Finally, the remaining participants underwent an exhaustive assessment of their accommodative and binocular vision status.

RESULTS

Eighty-nine VDU users (46 females and 43 males) were included in this study. They used flat-panel displays for an average of 5±1.9h a day. Twenty subjects presented A_NSBD (22.5%). Convergence excess was the most frequent non-strabismic binocular dysfunction (9 subjects), followed by fusional vergence dysfunction (3 subjects) and convergence insufficiency (2 subjects). Within the accommodative dysfunctions, accommodative excess was the most common (4 subjects), followed by accommodative insufficiency (2 subjects). Moderate to severe eye symptoms were found in 13 subjects with A_NSBD.

CONCLUSION

Significant eye symptoms in VDU users with accommodative and/or non-strabismic binocular dysfunctions often occur and should not be underestimated; therefore, an appropriate evaluation of accommodative and binocular vision status is more important for this population.

Is it possible to relate accommodative visual dysfunctions to neck pain?

The aim of this study was to establish whether there is a relationship between conditions of accommodative visual dysfunctions and cervical complaints. Fifty-two participants were included. Variables were accommodative amplitude, positive and negative relative accommodation (NRA), accommodative response, and accommodative facility. Subjects were classified as accommodative insufficiency, accommodative excess, or normal. Neck complaints were measured with the Neck Disability Index, the Visual Analogue Scale, and by cervical range of motion, deep flexor muscle activation score, and performance index. We found the following significant relationships: between NRA and both performance index and left-side bending; accommodative amplitude right-eye with right-side bending and with left-side bending; accommodative amplitude left-eye with right-side bending; and accommodative facility left-eye with both performance index and left-side bending. In accommodative amplitude right-eye, aIl participants showed significant values and greater than those with accommodative excess. In both groups, performance index values were decreased. Greater pain and lower right-rotation were found in participants with accommodative excess than in those with accommodative insufficiency. We conclude that accommodative dysfunctions are related to low performance index, decreased range of motion, as well as greater neck pain.

Real-Time Measurement of Ocular Wavefront Aberrations in Symptomatic Subjects

The purpose of this work was to study the real-time changes of the optical properties of the eye with accommodation in subjects with symptoms of accommodative disorders. From ocular aberrations, it is possible to compute several parameters like the response and lag of accommodation. The ocular aberrations were measured in 4 subjects, with different accommodative disorders, during several cycles of accommodation/disaccommodation and for different accommodative stimuli. The measurement was done continuously and in real time during different accommodative stimuli. It was possible to see the changes in accommodative response during the several stimuli of accommodation. Subjects with accommodative disorders showed different accommodative responses. The use of wavefront ocular aberrations can be a tool to diagnose accommodative disorders. In some subjects with complaints, this method showed irregularities even when the results of the usual clinical exams were normal.