Abstract

Purpose:

This multicenter study aimed to compare symptoms in pediatric and adolescent patients with and without concussion using the Convergence Insufficiency Symptom Survey (CISS). We further examined symptom profiles of concussed patients with and without vergence and/or accommodation deficits.

Methods:

Children aged 8 to <18 years, diagnosed with concussion 4 weeks to 12 months prior and visually normal controls underwent comprehensive testing of vergence and accommodation. Participants completed the 15-item CISS, with somatic (CISS-S), performance (CISS-P), and vision (CISS-V) subscores. Mann–Whitney U tests compared total CISS scores and normalized subscores between concussed and control groups, and concussed participants with and without vergence and/or accommodative deficits.

Results:

Among 66 eligible participants (34 concussed, median age 15.0 [interquartile range, IQR: 12.2–16.0]; 32 controls, median age 13.0 [11.0–14.0]), concussed individuals had substantially higher total CISS scores (median 26.0 [19.25–36.75] vs. 4.0 [1.0–7.0]; p < 0.0001) and higher CISS-S, CISS-P and CISS-V subscores than controls (all p < 0.001). Within the concussion group, 76.5% (26 of 34) demonstrated vergence and/or accommodative deficits, showing significantly higher total CISS scores (31.50 [22.25–38.75] vs. 19.50 [15.75–21.25]; p = 0.022), higher normalized CISS-V subscores (1.33 [0.75–2.25] vs. 0.50 [0.00–0.67]; p = 0.005) and CISS-P subscores [2.50 [2.05–3.20] vs. 1.50 [1.15–2.10]; p = 0.047] compared to those without such deficits. No significant difference in CISS-S (2.14 [1.61–2.82] vs. 1.43 [0.82–1.75], p = 0.084) was observed between concussed groups.

Conclusion:

Vergence and accommodation deficits were associated with higher CISS vision and performance related subscores. Elevated symptom reporting in the somatic and performance subscores in concussed may indicate strain in the vergence and accommodative system, as evidenced by the increased subjective discomfort and difficulty during tasks like reading and near work. Concurrent assessment of vergence and accommodation alongside CISS symptom subscores may identify patients for vision rehabilitation, aimed at improving vergence and accommodation function and reducing somatic and performance-related symptoms.

Introduction

Concussion, a form of mild traumatic brain injury (mTBI), is a significant and growing public health concern in the pediatric population. In 2022, approximately 2.3 million children and adolescents (3.2%) in the United States were diagnosed with a concussion or brain injury, with prevalence increasing with age: from 1.0% in children aged 0–5 years, to 2.3% in those 6–11 years, and 5.9% in adolescents aged 12–17 years (Elgaddal and Black, 2023). National surveys report lifetime concussion/head injury estimates in youth ranging from 2.5 to 18.3%, with the highest prevalence found in adolescents aged 13–17 years (Haarbauer-Krupa et al., 2021). Annually, over 120,000 emergency department visits occur in children under 18 due to mTBI, particularly in males (Singichetti et al., 2018). Approximately 87% of pediatric TBIs recorded in national trauma databases are classified as mild, and most children recover within a few weeks (Yue et al., 2016). However, a subset of children experience prolonged symptoms, hospitalization, or complications—demonstrating that even mild TBIs can lead to an extended recovery depending on injury severity, risk factors, and mechanism of injury (Yue et al., 2016).

After concussion, many children and adolescents experience a range of symptoms across physical, cognitive, emotional, and sleep related systems (Harmon et al., 2013). Given that processing of visual information is supported by extensive cortical circuitry, the visual system is particularly vulnerable post-concussion, making visual symptoms highly prevalent (Ventura et al., 2015; Wu et al., 2018). Commonly reported symptoms include double vision, blurred vision, headaches during near work, light sensitivity, and difficulty reading or focusing (Ventura et al., 2015; Gallaway et al., 2017; Wiecek et al., 2021; Schmitz et al., 2023). Studies consistently show that convergence insufficiency (CI) and accommodative dysfunction are among the most common diagnoses post-concussion (Gallaway et al., 2017; Gowrisankaran et al., 2021; Scheiman et al., 2021). Convergence insufficiency is a binocular vision-related disorder in which the eyes do not work together effectively during near tasks, resulting in difficulty maintaining alignment and fusion (Scheiman et al., 2020). Accommodative dysfunction is characterized by an impaired ability to focus and/or sustain focus during near visual activities (Daum, 1983; Scheiman et al., 2011).

In our recent study, we reported that these vision-related dysfunctions may persist for months post-injury and are associated with prolonged recovery and reduced quality of life (Marusic et al., 2024). Frequency of vergence or accommodative dysfunction in both the subacute (15 days–12 weeks) and chronic (>12 weeks–1 year) phases from the time since concussion were similar, indicating that such deficits may not resolve spontaneously and could benefit from evaluation by a specialized eye care provider (Marusic et al., 2024).

The Convergence Insufficiency Symptom Survey (CISS) is a 15-item questionnaire developed to assess symptoms in patients with CI (Scheiman, 2008). While initially designed and validated to diagnose symptomatic CI and used as an outcome measure in large clinical treatment trials like the CITT and CITT-Attention and Reading Trial (CITT-ART Investigator Group, 2019; Scheiman, 2008, 2015; Rouse et al., 2009), the CISS has since been adapted for use in concussion populations to capture symptom burden (Gowrisankaran et al., 2021) when doing near activities. The CITT established the clinical utility of the CISS in children aged 9–17 years, demonstrating the effectiveness of vergence/accommodative therapy in reducing symptoms (Scheiman, 2008) in symptomatic children with CI. Standard concussion scales such as the Post-Concussion Symptom Scale (PCSS) only assess whether a patient declares they have “Sensitivity to Light,” or have “vision problems” which does not capture the variety of vision-related symptoms that may present following concussion (Gowrisankaran et al., 2021). Although not a diagnostic tool for identifying CI following concussion, the CISS helps clinicians identify symptomatic individuals who may benefit from a comprehensive visual function assessment (Gowrisankaran et al., 2021; Vyas et al., 2025).

Our earlier retrospective study has shown that the CISS is sensitive to the broader symptomatology associated with post-concussion vergence and/or accommodation deficits and may offer a cost-effective, accessible tool for tracking symptoms outside of eye care clinics (Gowrisankaran et al., 2021). Additionally, studies suggest that dividing the CISS into subscores itemized into different domains such as somatic (e.g., headaches, eye strain), performance (e.g., re-reading lines, poor concentration), and vision-related (e.g., double vision, blurring) can help characterize symptom profiles following naturally occurring CI (Barnhardt et al., 2012), dyslexia (Raghuram et al., 2019b), and concussion (Vyas et al., 2025).

Using the CISS, we have demonstrated that individuals who have experienced a concussion report significantly higher somatic-related subscores in comparison to visually normal controls. Additionally, our research indicates that vergence and/or accommodation deficits following a concussion were associated with higher total CISS scores and vision-related subscores in a pediatric and adolescent cohort (Vyas et al., 2025). However, the previous study was retrospective and used a control group from a different study; in the current study, we aim to address these limitations to strengthen clinical recommendations for post-concussion care.

In this paper, we present a prospective study designed to compare vergence and/or accommodation deficits and symptom burden in children and adolescents with and without a history of concussion using the CISS. Our objectives are twofold: first, to evaluate total CISS scores and subscores across somatic-, performance-, and vision-related subscores between concussed and non-concussed participants; and second, to determine whether symptom severity as measured by the CISS differs between concussed individuals with and without identified vergence and/or accommodation deficits. We hypothesized that concussed participants would report significantly greater overall symptom burden than non-concussed controls, and within the concussion group, those with vergence and/or accommodation deficits would exhibit higher CISS subscores, particularly in vision-related subscores.

MethodsInstitutional review board approval

This study received approval from the Institutional Review Boards of Boston Children’s Hospital (Boston, Massachusetts, United States), Stanford University (Stanford, California, United States), and Salus University (Elkins Park, Pennsylvania, United States). Written informed consent was obtained from a parent or legal guardian of each participant, and written assent was obtained from all participants prior to enrolment in the study.

Participant recruitment and eligibility

Participants were recruited from Boston Children’s Hospital, Stanford University, and the Pennsylvania College of Optometry at Salus University. Control participants were enrolled through word-of-mouth referrals, departmental staff, local community, and patients attending routine eye examinations at the affiliated clinics. Participants with concussion were recruited from dedicated concussion clinics at Boston Children’s Hospital and Stanford University or were referred to the vision care practices of the senior investigators (TLR and AR) for post-concussion assessment. These referrals were made for individuals experiencing persistent post-concussion symptoms, regardless of vision-specific complaints.

The inclusion criteria for the concussion group required a physician-diagnosed concussion in accordance with the Berlin Consensus Statement on Concussion in Sport, with the study visit occurring 4 weeks to 12 months post-injury. Control participants were eligible if they had no history of concussion and no known accommodative or vergence deficits. All participants were aged between 8 and <18 years, demonstrated best-corrected distance visual acuity of 20/25 or better in each eye, and wore appropriate refractive correction. Detailed inclusion and exclusion criteria are provided in Table 1 and Supplementary methods 1.

Inclusion criteriaExclusion criteriaConcussed group:
Control group:

History of amblyopia

History of strabismus or diplopia

Prior in-office vision therapy

Ocular trauma affecting visual or oculomotor function

Structural abnormalities of the cornea, lens, or central retina

Constant/intermittent esotropia at distance or near

Constant exotropia at near or distance

Vertical heterophoria ≥2 prism diopters (Δ) at distance or near

Manifest or latent nystagmus

Neurological or ocular conditions affecting vergence, accommodation, or eye movements

Inability to reliably perform study-related vision assessments

Inclusion and exclusion criteria.

Symptom assessmentsConvergence insufficiency symptom survey

The CISS is a 15-item questionnaire (Table 2) validated for use in patients with CI (Scheiman, 2008). Each item is rated on a Likert scale ranging from “never” (0) to “always” (4), yielding a total score between 0 and 60, with higher scores indicating greater symptom severity. The CISS items were further divided into subcategories: 7 somatic-related symptoms (CISS-S), 5 performance-related symptoms (CISS-P), and 3 vision-related symptoms (CISS-V) (Scheiman, 2008; Barnhardt et al., 2012; Vyas et al., 2025). CISS subscores were normalized by dividing the category’s total response score by the number of items in the category to control for each subscore containing different numbers of items (Vyas et al., 2025).

SymptomNeverNot very oftenSome-timesFairly oftenAlways1. Do your eyes feel tired when reading or doing close work?012342. Do your eyes feel uncomfortable when reading or doing close work?012343. Do you have headaches when reading or doing close work?012344. Do you feel sleepy when reading or doing close work?012345. Do you lose concentration when reading or doing close work?012346. Do you have trouble remembering what you have read?012347. Do you have double vision when reading or doing close work?012348. Do you see the words move, jump, swim or appear to float on the page when reading or doing close work?012349. Do you feel like you read slowly?0123410. Do your eyes ever hurt when reading or doing close work?0123411. Do your eyes ever feel sore when reading or doing close work?0123412. Do you feel a “pulling” feeling around your eyes when reading or doing close work?0123413. Do you notice the words blurring or coming in and out of focus when reading or doing close work?0123414. Do you lose your place while reading or doing close work?0123415. Do you have to re-read the same line of words when reading?01234

Convergence insufficiency symptom survey (CISS).

Somatic-related symptoms (CISS-S) are shaded in blue, performance-related symptoms (CISS-P) in pink, vision-related symptoms (CISS-V) in yellow.

Vision and visual function assessment

Following the administration of the CISS, each participant underwent a comprehensive visual function examination conducted by a pediatric optometrist, including assessment of distance and near visual acuity, stereopsis, ocular motility, ocular alignment, vergence, and accommodation. Ocular alignment was evaluated using the cover-uncover test, with deviation magnitude measured by the prism and alternate cover test. The vergence assessment included near-point of convergence (NPC), near vergence facility, and fusional amplitudes for near convergence and divergence. Accommodation was evaluated using amplitude of accommodation (AA) and monocular accommodative facility. Any examiner- or participant-noted difficulties with base-out (convergence demand) or base-in (divergence demand) prisms during vergence facility testing were noted. Similarly, difficulties with minus (increased demand) or plus (decreased demand) lenses during accommodative facility testing were noted. Diagnoses related to vergence and accommodation were made based on visual function testing results and criteria described in Table 3 (Raghuram et al., 2019a; Gowrisankaran et al., 2021; Wu et al., 2025). Further details of the examination procedures can be found in Supplementary methods 1.

Clinical diagnosis and findingsCriteriaVergence diagnosesConvergence insufficiency
Near deviation
Near point of convergence
Convergence fusional amplitudes at near
Vergence facility (3ΔBI/12ΔBO)First criteria and one other must be met
≥4 Δ near exophoria more than distance
>6 cm
≤15 Δ blur/breaka or failing Sheard’s criterionb
≤9 cpm, BO prism harderConvergence deficit
Near point of convergence
Convergence fusional amplitudes at near
Vergence facility (3ΔBI/12ΔBO)First criteria and one other must be met
>6 cm
≤15 Δ blur/breaka or failing Sheard’s criterionb
≤9 cpm, BO prism harderConvergence excess
Near Deviation
Divergence fusional amplitudes at near
Vergence facility (3ΔBI/12ΔBO)First criteria and one other must be met
≥3 Δ esophoria at near
≤8 Δ blur/breaka or failing Sheard’s criterionb
≤9 cpm, BI prism harderDivergence deficit
Divergence fusional amplitudes at near
Vergence facility (3ΔBI/12ΔBO)Must meet both criteria
≤8 Δ blur/breaka or failing Sheard’s criterionb
≤9 cpm, BI prism harderFusional vergence dysfunction
Convergence fusional amplitudes at near
Divergence fusional amplitudes at near
Vergence facility (3ΔBI/12ΔBO)Must meet first two criteria OR fail third
≤15 Δ blur/breaka or failing Sheard’s criterionb
≤8 Δ blur/breaka or failing Sheard’s criterionb
≤9 cpm, BI and BO prisms both difficultAccommodative diagnosesAccommodative insufficiency
Accommodative amplitude
Accommodative facility (±2D)Must meet one criteria
<11 D
≤6 cpm, (−) lens difficultAccommodative excess
Accommodative Amplitude
Accommodative Facility (±2D)Must meet both criteria
≥11 D (normal)
≤6 cpm, (+) lens difficultAccommodative infacility
Accommodative infacility (±2D)Must meet criteria
≤6 cpm, (+) and (−) lens equally difficultAccommodative dysfunction
Accommodative Amplitude
Accommodative Facility (±2D)Most meet both criteria
<11 D
≤6 cpm, (+) lens difficultAccommodative insufficiency and accommodative infacility
Accommodative Amplitude
Accommodative Facility (±2D)Must meet both criteria
<11 D
≤ 6 cpm, (+) and (−) lens equally difficult

Vergence and accommodation diagnostic criteria.

BI, base-in prism; BO, base-out prism; cpm, cycles per minute; D, diopter; Δ, prism diopter.

a

Blur/break refers to the point at which the participant reports that the target is blurry, or if there is no blur, when it splits into two.

b

Sheard’s Criterion: Compensating vergence range (positive or negative fusional vergence) of at least two times near heterophoria.

Statistical analysis

Categorical data were summarized as proportions and frequencies, while continuous data were presented as medians and interquartile ranges (IQR). Since a Shapiro–Wilk test indicated non-normality for CISS scores, non-parametric Mann–Whitney U tests were conducted to compare total CISS scores as well as subscores between concussed and control participants. Separately for the control and concussed groups, Friedman tests were used to compare normalized subscores within each group. A two-sided alpha-value of 0.05 was set as the threshold for statistical significance in all analyses. Wilcoxon signed rank post-hoc tests were used for any pairwise comparisons between normalized subscores within each group, with an adjusted alpha-value of 0.017. Finally, Mann Whitney U tests were conducted to compare total CISS scores and subscores between concussed participants with and without vergence and/or accommodative deficits. To assess symptom severity scores in the concussed and control groups, the mean scores across participants for individual CISS items were calculated. All statistical tests were conducted using RStudio (version 4.4.1).

Results

Of the 71 participants recruited, 66 met inclusion criteria. Participants were excluded due to ineligible visual acuity (n = 3), reports of constant diplopia (n = 1), and esotropia (n = 1). Among the 66 remaining participants, 34 were concussed (25 female, 9 male; median age 15.0 years [IQR: 12.2 to 16.0]) and 32 were controls (18 female, 14 male; median age 13.0 years [IQR: 11.0 to 14.0]). All consecutive control participants recruited for the study were enrolled. No subjects were excluded based on binocular vision findings. Only one participant was excluded from the control group because of esotropia. The median time since concussion was 107.0 days (IQR: 80 to 118), with 24 participants (71%) reporting a sport-related concussion, 9 (26%) indicating other causes such as falls, and 1 (3%) being due to a motor vehicle accident. Participants reported having sustained 1, 2, or more than 3 concussions in 52, 35, and 13% cases, respectively.

CISS scores between concussed and control group

The Mann–Whitney U test showed that the median total CISS score [IQR] was significantly higher in concussed participants (26.0 [19.25 to 36.75]) than in controls (4.0 [1.0 to 7.0]; U = 1059.0, p < 0.0001; Figure 1). Compared with controls, concussed participants also had significantly higher normalized median subscores for CISS-S (concussed: 2.00 [(1.18 to 2.54)], controls: 0.29 [0.00 to 0.43]; U = 1023.1, p < 0.0001), CISS-P (concussed: 2.40 [1.40 to 2.80], controls: 0.20 [0.0 to 0.60]; U = 1020.5, p < 0.0001), and CISS-V (concussed: 1.00 [0.67 to 2.00], controls: 0.00 [0.00 to 0.00]; U = 983.0, p < 0.001; Figure 2).

Total CISS score in concussed and control participants. Box plot showing the distribution of total Convergence Insufficiency Symptom Survey (CISS) scores in concussed (orange) and control (green) participants. Individual data points are overlaid as semi-transparent circles. Boxes represent the interquartile range (IQR), red center lines indicate the median, and whiskers denote the minimum and maximum values.

Normalized CISS subscores in concussed and control groups. Box plots illustrating normalized CISS subscores for somatic (CISS-S), performance (CISS-P), and vision (CISS-V) domains in concussed (orange) and control (green) participants. Individual participant data are shown as semi-transparent circles. Boxes indicate the interquartile range, red center lines represent the median, and whiskers denote the minimum and maximum values.

CISS-P subscores were highest in both the concussed and control group, followed by CISS-S and CISS-V subscores. The Friedman test showed significant differences among the subscores in the concussed group [χ2(2) = 23.93, p < 0.001] as well as the control group [χ2(2) = 14.67, p < 0.001]. For the concussed group, Wilcoxon signed rank post-hoc tests indicated significantly higher scores for CISS-P (2.40 [1.40 to 2.80]) than CISS-V (1.00 [0.67 to 2.00]; z = −4.20, p < 0.001) and CISS-S (2.00 [1.18 to 2.54]) than CISS-V (1.00 [0.67 to 2.00]; z = −3.56, p < 0.001) but no significant difference between CISS-P (2.40 [1.40 to 2.80]) and CISS-S (2.00 [1.18 to 2.54]; z = −1.93, p = 0.054). In the control group the trend was similar, with scores for CISS-P (0.20 [0.0 to 0.60]) significantly higher than CISS-V (0.00 [0.00 to 0.00]; z = −3.19, p < 0.001) and CISS-S (0.29 [0.00 to 0.43]) than CISS-V (0.00 [0.00 to 0.00]; z = −3.18, p < 0.002). However, no significant difference was observed between CISS-P (0.20 [0.0 to 0.60]) and CISS-S (0.29 [0.00 to 0.43]; z = −1.24, p = 0.215) subscores.

CISS scores within concussed group

Among the 34 concussed participants, 26 (76.5%) had vergence and/or accommodation deficits. Twenty one (80.8%) had both vergence and accommodation deficits; 5 (19.2%) had only accommodation deficits; none of the participants had only vergence deficits (Wu et al., 2025; Tables 4, 5). The median total CISS scores were significantly higher in the concussed group with vergence and/or accommodation deficits (31.50 [22.25 to 38.75]) compared to concussed participants without deficits (19.50 [15.75 to 21.25]; U = 47, p = 0.022; Figure 3). Compared with participants without vergence and/or accommodation deficits, those with deficits also had significantly higher normalized median subscores for CISS-V (concussed with deficits: 1.33 [0.75 to 2.25], concussed without deficits: 0.50 [0.00 to 0.67]; U = 35, p < 0.01) and for CISS-P (concussed with deficits: 2.40 [2.05 to 3.20], concussed without deficits: 1.50 [1.15 to 2.10]; U = 54.5; p = 0.047). No significant group difference was observed for CISS-S (concussed with deficits: 2.14 [1.61 to 2.82], concussed without deficits 1.43 [0.82 to 1.75]; U = 61, p = 0.084; Figure 4).

GroupConcussed with deficitsConcussed without DeficitsN268Mean age (years) [IQR]15 [4]15.5 [3.5]Sex (% female)21 (80.8%)4 (50%)Median number of concussion [IQR]1 [1]1 [1]Median days since concussion [IQR]107 [41]103 [38.5]Median NPC Break [IQR] (cm)10.0 [6.7]5.42 [1.9]Median Break Positive Fusional Vergence at Near (Base Out) [IQR] (Δ)15.0 [15.3]20.7 [9.0]Median Break Negative Fusional Vergence at Near (Base In) [IQR] (Δ)14.0 [2]14.0 [2]Median vergence facility [IQR] (cpm)9.75 [7]11.0 [4.5]Median accommodative amplitude [IQR] (D)8.4 [2.9]11.7 [1.6]

Demographic and clinical findings of concussed participants with and without vergence and/or accommodation deficits.

Median CISS score [IQR]Concussed with deficits (26)Concussed without deficits (8)Mann–Whitney U statisticp-valueTotal CISS Score31.50 [16.5]19.50 [5.5]470.022Normalized Median CISS-V Subscore1.33 [1.5]0.50 [0.67]35< 0.01Normalized Median CISS-P Subscore2.40 [1.15]1.50 [0.95]54.50.047Nomalized Median CISS-S Subscore2.14 [1.21]1.43 [0.93]610.084

Descriptive CISS-subscores data for concussed participants with and without vergence and/or accommodation deficits.

Total CISS score in concussed participants with and without vergence and/or accommodation deficits. Box plot comparing total CISS scores between concussed participants with vergence and/or accommodation deficits (Concussed with Deficits; blue) and concussed participants without vergence or accommodation deficits (Concussed Normal; purple). Individual data points are overlaid. Boxes represent the interquartile range, the red center lines show median values, and whiskers indicate the minimum and maximum scores.

Normalized CISS subscores in concussed participants with and without vergence and/or accommodation deficits. Box plots showing normalized CISS subscores for somatic (CISS-S), performance (CISS-P), and vision (CISS-V) symptoms in concussed participants with vergence and/or accommodation deficits (blue) compared with concussed participants without vergence and/or accommodation deficits (purple). Individual data points are displayed as semi-transparent circles. Boxes represent the interquartile range, red center lines indicate the median, and whiskers denote the minimum and maximum values.

Symptom severity in control and concussed groups

Symptom severity across the 15 CISS items revealed distinct differences in symptom reporting trends between control and concussed participants. In the control group, symptom