Abstract
Purpose:
To evaluate the time course of improvements in clinical convergence measures for children with symptomatic convergence insufficiency treated with office-based vergence/accommodative therapy.
Methods:
We evaluated convergence measures from 205, 9- to 14-year-old children with symptomatic convergence insufficiency randomised to office-based vergence/accommodative therapy in the Convergence Insufficiency Treatment Trial - Attention and Reading Trial (CITT-ART). Near point of convergence (NPC) and near positive fusional vergence (PFV) were measured at baseline and after 4, 8, 12 and 16 weeks of therapy; mean change in NPC and PFV between these time points were compared using repeated measures analysis of variance. Rates of change in NPC and PFV from: 1) baseline to 4 weeks and 2) 4 to 16 weeks were calculated. For each time point, the proportion of participants to first meet the normal criterion for NPC (<6 cm), PFV blur (break if no blur; >15Δ and >2 times the exodeviation) and convergence composite (NPC and PFV both normal) were calculated.
Results:
The greatest change in NPC and PFV (7.6cm and 12.7Δ) and the fastest rate of improvement in NPC and PFV (1.9 cm/week and 3.2 Δ/week, respectively) were both found during the first four weeks of therapy, with both slowing over the subsequent 12 weeks. After 12 weeks of therapy, the NPC, PFV and convergence composite were normal in 93.2%, 91.7% and 87.8% of participants, respectively, and normalised with another four weeks of therapy in 4.4%, 2.0% and 4.4% of participants, respectively.
Conclusion:
Although the greatest improvements in NPC and PFV occurred in the first four weeks of therapy, most participants had weekly improvements over the subsequent 12 weeks of treatment. While most children with convergence insufficiency obtained normal convergence following 12 weeks of therapy, an additional four weeks of vergence/accommodative therapy may be beneficial for some participants.
Keywords: convergence insufficiency, near point of convergence, positive fusional vergence, treatment kinetics, vergence/accommodative therapy
Introduction
Near point of convergence (NPC) and positive fusional vergence at near (PFV) are the primary clinical convergence measures used to diagnose and monitor treatment for patients with convergence insufficiency.1–3 In fact, treatment success is often determined based on improvement or normalisation of these two clinical measures.4–10 In randomised clinical trials, NPC and PFV have been shown to normalise in at least 70% of children with symptomatic convergence insufficiency at the completion of office-based vision therapy.5, 10, 11 A more detailed understanding of the time course of improved convergence function is helpful when discussing estimated treatment duration with families, in determining if a patient is making the expected progress in therapy and when deciding to discontinue therapy.
The changes in NPC and PFV at 4-week time intervals for the 12-week office-based vergence-accommodative therapy (hereafter called vergence/accommodative therapy) programme prescribed in the randomised Convergence Insufficiency Treatment Trial (CITT) have been reported.12 In the more recent 16-week Convergence Insufficiency Treatment Trial - Attention and Reading Trial (CITT-ART),5, 13 we found that office-based vergence-accommodative therapy resulted in statistically significant greater improvements in NPC and PFV compared with office-based placebo therapy;14 these were similar to our findings in the CITT trial. However, the time course of improvement and the rate of change in improvement of NPC and PFV in the CITT-ART has not been reported.
The objective of this report is to describe the time course of improvements in NPC and PFV for school-age children with symptomatic convergence insufficiency over the course of 16 weeks of vergence/accommodative therapy in the CITT-ART study.5, 13 We report the improvement in NPC and PFV at each 4-week interval, the rate of change over the course of therapy and the time frame for achieving threshold “normal” measures of NPC, PFV and convergence composite.
Participants and Methods
The study was conducted at 9 clinical centres in the United States and the tenets of the Declaration of Helsinki were followed throughout the study. The institutional review boards of all participating sites approved the protocol and the Health Insurance Portability and Accountability Act (HIPAA) authorization-compliant consent and assent forms. A parent or guardian of each child gave written informed consent and each child gave written assent to participate in the study. An independent data and safety monitoring committee reviewed efficacy, safety and study progress throughout the trial. The study is registered at clinicaltrials.gov (CITT-ART: NCT02207517). The study design and methods15 and primary results13, 14 have been reported previously.
Participant Selection
The data reported herein are from the 205 children, aged 9 to 14 years, with symptomatic convergence insufficiency in the CITT-ART trial who were randomly assigned to vergence/accommodative therapy and completed their 16-week primary outcome visit.14 206 children were randomized to vergence/accommodative therapy, but one subject did not complete any visits beyond enrollment; data from the remaining 205 participants were used for analysis for this manuscript. Symptomatic convergence insufficiency was defined as a near exodeviation at least 4 prism dioptres (Δ) larger than the distance deviation measured by the prism and alternate cover test, a receded NPC (break ≥ 6 cm), insufficient PFV at near (either failing Sheard’s criterion16 [PFV blur (break if no blur) less than twice the near phoria] or PFV break ≤15Δ)15 and a score ≥16 on the Convergence Insufficiency Symptom Survey (CISS).17, 18 Best-corrected distance and near visual acuity were 6/6.6 (logMAR 0.04) or better in each eye. Refractive correction was required for spherical equivalent cycloplegic refractive errors of > 0.75 D of myopia, > 2.00 D of hyperopia, > 1.00 D of astigmatism or > 0.75 D of anisometropia. A complete list of inclusion/exclusion criteria have been previously published.15
Treatment Protocol
Participants attended weekly 1-hour sessions of in-office vergence/accommodative therapy, with home therapy procedures prescribed 15 minutes per day, 5 days per week for 16 weeks. The vergence/accommodative therapy regimen has been described in detail.15 Standardised sensorimotor evaluations were conducted by certified examiners masked to participant treatment assignment after 4, 8, 12 and 16 weeks of therapy (hereafter called the 4-, 8- and 12-week examinations and the 16-week outcome visit); NPC and PFV were measured at each of the 4-week follow-up visits.15
Outcome Measures – NPC and Near PFV
Participants wore their optical correction (if prescribed) while viewing a vertical line of 6/9 letters at eye level in the participant’s midsagittal plane at 40 cm (Printed Gulden fixation target for the Accommodative Rule or Gulden Fixation Stick #15302, Gulden Ophthalmics, guldenophthalmics.com) for NPC and near PFV measures. Three measures for NPC and PFV were obtained and the means calculated.
Near Point of Convergence
NPC break was measured with an Accommodative Convergence Rule (Gulden 1510, guldenophthalmics.com) with the edge of the rule placed on the forehead above the centre of the participant’s nasion (bridge of the nose). Participants were instructed to keep the letters single as long as possible while the target was moved at a speed of 1–2 cm/second towards the participant’s eyes. The NPC measure was the distance in centimetres (measured to the nearest half centimetre) from the participant’s nasion to the point of sustained diplopia (or loss of fusion was observed by the examiner).
Positive Fusional Vergence at Near
Participants were instructed to keep the letters clear and single for as long as possible, but to report when the letters became blurred or double. The examiner placed a horizontal prism bar before one eye and slowly (approximately 2Δ/second) introduced increasing magnitudes of base-out prism, starting at 1Δ, while pausing at each prism increment to confirm the letters remained “single and clear.” The prism magnitudes where sustained blur, diplopia (or the examiner observed loss of fusion), and recovery of fusion occurred were recorded as the blur, break, and recovery values, respectively.
Statistical Methods
NPC break (cm) and PFV blur (if present, otherwise break; Δ) were the outcomes of interest. A repeated measures analysis of covariance (ANCOVA) model, with a random effect for site, was used for analysis. Each model contained an indicator of study visit, the baseline value of the variable of interest and an interaction term. A significant interaction between study visit and baseline value (P <0.0001) was found for both NPC and PFV (i.e., changes in outcome between visits were dependent on the baseline value). To show the range of outcomes for different baseline values of NPC and PFV, adjusted means at each time point are provided for the group mean, as well as the 25th and 75th percentiles.
The mean square error estimate from the analysis was used to construct 95% confidence intervals (CI). The adjusted mean change and 95% CI for NPC and PFV at each 4-week timepoint (baseline and 4-, 8-, 12- and 16-weeks) and between each consecutive timepoint (baseline to 4 weeks, 4 to 8 weeks, 8 to 12 weeks and 12 to 16 weeks) were calculated. A positive value indicates improvement (i.e., decrease in NPC; increase in PFV). The Sidak method19 was used to control for multiple comparisons.
Kinetics, or the rate of change over time, for the NPC and PFV were calculated using the formula Average kinetics over time t = change in species A (i.e. change in NPC)/change in time. Because the improvement in NPC and PFV was greatest in the first 4 weeks of treatment (Figures 1 and 2), we used the two time intervals of baseline to week 4 and from week 4 to week 16 to calculate the treatment kinetics.
Figure 1:
Mean near point of convergence (NPC) break (cm) using baseline NPC of 8cm (25th percentile), 13.8 cm (mean) and 18cm (75th percentile).
Figure 2:
Positive fusional vergence (PFV) blur (if no blur, break) using baseline PFV of 9Δ (25th percentile), 12Δ (mean) and 14Δ (75th percentile)
The proportion of participants first meeting the pre-determined criterion for normal measures of NPC (<6 cm), PFV at near (>15Δ blur, or break if no blur and passing Sheard’s criteria) and convergence composite (normal NPC and PFV) were calculated for each 4-week time point. All analyses were completed using SAS Version 9.4 (sas.com), assuming an alpha level of 0.05.
After study completion, the Coordinating Center discovered 6 ineligible participants who were enrolled and randomized. In all cases, the participant failed only the eligibility criteria based on positive fusional vergence (i.e. ineligible participants). Sensitivity analysis was performed excluding these participants. The exclusions had negligible impact on the findings reported herein.
Results
Baseline Characteristics
Mean age ± standard deviation (SD) for the 205 participants was 10.8 ± 1.5 years; 59.5% were female (n = 122). The mean NPC and PFV blur (break, if no blur) was 13.8 ± 7.9 cm and 11.6 ± 4.3Δ, respectively. Other baseline demographic and clinical characteristics are shown in Table 1.
Table 1:
Baseline clinical and demographic characteristics.
| Mean (SD) | |
|---|---|
| Convergence Insufficiency Symptom Survey score | 29.1 (8.6) |
| Exodeviation - distance (Δ) | −2.1 (2.9) |
| Exodeviation - near (Δ) | −10.0 (4.1) |
| Near Point of Convergence break (cm) | 14.0 (8.0) |
| Positive Fusional Vergence (blur; break if no blur) (Δ) | 11.6 (4.3) |
| Age (years) | 10.8 (1.5) |
| Females (%) | 119 (59.5%) |
| Hispanic or Latino ethnicity (%) | 75 (37.5%) |
| Race (%) | |
| Black or African American | 50 (25.0%) |
| White | 123 (61.5%) |
| Other | 27 (13.5%) |
| Attention Deficit Hyperactivity Disorder (parental report) (%) | 36 (18.0%) |
SD = standard deviation; Δ = prism dioptre; cm = centimetre
Changes in Near Point of Convergence
Changes in NPC were evaluated adjusting for baseline NPC values of 8.3 cm (25th percentile), 13.8 cm (mean) and 17.2 cm (75th percentile). Using the mean baseline value (13.8 cm), NPC improved by 7.6 cm from baseline to week 4, with smaller improvements in the subsequent 4-week periods (Table 2). The improvement at week 4 was greatest when the 75th percentile (17.2 cm) was used as the baseline NPC and smallest using the 25th percentile (8.3cm) baseline NPC; however, the three mean NPC measures were similar at each of the 8-, 12- and 16-week examinations regardless of the initial baseline NPC value (Table 2, Figure 1). The mean improvement over the first four weeks of therapy (baseline to four weeks) was significantly greater compared with the second four weeks of therapy (4 to 8 weeks) for all three adjusted baseline NPC values (Table 3). The mean improvement over the second four weeks of therapy (4 to 8 weeks) was significantly different from the third four-week interval (8 to 12 weeks) for the mean and 75th percentile adjusted baseline NPC values (Table 3). The mean improvement for the remaining time period comparisons (i.e., 4 to 8 weeks compared with 8 to 12 weeks for the 25th percentile baseline NPC; 8 to 12 weeks compared with 12 to 16 weeks for all three adjusted baseline NPC measures) were not significantly different (Table 3).
Table 2:
Mean and 95% confidence interval (CI) for each outcome measure, by study visit and baseline measure
| Measure | Study visit | Using Baseline NPC of | ||
|---|---|---|---|---|
| 8.3 cm† (25%) |
13.8 cm‡ (mean) |
17.2 cm§ (75%) |
||
| Near Point of Convergence (cm)¶ | Baseline | 8.3 (7.7 to 8.9) |
13.7 (13.2 to 14.2) |
17.1 (16.5 to 17.7) |
| Week 4 | 5.4 (4.7 to 6.0) |
6.1 (5.6 to 6.6) |
6.5 (6.0 to 7.1) |
|
| Change from Baseline to Week 4 | 2.9 (2.1 to 3.7) |
7.6 (7.0 to 8.3) |
10.6 (9.9 to 11.2) |
|
| Week 8 | 4.4 (3.8 to 5.1) |
4.7 (4.2 to 5.2) |
4.9 (4.3 to 5.4) |
|
| Change from Week 4 to Week 8 | 1.0 (0.2 to 1.7) |
1.4 (0.8 to 2.0) |
1.7 (1.0 to 2.4) |
|
| Week 12 | 4.1 (3.5 to 4.8) |
4.6 (4.1 to 5.1) |
4.9 (4.3 to 5.5) |
|
| Change from Week 8 to Week 12 | 0.3 (−0.5 to 1.1) |
0.09 (−0.6 to 0.7) |
−0.03 (−0.7 to 0.7) |
|
| Week 16 | 3.5 (2.9 to 4.2) |
3.8 (3.3 to 4.4) |
4.0 (3.5 to 4.6) |
|
| Change from Week 12 to Week 16 | 0.6 (−0.2 to 1.4) |
0.8 (0.1 to 1.4) |
0.9 (0.2 to 1.6) |
|
| Measure | Study visit | Using Baseline PFV of | ||
| 8.7Δ†
(25%) |
11.6Δ‡ (mean) |
14Δ§ (75%) |
||
| Positive Fusional Vergence (Δ)€ | Baseline | 8.7 (7.0 to 10.3) |
11.6 (10.2 to 13.0) |
14.0 (12.4 to 15.6) |
| Week 4 | 22.7 (21.0 to 24.4) |
24.3 (22.9 to 25.7) |
25.6 (24.0 to 27.2) |
|
| Change from Baseline to Week 4 | 14.0 (12.2 to 15.9) |
12.7 (11.2 to 14.3) |
11.6 (9.9 to 13.4) |
|
| Week 8 | 29.4 (27.7 to 31.0) |
30.5 ((29.1 to 31.9) |
31.4 (29.8 to 33.0) |
|
| Change from Week 4 to Week 8 | 6.7 (4.8 to 8.5) |
6.2 (4.6 to 7.7) |
5.8 (4.0 to 7.6) |
|
| Week 12 | 31.7 (30.0 to 33.3) |
32.6 (31.2 to 34.0) |
33.3 ((31.8 to 34.9) |
|
| Change from Week 8 to Week 12 | 2.3 (0.4 to 4.1) |
2.1 (0.6 to 3.6) |
1.9 (0.2 to 3.7) |
|
| Week 16 | 34.4 (32.8 to 36.1) |
34.4 (33.0 to 35.8) |
34.4 (32.8 to 36.1) |
|
| Change from Week 12 to Week 16 | 2.8 (0.9 to 4.6) |
1.9 (0.3 to 3.4) |
1.1 (−0.7 to 2.9) |
|
25th percentile of baseline distribution
The mean of baseline distribution
75th percentile of baseline distribution
Means adjusted for NPC break (cm) at baseline and interaction between baseline value and study visit
Means adjusted for PFV blur (or /break if no blur) (Δ) at baseline and interaction between baseline value and study visit
Δ = prism dioptres
Table 3:
Difference (95% CI) and p-value comparing mean change in near point of convergence (NPC) and positive fusional vergence (PFV) between successive time periods.
| Near point of convergence, break (cm) | ||||||
|---|---|---|---|---|---|---|
| Comparison | Baseline NPC | Baseline NPC | Baseline NPC | |||
| 8.3 cm† | p-value | 13.8 cm‡ | p-value | 17.2 cm§ | p-value | |
| First 4 weeks vs 4 to 8 weeks |
1.9 (0.6 to 3.3) |
0.005 | 6.2 (5.1 to 7.3) |
<0.001 | 8.9 (7.7 to 10.1) |
<0.001 |
| 4 to 8 weeks vs 8 to 12 weeks |
0.7 (−0.7 to 2.0) |
0.31 | 1.3 (0.2 to 2.4) |
0.018 | 1.7 (0.5 to 2.9) |
0.005 |
| 8 to 12 weeks vs 12 to 16 weeks |
−0.3 (−1.7 to 1.0) |
0.58 | −0.7 (−1.8 to 0.4) |
0.21 | −0.9 (−2.1 to 0.3) |
0.14 |
| Positive fusional vergence, blur or break if no blur (Δ) | ||||||
| Comparison | Baseline PFV | Baseline PFV | Baseline PFV | |||
| 8.7 Δ† | p-value* | 11.6 Δ‡ | p-value* | 14 Δ§ | p-value* | |
| First 4 weeks vs 4 to 8 weeks |
7.4 (4.1 to 10.6) |
<0.001 | 6.5 (3.9 to 9.2) |
<0.001 | 5.9 (2.8 to 8.9) |
<0.001 |
| 4 to 8 weeks vs 8 to 12 weeks |
4.4 (1.2 to 7.6) |
0.008 | 4.1 (1.4 to 6.7) |
0.003 | 3.8 (0.7 to 6.9) |
0.016 |
| 8 to 12 weeks vs 12 to 16 weeks |
−0.5 (−3.7 to 2.7) |
0.77 | 0.2 (−2.4 to 2.9) |
0.86 | 0.9 (−2.2 to 4.0) |
0.59 |
25th percentile of baseline distribution
Mean of baseline distribution
75th percentile of baseline distribution
p-value comparing mean difference to zero
Δ = prism dioptres, cm = centimetres, vs= versus
The rate of change of NPC over time (i.e., treatment kinetics) was calculated for the first four weeks of therapy (baseline through week 4) and for the subsequent 12-week time frame (between weeks 4 and 16). Using the baseline mean of 13.8 cm, NPC improved at an average rate of 1.9 cm per week (95% CI: 1.7 to 2.1) over the first four weeks of therapy, and then slowed to 0.2 cm per week (95% CI: 0.1 to 0.2) over the subsequent 12 weeks. Compared with using the mean (13.8 cm) baseline values, the rate of improvement over the first four weeks was much slower using the 25th percentile (8.3cm) baseline NPC value (0.7 cm/week, 95% CI: 0.5 to 0.9) and faster using the 75th percentile (17.2 cm) baseline value (2.6 cm/week, 95% CI: 2.5 to 2.8). Between weeks 4–16, the rate of improvement in NPC was similar regardless of the baseline NPC value used (Table 4).
Table 4:
Treatment Kinetics – Change in Near Point of Convergence (NPC) and Positive Fusional Vergence (PFV) per week for first four weeks and for the subsequent 12 weeks of vergence-accommodative therapy.
| Time period | Baseline NPC of 8.3 cm† | Baseline NPC of 13.8 cm‡ | Baseline NPC of 17.2 cm§ | |||
|---|---|---|---|---|---|---|
| Mean | 95% CI | Mean | 95% CI | Mean | 95% CI | |
| Near point of convergence, break (cm) | ||||||
| Baseline to Week 4 | 0.7 | 0.5 to 0.9 | 1.9 | 1.7 to 2.1 | 2.6 | 2.5 to 2.8 |
| Week 4 to Week 16 | 0.2 | 0.1 to 0.2 | 0.2 | 0.1 to 0.2 | 0.2 | 0.1 to 0.3 |
| Time period | Baseline PFV of 8.7 Δ† | Baseline PFV of 11.6 Δ‡ | Baseline PFV of 14 Δ§ | |||
| Mean | 95% CI | Mean | 95% CI | Mean | 95% CI | |
| Positive fusional vergence, blur or break if no blur (Δ) | ||||||
| Baseline to Week 4 | 3.5 | 3.0 to 4.0 | 3.2 | 2.8 to 3.6 | 2.9 | 2.5 to 3.3 |
| Week 4 to Week 16 | 1.0 | 0.8 to 1.1 | 0.8 | 0.7 to 1.0 | 0.7 | 0.6 to 0.9 |
25th percentile of baseline distribution
Mean of baseline distribution
75th percentile of baseline distribution
Δ = prism dioptres, cm = centimetres
In total, 97.6% (200 of 205) of participants achieved a normal NPC at or before the end of the 16-week treatment programme (Figure 3). After the first four weeks of therapy, 65.9% (135 of 205) of participants had a normal NPC, with an additional 19% (39 of 205), 8.3% (17 of 205) and 4.4% (9 of 205) first demonstrating a normal NPC after 8, 12 and 16 weeks, respectively. Of the 14 participants who never demonstrated a normal NPC in the first 12 weeks of therapy, nine (64.3%) had a normal NPC after the final four weeks of therapy.
Figure 3:
Percentages of participants who had normal values for near point of convergence (NPC < 6cm), positive fusional vergence (PFV >15Δ blur and passing Sheard’s Criteria), and normal convergence composite (normal NPC and PFV) at each time point during the study.
Changes in Near Positive Fusional Vergence
Changes in PFV were evaluated using the mean (11.6 Δ), the 25th percentile (8.7 Δ), and the 75th percentile (14.0 Δ) of the baseline distribution. The greatest mean improvement in PFV occurred between baseline and four weeks. Using the group mean baseline value of 11.6Δ, mean improvement for the first four weeks of therapy was 12.7Δ (95% CI: 11.2 to 14.3). Improvement was slightly greater (14.0Δ; 95% CI: 12.1 to 15.9) using the 25th percentile mean PFV (8.7Δ) and slightly smaller (11.6Δ; 95% CI: 9.8 to 13.4) using the 75th percentile mean PFV of 14Δ (Table 2). Regardless of the baseline PFV value used, when compared with the first four weeks of therapy, smaller improvements were found between weeks 4 to 8, weeks 8 to 12 and weeks 12 to 16 (Table 2). In comparing the mean improvements in PFV between successive times periods, the difference between successive time periods up to week 12 (i.e., change from baseline to four weeks compared to 4 to 8 weeks, and 4 to 8 weeks compared with 8 to 12 weeks) were all significantly different regardless of the baseline value used. Mean PFV changes from weeks 8 to 12 to weeks 12 to 16 were not significantly different for any of the three baseline PFV values (Table 3).
The rate of change over time (i.e., treatment kinetics) was calculated for: 1) baseline to week 4 and 2) weeks 4 to 16 (Table 4). Using the group mean of 11.6Δ, the mean improvement in PFV was 3.2Δ per week (95% CI: 2.8 to 3.6) during the first four weeks of therapy, which then slowed to a mean rate of improvement of 0.8Δ per week (95% CI: 0.7 to 1.0) for the subsequent 12-week period. Similar rates of change in PFV were found using the 25th (3.5Δ/week) and 75th (2.9Δ/week) percentile baseline means. The rate of improvement was similar for the remaining 12-week period of therapy for all three baseline PFV values (Table 4).
Of the 205 participants, 192 (93.7%) had a normal PFV by the end of the 16-week therapy programme. After four weeks, PFV was in the normal range for 142 (69.3%), with an additional 34 (16.6%), 12 (5.9%) and 4 (2.0%) individuals first demonstrating a normal PFV after 8, 12 and 16 weeks, respectively. Of the 17 participants who had not achieved a normal PFV after 12 weeks, four (23.5%) had attained a normal PFV by the 16-week outcome visit.
Convergence Composite Criterion Success
At the end of the 16-week therapy programme, 189 of 205 participants (92.2%) met the convergence composite criterion for success (both a normal NPC and normal PFV). This criterion was met at the 4-week exam by 105 (51.2%) participants, at the 8-week exam by 51 (24.9%) participants, at 12-weeks by 24 (11.7%) participants and at the 16-week outcome exam by 9 (4.4%) participants (Figure 3).
Sensitivity Analysis
All analyses reported herein were repeated after excluding the 6 participants found to be ineligible after completion of the CITT-ART study. The estimated change per week in near point of convergence increased by 0.1 cm/week when the group mean and 75th percentile values were used as baseline means. No changes were observed in the reported kinetics estimates for near positive fusional vergence. Negligible effects were observed on the percentage with normal findings for near point of convergence and near positive fusional vergence; the same was true for percentage successful based on the convergence composite criterion.
Discussion
We evaluated the time course of improvements in NPC and PFV in children with symptomatic convergence insufficiency treated with a 16-week vergence/accommodative therapy programme. For both clinical measures, the majority of improvement occurred and the rate of change was fastest during the first four weeks of therapy. Nonetheless, meaningful gains continued in both NPC and PFV throughout the subsequent 12 weeks of therapy. Approximately two thirds of participants achieved normal NPC after four weeks of therapy; the same was observed for PFV. However, only 51.2% of participants had both a normal NPC and normal PFV at four weeks, which subsequently increased to 92.2% at 16 weeks.
Our analysis showed a significant interaction between changes in outcome at each study visit and the baseline value (i.e., between-visit changes were dependent on the baseline value) for both the NPC and PFV, and thus our analyses were adjusted for the mean baseline value and both the 25th and 75th percentile values of these measures. This approach allowed us to evaluate the influence of the baseline measure on the change at each time point. Interestingly, regardless of baseline adjustment, the NPC measures were very similar at week 4 and virtually the same by week 8. A similar trend was observed for PFV. Thus, regardless of the child’s baseline NPC or PFV measure, the largest improvements occurred over the first eight weeks of therapy, with similar mean measures present at eight weeks.
The findings from the present CITT-ART trial are comparable to those from our prior CITT study10 (Figure 4). The mean NPC and PFV measures are quite similar at all time points, with the largest improvements having occurred in the first four weeks of therapy and continued smaller gains over the subsequent weeks of therapy. These results should be predictive of what would occur, on average, for a child with convergence insufficiency treated with a vergence-accommodative therapy protocol similar to that implemented in our trials.5, 10 The time course of improvements in convergence measures can be used to estimate the expected treatment duration and to monitor therapy progress. These findings suggest that it would be prudent to evaluate a child’s progress after four weeks of therapy (given a programme like the one used in the present study). Little or no improvement in the NPC and/or PFV should prompt one to investigate possible reasons for lack of progress, such as an incorrect diagnosis or poor adherence with prescribed home therapy.
Figure 4:
Comparison of the mean near point of convergence (NPC) in cm in the Convergence Insufficiency Treatment Trial (CITT) and the Convergence Insufficiency Treatment Trial - Attention and Reading Trial (CITT-ART) trial.
The vergence/accommodative therapy regimen in the present CITT-ART study was four weeks longer than the therapy programme prescribed in our previous CITT trial.10 Although neither trial was designed to determine the ideal duration of treatment, we can compare the 12-week results to the 16-week results found in the CITT-ART trial to determine if the additional four weeks of therapy appear to be beneficial. The data show that while most participants had minimal improvements in NPC and PFV between weeks 12 and 16, the additional four weeks of therapy resulted in normal clinical findings for two-thirds of the participants who still had a reduced NPC and for nearly 25% of those who still had reduced PFV at 12 weeks. This suggests that if a patient does not have normal convergence measures after 12 weeks of therapy, an additional four weeks may be of value.
In addition to the large sample size, particular strengths of this study are that the outcome measures were collected prospectively in a standardised manner by eye care professionals trained and certified for the study protocol who were masked to participant treatment assignment. It should be noted that our results are limited to children 9 to 14 years of age with convergence insufficiency. Although similar changes to NPC and PFV were found in the prior CITT trial of children 9 – 17 years of age,12 these results may not be generalisable to adult patients or children younger than nine years of age with convergence insufficiency. Furthermore, the expected improvements in NPC and PFV only apply for children undergoing an office-based accommodative-vergence therapy programme similar to the one implemented in our trial.15 This therapy programme was designed specifically for uncomplicated cases of convergence insufficiency, although 56% of participants in the CITT-ART trial had a coexisting accommodative dysfunction.20 Other than simple accommodative therapy procedures, we did not include management of coexisting visual dysfunctions or visual information processing deficits, which if present, would likely extend the expected duration of treatment and the time frame for normalisation of NPC and near PFV. Some might consider it a limitation that the present analyses only address the time course of improvements in NPC and PFV and not that of symptoms. While symptoms are usually the reason that affected individuals seek treatment, the initial normalization of NPC and PFV do not necessarily correspond with the abatement of symptoms as shown in our previous CITT trial; only 30% of participants in the office-based vergence and accommodative therapy group were asymptomatic at 8 weeks while 68% had normal NPC and 70% normal PFV.12 Thus, it was not the intent of this paper on convergence measures to include analyses for changes in symptoms.
Conclusions
In 9–14 year old children with symptomatic convergence insufficiency, the largest magnitude and the fastest rate of improvements in NPC and PFV occur during the first four weeks of vergence/accommodative therapy. While both NPC and PFV normalised after four weeks of therapy in half of the participants, there were continued smaller and slower incremental gains in both clinical measures throughout the subsequent 12 weeks of treatment, with some participants still making significant improvements and only attaining normal convergence function between 12 and 16 weeks of therapy. These findings highlight the importance of monitoring therapy progress by measuring NPC and PFV after four weeks of therapy, and can also be used to inform clinical practice estimates of therapy duration.
Figure 5:
Comparison of the mean positive fusional vergence (PFV) in Δ (pd) in the Convergence Insufficiency Treatment Trial (CITT) and the Convergence Insufficiency Treatment Trial - Attention and Reading Trial (CITT-ART) trial.
Key Points.
The greatest overall improvement in near point of convergence and positive fusional vergence occurred in the first four weeks of vergence/accommodative therapy in children with convergence insufficiency
The rate of improvement in near point of convergence and positive fusional vergence occurred in the first four weeks of vergence/accommodative therapy in children with convergence insufficiency
A majority of children had obtained a normal near point of convergence and near positive fusional vergence following 12 weeks of therapy, but an additional four weeks of therapy allowed a small percentage of participants to achieve normal convergence clinical findings
Funding/Support:
This work was supported by National Eye Institute of National Institutes of Health, Department of Health and Human Services (grant number 5U10EY022599 to MMS, 5U10EY022601 to GLM, 5U10EY022595 to SC, 5U10EY022592 to MK, 5U10EY022586 to ES, 5U10EY022600 to RH, 5U10EY022587 to MG, 5U10EY022596 to RC, 5U10EY022594 to KH, and 5U10EY022591 to ST). The funding organization had no role in the design or conduct of this research. Meeting presentation: This manuscript was presented in part at the American Academy of Optometry Annual Meeting (November 2019 in Orlando, FL).
The Convergence Insufficiency Treatment Trial – Attention & Reading Trial Investigator Group Clinical Sites
Sites are listed in order of the number of participants enrolled in the study, with the number enrolled listed in parentheses preceded by the clinical site name and location. Personnel are listed as (PI) for principal investigator, (SC) for coordinator, (ME-ART) for masked examiner or attention and reading testing, (ME-VIS) for masked examiner for visual function testing, (VT) for vision therapist, and (UnM) for unmasked examiners for baseline testing.
Study Centre: SUNY College of Optometry (45)
Jeffrey Cooper, MS, OD (PI 06/14 – 04/15); Erica Schulman, OD (PI 04/15 - present); Kimberly Hamian, OD (ME-VIS); Danielle Iacono, OD (ME-VIS); Steven Larson, OD (ME-ART); Valerie Leung, Boptom (SC); Sara Meeder, BA (SC); Elaine Ramos, OD (ME-VIS); Steven Ritter, OD (VT); Audra Steiner, OD (ME-VIS); Alexandria Stormann, RPA-C (SC); Marilyn Vricella, OD (UnM); Xiaoying Zhu, OD (ME-VIS). Study Centre: Bascom Palmer Eye Institute (44) Susanna Tamkins, OD (PI); Naomi Aguilera, OD (VT); Elliot Brafman, OD (ME-VIS); Hilda Capo, MD (ME-VIS); Kara Cavuoto, MD (ME-VIS); Isaura Crespo, BS (SC); Monica Dowling, PhD (ME-ART); Kristie Draskovic, OD (ME-VIS); Miriam Farag, OD (VT); Vicky Fischer, OD (VT); Sara Grace, MD (ME-VIS); Ailen Gutierrez, BA (SC); Carolina Manchola-Orozco, BA (SC); Maria Martinez, BS (SC); Craig McKeown, MD (UnM); Carla Osigian, MD (ME-VIS); Tuyet-Suong Pham, OD (VT); Leslie Small, OD (ME-VIS); Natalie Townsend, OD (ME-VIS).
Study Centre: Pennsylvania College of Optometry (43)
Michael Gallaway, OD (PI); Mark Boas, OD, MS (VT); Christine Calvert, Med (ME-ART); Tara Franz, OD (ME-VIS); Amanda Gerrouge, OD (ME-VIS); Donna Hayden, MS (MEART); Erin Jenewein, OD,MS (VT); Zachary Margolies, MSW, LSW (ME-ART); Shivakhaami Meiyeppen, OD (ME-VIS); Jenny Myung, OD (ME-VIS); Karen Pollack, (SC), Mitchell Scheiman, OD, PhD (ME-VIS); Ruth Shoge, OD (ME-VIS); Andrew Tang, OD (ME-VIS); Noah Tannen, OD (ME-VIS); Lynn Trieu, OD, MS (VT); Luis Trujillo, OD (VT)
Study Centre - The Ohio State University College of Optometry (40)
Marjean Kulp, OD, MS (PI); Michelle Buckland, OD, MS (ME-VIS); Allison Ellis, BS, MEd (ME-ART); Jennifer Fogt, OD, MS (ME-VIS); Catherine McDaniel, OD, MS (ME-VIS); Taylor McGann, OD (ME-VIS); Ann Morrison, OD, MS (ME-VIS); Shane Mulvihill, OD, MS (VT); Adam Peiffer, OD, MS (ME-VIS); Maureen Plaumann, OD (ME-VIS); Gil Pierce, OD, PhD (ME-VIS); Julie Preston, OD, PhD, MEd (ME-ART); Kathleen Reuter, OD (VT); Nancy Stevens, MS, RD, LD (SC); Jake Teeny, MA (ME-ART); Andrew Toole, OD, PhD (VT); Douglas Widmer, OD, MS (ME-VIS); Aaron Zimmerman, OD, MS (ME-VIS)
Study Centre: Southern California College of Optometry (38)
Susan Cotter, OD, MS (PI); Carmen Barnhardt, OD, MS (VT); Eric Borsting, OD, MSEd (ME-ART); Angela Chen, OD, MS (VT); Raymond Chu, OD, MS (ME-VIS); Kristine Huang, OD, MPH (ME-VIS); Susan Parker (SC); Dashaini Retnasothie (UnM); Judith Wu (SC) Study Center: Akron Childrens Hospital (34) Richard Hertle, MD (PI); Penny Clark (ME-ART); Kelly Culp, RN (SC); Kathy Fraley CMA/ASN (ME-ART); Drusilla Grant, OD (VT); Nancy Hanna, MD (UnM); Stephanie Knox (SC); William Lawhon, MD (ME-VIS); Lan Li, OD (VT); Sarah Mitcheff (ME-ART); Isabel Ricker, BSN (SC); Tawna Roberts, OD (VT); Casandra Solis, OD (VT); Palak Wall, MD (ME-VIS), Samantha Zaczyk, OD (VT)
Study Centre: UAB School of Optometry (32)
Kristine Hopkins, OD (PI 12/14 - present); Wendy Marsh-Tootle, OD, MS (PI 06/14 – 2/14); Michelle Bowen, BA (SC); Terri Call, OD (ME-VIS); Kristy Domnanovich, PhD (ME-ART); Marcela Frazier, OD MPH (ME-VIS); Nicole Guyette, OD, MS (ME-ART); Oakley Hayes, OD, MS (VT); John Houser, PhD (ME-ART); Sarah Lee, OD, MS (VT); Jenifer Montejo, BS (SC); Tamara Oechslin, OD, MS (VT); Christian Spain (SC); Candace Turner, OD (MEART); Katherine Weise, OD, MBA (ME-VIS)
Study Centre: NOVA Southeastern University (31)
Rachel Coulter, OD (PI); Deborah Amster, OD (MEVIS); Annette Bade, OD, MCVR (SC); Surbhi Bansal, OD (ME-VIS); Laura Falco, OD (ME-VIS); Gregory Fecho, OD (VT); Katherine Green, OD (ME-VIS); Gabriela Irizarry, BA (ME-ART); Jasleen Jhajj, OD (VT); Nicole Patterson, OD, MS (ME-ART); Jacqueline Rodena, OD (ME-VIS); Yin Tea, OD (VT); Julie Tyler, OD (SC); Dana Weiss, MS (ME-ART); Lauren Zakaib, MS (ME-ART)
Study Centre: Advanced Vision Care (15)
Ingryd Lorenzana, OD (PI); Yesena Meza (ME-VIS); Ryan Mann (ME-ART); Mariana Quezada, OD (VT); Scott Rein, BS (ME-ART); Indre Rudaitis, OD (ME-VIS); Susan Stepleton, OD (ME-VIS); Beata Wajs (VT)
National Eye Institute, Bethesda, MD
Maryann Redford, DDS, MPH
CITT-ART Executive Committee
Mitchell Scheiman, OD, PhD; G. Lynn Mitchell, MAS; Susan Cotter, OD, MS; Richard Hertle, MD; Marjean Kulp, OD, MS; Maryann Redford, DDS, MPH; Carolyn Denton, PhD; Eugene Arnold, MD; Eric Borsting, OD, MSEd; Christopher Chase, PhD
CITT-ART Reading Centre
Carolyn Denton, PhD (PI); Sharyl Wee (SC); Katlynn Dahl-Leonard (SC); Kenneth Powers (Research Assistant); Amber Alaniz (Research Assistant)
Data and Safety Monitoring Committee
Marie Diener-West, PhD, Chair; William V. Good, MD; David Grisham, OD, MS, FAAO; Christopher J. Kratochvil, MD; Dennis Revicki, PhD; Jeanne Wanzek, PhD
CITT-ART-Study Chair
Mitchell Scheiman, OD, PhD (study chair); Karen Pollack (study coordinator); Susan Cotter, OD, MS; (vice chair); Marjean Kulp, OD, MS (vice chair)
CITT-ART Data Coordinating Centre
G Lynn Mitchell, MAS (PI); Mustafa Abraham (Student worker); Julianne Dangelo, BS (Program Assistant); Jordan Hegedus (Student worker); Ian Jones (Student worker); Lisa A Jones-Jordan, PhD (Epidemiologist); Alexander Junglas (Student worker); Jihyun Lee (Programmer); Jadin Nettles (Student worker); Curtis Mitchell (Student worker); Mawada Osman (Student worker); Gloria Scott-Tibbs, BA (Project Coordinator); Loraine Sinnott, PhD (Biostatistician); Chloe Teasley (Student worker); Victor Vang (Student worker); Robin Varghese (Student worker).
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