# The Impact of the Test Dissociation on the Binocular Balance of Children

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## Abstract

**:**

## 1. Introduction

## 2. Methodology

- (i)
- Age 5.06 to 17.11;
- (ii)
- VA ≥ 0.3 logMar;
- (iii)
- No previous visual treatments;
- (iv)
- No symptoms of visual distress.

- Evaluation date: 12 June 2023;
- Birth date: 10 May 2016;
- Chronological age: 02-01-07 (rounded to 7 years, 1 month = 7.01).

#### 2.1. The Evaluation Followed Three Steps (One Step per Day)

**Step one:**detailed personal medical history of the patient and their family background.**Step two:**determine the best optical prescription under the cycloplegic effect of 1% tropicamide [15], and subjective refraction afterwards.**Step three:**evaluate the visual efficacy with the new prescription using the following motor and sensorial tests:- (1)
- Visual acuity at 40 cm and 3 m using Bailey–Lovely charts (logMar).
- (2)
- Stereopsis at 40 cm using the Random-Dot 2 test, which goes from 500 (gross) to 12.5 (fine) seconds of arc.
- (3)
- Howell test at 33 cm and 3 m using the Howell test phoria card and a six-base down prism in front of the right eye.
- (4)
- Alternate Cover Test using a translucid occluder: at near fixation (40 cm) using a 20/30 single letter on the Gulden fixation stick, and at a distance (3 m), by isolating a 20/30 letter on the distance visual acuity chart.
- (5)
- Thorington test at 40 cm and 3 m holding a Maddox rod (with its horizontal axis) in front of the right eye and the penlight against the back of the card.
- (6)
- Worth dot test at 33 cm and 3 m, respectively, to evaluate flat fusion and suppression.
- (7)
- Near point of convergence test (NPC) and its recovery, using an accommodative target (four repetitions in total), and its mean value was recorded as the final one.
- (8)
- Monocular, estimated method retinoscopy at 40 cm (MEM), using the appropriate card based on the age and grade level of the patient.

#### 2.2. Howell Test

#### 2.3. Alternate Cover Test

#### 2.4. Thorington Test

#### 2.5. Statistical Analysis

## 3. Results

#### 3.1. Descriptive Statistics and Analysis Based on Gender

#### 3.2. Comparison of the Magnitude of Phorias at Near and Distance, Measured through the Alternate Cover Test, Howell and Thorington Test

#### 3.3. Bland–Altman Plot to Analyze the Agreement between the Used Techniques

#### 3.4. Regression Analysis to Determine Variables That Could Predict the Degree of Stereopsis

#### 3.5. Statistical Analysis of the Stereopsis Degree, Phoria State and the Break of NPC Based on Age

#### 3.6. Statistical Analysis of the Stereopsis Degree and Phoria State Based on the Break Value of NPC

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Abbreviations

CT | Cover test |

CI | confidence interval |

EF | esophoria |

F | far |

H | Howell test |

N | near |

U | upper |

L | lower |

NPC | near point of convergence |

OD | oculus dexter |

OS | oculus sinister |

Std | standard deviation. |

TH | Thorington test |

t-value | t-value of Paired Samples t-test for XF |

VA | visual acuity |

XF | exophoria |

z-value | z-value of Wilcoxon Test for EFk |

p-value | p-value for parametric statistics |

p_$np$-value | $p\_np$-value for non-parametric statistics |

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**Figure 1.**Depicts the Bland–Altman plot for the degree of esophoria at far, measured using the Howell and Thorington techniques. The BLACK line represents the mean value (0.23), while the green and red lines show the upper (2.41) and lower (−1.95) 95% CI, respectively ($\pm 1.96$ standard deviations). Few outliers can be observed, whereas most data fit into $\pm 1.96$ standard deviations.

**Figure 2.**Depicts the correlation found between the stereopsis degree and the break of NPC, where ${\mathrm{R}}^{2}$ = 0.208. A decreasing trend on the stereopsis degree is observed when the NPC value increases. Therefore, worse stereopsis is expected in patients with higher NPC value.

**Figure 3.**Illustrates the correlation found between the stereopsis degree and the exophoria state at near measured using the Howell test, where ${\mathrm{R}}^{2}$ = 0.189. As the exophoria at near increases, the stereopsis decreases. Therefore, worse stereopsis is expected in patients with higher exophoria at near distances.

**Figure 4.**Represents the correlation state between the break and recovery of NPC, where ${\mathrm{R}}^{2}$ = 0.916. As is to be expected, participants with a high break of NPC present higher recovery value as well, being that their values are proportional to each other.

**Figure 5.**Shows the mean stereopsis degree as a dependent variable of the break value of NPC, where the third group (break of 11–25 cm) obtained the lowest value and the first one (break of 0–5 cm), the highest one. Statistically significant differences can be appreciated when the third group (11–25 cm) is compared to the first (0–5 cm) and second (6–10 cm). As expected, no differences were seen between the first (0–5 cm) and second group (6–10 cm), with values from 0–10 cm considered within normal limits.

**Figure 6.**Presents the exophoria state at near as a dependent variable of the break value of NPC, where the third group (break of 11–25 cm) obtained the highest value and the first one (break of 0–5 cm), the lowest one. Statistically significant differences can be appreciated when the third group (11–25 cm) is compared to the first (0–5 cm) and second (6–10 cm). No differences were found between the first (0–5 cm) and the second group (6–10 cm). These values were considered within normal limits.

**Table 1.**Descriptive statistics of the analyzed variables based on gender, where mean values, Std, and p-values are presented. The independent sample t-test was used for most of them except for the esophoria state, myopia, and astigmatism, where the analysis was performed using the Mann–Whitney test considering the small sample and the non-normal data distribution analyzed by the Shapiro–Wilk test.

Boys | Girls | p-Value | Total | |
---|---|---|---|---|

Variables | Mean ± Std | Mean ± Std | Mean ± Std | |

Age | 7.90 ± 2.03 | 8.90 ± 3.08 | 0.006 | 8.30 ± 2.48 |

VA OD F | 0.04 ± 0.07 | 0.04 ± 0.08 | 0.941 | 0.04 ± 0.07 |

VA OS F | 0.04 ± 0.08 | 0.03 ± 0.07 | 0.467 | 0.04 ± 0.07 |

VA OD N | 0.05 ± 0.07 | 0.06 ± 0.08 | 0.281 | 0.05 ± 0.08 |

VA OS N | 0.06 ± 0.09 | 0.05 ± 0.08 | 0.685 | 0.06 ± 0.09 |

Stereopsis | 32.36 ± 14.82 | 33.61 ± 16.39 | 0.565 | 32.86 ± 15.45 |

EF F CT/H/TH | 2.65±2.55 | 3.38 ± 3.07 | 0.135 | 2.95 ± 2.76 |

1.96 ± 1.64 | 2.13 ± 1.75 | 0.417 | 2.03 ± 1.64 | |

1.78 ± 1.23 | 1.88 ± 1.63 | 0.071 | 1.82 ± 1.37 | |

EF N CT/H/TH | 8.74 ± 4.11 | 9.25 ± 3.92 | 0.637 | 8.95 ± 3.99 |

5.75 ± 3.17 | 5.38 ± 3.03 | 0.740 | 5.60 ± 3.08 | |

7.09 ± 2.95 | 7.56 ± 2.78 | 0.407 | 7.28 ± 2.86 | |

XF F CT/H/TH | 2.11 ± 2.59 | 2.11 ± 2.62 | 0.523 | 2.11 ± 2.60 |

1.14 ± 1.47 | 1.01 ± 1.46 | 0.783 | 1.09 ± 1.46 | |

1.39 ± 1.44 | 1.26 ± 1.36 | 0.265 | 1.34 ± 1.41 | |

XF N CT/H/TH | 10.81 ± 5.04 | 10.79 ± 4.54 | 0.571 | 10.80 ± 4.80 |

5.76 ± 3.44 | 5.49 ± 3.34 | 0.926 | 5.60 ± 3.39 | |

8.50 ± 3.97 | 8.08 ± 3.65 | 0.741 | 8.34 ± 3.84 | |

Stereopsis | 32.36 ± 14.82 | 33.61 ± 16.4 | 0.557 | 32.86 ± 15.45 |

Myopia OD | −1.48 ± 0.96 | −2.56 ± 2.12 | 0.226 | −1.89 ± 1.56 |

Myopia OS | −1.52 ± 0.93 | −2.25 ± 1.76 | 0.378 | −1.80 ± 1.32 |

Hyperopia OD | 0.88 ± 0.43 | 1.39 ± 1.61 | 0.035 | 1.12 ± 1.17 |

Hyperopia OS | 0.84 ± 0.43 | 1.49 ± 1.77 | 0.017 | 1.15 ± 1.29 |

Astigmatism OD | −0.86 ± 1.44 | −1.45 ± 1.29 | 0.143 | −1.15 ± 1.39 |

Astigmatism OS | −0.98 ± 1.29 | −1.58 ± 1.41 | 0.204 | −1.29 ± 1.38 |

**Table 2.**(

**a**) Phoria tests comparison using the One-Way ANOVA for repeated measures for XF at far and near fixation, where the p-value reflects the differences between them. Confidence Intervals are presented for a better understanding of the relationship between the analyzed variables. (

**b**) Phoria tests comparison using the Wilcoxon signed-rank for EF at far and near fixation, where the z-value and p_$np$-value reflect the differences between them.

(a) | |||

Pairwise comparisons | |||

XF at Near | |||

95% Confidence Interval for Difference | |||

Tests compared | $\mathit{p}$-value | Lower Bound | Upper Bound |

Cover Test/Howell | <0.001 | 4.663 | 5.746 |

Cover Test/Thorington | <0.001 | 1.977 | 2.907 |

Thorington/Howell | <0.001 | 2.238 | 3.287 |

XF at Far | |||

Cover Test/Howell | <0.001 | 0.728 | 1.316 |

Cover Test/Thorington | <0.001 | 0.460 | 1.064 |

Thorington/Howell | 0.012 | 0.045 | 0.474 |

(b) | |||

Pairwise comparisons | |||

EF at Far | |||

Tests compared | $\mathit{z}$-value | p _$np$-value | |

Cover Test/Howell | 3.14 | 0.002 | |

Cover Test/Thorington | 3.88 | <0.001 | |

Thorington/Howell | −1.16 | 0.252 | |

EF at Near | |||

Cover Test/Howell | 5.55 | <0.001 | |

Cover Test/Thorington | 4.67 | <0.001 | |

Thorington/Howell | 4.76 | <0.001 |

**Table 3.**Predictive models for the degree of stereopsis for each phoria test used at near fixation and the break of NPC using the regression analysis. Standardized $beta$-value, F-value, p-value, adjusted R-square, R-value, t-value, and Confidence Intervals are presented for better understanding of the relationship between the analyzed variables.

STEREOPSIS | |||||||
---|---|---|---|---|---|---|---|

Standardized Beta-Value | $\mathit{t}$-Value | $\mathit{p}$-Value | $\mathit{R}$-Value | Adjusted $\mathit{R}$ Square | $\mathit{F}$-Value | 95% CI L–U | |

Break of NPC | 0.46 | 7.58 | <0.001 | 0.46 | 0.208 | 57.39 | 0.87–1.48 |

XF Near Cover Test | 0.39 | 5.87 | <0.001 | 0.40 | 0.159 | 34.95 | 0.85–1.7 |

XF Near Howell | 0.44 | 6.46 | <0.001 | 0.43 | 0.189 | 41.78 | 1.36–2.56 |

XF Near Thorington | 0.27 | 3.76 | <0.001 | 0.27 | 0.071 | 14.12 | 0.52–1.65 |

**Table 4.**Illustrates the mean value and Std for the stereopsis degree and the break of NPC based on age-groups. It depicts how age can affect the near point of convergence and the stereopsis level of our participants. The p and F-values are represented to show the differences among them and their statistical significance.

Group | Stereopsis Mean ± Std | Break Mean ± Std | Compared Groups | p-Value Stereo/Break | F-Value Stereo/Break | p-Value Stereo/Break | |
---|---|---|---|---|---|---|---|

1 | 40.49 ± 16.46 | 6.85 ± 6.84 | 1/2 | <0.001 | 0.040 | 11.63/4.99 | <0.001/0.008 |

2 | 29.57 ± 13.62 | 4.58 ± 5.39 | 1/3 | 0.002 | 0.912 | ||

3 | 30.57 ± 14.94 | 7.32 ± 5.55 | 2/3 | 0.919 | 0.021 |

**Table 5.**Illustrates the mean value and Std for the stereopsis degree, based on the break value. These results explain how the near point of convergence can impact the stereopsis level of our participants. The p and F-values are represented to show the differences among them and their statistical significance.

Group | Stereopsis Mean ± Std | Compared Groups | p-Value | F-Value | p-Value |
---|---|---|---|---|---|

1 | 28.59 ± 12.56 | 1/2 | 0.509 | 30.14 | <0.001 |

2 | 31.06 ± 12.31 | 1/3 | <0.001 | ||

3 | 47.29 ± 18.01 | 2/3 | <0.001 |

**Table 6.**Illustrates the mean value and Std for the exophoria state at far and neardistance, as a dependent variable of the break value of NPC. The obtained data show how the near point of convergence can relate to the amount of exophoria at near fixation. The p and F-values are represented to show the differences among them and their statistical significance.

Group | XF at Far Mean ± Std | XF at Near Mean ± Std | Compared Groups | p-Value XF F/N | F-Value XF F/N | p-Value XF F/N |
---|---|---|---|---|---|---|

1 | 1.71 ± 2.41 | 9.40 ± 4.38 | 1/2 | 0.989/0.618 | 7.99/20.68 | <0.001 |

2 | 1.66 ± 2.28 | 10.10 ± 3.88 | 1/3 | 0.001/<0.001 | ||

3 | 3.44 ± 2.89 | 14.50 ± 4.67 | 2/3 | 0.003/<0.001 |

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## Share and Cite

**MDPI and ACS Style**

Ibrahimi, D.; Aviles, M.; Rodríguez-Reséndiz, J.
The Impact of the Test Dissociation on the Binocular Balance of Children. *Clin. Pract.* **2023**, *13*, 977-993.
https://doi.org/10.3390/clinpract13040088

**AMA Style**

Ibrahimi D, Aviles M, Rodríguez-Reséndiz J.
The Impact of the Test Dissociation on the Binocular Balance of Children. *Clinics and Practice*. 2023; 13(4):977-993.
https://doi.org/10.3390/clinpract13040088

**Chicago/Turabian Style**

Ibrahimi, Danjela, Marcos Aviles, and Juvenal Rodríguez-Reséndiz.
2023. "The Impact of the Test Dissociation on the Binocular Balance of Children" *Clinics and Practice* 13, no. 4: 977-993.
https://doi.org/10.3390/clinpract13040088