Predictive factors of stereopsis outcomes following strabismus surgery

Demographic and clinical characteristics and risk factors of stereoacuity in convergence insufficiency-type intermittent exotropia

Purpose

To investigate characteristics and risk factors of poor stereoacuity of Convergence insufficiency-type Intermittent Exotropia (CI-type X(T)).

Design

Observational, cross-sectional study.

Methods

The medical records of 615 CI-type X(T) and 222 basic-type intermittent exotropia (X(T)) were enrolled from January 2018 to January 2022. The characteristics were compared between the two types, and the associations between clinical factors and poor stereoacuity were examined using logistic regression.

Results

Compared with basic-type X(T), earlier surgery age, shorter misalignment duration, and the smaller distance exodeviation were observed in CI-type X(T). The CI-type X(T) demonstrated better sensory status and lower incidence of ocular muscle dysfunction than did the basic-type X(T). The surgery age between 6 and 12 years (odds ratio [OR], 0.595; compared with ≤6 years) was inversely associated with poor near stereoacuity, whereas duration more than 4 years (OR, 2.474), amblyopia (OR, 4.057), large distance exodeviation (>60PD: OR, 2.462) and anisometropia (>2.00D: OR, 3.874) were positively associated with poor near stereoacuity. The onset age older than 6 years (6-9 years: OR, 0.397; >9 years: OR, 0.317) was associated with better distance stereoacuity, whereas large distance exodeviation (>60PD: OR, 23.513), and dominant eye best corrected visual acuity (BCVA) worsen than 0.20 (OR, 2.987) were positively associated with poor distance stereoacuity.

Conclusion

CI-type X(T) declined surgery early, with small distance exodeviation, better sensory status, and low incidence of ocular muscle dysfunction. A strong dose-dependent link between early onset age, long misalignment duration, worse dominant eye BCVA, distance exodeviation, amblyopia, anisometropia, and poor stereoacuity was confirmed.

Factors Determining Improvement in Stereopsis and Binocularity After Good Postoperative Alignment in Patients With Childhood-Onset Strabismus

Introduction: The purpose of the present study was to determine the factors that affect the outcome of strabismus surgery in terms of improvement in stereopsis and binocularity.

Methods: Data were collected prospectively from patients with childhood-onset, concomitant, constant strabismus greater than 30 prism diopters (PD) with postoperative alignment within 10 PD. Pre- and postoperative stereopsis and binocularity testing were performed using the Titmus fly test, random dot test, Bagolini striated glass test, and Worth four dot test at one, four, and 12 weeks postoperatively.

Results: A total of 73 patients (55% males and 45% females) who underwent surgery at our center were studied. The mean age at the time of surgery was 16 ± 7.7 years (range: 5-35 years). We found that factors such as age of strabismus onset, type of deviation, and amblyopia had a statistically significant influence on the postoperative surgical outcome. A statistically insignificant relationship was noted with gender, refractive error, and duration of strabismus. Patients who had strabismus after six months of age noticed a significant improvement in stereopsis (p-value = 0.000) than those who had strabismus before six months of age (p-value = 0.660). Further, there was a statistically significant improvement in patients having exotropia (p-value = 0.018) or combined horizontal and vertical deviations (p-value = 0.000), but there was no significant improvement in patients with esotropia (p-value = 0.180). Moreover, non-amblyopes had a significantly better postoperative stereopsis than amblyopes (p-value = 0.006). Although there was no association between preoperative deviation and improvement in stereopsis (p-value = 0.081), patients having preoperative deviation in the range of 31-45 PD had a statistically significant improvement in stereopsis (p-value = 0.000). There was no significant difference between postoperative residual deviation and final stereopsis (p-value > 0.05). All the results were the same for both the Titmus test and the random dot test. Binocular fusion was observed in 34 subjects, and uniocular suppression was noted in 38 subjects preoperatively. It was observed that only one patient gained binocular single vision postoperatively.

Conclusion: The presence of amblyopia, esotropia, early onset of strabismus (within six months of age), and a larger preoperative deviation (>45 PD) were associated with poorer stereopsis. In patients with horizontal strabismus, the coexistence of vertical deviation had a positive impact on the postoperative stereopsis. Gender, refractive error, and duration of strabismus did not influence the final stereopsis in our study.