• PURPOSE
    • To determine the frequency of strabismus among children initially diagnosed with pseudostrabismus using big data.
  • DESIGN
    • Population-based retrospective cohort study.
  • METHODS
    • Setting: Population-based retrospective cohort study using claims data. StudyPopulation: 17,885 children diagnosed with pseudostrabismus at age ≤3 years who were later diagnosed with strabismus using the Optum deidentified Clinformatics Data Mart Database (2003-2016). We excluded patients diagnosed with strabismus before the diagnosis of pseudostrabismus or diagnosed simultaneously with strabismus and pseudostrabismus.
  • OBSERVATIONS
    • We assessed age, refractive error, and presence of amblyopia. Patients with pseudostrabismus were compared to a group of patients from the Optum data set diagnosed with esotropia, exotropia, and unspecified heterotropia who had not been previously diagnosed with pseudostrabismus. MainOutcomeMeasures: Incidence of strabismus, among patients initially diagnosed with pseudostrabismus vs those without an initial diagnosis of pseudostrabismus.
  • RESULTS
    • Strabismus was diagnosed in 9.6% (n = 1,725) of children initially diagnosed with pseudostrabismus at a median age of 1.65 years (IQR: 1.17-2.46) compared to 1.7% (136,047 of 7,787,743) of children in the control group (P < .001). Strabismus was diagnosed more than a year later in the pseudostrabismus group (3.32 years; IQR: 2.28-4.74) compared with the control group (2.28 years, IQR: 1.43-3.16) (P < .001). Esotropia was the most common type of strabismus in both groups (pseudostrabismus, 69.7%; control, 62.1%). A total of 377 children (21.9%) in the pseudostrabismus group underwent strabismus surgery compared with 12.1% of children in the control group (P < .001).
  • CONCLUSIONS
    • Young children diagnosed with pseudostrabismus are at increased risk of developing strabismus and undergoing strabismus surgery.