Factors related to strabismus decompensation after a period of prolonged postoperative stability

PurposeTo identify factors associated with late decompensation of horizontal strabismus after a period of prolonged (>12 months) postoperative stability.MethodsCharts from all pediatric horizontal strabismus surgical cases from 1999 to 2009 were reviewed. Patients with a distance or near alignment of <10Δ at the first visit >12 months following surgery were included. The primary outcome was time from surgery to strabismus decompensation. Multiple variables were analyzed using the Cox proportional hazards model.ResultsA total of 185 cases were included. Mean age at surgery was 5.1 years and mean follow-up was 62.2 months. Late decompensation rate was 31%; of these, 54% underwent reoperation. Using two different models, a higher risk of decompensation was associated with both the presence of preoperative oblique dysfunction (P = 0.023/0.002) and larger distance/near deviations at the first >12 months postoperative visit (P = 0.033/0.012).ConclusionsWorsening of alignment >12 months after horizontal strabismus surgery occurs in almost one-third of patients. Preoperative oblique dysfunction is associated with long-term instability, possibly because it is a surrogate for sensory torsion and poor fusion. Additionally, larger distance and near deviations at >12 months after surgery were each associated with late decompensation. The rate of decompensation for patients with deviations of 0Δ to <4Δ was less than those with deviations of 4Δ to <8Δ and >8Δ, suggesting that the biologic behavior of all deviations within the monofixation range (0Δ to 8Δ) is not uniform.