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

To identify factors associated with late decompensation of horizontal strabismus after a period of prolonged (>12 months) postoperative stability.

Charts from all pediatric horizontal strabismus surgical cases from 1999 to 2009 were reviewed. Patients with a distance or near alignment of <10(Δ) 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.

A 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).

Worsening 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 0(Δ) to <4(Δ) was less than those with deviations of 4(Δ) to <8(Δ) and >8(Δ), suggesting that the biologic behavior of all deviations within the monofixation range (0(Δ) to 8(Δ)) is not uniform.