Management of Strabismus Associated With Infantile Nystagmus Syndrome: A Novel Classification to Assist in Surgical Planning.

PURPOSE: There is no consensus on the surgical management of head position associated with infantile nystagmus syndrome (INS) when strabismus coexists, and few outcome data have been published. We propose classifying strabismus into concordant or discordant based on the relationship between head positioning and strabismus and then modifying surgery accordingly. Our objective is to describe this system and to review surgical outcomes.

DESIGN: Retrospective observational case series.

METHODS: Twenty-eight patients with INS and coexisting horizontal strabismus underwent surgery for horizontal head positioning and had ≥2 months of follow-up from 1995-2018 at the Vanderbilt Eye Institute. Outcome variables included head positioning (minimal, ≤10°; mild, 11-30°; moderate 31-44°; and severe ≥45°), strabismus (range 0-70 prism diopters [PDs]; minimal ≤10 PD), and reoperation rates. Nonparametric Wilcoxon signed rank, Fisher exact, and Mann-Whitney U tests were used for statistical analysis.

RESULTS: Twenty-one cases were concordant and 7 were discordant; the mean follow-up was 4.1 years. Ninety-six percent of patients had moderate to severe head positioning at baseline. Correction rates (to minimal) were 100% at 2-5 months postoperatively and 86% at last follow-up (P < .0001 at both time points compared with preoperatively). The magnitude of strabismus decreased compared with preoperative strabismus (30.8 ± 10.8 PDs; n = 28), strabismus at 2-5 months (9.1 ± 11.9 PDs; P = .0001; n = 26), and last follow-up (12.0 ± 14.1 PDs; P = .0003; n = 28). The overall reoperation rate was 32%.

CONCLUSIONS: Our classification system in patients with INS allows a systematic way to surgically improve head positioning and strabismus in cases of moderate to severe baseline head positioning.