[High-dose medialis recession in latent nystagmus].

Background: Large muscle recessions reduce anomalous head turn (AHT) in infantile nystagmus syndrome (INS). Their quantitative effect to reduce AHT in fusion maldevelopment nystagmus syndrome (FMNS) is unknown.

Aim Of The Study: To evaluate the reduction of AHT by large medial rectus muscle recession in patients with FMNS.

Methods: We analyzed data of 12 patients with pure FMNS who received large medial rectus muscle recessions on the sound eye or only eye between 2014 and 2019. Medians and ranges (min-max) were: age at surgery 14 years (3-43 years); decimal BCVA sound eye/fellow eye 0.56 (0.4-1.0)/0.01 (0-0.4); AHT at 5 m/0.3 m fixation distance 35° (15-45°)/20° (0-45°); amount of recession 13 mm (11.5-15 mm); follow-up 13 (4-39) months.

Results: At the final visit, AHT at 5 m/0.3 m was 10° (0-20°/0-15°). The individual reduction of AHT at 5 m amounted to 25° (8-35°) without any overcorrection. The available visual field of functionally monocular patients increased correspondingly. Slight overcorrection at 0.3 m occurred in 2 cases. Adduction of the sound eye was limited to 25e-40°). BCVA and anomalous head posture in vertical and frontal planes did not improve.

Conclusion: Large medial rectus muscle recession on the sound eye improves AHT in FMNS by a similar amount compared to INS and the available visual field of functionally monocular patients.