Longitudinal Studies and Eye-Movement-Based Treatments of Infantile Nystagmus Syndrome: Estimated and Measured Therapeutic Improvements in Three Complex Cases.

ABSTRACT

INTRODUCTION AND PURPOSE: To demonstrate the utility of using eye-movement data to reveal the diagnostic characteristics of infantile nystagmus syndrome (INS), determine treatment, and both estimate and document therapeutic improvements in three patients with well-developed foveation periods, fairly broad, lateral gaze "nulls," head turns, strabismus, and complex, multiplanar nystagmus. PATIENTS AND METHODS: Infrared reflection, magnetic search coil, and high-speed digital video systems were used to record the eye movements of INS patients, pre- and post-Kestenbaum null-point correction surgery (horizontal or vertical). Data were analyzed and estimations made, using the eXpanded Nystagmus Acuity Function (NAFX) that is part of the OMtools toolbox for MATLAB. RESULTS: In all three subjects (S1-S3), both peak NAFX and longest foveation domain (LFD) improved from their pre-Kestenbaum values. S1 0.700-0.745 (6.4%) and 25-34° (36%), respectively. S2 0.445-0.633 (42.4%) and >40° to >50° (10%), respectively. S3 0.250-0.300 (20%) and 13° to ≫18° (see text), respectively. CONCLUSIONS: S1 Even at the high ends of the pre-therapy NAFX and LFD spectra, INS foveation (and therefore, visual-function) improvements may be adequate to justify nystagmus surgery and provide clinical improvements beneficial to the patient. S2 INS foveation improvements in the vertical plane are equal to those originally estimated using the horizontal data in prior patients. S3 Two apparent NAFX peaks can be converted into a very broad peak by surgery based on the preferred lower peak.