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.

KEYWORDS:

• Infantile nystagmus syndrome
• eye movements
• diagnosis
• surgery
• foveation
• acuity

Acknowledgments

We are grateful to Dr L. Parker, who initially referred S2 to us in 1995 and again in 2008 and to Dr R. J. Leigh, who provided the magnetic search coil and assisted in recording the pre-Kestenbaum eye movements of S2. We also thank Dr R. A. Burnstine, who referred S3 to us in 2003 and performed the surgeries.

Dedications

This paper is dedicated to the memory of Martin Steinbach (31 October 1941–24 June 2017), whom I first met in 1967 when I gave a lecture on nystagmus waveforms and control-system modeling to an MIT graduate class of Professor Larry Young; Marty was a student in that class. Over the ensuing 50 years, we maintained a friendship punctuated by getting together at ARVO and other eye-movement meetings, including the 2007 festschrift held in my honor in Cleveland. In addition to his sharp mind and our common scientific interests, Marty was a kind and good friend; I and all who were fortunate enough to know him will miss him.

-L. F. Dell’Osso

I am honored to be part of this paper dedicated to the memory of Dr Steinbach. I got to know him during my PhD studies with Dr Dell’Osso, and had many exchanges with him at the ARVO conferences held in Fort Lauderdale. Back in 2008, Dr Steinbach generously helped me with my green card application. He was very understanding when I reached out to him to ask for his help, wrote for me whatever I needed, and kindly got back to me very quickly despite his busy schedule. Thanks to his help, my application went through smoothly. I am so sorry to hear about his passing. He will be missed by many good friends and colleagues whom he has generously helped over the years.

-Z. I. Wang

Additional information

Funding

This work was supported in part by the Office of Research and Development, Medical Research Service, Department of Veterans Affairs.