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Alaska Blind Child Discovery

A cooperative, charitable research project to vision screen every preschool Alaskan

Amblyopia due to Nystagmus

Nystagmus is a pattern of relatively rapid, involuntary, to-and-fro movement of the eyes. Since the fixation of the eyes is not perfectly steady, nystagmus usually is associated with a decrease in visual acuity. Two common forms of nystagmus are Infantile Nystagmus Syndrome (INS- formerly called "Congenital Nystagmus") and Fusion Maldevelopment Nystagmus Syndrome (FMDS- formerly called "Sensory Nystagmus"). Nystagmus experts have laboratories that can define types of nystagmus using special video cameras and electronic monitoring contact lenses. Infants and children with nystagmus with diminished visual acuity may have a form of amblyopia (deficient brain learning of vision) that potentially could and should be improved with strabismus surgery.  
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Fusion Maldevelopment (Latent/Manifest Latent) Nystagmus Syndrome: Effects of Four-Muscle Tenotomy and Reattachment
Louis F. Dell’Osso, PhD; Faruk H. Orge, MD; Jonathan B. Jacobs, PhD; Zhong I. Wang, PhD

Journal of Pediatric Ophthalmology and Strabismus
May/June 2014 - Volume 51 · Issue 3: 180-188

To examine the waveform and clinical effects of the four-muscle tenotomy and reattachment procedure in fusion maldevelopment nystagmus syndrome (FMNS) and to compare them to those documented in infantile nystagmus syndrome (INS) and acquired nystagmus.

Both infrared reflection and high-speed digital video systems were used to record the eye movements in a patient with FMNS (before and after tenotomy and reattachment). Data were analyzed using the eXpanded Nystagmus Acuity Function (NAFX) that is part of the OMtools software. Model simulations and predictions were performed using the authors’ behavioral ocular motor system model in MATLAB Simulink (The MathWorks, Inc., Natick, MA).

The model predicted, and the patient’s data confirmed, that the tenotomy and reattachment procedure produces improvements in FMN waveforms across a broader field of gaze and decreases the Alexander’s law variation. The patient’s tenotomy and reattachment plots of NAFX after surgery versus gaze angle were higher and had lower slope than before surgery. Clinically, despite moderate improvements in both peak measured acuity and stereoacuity, dramatic improvements in the patient’s abilities and lifestyle resulted.

The four-muscle tenotomy and reattachment nystagmus surgery produced beneficial therapeutic effects on FMN waveforms that are similar to those demonstrated in INS and acquired nystagmus. These results support the authors’ prior recommendation that tenotomy and reattachment nystagmus should be added to required strabismus procedures in patients who also have FMNS (ie, perform tenotomy and reattachment on all unoperated muscles in the plane of the nystagmus). Furthermore, when strabismus surgery is not required, four-muscle tenotomy and reattachment may be used to improve FMN waveforms and visual function.

[J Pediatr Ophthalmol Strabismus 2014;51(3):180–188.]

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