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R. W. Hertle, D. Yang, L. Reznick; Clinical and Electrophysiological Effects of Extraocular Muscle Surgery on Patients With Infantile Periodic Alternating Nystagmus Syndrome (IPANS). Invest. Ophthalmol. Vis. Sci. 2007;48(13):2838.
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The purpose of this report is to characterize, clinical and electrophysiological effects following extraocular muscle surgery in a series of patients with oculographically and clinically diagnosed IPANS.
This is a prospective, non-comparative, interventional case series of 27 patients with IPANS all of whom had surgery on previously unoperated extraocular muscles and were followed for a minimum of 6 months after surgery. The indications for surgery included an anomalous head posture, strabismus alone, strabismus plus an anomalous head posture, or the nystagmus alone. Outcome Measures Included: Pre- and Post-Operative Binocular Best Optically Corrected Acuity (BCA), Anomalous Head Posture (AHP), Null Zone/PAN Cycle Dynamics (NZD), Best Null Foveation Time (FOV) and INS waveform changes.
The most common associated ocular condition was albinism. Although the IPAN cycle was not eliminated there were favorable changes after surgery. Patients significantly (p < 0.05)improved in BCA, AHP, NZD and FOV. The INS Waveforms favorable improved especially during the NZD. BCA increased .1 LogMar to .3 LogMar in 24 of 27 patients. Effective strabismus alignment was also achieved postoperatively. There were some differences in outcome measures that were dependent on age, preoperative BCA, regularity of cycle and associated ocular conditions.
This study prvides further evidence that surgery on previously unoperated horizontal extraocular muscles in patients with INS waveforms favorably changes their nystagmus. The effect of surgery on the IPANS cycle and the eye oscillation is independent from mechanical repositioning of the eyes, head or eye muscles. The nystagmus changes that result from surgery on these patients improves acuity and may improve other visual functions.
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