title: Retrospective study of recession of four horizontal rectus muscle in periodic alternating nystagmus.
abstract: OBJECTIVE
  Periodic alternating nystagmus (PAN) is a spontaneous horizontal nystagmus observed in disorders of the central nervous system. Patients with congenital PAN complain of oscillating vision at high rates. Medication is the first-choice treatment for PAN; however, clinicians still seek better therapy. The aim of this study was to evaluate outcomes of recession of four horizontal rectus muscle (R-FHR) in patients with congenital PAN.
  
  
  METHODS
  This study reports a retrospective case series of ten patients (seven males and three females; mean age 24.4±10.9) with congenital PAN who underwent R-FHR between 2007 and 2012, which was performed by the same surgeon at the Hyogo College of Medicine. Patients were evaluated for complications, recession amount, deviation angle, eye movements including a nystagmus amplitude, and visual acuity during pre- and post-operative periods.
  
  
  RESULTS
  Pre-operatively, patients complained of oscillating vision, abnormal head posture, esotropia, and congenital superior oblique palsy. Post-operatively, changes from the previous observations of nystagmus amplitudes and abnormal head posture demonstrated a complete reversal in all patients. In addition, visual acuity determined with a Snellen chart improved in two patients. However, esotropia occurred in three patients who underwent additional strabismus surgery 2 days after R-FHR. R-FHR was particularly effective in eight patients who pre-operatively had periodic oscillating vision with a regular pattern of periodic nystagmus.
  
  
  CONCLUSIONS
  We demonstrated that ten patients with congenital PAN had improved vision following R-FHR, indicating that R-FHR was an effective procedure, especially in patients suffering PAN with periodic oscillating vision.
authors.affiliation: Department of Ophthalmology, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Mimura
authors.affiliation: Department of Ophthalmology, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan ; Department of Neurosurgery and Brain Repair, University of South Florida, Tampa, FL, USA.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Ishikawa
authors.affiliation: Department of Ophthalmology, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Kimura
authors.affiliation: Department of Ophthalmology, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Kimura
authors.affiliation: Department of Neurosurgery and Brain Repair, University of South Florida, Tampa, FL, USA.
authors.forename: Cesar V
authors.initials: CV
authors.lastname: Borlongan
keywords: congenital nystagmus; electro-oculogram; null point nystagmus; ocular torticollis; oscillating vision; strabismus surgery