title: Test-Retest Intervisit Variability of Functional and Structural Parameters in X-Linked Retinoschisis.
abstract: OBJECTIVE
  To examine the variability of four outcome measures that could be used to address safety and efficacy in therapeutic trials with X-linked juvenile retinoschisis.
  
  
  METHODS
  Seven men with confirmed mutations in theRS1gene were evaluated over four visits spanning 6 months. Assessments included visual acuity, full-field electroretinograms (ERG), microperimetric macular sensitivity, and retinal thickness measured by optical coherence tomography (OCT). Eyes were separated into Better or Worse Eye groups based on acuity at baseline. Repeatability coefficients were calculated for each parameter and jackknife resampling used to derive 95% confidence intervals (CIs).
  
  
  RESULTS
  The threshold for statistically significant change in visual acuity ranged from three to eight letters. For ERG a-wave, an amplitude reduction greater than 56% would be considered significant. For other parameters, variabilities were lower in the Worse Eye group, likely a result of floor effects due to collapse of the schisis pockets and/or retinal atrophy. The criteria for significant change (Better/Worse Eye) for three important parameters were: ERG b/a-wave ratio (0.44/0.23), point wise sensitivity (10.4/7.0 dB), and central retinal thickness (31%/18%).
  
  
  CONCLUSIONS
  The 95% CI range for visual acuity, ERG, retinal sensitivity, and central retinal thickness relative to baseline are described for this cohort of participants with X-linked juvenile retinoschisis (XLRS).
  
  
  CONCLUSIONS
  A quantitative understanding of the variability of outcome measures is vital to establishing the safety and efficacy limits for therapeutic trials of XLRS patients.
authors.affiliation: National Eye Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Brett G
authors.initials: BG
authors.lastname: Jeffrey
authors.affiliation: National Eye Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Cukras
authors.affiliation: National Eye Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Susan
authors.initials: S
authors.lastname: Vitale
authors.affiliation: National Eye Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Amy
authors.initials: A
authors.lastname: Turriff
authors.affiliation: Current address: College of Optometry, University of Houston, TX ; National Eye Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Kristin
authors.initials: K
authors.lastname: Bowles
authors.affiliation: National Eye Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Sieving
keywords: MP1; OCT; XLRS; electroretinogram; retinoschisis