title: Spectral-domain optical coherence tomography measures of outer segment layer progression in patients with X-linked retinitis pigmentosa.
abstract: OBJECTIVE
  Determining the annual rate of change in the width of the inner segment ellipsoid zone (EZ; ie, inner/outer segment border) in the context of short-term variability should allow us to better understand the value of this measure for future treatment trials in X-linked retinitis pigmentosa (XLRP).
  
  
  OBJECTIVE
  To identify the width of the central region showing an EZ and to determine the short-term repeat variability and the annual rate of change in the width of the EZ from spectral-domain optical coherence tomography (SD-OCT) measures in RP.
  
  
  METHODS
  Patients with recessive or simplex RP (age range, 8-65 years; mean age, 40.5 years) underwent scanning twice on the same day to evaluate test-retest variability. Patients with XLRP (age range, 8-27 years; mean age, 15.2 years) from a larger group participating in an ongoing double-blind treatment trial (docosahexaenoic acid vs placebo; clinicaltrials.gov NCT00100230) underwent spectral-domain optical coherence tomography line scanning across the horizontal meridian at 3 yearly intervals.
  
  
  METHODS
  Research center specializing in medical retina.
  
  
  METHODS
  Forty-eight patients with RP, including 20 with recessive or simplex RP and 28 with XLRP, and 23 healthy control subjects.
  
  
  METHODS
  Widths of the EZ calculated and compared among the 3 annual visits.
  
  
  RESULTS
  Test-retest differences were normally distributed, and the magnitude of the difference was independent of mean EZ width. The mean (SD) for test-retest differences in EZ width was 0.08° (0.22°) (range, -0.30° to 0.60°). Thus, 95% of all test-retest differences fall within ± 0.43° (124 μm). Of the 28 patients with XLRP, 27 showed a significant decrease in EZ width after 2 years. Patients with XLRP showed a mean annual decrease in EZ width of 0.86° (248 μm, or 7%).
  
  
  CONCLUSIONS
  The mean rate of decline in EZ width (7%) translates into a mean rate of change of 13% for the equivalent area of functioning retina. This rate of change is consistent with that reported for visual fields and full-field electroretinograms. Unlike visual fields and electroretinograms, however, the repeat variability is less than the annual rate of change. These results support the validity of EZ width as an outcome measure in prospective clinical trials in RP.
authors.affiliation: Retina Foundation of the Southwest, Dallas, Texas2Department of Ophthalmology, The University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: David G
authors.initials: DG
authors.lastname: Birch
authors.forename: Kirsten G
authors.initials: KG
authors.lastname: Locke
authors.forename: Yuquan
authors.initials: Y
authors.lastname: Wen
authors.forename: Kelly I
authors.initials: KI
authors.lastname: Locke
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Hoffman
authors.forename: Donald C
authors.initials: DC
authors.lastname: Hood
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D018450:Disease Progression; D004281:Docosahexaenoic Acids / Q000627:therapeutic use; D004311:Double-Blind Method; D004596:Electroretinography; D005260:Female; D040181:Genetic Diseases, X-Linked / Q000175:diagnosis* / Q000188:drug therapy / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D055211:Retinal Photoreceptor Cell Inner Segment / Q000473:pathology*; D055214:Retinal Photoreceptor Cell Outer Segment / Q000473:pathology*; D012174:Retinitis Pigmentosa / Q000175:diagnosis* / Q000188:drug therapy / Q000235:genetics; D041623:Tomography, Optical Coherence; D058609:Visual Field Tests; D014794:Visual Fields; D055815:Young Adult
chemical_list: D004281:Docosahexaenoic Acids