title: A Novel Method for Quantitative Serial Autofluorescence Analysis in Retinitis Pigmentosa Using Image Characteristics.
abstract: OBJECTIVE
  Identifying potential biomarkers for disease progression in retinitis pigmentosa (RP) is highly relevant now that gene therapy and other treatments are in clinical trial. Here we report a novel technique for analysis of short-wavelength autofluorescence (AF) imaging to quantify defined regions of AF in RP patients.
  
  
  METHODS
  Fifty-five-degree AF images were acquired from 12 participants with RP over a 12-month period. Of these, five were identified as having a hyperfluorescent annulus. A standard Cartesian coordinate system was superimposed on images with the fovea as the origin and eight bisecting lines traversing the center at 45 degrees to each other. Spatial extraction software was programmed to highlight pixels corresponding to varying degrees of percentile fluorescence such that the parafoveal AF ring was mapped. Distance between the fovea and midpoint of the AF ring was measured. Percentage of low luminance areas was utilized as a measure of atrophy.
  
  
  RESULTS
  The hyperfluorescent ring was most accurately mapped using the 70th percentile of fluorescence. Both the AF ring and peripheral hypofluorescence showed robust repeatability at all time points noted (P= 0.93).
  
  
  CONCLUSIONS
  Both a hypofluorescent ring and retinal pigment epithelium atrophy were present on a significant proportion of RP patients and were consistently mapped over a 12-month period. There is potential extrapolation of this methodology to wide-field imaging as well as other retinal dystrophies. This anatomical change may provide a useful anatomical biomarker for assessing treatment end points in RP.
  
  
  CONCLUSIONS
  Spatial extraction software can be a valuable tool in the assessment of ophthalmic imaging data.
authors.affiliation: Nuffield Department of Clinical Neurosciences, Oxford Biomedical Research Centre, University of Oxford, Oxford, UK ; Oxford Eye Hospital, John Radcliffe Hospital, Oxford, UK ; Moorfields Eye Hospital-UCL Institute of Ophthalmology NIHR Biomedical Research Centre, London, UK.
authors.forename: Jasleen K
authors.initials: JK
authors.lastname: Jolly
authors.affiliation: Nuffield Department of Clinical Neurosciences, Oxford Biomedical Research Centre, University of Oxford, Oxford, UK ; Oxford Eye Hospital, John Radcliffe Hospital, Oxford, UK ; Moorfields Eye Hospital-UCL Institute of Ophthalmology NIHR Biomedical Research Centre, London, UK.
authors.forename: Siegfried K
authors.initials: SK
authors.lastname: Wagner
authors.affiliation: LightPear, Oxfordshire, UK.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Moules
authors.affiliation: University Hospital Eye Clinic, Stuttgart, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Gekeler
authors.affiliation: Moorfields Eye Hospital-UCL Institute of Ophthalmology NIHR Biomedical Research Centre, London, UK.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Webster
authors.affiliation: Nuffield Department of Clinical Neurosciences, Oxford Biomedical Research Centre, University of Oxford, Oxford, UK ; Oxford Eye Hospital, John Radcliffe Hospital, Oxford, UK.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Downes
authors.affiliation: Nuffield Department of Clinical Neurosciences, Oxford Biomedical Research Centre, University of Oxford, Oxford, UK ; Oxford Eye Hospital, John Radcliffe Hospital, Oxford, UK ; Moorfields Eye Hospital-UCL Institute of Ophthalmology NIHR Biomedical Research Centre, London, UK.
authors.forename: Robert E
authors.initials: RE
authors.lastname: MacLaren
keywords: autofluorescence; quantification; retinal degeneration; retinitis pigmentosa