title: An objective scatter index based on double-pass retinal images of a point source to classify cataracts.
abstract: OBJECTIVE
  To propose a new objective scatter index (OSI) based in the analysis of double-pass images of a point source to rank and classify cataract patients. This classification scheme is compared with a current subjective system.
  
  
  METHODS
  We selected a population including a group of normal young eyes as control and patients diagnosed with cataract (grades NO2, NO3 and NO4) according to the Lens Opacities Classification System (LOCS III). For each eye, we recorded double-pass retinal images of a point source. In each patient, we determined an objective scatter index (OSI) as the ratio of the intensity at an eccentric location in the image and the central part. This index provides information on the relevant forward scatter affecting vision. Since the double-pass retinal images are affected by both ocular aberrations and intraocular scattering, an analysis was performed to show the ranges of contributions of aberrations to the OSI.
  
  
  RESULTS
  We used the OSI values to classify each eye according to the degree of scatter. The young normal eyes of the control group had OSI values below 1, while the OSI for subjects in LOCS grade II were around 1 to 2. The use of the objective index showed some of the weakness of subjective classification schemes. In particular, several subjects initially classified independently as grade NO2 or NO3 had similar OSI values, and in some cases even higher than subjects classified as grade NO4. A new classification scheme based in OSI is proposed.
  
  
  CONCLUSIONS
  We introduced an objective index based in the analysis of double-pass retinal images to classify cataract patients. The method is robust and fully based in objective measurements; i.e., not depending on subjective decisions. This procedure could be used in combination with standard current methods to improve cataract patient surgery scheduling.
authors.affiliation: Laboratorio de Óptica, Universidad de Murcia, Murcia, Spain. pablo@um.es
authors.forename: Pablo
authors.initials: P
authors.lastname: Artal
authors.forename: Antonio
authors.initials: A
authors.lastname: Benito
authors.forename: Guillermo M
authors.initials: GM
authors.lastname: Pérez
authors.forename: Encarna
authors.initials: E
authors.lastname: Alcón
authors.forename: Alvaro
authors.initials: A
authors.lastname: De Casas
authors.forename: Jaume
authors.initials: J
authors.lastname: Pujol
authors.forename: José M
authors.initials: JM
authors.lastname: Marín
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001071:Appointments and Schedules; D002386:Cataract / Q000145:classification* / Q000175:diagnosis; D002387:Cataract Extraction / Q000379:methods; D003952:Diagnostic Imaging / Q000379:methods; D006305:Health Status Indicators; D006801:Humans; D008027:Light; D008954:Models, Biological; D011859:Radiography; D012160:Retina / Q000000981:diagnostic imaging*; D012542:Scattering, Radiation; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult