title: Iris recognition as a biometric method after cataract surgery.
abstract: BACKGROUND
  Biometric methods are security technologies, which use human characteristics for personal identification. Iris recognition systems use iris textures as unique identifiers. This paper presents an analysis of the verification of iris identities after intra-ocular procedures, when individuals were enrolled before the surgery.
  
  
  METHODS
  Fifty-five eyes from fifty-five patients had their irises enrolled before a cataract surgery was performed. They had their irises verified three times before and three times after the procedure, and the Hamming (mathematical) distance of each identification trial was determined, in a controlled ideal biometric environment. The mathematical difference between the iris code before and after the surgery was also compared to a subjective evaluation of the iris anatomy alteration by an experienced surgeon.
  
  
  RESULTS
  A correlation between visible subjective iris texture alteration and mathematical difference was verified. We found only six cases in which the eye was no more recognizable, but these eyes were later reenrolled. The main anatomical changes that were found in the new impostor eyes are described.
  
  
  CONCLUSIONS
  Cataract surgeries change iris textures in such a way that iris recognition systems, which perform mathematical comparisons of textural biometric features, are able to detect these changes and sometimes even discard a pre-enrolled iris considering it an impostor. In our study, re-enrollment proved to be a feasible procedure.
authors.affiliation: Department of Ophthalmology, Federal University of Sao Paulo-Vision Institute, Sao Paulo, Brazil. rrtt@uol.com.br
authors.forename: Roberto
authors.initials: R
authors.lastname: Roizenblatt
authors.forename: Paulo
authors.initials: P
authors.lastname: Schor
authors.forename: Fabio
authors.initials: F
authors.lastname: Dante
authors.forename: Jaime
authors.initials: J
authors.lastname: Roizenblatt
authors.forename: Rubens
authors.initials: R
authors.lastname: Belfort
mesh_terms: D000465:Algorithms; D001699:Biometry / Q000379:methods*; D006801:Humans; D007498:Iris / Q000033:anatomy & histology* / Q000473:pathology; D010363:Pattern Recognition, Automated; D018918:Phacoemulsification; D015203:Reproducibility of Results; D012637:Security Measures