title: The differential effect of ultraviolet light exposure on cataract rate across regions of the lens.
abstract: OBJECTIVE
  In studies of cortical cataract, a severity score representing the area covered by cataract is often used as the primary outcome. However, additional disease information may exist in the spatial distribution of opacities. Further, it has been hypothesized that the lower nasal region of the lens is the most susceptible to damage by environmental ultraviolet light exposure.
  
  
  METHODS
  In a sample of 107 lens images from the Salisbury Eye Evaluation Study, a digital cortical cataract grading algorithm was used to capture the location of opacities in binary images. These images were used to estimate the severity of cataract in 16 regions around the lens. The effect of individual cumulative lifetime ocular exposure to ultraviolet B light on cortical cataract risk for each lens region was examined, as estimated by using an empiric model and baseline occupation and leisure activities data, in a linear mixed-effects model.
  
  
  RESULTS
  The lower nasal regions had the highest cortical cataract severity in both the right and left eyes. In the combined data, region 9 (the lower nasal corner of the lens) was estimated to have the highest severity. In an assessment of the high- and low-exposure ultraviolet light groups (dichotomized at the median exposure level), higher exposure had the most effect in the lower regions of the lens.
  
  
  CONCLUSIONS
  These results indicate that there are regional lens differences in the association between cataract and exposure to ultraviolet light but that ultraviolet light may not entirely explain the variations in cortical cataract severity across the lens.
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA. aabraham@jhsph.edu
authors.forename: Alison G
authors.initials: AG
authors.lastname: Abraham
authors.forename: Christopher
authors.initials: C
authors.lastname: Cox
authors.forename: Sheila
authors.initials: S
authors.lastname: West
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002386:Cataract / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007908:Lens, Crystalline / Q000528:radiation effects*; D008297:Male; D008396:Maryland / Q000453:epidemiology; D009790:Occupations; D011832:Radiation Injuries / Q000175:diagnosis / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D014466:Ultraviolet Rays