title: Effect of cataract on frequency doubling perimetry in the screening mode.
abstract: OBJECTIVE
  To determine the effect of cataract on frequency doubling perimetry in the screening mode.
  
  
  METHODS
  Frequency doubling technology perimetry in the C-20-5 screening mode was performed prospectively on 34 patients with otherwise healthy eyes before and after phacoemulsification. Cataracts were scored using the LOCS III classification, and the number of missed points (at any level of severity) on the screening field was compared before and after surgery.
  
  
  RESULTS
  Nine patients missed at least one point pre-operatively and had no misses post-operatively. Those patients with posterior subcapsular (PSC) cataract were significantly more likely to miss points on the screening frequency doubling technology perimetry than those without posterior subcapsular cataracts (P < 0.001; Fisher exact test). In addition, the degree of posterior subcapsular cataract strongly correlated with the number of missed points pre-operatively (r = 0.97). The degree of nuclear sclerotic cataract did not correlate strongly with the number of missed points (r = 0.26), but the correlation was slightly stronger in the presence of cortical cataract (r = 0.36).
  
  
  CONCLUSIONS
  Advanced age-related cataracts may cause false positive results on the screening frequency doubling technology, and the presence of even mild posterior subcapsular cataract may be a cause of false positive results and should be taken into consideration when interpreting the screening frequency doubling technology perimetry results.
authors.affiliation: Stoke Mandeville Ophthalmology Department, Stoke Mandeville Hospital, Mandeville Road, Ayelsbury, Buckinghamshire, UK. robertcasson@bigpond.com
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Casson
authors.forename: Bruce
authors.initials: B
authors.lastname: James
mesh_terms: D000368:Aged; D002386:Cataract / Q000150:complications*; D005189:False Positive Reactions; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D008297:Male; D018918:Phacoemulsification; D011237:Predictive Value of Tests; D011446:Prospective Studies; D014786:Vision Disorders / Q000175:diagnosis*; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields