title: Influence of pupil size and cataract on retinal nerve fiber layer thickness measurements by Stratus OCT.
abstract: OBJECTIVE
  To investigate whether retinal nerve fiber layer (RNFL) thickness, as measured by optical coherence tomography (OCT), is influenced by pupil size and cataract.
  
  
  METHODS
  RNFL thickness was measured by means of Stratus OCT (RNFL Thickness 3.4 acquisition protocol) in a group of consecutive patients undergoing phacoemulsification and intraocular lens implantation. Measurements were taken preoperatively without pupil dilation (PR1), preoperatively with pupil dilation (PR2), and 1 month postoperatively without pupil dilation.
  
  
  RESULTS
  Twenty-five eyes of 25 patients were enrolled in the study and underwent statistical analysis. Pupil dilation caused RNFL thickness measurements to increase slightly in PR2 compared with PR1; the difference showed to be statistically significant in the 360-degree average measurement (P=0.0456) and in the nasal quadrant (P=0.032), but not in the remaining quadrants. Postoperative measurements were higher than those of PR1 in all quadrants (temporal P=0.011; superior P=0.0098; nasal P<0.0001; inferior P=0.0081) and in 360 degrees average (P<0.0001), suggesting that the presence of cataract significantly influences RNFL thickness as measured by Stratus OCT. More advanced degrees of lens opacity were correlated to a higher decrease in RNFL thickness values (r=0.4071, P=0.0434).
  
  
  CONCLUSIONS
  While pupil size only marginally affects RNFL measurements performed by Stratus OCT, the presence and degree of cataract seem to have a significant impact. This effect should be taken in consideration when using this technology for the diagnosis of glaucoma and other neuro-ophthalmologic disorders possibly affecting the RNFL.
authors.affiliation: Centro Salus, Bologna, Italy. giacomo.savini@alice..it
authors.forename: Giacomo
authors.initials: G
authors.lastname: Savini
authors.forename: Maurizio
authors.initials: M
authors.lastname: Zanini
authors.forename: Piero
authors.initials: P
authors.lastname: Barboni
mesh_terms: D000368:Aged; D002386:Cataract / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009412:Nerve Fibers / Q000473:pathology*; D011446:Prospective Studies; D011680:Pupil; D012160:Retina / Q000473:pathology*; D012307:Risk Factors; D012720:Severity of Illness Index; D041623:Tomography, Optical Coherence / Q000379:methods*