title: Atypical birefringence pattern and the diagnostic ability of scanning laser polarimetry with enhanced corneal compensation in glaucoma.
abstract: OBJECTIVE
  To evaluate the effect of typical scan score (TSS), when within the acceptable limits, on the diagnostic performance of retinal nerve fibre layer (RNFL) parameters with the enhanced corneal compensation (ECC) protocol of scanning laser polarimetry (SLP) in glaucoma.
  
  
  METHODS
  In a cross-sectional study, 203 eyes of 160 glaucoma patients and 140 eyes of 104 control subjects underwent RNFL imaging with the ECC protocol of SLP. TSS was used to quantify atypical birefringence pattern (ABP) images. Influence of TSS on the diagnostic ability of SLP parameters was evaluated by receiver operating characteristic (ROC) regression models after adjusting for the effect of disease severity [based on mean deviation (MD)] on standard automated perimetry).
  
  
  RESULTS
  Diagnostic abilities of all RNFL parameters of SLP increased when the TSS values were higher. This effect was statistically significant for TSNIT (coefficient: 0.08, p<0.001) and inferior average parameters (coefficient: 0.06, p=0.002) but not for nerve fibre indicator (NFI, coefficient: 0.03, p=0.21). In early glaucoma (MD of -5 dB), predicted area under ROC curve (AUC) for TSNIT average parameter improved from 0.642 at a TSS of 90 to 0.845 at a TSS of 100. In advanced glaucoma (MD of -15 dB), AUC for TSNIT average improved from 0.832 at a TSS of 90 to 0.947 at 100.
  
  
  CONCLUSIONS
  Diagnostic performances of TSNIT and inferior average RNFL parameters with ECC protocol of SLP were significantly influenced by TSS even when the TSS values were within the acceptable limits. Diagnostic ability of NFI was unaffected by TSS values.
authors.affiliation: VST Glaucoma Center, L V Prasad Eye Institute, Hyderabad, India; Center for Clinical Epidemiology and Biostatistics, L V Prasad Eye Institute, Hyderabad, India.
authors.forename: Harsha L
authors.initials: HL
authors.lastname: Rao
authors.forename: Ravi K
authors.initials: RK
authors.lastname: Yadav
authors.forename: Viquar U
authors.initials: VU
authors.lastname: Begum
authors.forename: Uday K
authors.initials: UK
authors.lastname: Addepalli
authors.forename: Sirisha
authors.initials: S
authors.lastname: Senthil
authors.forename: Nikhil S
authors.initials: NS
authors.lastname: Choudhari
authors.forename: Chandra S
authors.initials: CS
authors.lastname: Garudadri
mesh_terms: D000328:Adult; D001718:Birefringence; D003315:Cornea / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D012372:ROC Curve; D012165:Retinal Ganglion Cells / Q000473:pathology*; D057109:Scanning Laser Polarimetry / Q000379:methods*; D014792:Visual Acuity / Q000502:physiology; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology
keywords: atypical birefringence pattern image; enhanced corneal compensation; glaucoma; scanning laser polarimetry; typical scan score