title: Suitability of the Visual Field Index according to Glaucoma Severity.
abstract: OBJECTIVE
  To investigate the suitability of the visual field index (VFI) in different degrees of disease severity in glaucoma patients.
  
  
  METHODS
  In this cross-sectional study, we consecutively enrolled patients with primary open-angle glaucoma and glaucoma suspects (ocular hypertension). All eyes required a reliable standard automated perimetry (SAP) test to be included. Subjects were categorized into five groups based on glaucoma severity using SAP's mean deviation (MD). To evaluate the correlation among VFI, MD and pattern standard deviation (PSD), a linear regression model was built. To evaluate the nature of the correlation (i.e. linear vs nonlinear), results were plotted in a scatterplot graph.
  
  
  RESULTS
  One hundred and twenty-two eyes of 81 patients (mean age, 59.8 ± 14.5 years) were included. A strong, positive association was found between MD and VFI values (R(2) = 0.98, p < 0.001), showing a 3.2% reduction in the VFI for each dB loss in the MD index. It was noticed that 15% of eyes with mild glaucoma (average MD of -3.1 dB) had VFI > 99%. Considering only the eyes with mild and moderate damage in the regression, we found a weaker (nonlinear) correlation than the one we found using all eyes (R(2) = 0.85, p < 0.001). There was also a significant, nonlinear correlation between VFI and PSD (R(2) = 0.85, p < 0.001). Although higher PSD values were found with increasing visual field damage, this initial trend was reversed when VFI became smaller than 50%, approximately.
  
  
  CONCLUSIONS
  Visual field index had a strong correlation with MD; however, this correlation was weaker in mild disease, as some patients with early disease had very high VFI values (ceiling effect). Therefore, initial deterioration in visual field status (as assessed by MD values) in patients with early disease may not be detectable using the VFI alone. How to cite this article: Sousa MCC, Biteli LG, Dorairaj S, Maslin JS, Leite M, Prata TS. Suitability of the Visual Field Index according to Glaucoma Severity. J Curr Glaucoma Pract 2015;9(3):65-68.
authors.affiliation: Resident, Department of Ophthalmology, Federal University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Marina Cc
authors.initials: MC
authors.lastname: Sousa
authors.affiliation: Preceptor, Glaucoma Service, Department of Ophthalmology, Federal University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Luis G
authors.initials: LG
authors.lastname: Biteli
authors.affiliation: Associate Professor, Department of Ophthalmology, Mayo Clinic, Florida, USA.
authors.forename: Syril
authors.initials: S
authors.lastname: Dorairaj
authors.affiliation: Resident, Department of Ophthalmology and Visual Science, Yale University School of Medicine, CT, USA.
authors.forename: Jessica S
authors.initials: JS
authors.lastname: Maslin
authors.affiliation: Medical Staff, Glaucoma Service, Department of Ophthalmology, Federal University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Mauro T
authors.initials: MT
authors.lastname: Leite
authors.affiliation: Assistant Professor, Department of Ophthalmology, Federal University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Tiago S
authors.initials: TS
authors.lastname: Prata
keywords: Functional correlation; Functional evaluation; Glaucoma blindness; Stages of glaucoma; Visual field index.