title: Performance of the visual field index in glaucoma patients with moderately advanced visual field loss.
abstract: OBJECTIVE
  To explore the relationship between the visual field index (VFI) and the visual field mean deviation (MD) in glaucoma patients with moderately advanced perimetric damage and to identify the magnitude of the boundary effect of VFI that occurred when the VFI estimation strategy changed from pattern deviation probability value to total deviation probability value as the MD crossed -20 dB in longitudinal visual field (VF) series.
  
  
  METHODS
  A retrospective cohort study of longitudinal data analysis.
  
  
  METHODS
  The MD and VFI values obtained from VF tests conducted on 148 eyes of 148 glaucoma patients having an MD around -20 dB were studied. A total of 1286 VFs with MD values within the range of -16 dB to -24 dB were included. The eyes were divided into 2 groups, with the first having serial MDs all better than or all worse than -20 dB and the second with serial MDs crossing the -20 dB value. Change in MD (ΔMD) was defined as the absolute difference between the MD values of 2 consecutive VFs. Based on the 2 VFI values of the same VFs, the absolute value of change in VFI (ΔVFI) was calculated.
  
  
  RESULTS
  The means (± standard deviation) for the ΔVFI were 4.17% (± 3.3%) in the group of eyes with MDs on either side of -20 dB, and were 15.8% (± 8.4%) in the group with MDs crossing -20 dB (P < .0001). For ΔVFI/ΔMD, these values were 6.8%/dB (± 10.5%) when the range of MD falls on either side of -20 dB, and 7.9%/dB (± 6.2%) when the range of MD crosses the -20 dB values (P = .042).
  
  
  CONCLUSIONS
  The values of the VFI become highly variable in serial VFs of eyes with MDs crossing -20 dB, in comparison to those VFIs associated with MDs on either side of -20 dB. The likelihood for this effect is the change from use of pattern deviation probability value to total deviation probability value in the points included in the calculation of VFI at -20 dB of MD. The development of indices to measure VF rates that are free from this boundary effect in moderately advanced glaucoma is desirable.
authors.affiliation: The Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Jun Mo
authors.initials: JM
authors.lastname: Lee
authors.affiliation: The Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Nila
authors.initials: N
authors.lastname: Cirineo
authors.affiliation: The Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Meera
authors.initials: M
authors.lastname: Ramanathan
authors.affiliation: The Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Kouros
authors.initials: K
authors.lastname: Nouri-Mahdavi
authors.affiliation: The Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Esteban
authors.initials: E
authors.lastname: Morales
authors.affiliation: The Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Anne L
authors.initials: AL
authors.lastname: Coleman
authors.affiliation: The Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, California. Electronic address: Caprioli@jsei.ucla.edu.
authors.forename: Joseph
authors.initials: J
authors.lastname: Caprioli
mesh_terms: D000368:Aged; D005500:Follow-Up Studies; D005901:Glaucoma / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D011336:Probability; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014786:Vision Disorders / Q000175:diagnosis* / Q000503:physiopathology; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology*