title: Progressive loss of retinal ganglion cell function precedes structural loss by several years in glaucoma suspects.
abstract: OBJECTIVE
  We determined the time lag between loss of retinal ganglion cell function and retinal nerve fiber layer (RNFL) thickness.
  
  
  METHODS
  Glaucoma suspects were followed for at least four years. Patients underwent pattern electroretinography (PERG), optical coherence tomography (OCT) of the RNFL, and standard automated perimetry testing at 6-month intervals. Comparisons were made between changes in all testing modalities. To compare PERG and OCT measurements on a normalized scale, we calculated the dynamic range of PERG amplitude and RNFL thickness. The time lag between function and structure was defined as the difference in time-to-criterion loss between PERG amplitude and RNFL thickness.
  
  
  RESULTS
  For PERG (P < 0.001) and RNFL (P = 0.030), there was a statistically significant difference between the slopes corresponding to the lowest baseline PERG amplitude stratum (≤50%) and the reference stratum (>90%). Post hoc comparisons demonstrated highly significant differences between RNFL thicknesses of eyes in the stratum with most severely affected PERG (≤50%) and the two strata with least affected PERG (>70%). Estimates suggested that the PERG amplitude takes 1.9 to 2.5 years to lose 10% of its initial amplitude, whereas the RNFL thickness takes 9.9 to 10.4 years to lose 10% of its initial thickness. Thus, the time lag between PERG amplitude and RNFL thickness to lose 10% of their initial values is on the order of 8 years.
  
  
  CONCLUSIONS
  In patients who are glaucoma suspects, PERG signal anticipates an equivalent loss of OCT signal by several years.
authors: Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida 33136, USA. mbanitt@med.miami.edu
authors: Michael R
authors: MR
authors: Banitt
authors: Lori M
authors: LM
authors: Ventura
authors: William J
authors: WJ
authors: Feuer
authors: Eleonore
authors: E
authors: Savatovsky
authors: Gabriel
authors: G
authors: Luna
authors: Olga
authors: O
authors: Shif
authors: Brandon
authors: B
authors: Bosse
authors: Vittorio
authors: V
authors: Porciatti
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D004596:Electroretinography; D005260:Female; D005901:Glaucoma / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012165:Retinal Ganglion Cells / Q000473:pathology / Q000502:physiology*; D013997:Time Factors; D041623:Tomography, Optical Coherence; D014794:Visual Fields / Q000502:physiology