title: Structure-function relationship in ocular hypertension and glaucoma: interindividual and interocular analysis by OCT and pattern ERG.
abstract: BACKGROUND
  Pattern electroretinogram (PERG) and optical coherence tomography (OCT) represent objective probes to investigate respectively the function of retinal ganglion cells and their structure as retinal nerve fiber layer (RNFL) thickness. We examined interindividual (II) correlations of PERG amplitude and RNFL thickness, as well as correlations between interocular (IO) differences in both measures, in ocular hypertension (OHT) and early glaucoma (EG) patients.
  
  
  METHODS
  Thirty-one OHT, 34 EG (mean deviation: -1 to -6 dB) and 16 age-matched controls were examined in both eyes. Participants had clear optical media, no or moderate refractive errors and no concomitant ocular or systemic diseases. PERGs were elicited by counterphased (16.28 reversals/second) gratings (1.6 cycles/degree spatial frequency). The Fourier isolated 2nd harmonic PERG amplitude and phase were measured. RNFL thickness was quantified by means of OCT Stratus according to a standard protocol. Average, superior and inferior RNFL thicknesses were considered.
  
  
  RESULTS
  Mean PERG amplitude was decreased (p < 0.01) in both OHT and EG patients compared to controls. Mean RNFL thicknesses were reduced (p < 0.01) in EG patients compared to both OHT and controls. In OHT patients, PERG amplitude did not correlate significantly with RNFL thickness in both II and IO analysis. In EG patients, PERG amplitude was positively correlated with RNFL thickness in both II (p < 0.005) and IO (p < 0.001) analysis. The slope of the correlation predicted that PERG losses exceeded systematically RNFL losses when the latter were between 0 and -0.25 log units.
  
  
  CONCLUSIONS
  Both II and IO analyses revealed a lack of structure-function relationship in OHT, suggesting that, at this disease stage, PERG losses appear to affect primarily retinal/optic nerve head function. In EG they reflect both dysfunction and RNFL loss.
authors.affiliation: Institute of Ophthalmology, Catholic University, Largo Francesco Vito 1, 00168, Rome, Italy. md0571@mclink.it
authors.forename: Benedetto
authors.initials: B
authors.lastname: Falsini
authors.forename: Dario
authors.initials: D
authors.lastname: Marangoni
authors.forename: Tommaso
authors.initials: T
authors.lastname: Salgarello
authors.forename: Giovanna
authors.initials: G
authors.lastname: Stifano
authors.forename: Lucrezia
authors.initials: L
authors.lastname: Montrone
authors.forename: Francesca
authors.initials: F
authors.lastname: Campagna
authors.forename: Stefania
authors.initials: S
authors.lastname: Aliberti
authors.forename: Emilio
authors.initials: E
authors.lastname: Balestrazzi
authors.forename: Alberto
authors.initials: A
authors.lastname: Colotto
mesh_terms: D004596:Electroretinography; D005260:Female; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009798:Ocular Hypertension / Q000503:physiopathology; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000503:physiopathology*; D010364:Pattern Recognition, Visual; D012165:Retinal Ganglion Cells / Q000502:physiology*; D041623:Tomography, Optical Coherence