title: Evaluation of hemifield sector analysis protocol in multifocal visual evoked potential objective perimetry for the diagnosis and early detection of glaucomatous field defects.
abstract: OBJECTIVE
  Multifocal visual evoked potential (mfVEP) is a newly introduced method used for objective visual field assessment. Several analysis protocols have been tested to identify early visual field losses in glaucoma patients using the mfVEP technique, some were successful in detection of field defects, which were comparable to the standard automated perimetry (SAP) visual field assessment, and others were not very informative and needed more adjustment and research work. In this study we implemented a novel analysis approach and evaluated its validity and whether it could be used effectively for early detection of visual field defects in glaucoma.
  
  
  METHODS
  Three groups were tested in this study; normal controls (38 eyes), glaucoma patients (36 eyes) and glaucoma suspect patients (38 eyes). All subjects had a two standard Humphrey field analyzer (HFA) test 24-2 and a single mfVEP test undertaken in one session. Analysis of the mfVEP results was done using the new analysis protocol; the hemifield sector analysis (HSA) protocol. Analysis of the HFA was done using the standard grading system.
  
  
  RESULTS
  Analysis of mfVEP results showed that there was a statistically significant difference between the three groups in the mean signal to noise ratio (ANOVA test, p < 0.001 with a 95% confidence interval). The difference between superior and inferior hemispheres in all subjects were statistically significant in the glaucoma patient group in all 11 sectors (t-test, p < 0.001), partially significant in 5 / 11 (t-test, p < 0.01), and no statistical difference in most sectors of the normal group (1 / 11 sectors was significant, t-test, p < 0.9). Sensitivity and specificity of the HSA protocol in detecting glaucoma was 97% and 86%, respectively, and for glaucoma suspect patients the values were 89% and 79%, respectively.
  
  
  CONCLUSIONS
  The new HSA protocol used in the mfVEP testing can be applied to detect glaucomatous visual field defects in both glaucoma and glaucoma suspect patients. Using this protocol can provide information about focal visual field differences across the horizontal midline, which can be utilized to differentiate between glaucoma and normal subjects. Sensitivity and specificity of the mfVEP test showed very promising results and correlated with other anatomical changes in glaucoma field loss.
authors: Department of Ophthalmology, Hamad Medical Corporation, Doha, Qatar.
authors: Mohammad F
authors: MF
authors: Mousa
authors: School of Life and Health Sciences, Aston University, Birmingham, UK.
authors: Robert P
authors: RP
authors: Cubbidge
authors: Department of Ophthalmology, Hamad Medical Corporation, Doha, Qatar.
authors: Fatima
authors: F
authors: Al-Mansouri
authors: Department of Medical Statistics & Epidemiology, Hamad Medical Corporation, Doha, Qatar. ; Department of Public Health, Weill Cornell Medical College, Doha, Qatar. ; Department Evidence for Population Health Unit, School of Epidemiology and Health Sciences, The University of Manchester, Manchester, UK.
authors: Abdulbari
authors: A
authors: Bener
mesh_terms: D000328:Adult; D000368:Aged; D042241:Early Diagnosis; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D005901:Glaucoma / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012607:Scotoma / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult
keywords: Glaucomatous field loss; Multifocal visual evoked potential; Objective perimetry; Standard automated perimetry