title: Spatiotemporal Summation of Perimetric Stimuli in Early Glaucoma.
abstract: OBJECTIVE
  To investigate achromatic temporal summation under the conditions of standard automated perimetry (SAP), using a Goldmann III (GIII) stimulus and a stimulus scaled to the local area of complete spatial summation (Ricco's area) in open-angle glaucoma (OAG) patients and healthy age-similar control participants.
  
  
  METHODS
  Twenty patients with OAG (mean age, 63 years; mean MD, -3.3 dB) and 15 healthy controls (mean age, 64 years) were recruited. Contrast thresholds were measured for seven stimulus durations (1-24 frames, 1.8-191.9 ms) using a near-GIII stimulus (0.48° diameter) and stimuli scaled to the local Ricco's area, in four oblique meridians at 8.8° eccentricity in the visual field. The upper limit of complete temporal summation (critical duration) was estimated using iterative two-phase regression analysis.
  
  
  RESULTS
  Median critical duration values were significantly longer (P < 0.05) in the OAG group for the near-GIII (107.2 ms; interquartile range [IQR], 38.0-190.5) and Ricco's area-scaled (83.2 ms, 41.7-151.4) stimuli, compared to those in healthy subjects (near-GIII, 34.7 ms; 18.2-47.9; Ricco's area-scaled, 49.0 ms; 25.1-64.6). The greatest difference in contrast thresholds between healthy and OAG subjects (i.e., disease signal) was found when stimuli were scaled to Ricco's area and shorter than or equal to the critical duration in healthy observers.
  
  
  CONCLUSIONS
  Temporal summation is altered in glaucoma. The stimulus duration and area of conventional SAP may be suboptimal for identifying early functional damage. Simultaneously modulating stimulus duration, area, and luminance during the examination may improve the diagnostic capability of SAP and expand the dynamic range of current instruments.
authors.affiliation: National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom 2Vision Science Research Group, School of Biomedical Sciences, University o.
authors.forename: Pádraig J
authors.initials: PJ
authors.lastname: Mulholland
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom.
authors.forename: Tony
authors.initials: T
authors.lastname: Redmond
authors.affiliation: National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom.
authors.forename: David F
authors.initials: DF
authors.lastname: Garway-Heath
authors.affiliation: Vision Science Research Group, School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, United Kingdom.
authors.forename: Margarita B
authors.initials: MB
authors.lastname: Zlatkova
authors.affiliation: National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom 2Vision Science Research Group, School of Biomedical Sciences, University o.
authors.forename: Roger S
authors.initials: RS
authors.lastname: Anderson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods; D041623:Tomography, Optical Coherence / Q000379:methods; D014792:Visual Acuity / Q000502:physiology*; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields / Q000502:physiology*