title: Spatial differences in corneal electroretinogram potentials measured in rat with a contact lens electrode array.
abstract: OBJECTIVE
  It has been known for several decades that the magnitude of the corneal electroretinogram (ERG) varies with position on the eye surface, especially in the presence of focal or asymmetric stimuli or retinal lesions. However, this phenomenon has not been well-characterized using simultaneous measurements at multiple locations on the cornea. This work provides the first characterization of spatial differences in the ERG across the rat cornea.
  
  
  METHODS
  A contact lens electrode array was employed to record ERG potentials at 25 corneal locations simultaneously following brief full-field flash stimuli in normally sighted Long-Evans rats. These multi-electrode electroretinogram (meERG) responses were analyzed for spatial differences in a-wave and b-wave amplitudes and implicit times.
  
  
  RESULTS
  Spatially distinct ERG potentials could be recorded reliably. Comparing relative amplitudes across the corneal locations suggested a slight non-uniform distribution when using full-field, near-saturating stimuli. Amplitudes of a- and b-waves were approximately 3 % lower in the inferior quadrant than in the superior quadrant of the cornea.
  
  
  CONCLUSIONS
  The present results comprise the start of the first normative meERG database for rat eyes and provide a basis for comparison of results from eyes with functional deficit. Robust measures of spatial differences in corneal potentials will also support optimization and validation of computational source models of the ERG. To fully utilize the information contained in the meERG data, a detailed understanding of the roles of the many determinants of local corneal potentials will eventually be required.
authors.affiliation: Department of Bioengineering, University of Illinois at Chicago, 851 South Morgan Street, Rm 232, M/C 063, Chicago, IL, 60607-7052, USA.
authors.forename: Yelena
authors.initials: Y
authors.lastname: Krakova
authors.forename: Hadi
authors.initials: H
authors.lastname: Tajalli
authors.forename: Sanitta
authors.initials: S
authors.lastname: Thongpang
authors.forename: Zahra
authors.initials: Z
authors.lastname: Derafshi
authors.forename: Tamas
authors.initials: T
authors.lastname: Ban
authors.forename: Safa
authors.initials: S
authors.lastname: Rahmani
authors.forename: Ashley N
authors.initials: AN
authors.lastname: Selner
authors.forename: Amani
authors.initials: A
authors.lastname: Al-Tarouti
authors.forename: Justin C
authors.initials: JC
authors.lastname: Williams
authors.forename: John R
authors.initials: JR
authors.lastname: Hetling
mesh_terms: D000818:Animals; D003261:Contact Lenses; D003315:Cornea / Q000502:physiology*; D004566:Electrodes; D004596:Electroretinography / Q000379:methods*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D010775:Photic Stimulation; D051381:Rats; D020318:Rats, Long-Evans