title: Light- and dark-adapted electroretinograms (ERGs) and ocular pigmentation: comparison of brown- and blue-eyed cohorts.
abstract: This study characterizes differences in human ERGs based on ocular pigmentation. Light- and dark-adapted luminance-response (LR) series for a-, b- and i-waves and light-adapted oscillatory potentials (OPs) were recorded in 14 healthy volunteers (7 blue-eyed Caucasians; 7 brown-eyed Asians, aged 20-22 years). Amplitude interpolations were by logistic growth (Naka-Rushton), Gaussian or the combined 'photopic hill' functions. Implicit times (IT) for dark-adapted a- and b-waves, and for light-adapted a-, b- and i-waves were earlier in the blue-eyed group than in the brown-eyed group across all flash strengths (P < 0.05). For dark-adapted ERGs, saturated a-wave amplitude was larger for blue eyes (397 vs. 318 μV, P < 0.05) as was the a-wave to strong flash (10 cd·s/m(2); 357 vs. 293 μV, P < 0.05) and the b-wave to ISCEV standard 0.01 (354 vs. 238 μV, P < 0.05). Light-adapted b-waves for midrange flash stimuli were much larger for the blue-eyed group (photopic hill, Gaussian peak: 155 vs. 82 μV, P < 0.001) with no difference in saturated amplitudes. Similarly, interpolated i-wave amplitudes were larger (48 vs. 18 μV, P < 0.01). For a light-adapted 2.6 stimulus, a- and b-waves were larger for the blue-eyed group (52 vs. 39 μV; 209 vs. 133 μV, P < 0.01) as were OP4 and OP5 (37.2 vs. 15.6 μV; 47.5 vs. 22.2 μV, P < 0.01), but OP1-OP3 did not differ. ERGs have shorter ITs in people with blue irides than in those with dark pigmentation. Amplitude differences are highly non-linear and substantially larger from eyes with light pigmentation for components thought to be associated with the OFF retinal pathways.
authors.affiliation: Department of Vision Sciences, Glasgow Caledonian University, Glasgow, G4 0BA, UK. saed.alabdlseaed@gcal.ac.uk
authors.forename: Abdlsaed
authors.initials: A
authors.lastname: Al Abdlseaed
authors.forename: Yvonne
authors.initials: Y
authors.lastname: McTaggart
authors.forename: Thomas
authors.initials: T
authors.lastname: Ramage
authors.forename: Ruth
authors.initials: R
authors.lastname: Hamilton
authors.forename: Daphne L
authors.initials: DL
authors.lastname: McCulloch
mesh_terms: D003623:Dark Adaptation; D004596:Electroretinography; D005127:Eye Color / Q000502:physiology*; D006801:Humans; D009991:Oscillometry; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology*; D055815:Young Adult