Light-adapted ERG differences in autism spectrum disorder

Purpose: To determine if retinal signals measured using the lightadapted
ERG (LA ERG) differ in size or timing in young people with
autism spectrum disorder (ASD), a neurodevelopmental disorder.
Methods: LA ERGs were recorded from 90 ASD individuals, mean
age 13.0 ± 4.2 years, and compared with those from a control group
of 87 individuals, mean age 13.8 ± 4.8 years. A Troland based,
random nine-step, full-field LA ERG flash series and the ISCEV
standard LA3 was performed on both eyes of each subject using the
RETeval (LKC Technologies Inc, Gaithersburg, MD, USA) at 2/s, on
a 30 cd.m-2 white background. The timing and amplitudes of the aand
b-waves, and the ratio of b:a amplitude produced by each flash
strength were measured. Mathematical models of the photopic hill
function using a sum of Gaussian (representing OFF-bipolar cell
input) and logistic functions (representing ON-bipolar cell input), as
detailed by Hamilton et al. (Vision Res 2007,47:2968–72) and random
effects statistical analysis were carried out to compare the retinal
responses between the two groups. Each subject contributed data
from one eye.
Results: LA b-wave amplitudes were smaller in the ASD group, most
markedly at higher flash strengths, 13 and 16 cd.s.m-2 (p\0.004)
with slower b-wave time to peaks (p = 0.001). The ON-bipolar cell
input to the photopic hill was significantly different between groups
and a higher flash strength was required by the ASD group to attain
the photopic hill maxima (p\.001).
Conclusion: Retinal signals differ in young people with ASD.
Smaller LA b-waves noted at high flash strengths appear associated
with an altered ON-bipolar input. The results from this large study
support the potential of using the ERG to quantify differences in the
CNS in neurodevelopmental conditions.
Acknowledgment: The authors would like to thank the participants
and their families for their support and Quentin Davis and Joshua
Santosa of LKC Technologies for programming the RETeval custom
protocol.
Financial support: Alan B Slifka Foundation; National Institute of
Health U19 MH108206; National Institute for Health R01
MH100173; The Gilbert Trust, UCLA.