Optical coherence tomography findings in autism spectrum disorder and healthy controls

OBJECTIVE: The studies conducted in the field of brain anatomy, physiology, histology, and functions in the past half a century since the definition of autism spectrum disorder (ASD) as a disorder caused by genetic, familial, and environmental factors have provided that this complex syndrome is a neurobiological disorder and that it has a negative effect on the social interaction, communication skills, interests and behaviours of the individual due to this disorder. In this study, we aimed to examine the optical coherence tomography (OCT) parameters including retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL) and choroidal thickness with more patients and controls, the relationship between the severity of the disease and OCT parameters in patients, the duration of the disease and OCT parameters, and the relationship between OCT parameters and IQ in ASD subjects.

METHODS: This study involved 40 ASD patients who were being followed by the Child and Adolescent Psychiatry Department of Adiyaman University Medical School and 40 healthy volunteers as control. OCT measurements were performed for both groups. The RNFL, IPL thickness, and GCL volumes were measured and recorded automatically by a spectral OCT device.

RESULTS: When all the lower layers of RNFL were evaluated in both eyes; there was no difference in the RNFL layers between the ASD group and the control group (p>0.05) in right eye. In left eye, N (p=0.016) and NS (p=0.023) sectors of RNFL were significantly different from the control group. The mean choroidal thickness, which is the mean value of the measurements from three regions, was significantly decreased in the patients with ASD compared with the controls in both eyes (p<0.05). The GCL and IPL volumes were significantly decreased in the patients with ASD compared with the controls in both eyes (p<0.05). According to the Pearson correlation analysis, a significant correlation was found between Childhood Autism Rating Scale (CARS) and left GCL (r=- 0.396, p=0.013), left IPL (r=-0.337, p=0.036); between duration of disease and right NI (r=-0.368, p=0.020), right TI (r=-0.412, p=0.008), right TS (r=-0.522, p=0.001), right mean (r=-0.439, p=0.005), left NS (r=-0.345, p=0.029).

CONCLUSIONS: We revealed that ASD subjects present with significant differences only at some locations in terms of RNFL sublayers, choroid, GCL, and IPL. The whole patient group displayed a significant retinal thinning in the left nasal quadrant compared to controls. Cross-sectional design of this present study limits conclusions about progressive degeneration during the course of ASD.