Supplementary Material for: Optical coherence tomography measurements of retina and choroid in autism spectrum disorder: a systematic review and meta-analysis

Introduction: The purpose of this systematic review and meta-analysis is to compare optical coherence tomography (OCT) retinal measurements between patients with autism spectrum disorder (ASD) and the neurotypical controls, exploring the potential of OCT as a non-invasive biomarker for ASD-related neurodevelopmental alterations. Methods: PubMed, Embase, and Scopus databases were explored to determine eligible articles reporting OCT measurements of retina and choroid in patients with ASD compared to healthy controls. Statistical analysis of OCT metrics was performed if reported in at least three discrete studies. In the process, fixed and random effects models were utilized, depending on the heterogeneity level between studies. Subgroup analysis based on the age group of cases, the method of eye selection, age and sex matching of cases and controls, and the OCT device used was also conducted. Results: Ten studies with 373 ASD cases (with a total of 640 eyes) and 443 controls (with a total of 760 eyes) were included in this study. No significant alteration was observed in the average total macular layer, macular inner nuclear layer (INL), macular inner plexiform layer (IPL), macular ganglion cell layer (GCL), and macular retinal nerve fiber layer (RNFL) thickness. There was also no significant difference in the peripapillary retinal nerve fiber layer (pRNFL) thickness of the eyes of cases with ASD compared to healthy controls, except for the inferonasal portion of the pRNFL, which was significantly thicker in ASD subjects when compared to controls (p = 0.02). Conclusion: The findings of the present meta-analysis indicate a localized thickening of the inferonasal pRNFL with no alteration of other portions of pRNFL and macular layers (IPL, INL, GCL, RNFL). Although OCT may reflect subtle neurodevelopmental differences in ASD, current evidence is limited by small sample sizes, methodological heterogeneity, and potential confounders.