OCT Identifies Increased Inner Retinal Layer Thickness in Autistic Adults

Previous studies have established connections between the behavioral symptoms of autism spectrum disorder and biological variations in the brain. The retina, an extension of the central nervous system with structural and embryological similarities to the brain, has recently emerged as a potential window into neurological conditions. Because of this, authors of a recent study investigated the potential of retinal thickness measurements on OCT as accessible, noninvasive indicators to aid in diagnosing autism. They found that autistic individuals showed significantly greater thickness in the inner retina, as well as the retinal nerve fiber layer (RNFL), inner plexiform layer (IPL) and inner nuclear layer (INL). The findings were reported in Ophthalmology Science. These images from the study show cortical regions of interest that exhibit positive (red) and negative correlations (blue) with RNFL thickness. While cognitive function did not correlate with inner retinal thickness, a decrease in the photoreceptor inner segment thickness was linked to a higher likelihood of cognitive impairment in individuals on the autism spectrum. Adapted from Cox SR, et al. Intelligence. 2019; 76,101376. Click image to enlarge. A total of 240 eyes were examined, including 80 from autistic participants and 160 from matched neurotypical controls. Exclusion criteria included a history of neurodegenerative diseases, optic nerve pathology, retinal disorders, glaucoma surgery, high refractive error or intraocular pressure outside the range of 6mm Hg to 21mm Hg.Using OCT images, nine distinct retinal layers were segmented: RNFL IPL INL ganglionic cell layer combined outer plexiform layer and outer nuclear layer photoreceptor inner segment photoreceptor outer segmentretinal pigment epitheliumchoroidoscleral interfaceCognitive function was evaluated using four standardized tests: pairs-matching, prospective memory, numerical/verbal reasoning and reaction time. Additionally, brain imaging-derived phenotypes were included in the analysis.There was a significant increase in inner retinal layer thickness in autistic adults, specifically the RNFL, IPL and INL. Notably, increased inner retinal thickness correlated positively with total brain volume and the posterior corpus callosum, while showing negative correlations with the volume of the hippocampus and the inferior temporal gyrus.No significant correlation was found between inner retinal thickness and cognitive impairment. However, brain MRI data indicated associations between inner retinal thickness and volumes of the total brain, corpus callosum, hippocampus and temporal gyrus.Additionally, RNFL thickness showed positive correlations with the volume of several brain areas. In contrast, it was negatively associated with the cerebellar cortex, mid-posterior corpus callosum, the frontal orbital cortex and the medial frontal cortex in autistic individuals.“Interestingly, cognitive function did not correlate with inner retinal thickness, though a decrease in the photoreceptor inner segment thickness was linked to a higher likelihood of cognitive impairment in individuals on the autism spectrum,” the authors wrote in their Ophthalmology Science paper.They continued by saying the observed retinal thickening in autism may result from neuroinflammatory changes, such as microglial activation, vascular anomalies or reflect atypical neurodevelopmental processes in the brain. Some studies highlighted accelerated brain growth during the first two years of life on the autism spectrum, which may normalize or persist into adulthood.“While we did not observe significant differences in overall brain volume between autistic and non-autistic individuals, our results showed the associations between increased inner retinal thickness and brain volumes in autistic adults, suggesting a potential link between retinal thickness and certain structural alterations in the brain,” the authors wrote.In conclusion, these findings suggest that OCT may serve as a valuable addition to existing diagnostic tools for autism by providing insights into the associations between retinal structure and brain morphology.“The observed complex correlations between retinal layers and cortical regions involved in visual processing highlight the need for further research to better understand the mechanisms underlying these associations, particularly in autism spectrum disorder subgroups with similar clinical and neuroanatomical characteristics,” the authors concluded in their article.Click here for the journal source. Montazeri F, Liu YA, Emani-Naeini P. Retinal structures in autism spectrum disorder: results from a case-control study. Ophthalmology Sci. May 20, 2025. [Epub ahead of print.]