Nilsu Atilgan^1,2, Ben D. Sawyer²; ¹Bilkent University, ²University of Central Florida

Visual span, the number of letters that can be recognized reliably without eye movement, is considered a key sensory bottleneck for reading efficiency. Prior work shows that visual span is associated with reading speed in both typical and low-vision populations (Legge et al., 2007). In a preliminary laboratory study, we investigated visual span and reading performance in individuals with dyslexia. Relative to typical readers, the dyslexia group exhibited significantly smaller visual spans (p = 0.022) and slower reading rates (p < 0.001). Crucially, visual span size showed a strong positive correlation with reading speed (r(19) = 0.45). We adapted this paradigm for online testing to enable larger-scale assessment. A validation study confirmed the reliability of the online paradigm in a small sample, showing a strong positive correlation between visual span size and reading speed (r(12) = 0.63). We then collected data from 45 self-reported individuals with dyslexia (age range: 20–59; M = 34.13), using the online visual span test and an online MNREAD test. Consistent with our laboratory findings, this group demonstrated slower reading performance (Words per minute [WPM]: 123 ± 43) compared to typical readers (162 ± 21 WPM). Most importantly, visual span size again showed a strong correlation with reading speed across the heterogeneous sample (r(45) = 0.60). Collectively, these findings demonstrate two key implications. First, they confirm that, despite considerable heterogeneity, individuals with dyslexia show a reliable group-level pattern where a smaller visual span predicts slower reading. Second, the successful replication across laboratory and online settings demonstrates that a brief, psychophysically grounded visual span test can be administered reliably online, enabling scalable and valid assessment in larger populations. Our ongoing work examines whether asymmetries in visual span between the left and right visual fields further contribute to performance variability in dyslexia.