Sarah J Waugh¹ (), Emma Martindale, Monika A Formankiewicz, Leticia Álvaro, Denis G Pelli; ¹University of Huddersfield, ²Anglia Ruskin University, ³Universidad Complutense de Madrid, ⁴New York University

Visual acuity and crowding distance develop differently but which measure relates better to reading ability and/or reading speed? Visual acuity with isolated Sloan letters and crowding distance with Pelli trigrams and repeated optotypes (Pelli, Waugh, Martelli et al., 2016) were measured. In Group 1 (N=200 children aged 3-11 years), teacher-assessed literacy/reading indicators were also obtained. In Group 2 (N=72 children aged 4-10 years), reading speed was measured with a Rapid Serial Visual Presentation (RSVP) and an “Ordinary” reading task. Teacher-assessed PiRA (Progress in Reading Assessment) reading ages were also obtained. In Group 1, log visual acuity (r=-0.35) and log crowding distance (r=-0.66 and -0.65) decreased and teacher-assessed reading performance (r=0.94) increased with age (Pearson r; p<0.0001). Removing age through partial correlation revealed a significant impact of crowding distance (trigram and repeated optotypes; r=-0.24 and -0.25, both p<0.001) on teacher-assessed literacy/reading performance, not true for visual acuity (r=-0.13, p>0.05). In Group 2, relationships between log visual acuity (r=-0.36), log crowding distance (r=-0.72 and -0.71) and teacher-assessed reading age (r=0.90) with actual age were similar to those in Group 1 (Pearson r; p<0.01). In readers, crowding distances were significantly correlated with PiRA reading age (r=-0.59, -0.51, p<0.0001), whereas visual acuity was not (r=-0.04, p>0.1). Reading speed in readers improved with age (RSVP r=0.62; Ordinary r=0.63; p<0.0001)) and teacher-assessed reading age (RSVP r=0.67; Ordinary r=0.72; p<0.0001). Crowding distance was significantly correlated with RSVP reading speed (r=-0.50, -0.45; p<0.001), whereas visual acuity was not (r=0.057; p>0.10). Similarly, crowding distance had a stronger relationship with ordinary reading speed (r=-0.63, -0.52; p<0.0001) than did visual acuity (r=-0.29, p<0.05). Foveal crowding distance is much better than acuity at predicting children’s reading ability. Thus clinically, measurement of crowding distance could prove valuable, especially in children whose reading might be impaired by vision.

Acknowledgements: URN020-01 from University of Huddersfield to Waugh. R01 EY027964-01A1 to Pelli.