Thesis defence of Éole LAPEYRE (Éq. Sens Mouvement & Perception) will take place on the 12th of December at 2pm in Amphi Charve in Marseille (bâtiment 9, campus St. Charles, 3 place Victor Hugo) and online (see below for the link).

The defence will be in English.

You are also very welcome to join for the pot de thèse in salle Colette after the defence.

Title: Adapting to eccentric reading: visual and psycholinguistic constraints under simulated and pathological central vision loss.

Abstract: In developed countries, central visual field loss (CVL) is the leading cause of visual impairment among people over 50, gradually causing them to lose the ability to read and recognize faces. CVL is caused by incurable retinal diseases such as diabetic maculopathy, myopic maculopathy, or age-related macular degeneration (AMD). Patients with these conditions develop a blind spot called a scotoma, located in the center of their visual field, up to 20°.

Forced to rely on their peripheral vision, most affected individuals eventually develop one (or more) peri-foveal regions outside the damaged area that they preferentially use to focus, known as the Preferred Retinal Locus (PRL). Despite these adaptive strategies, reading – a complex task involving both visual and cognitive processes – becomes the primary complaint of patients. Over 30% of them eventually give up daily reading activities altogether, and the underlying causes of this deficit remain poorly understood.

Due to the aging population and its strong correlation with the prevalence of eye diseases, the number of patients affected by CVL is expected to increase in the coming years (60 million in Europe / 288 million worldwide by 2030). Given its significant importance for quality of life and independence, the ability to read must be preserved at all costs for these individuals. Therefore, there is a real societal need to overcome their difficulties and restore their (fluent) reading abilities.

This dissertation proposes an innovative and multidisciplinary approach aimed at better understanding the underlying causes of poor reading performance in individuals affected by CVL, combining psycholinguistic and visual approaches. By investigating the influence of lexical, semantic and visual factors, the aim of this work was twofold: 1) to identify the psycholinguistic factors that significantly influence reading performance in the presence of a central scotoma, and 2) to highlight their impact on the oculomotor and visuo-attentional strategies that affected individuals use during reading to compensate for their impairment.

Using a psychophysical approach, we conducted a series of experiments to examine sentence reading performance and eye-movement behavior in both patients with CVL and normally sighted adults reading with a gaze-contingent simulated scotoma. The results showed that the key psycholinguistic variables known to most influence normal reading also strongly modulate reading under central vision loss. In addition, we developed and validated novel metrics of visual ambiguity based on letter-shape similarity, revealing that the visual confusability of letters and words contributes to reading difficulty independently of classical lexical properties. These psycholinguistic and visual effects were observed across both young and older readers; however, older adults – particularly those with pathological CVL who had reduced reading practice – showed slower adaptation and relied more on word-by-word (length-based) strategies. Analysis of eye movements further characterized the adaptive oculomotor responses enabling eccentric reading, notably the development of pseudo-PRLs and specific fixation patterns allowing eccentric reading. 

As this is the first work to comprehensively characterize psycholinguistic influences on reading in a low-vision population, it provides novel insights into the interplay of high-level linguistic cues and low-level visual constraints in reading, and highlights the plasticity of oculomotor strategies that support fluent reading despite central visual field loss.

Keywords: reading, eye movements, reading impairment, central vision loss, psycholinguistics, simulated scotoma

Jury: