Word Mode: a crowding-free reading protocol for individuals with macular disease

The temporal dynamics of visual crowding in letter recognition: Modulating crowding with alternating flicker presentations

Visual crowding reduces the visibility of a peripherally presented group of stimuli. This is especially challenging for peripheral reading because adjacent letters or characters perceptually crowd one another. We investigated the temporal course of spatial visual crowding by sequentially alternating the visibility of the target and flanking letters within a trigram letter stimulus presented 9° below fixation. We found that alternation rates of roughly 3 Hz released half of the total effect of crowding, whereas 10 Hz alternation rates elicited near-crowded performance. Furthermore, we found a robust performance asymmetry whereby presenting the target first elicited better performance than presenting the flankers first, an effect resembling forward masking. These results held for conditions of high, medium, and low spatial crowding. Future work will determine whether the alternation rates found in the current study can improve peripheral reading.

A comparison of reading, in people with simulated and actual central vision loss, with static text, horizontally scrolling text, and rapid serial visual presentation

Reading with central vision loss (CVL), as caused by macular disease, may be enhanced by presenting text using dynamic formats such as horizontally scrolling text or rapid serial visual presentation (RSVP). The rationale for these dynamic text formats is that they can be read while holding gaze away from the text, potentially supporting reading while using the eccentric viewing strategy. This study was designed to evaluate the practice of reading with CVL, with passages of text presented as static sentences, with horizontal scrolling sentences, or as single-word RSVP. In separate studies, normally sighted participants with a simulated (artificial) central scotoma, controlled by an eye-tracker, or participants with CVL resulting from macular degeneration read passages of text using the eccentric viewing technique. Comprehension was better overall with scrolling text when reading with a simulated CVL, whereas RSVP produced lower overall comprehension and high error rates. Analysis of eye movement behavior showed that participants consistently adopted a strategy of making multiple horizontal saccades on the text itself. Adherence to using eccentric viewing was better with RSVP, but this did not translate into better reading performance. Participants with macular degeneration and an actual CVL also showed the highest comprehension and lowest error rates with scrolling text and the lowest comprehension and highest errors with RSVP. We conclude that scrolling text can support effective reading in people with CVL and has potential as a reading aid.

The inhibitory effect of word neighborhood size when reading with central field loss is modulated by word predictability and reading proficiency

For normally sighted readers, word neighborhood size (i.e., the total number of words that can be formed from a single word by changing only one letter) has a facilitator effect on word recognition. When reading with central field loss (CFL) however, individual letters may not be correctly identified, leading to possible misidentifications and a reverse neighborhood size effect. Here we investigate this inhibitory effect of word neighborhood size on reading performance and whether it is modulated by word predictability and reading proficiency. Nineteen patients with binocular CFL from 32 to 89 years old (mean ± SD = 75 ± 15) read short sentences presented with the self-paced reading paradigm. Accuracy and reading time were measured for each target word read, along with its predictability, i.e., its probability of occurrence following the two preceding words in the sentence using a trigram analysis. Linear mixed effects models were then fit to estimate the individual contributions of word neighborhood size, predictability, frequency and length on accuracy and reading time, while taking patients' reading proficiency into account. For the less proficient readers, who have given up daily reading as a consequence of their visual impairment, we found that the effect of neighborhood size was reversed compared to normally sighted readers and of higher amplitude than the effect of frequency. Furthermore, this inhibitory effect is of greater amplitude (up to 50% decrease in reading speed) when a word is not easily predictable because its chances to occur after the two preceding words in a specific sentence are rather low. Severely impaired patients with CFL often quit reading on a daily basis because this task becomes simply too exhausting. Based on our results, we envision lexical text simplification as a new alternative to promote effective rehabilitation in these patients. By increasing reading accessibility for those who struggle the most, text simplification might be used as an efficient rehabilitation tool and daily reading assistive technology, fostering overall reading ability and fluency through increased practice.

Asymmetries of reading eye movements in simulated central vision loss

Patients with central vision loss are forced to use an eccentric retinal location as a substitute for the fovea, called a preferred retinal locus, or PRL. Clinical studies have shown that patients habitually choose a PRL located either to the left, and/or below the scotoma in the visual field. The position to the right of the scotoma is almost never chosen, even though this would be theoretically more suitable for reading, since the scotoma no longer blocks the upcoming text. In the current study, we tested whether this asymmetry may have an oculomotor basis. Six normally sighted subjects viewed page-like text with a simulated scotoma, identifying embedded numbers in "words" comprising random letters. Subjects trained and tested with three different artificial PRL ("pseudo-PRL," or pPRL) locations: inferior, to the right, or to the left of the scotoma. After several training blocks for each pPRL position, subjects were found to produce reliable oculomotor control. Both reading speed and eye movement characteristics reproduced observations from traditional paradigms such as page-mode reading and RSVP for an advantage for an inferior pPRL. While left and right positions resulted in similar reading speeds, we observed that a right pPRL caused excessively large saccades and more direction switches, exhibiting a zig-zag pattern that developed spontaneously. Thus, we propose that patients' typical avoidance of pPRL positions to the right of their scotoma could have an oculomotor component: the erratic eye motion might potentially negate the perceptual benefit that this pPRL would offer.