Rapid advances in technology are facilitating the electronic distribution of information, especially via auditory formats. These methods of acquiring information are prevalent in educational settings, such as the use of audiobooks. While auditory formats may be more

convenient and economical, they may not be the most beneficial for comprehension ability. In fact, previous research has shown that reading rather than listening leads to superior comprehension among sighted individuals. Two possible explanations for this benefit in

comprehension exist: (1) Visual processing is fundamental for reading comprehension, or (2) Reading text is more physically-engaging and effortful than listening, leading to better comprehension ability. This dissertation presents research that contributes to this debate by

comparing reading and listening comprehension between sighted individuals and blind, fluent braille readers.

The findings from this research clarify how distributing reading material using different technologies and presentation modes affects comprehension ability. These results are particularly essential for the blind community because previous research on this topic is severely lacking, and currently-used assistive technology primarily presents reading materials in auditory formats. Furthermore, this research is the first to create an assessment that accurately measures comprehension ability among two distinct participant populations, allowing for comparisons between blind and sighted individuals. The benefit of making such comparisons for elucidating the neural underpinnings of cognitive processes, such as comprehension, will be discussed as a novel methodological technique.

Patients with cerebral visual impairment (CVI, formerly cortical visual impairment) have vision loss resulting from an insult to the brain rather than to ocular structures. These children and their parents must attempt to understand their unique form of vision loss which often develops in an unpredictable fashion, and can go undiagnosed by an eye care provider. Furthermore, it can be difficult to advocate for children with CVI as many individuals and professionals who may interact with the child are unfamiliar with the condition. Although there is much interest in CVI as it is currently the leading cause of vision loss in children in the developed world, many aspects of vision loss in CVI are not well understood nor quantified.

The first two studies were aimed at understanding the effect of contour interaction on visual acuity in children with CVI. The first study shows a negative effect of contour interaction, the deleterious effect of identifying an object in the presence of other objects, on visual acuity in children with CVI as well as normally sighted children. This difference is more significant for children with CVI – and for this group, the greater the reduction of visual acuity, the greater the reduction in acuity with increased contour interaction. The second study shows that the critical spacing of this effect is about twice as large in children with CVI as compared to normally sighted children. The fifth study compared this effect in children with CVI to children with retinal disease. Surprisingly, there was minimal difference in the contour interaction effect between the two groups when looking at the average difference between measures. However, the slope of the trend was quite different for children with CVI versus children with retinal disease, implying that the underlying mechanism is quite different for the two groups. These two groups behave differently in the presence of contour interaction.

The third study involves comparing a commonly used pediatric visual acuity test, the Cardiff Acuity Test, to measuring vision with the same method used for the other studies - single Lea symbols surrounded by contour bars at half the optotype width away (50%) or the full optotype width away (100%). For 93% of the patients with CVI, 50% and 100% Lea symbols yielded a more reduced acuity compared to the Cardiff Acuity Test; the latter only requires detection of the symbols, whereas the Lea symbols require discrimination between an apple and a house optotype.

Finally, the fourth study examined the relationship between contour interaction and contrast sensitivity in children with CVI. Preliminary findings show a positive correlation between contour interaction and contrast sensitivity. Understanding how object contrast affects contour interaction can be translated into real world recommendations for parents and teachers and can also serve as a basis for designing perceptual learning interventions.

The overarching goal of this research is to translate measurements into usable interventions to improve the lives of patients with CVI. In general, measuring visual acuity in children with CVI in the presence of contour interaction may give a better understanding of the child's visual potential and could be most useful when making recommendations to the child's family and care team.

This dissertation reports on two early childhood developments, joint engagement and attachment patterns, and explores a possible relationship between the two in a sample of 20 infants with various levels of visual impairments, without additional disabilities. Joint engagement and security and organization of attachment patterns have been associated with positive developmental outcomes, such as better language and socio-emotional skills, better performance in theory of mind tests, and reduced risk for psychopathology. There is a need for research on these topics in the population of children with visual impairments, and the relationship between joint engagement and attachment patterns has not been explored in this population.

Study 1 focuses on joint engagement, that is, infants’ coordination of their attention between a social partner and an external focus of shared interest. Infants and their caregivers were videotaped during 30-minute free play sessions at their homes. Videos were coded to establish the duration of joint engagement episodes, and the overall time dyads participated in it. Results showed that all infants tested participated in joint engagement and that the percentage of time it represented of the 30-minute free play session significantly increased between ages 12 and 18 months. The average duration of single episodes of joint engagement increased but only approached significance. The level of each infants’ visual impairment was described as reductions from norms in visual acuity and contrast sensitivity as measured using both visual evoked potential and preferential looking techniques. Of the visual measurements, infants’ reduction in contrast sensitivity measured with preferential looking technique predicted infants’ percentage of time in joint engagement across ages. This finding supports the importance of considering contrast sensitivity levels, rather than only those of visual acuity, in research with this population.

Study 2 focuses on attachment patterns. Infants and their caregivers underwent the Strange Situation Paradigm with added instructions to accommodate for the perceptual needs of infants with visual impairments. Results showed that all but 1 of the 27 SSPs collected were deemed classifiable. Most attachment patterns were secure, ranging between 56% in the younger group of infants tested, and 70% in the older group. Attachments coded as disorganized ranged between 22% and 6% in the younger and older groups respectively.

Study 3 explores the relationship between infants’ security of attachment and the percentage of time they participated in joint engagement with their caregivers during free play. Results did not find a significant effect. This is in line with the mixed results in the literature on the connections of attachment and joint engagement, which not only varies in the finding of significant effects within a given population, but also varies between the results in different populations.

Purpose

Methods

Results

Conclusions

Purpose

Methods

Results

Conclusions