M.Phil. (Optometry) / An investigation of the nature of variability or variation of refractive behaviour (in a sample of universi ty students studying optometry) is described. Measurements of refractive behaviour were obtained by means of autorefraction. This study was based upon multivariate methods of statistical analysis which have only recently become available in optometric science. Variation is examined using both quali tative and quanti tative methods including stereo-pair scatter plots, confidence and distribution ellipsoids, trajectories of change of dioptric power, meridional profiles, testing of hypotheses on means and variance-covariance, and graphs which represent the type of uniform variation in a 2-dimensional plane known as the i)-plane. These methods are of great assistance in developing an understanding of the nature of the variation shown, as well as, in developing an awareness of the distribution or spread of the population from which the sample was drawn. Analyses of variability of refractive behaviour on both an artificial, or test eye, and on several individual human eyes are also described. The significance of some important aspects of variabili ty of refractive behaviour involving normality and departures therefrom (such as results from outliers) are discussed and illustrated by means of examples. Distributions were found in which more than one mode was present (polymodal or multimodal behaviour). Distributions were also observed to vary from having an almost spherical spread of measurements (of refractive behaviour) to having a spindle or rod-like spread of measurements instead...

M.Phil. (Optometry) / Previous studies of corneal and keratometric variation used incomplete or incorrect statistical methods. For the first time, proper multivariate statistical methods are applied to evaluate short-term keratometric variation in human eyes. Keratometric variation is represented graphically by means of stereo-pair scatter plots, trajectories of change in dioptric power, ellipsoidal confidence regions for mean dioptric power, as well as meridional profiles. Quantitative expressions of variation are given in terms of mean values, variance-covariance matrices and volumes of 95% distribution ellipsoids. Manual and automatic keratometry is compared, both on a steel ball and on an eye. It appears that the automatic keratometer exhibits less variation than the manual keratometer....

M.Phil. / Using newly developed statistical analysis methods for refractive error this study examines the difference between autorefraction and subjective refraction and how it is related to age. The term autorefractive excess refers to the amount obtained by subtracting the subjective refraction from the autorefraction. The clinical sample consisted of five groups of fifty subjects each. The subjects in group 1 ranged in age from 1 to 10 years, group 2 from 11 to 20 years, group 3 from 21 to 30 years, group 4 from 31 to 40 years and group 5 from 41 years and older. Only one examiner (the author) and one autorefractor (Allergan-Humphrey 580) were used. The study found that there was a difference between the mean autorefractive excesses for the different age groups and that the difference between autorefraction and subjective refraction was statistically significant in both the left and the right eyes of all age groups. Left and right eyes exhibited similar behavior. The autorefractive excess for both the left and the right eyes together of group 1 was approximately -0.25/-0.18 x180 in conventional and (-0.25 0.00 -0.43)' in h-notation. The autorefractive excess increases by approximately (0.10 0.00 0.10)' per decade. There is an astigmatic component of approximately -0.18 x180 in both eyes of all age groups. Approximately 60% of the subjects had sphere-equivalent strengths of autorefractive excesses of under 0.50 D. Therefore 60% of subjects might be content with a prescription given from the autorefractor reading. Approximately 50% of subjects had cylinderequivalent strengths of autorefractive excesses of under 0.50 D.

M.Phil. / The aim of this study was to use auto refraction to investigate both the short-term intra-ocular variation of refractive status among primary school children and the spread of refractive status across eyes. The sample consisted of 90 Caucasian school children from a primary school in a small town, Eloff, in the Mpumalanga province of South Africa ...

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Twelve spatial-cueing experiments examined stimulus-driven and goal-driven control of visual attention orienting under multiple-cue conditions. Spatial cueing involves presenting a cue at a potential target location before a target appears in a display, and measuring the cue's effect on responses to the target stimulus. Under certain conditions, a cue that appears abruptly in a display (direct cue) can speed responses to a target appearing at the previously cued location relative to other uncued locations (called the cue effect). The experiments in this dissertation used a new multiple-cue procedure to decouple the effects of stimulus-driven and goal-driven processes on the control of attention. This technique involved simultaneously presenting a red direct cue (Unique Cue) that was highly predictive of the target location along with multiple grey direct cues (Standard Cues) that were not predictive of the target location. The basic finding was that while cue effects occurred at all cued locations, they were significantly larger at the Unique-Cue location. This finding was interpreted as evidence for stimulus-driven cue effects at all cued locations with additional goal-driven cue effects at the Unique-Cue location. Further experiments showed that Standard-Cue effects could occur independently at multiple locations, that they seemed to involve a sensory-based interaction between the cues and the target, and that they were mediated by a limitedcapacity tracking mechanism. In addition, Unique-Cue effects were found to be the product of goal-driven operations, to interact with Standard-Cue effects, and to involve inhibited processing at unattended locations. These results were explained in terms of a filter-based model of attention control that assigns priority to potential attention-shift destinations. According to this model, stimulus-driven and goal-driven factors generate signals (activity distributions) that drive a filter to open an attention channel at the highest priority location by suppressing the signals at other locations. The final experiments confirmed the central assumptions of this model by providing evidence that the prioritydestination process was sufficient to produce cue effects independent of attention, and that attending to a location involved a suppression of processing at unattended locations. The implications of this model for the larger visual attention literature were also discussed. / Arts, Faculty of / Psychology, Department of / Graduate

Robotics have advanced to include highly anthropomorphic (human-like) entities. A novel eye-tracking paradigm was developed to assess infants’ sensitivity to communicative gestures by human and robotic informants. Infants from two age groups (5-9 months, n = 25; 10-15 months, n = 9) viewed a robotic or human informant pointing to locations where events would occur during experimental trials. Trials consisted of three phases: gesture, prediction, and event. Duration of looking (ms) to two areas of interest, target location and non-target location, was extracted. A series of paired t-tests revealed that only older infants in the human condition looked significantly longer to the target location during the prediction phase (p = .036). Future research is needed to tease apart what components of the robotic hand infants respond to differentially, and whether a robotic hand can be manipulated to increase infants’ sensitivity to social communication gestures executed by said robotic hand. / Includes bibliography. / Thesis (MA)--Florida Atlantic University, 2021. / FAU Electronic Theses and Dissertations Collection

archives@tulane.edu / Making eye contact is one of the earliest, most important forms of communication. Newborns are sensitive to adults’ gaze direction (Farroni, Massaccesi, Pividori, & Johnson, 2004), and by 4 months infants learn more about an object that an adult has looked at (Reid & Striano, 2005). Emotional facial expressions influence infants’ scanning of adults’ eyes (Shepard & Spence, 2012), which may affect their sensitivity to eye gaze cues. In two experiments, we examined the effects of silent dynamic emotional messages on 6-month-old infants’ scanning of face features, as well as their sensitivity to and learning from eye gaze cues. In Experiment 1, infants completed a gaze cueing task in which speakers delivered silent approving, comforting, prohibition, and neutral messages and then shifted their eye gaze to a peripheral target. Although infants showed increased attention to the eyes during prohibition and comforting messages, all infants showed enhanced gaze cueing in the context of approving messages. Moreover, female infants showed trend-level gaze cueing following approving messages, whereas male infants showed trend-level gaze cueing following neutral messages. In Experiment 2, a separate group of infants completed a similar gaze cueing task that included a visual paired comparison test phase to examine learning of the gaze-cued and non-cued targets, based on the hypothesis that increased sensitivity to gaze cues would enhance learning of the cued targets. As in Experiment 1, infants showed increased attention to the eyes during comforting messages. However, we did not find any reliable gaze cueing effects. Infants spent more time looking at test targets following approving messages but did not show evidence of enhanced learning of cued targets. Overall, findings from both experiments suggest that 6-month-olds are more responsive to gaze cues in the context of approving messages, underscoring the significance of positive infant-directed interactions to the development of early joint attention. We conclude by discussing clinical implications, limitations (including a relevant error in Experiment 2), and future directions. / 1 / Claire Frances Noonan

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