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The aim of this thesis is to develop a method of optical modelling that can be used to predict visual performance of the eye. It is intended to give visual acuity estimates under normal circumstances and under a wide range of optical treatments such as photorefractive keratectomy (PRK) to correct refractive error. Visual performance refers to the performance of the eye under various conditions such as decreased object contrast, defocus and change in pupil size. (For complete abstract open document)

Thesis (Optometry, M.S.) --Nova Southeastern University in Ft. Lauderdale, Florida, 2008. / Includes bibliographical references. Typescript. "A Thesis Submitted to NOVA Southeastern University's Clinical Vision Research Graduate Program in Partial Fulfillment of the Requirements for the Degree of Master of Science." Also available online via ProQuest : Dissertations & Theses

Issued also as author's dissertation. / Columbia contributions to philosophy and psychology, vol. XX, no. 2.

M.Phil. / Tinted spectacle lenses have long been worn to provide ocular protection from harmful electromagnetic radiation during recreational activities. Controversy exists surrounding the colour of the spectacle tints and the environmental conditions under which these tints are worn. There is little scientific evidence to substantiate the many opinions of authors on the effects of tinted spectacle lenses on visual skills and, ultimately, on overall performance in recreational situations. This study serves to provide scientific data concerning the effects of tinted lenses on static visual acuity, contrast sensitivity, colour vision, stereopsis and visual evoked potential (VEP). These results are related to the visible spectrum transmission curve for each experimental lens. recommendations are then made concerning the environmental conditions under which each lens tint should be worn. The HOYA ULT-2000 Light Transmission Metre was used to establish the percentage of visible light being transmitted through each of the experimental lenses. The DMS 80/90 Visible Spectrophotometer was used to generate a visible spectrum transmission curve for each of the 8 experimental lenses used in this study. 30 subjects (Group A) were randomly selected from the RAU student population for the assessment of the effects of tinted lenses static visual acuity, contrast sensitivity, colour vision and stereopsis. 10 students (Group B) were then randomly selected from the RAU student population for the assessment of the effects of tinted experimental lenses on visual evoked potential (VEP). The ametropic subjects in Groups A and B all wore their habitual spectacle or contact lens corrections throughout the testing procedure. The following lens tint colours were used: clear, black, grey, yellow, green, blue, red and pink. The subjects were evaluated binocularly without any tinted lens being worn, then through each of the 8 tinted experimental lenses (randomly presented). Results of the visual skills and VEP testing were analysed as follows: Group A: An average score was calculated for the results achieved on the static visual acuity, contrast sensitivity, colour vision and stereopsis tests when no experimental lenses were worn. This average was then compared to the average static visual acuity, contrast sensitivity, colour vision and stereopsis scores for each of the 8 experimental lenses. Group B: An average score was calculated for each of the amplitude and latency components of the VEP waveforms generated when no experimental lenses are worn. This average was then compared to the average amplitude and latency components generated when each of the 8 experimental lenses (as for Group A) are worn. Static visual acuity was assessed using a Snellen visual acuity letter chart at 6m. Contrast sensitivity was assessed using a Vistech VCTS 6500 Contrast Sensitivity Chart at 3m. Colour vision assessment was performed using the lshihara Colour Vision Test and the City University Colour Vision Test. The Random Dot Near Stereo Test was used to assess stereopsis. The Nicolet Pathfinder II was used to assess visual evoked potentials (VEPs). The results of this study show that the black, grey, yellow, green, blue, red and pink tinted lenses have a statistically significant influence on visual efficiency only when subjective methods (i.e. static visual acuity, contrast sensitivity, colour -vision and stereopsis) of visual efficiency assessment are used. The tinted lenses had little effect on visual efficiency when an objective means (i.e. VEP) of assessment was used, as there were no statistically significant differences between the lenses. The results of this research project indicate that the colour of the lens tint has little real effect on visual efficiency, when measured objectively. The effect of the lens tint is shown to be highly subjective. Tinted lens selection would therefore be based on personal preference and the amount of protection that the lens provides from harmful electromagnetic radiation. It can be concluded that no single lens tint is therefore suitable for all individuals under the same environmental conditions.

Thesis advisor: Sara Cordes / Throughout early childhood, children learn various symbolic systems to represent abstract concepts such as quantity. Yet it is unclear how the acquisition of symbols for quantity (e.g., number words; measurement concepts of “seconds”, “minutes”… for time, etc.) may shape nonsymbolic representations of these quantities. While previous work hints at the possibility that acquiring numerical symbols refines numerical acuity (i.e., “refinement hypothesis”), these data are correlational in nature, making it impossible to assess causality. As such, experimental manipulations training the symbolic system are necessary in order to determine whether a causal relation exists. Moreover, these investigations have been limited to the domain of number, making it unclear if similar relations exist in continuous quantities, such as time and space. My dissertation tests whether the relation between symbolic and nonsymbolic abilities holds for the inherently continuous quantity of time, while also providing one of the first investigations of the refinement hypothesis outside of the domain of number. Results reveal that nonsymbolic and symbolic timing are related in childhood, both before and during formal instruction on temporal units of measurement (Experiment 1 & 2), but not in adulthood (Experiment 3). Further, I find no support for the refinement hypothesis: learning temporal symbols did not result in improved temporal acuity (Experiment 2), nor did shifting adults’ symbolic mapping of time shape temporal acuity (Experiment 3). Similarly, learning labels for surface area did not enhance adults’ spatial acuity (Experiment 4). Broader educational implications and areas of future investigation are also discussed. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.

Dynamic Visual Acuity (DVA) refers to an observer's ability to resolve a critical detail in a visual target under conditions of relative motion between an observer and a target. DVA research has conventionally used visual targets originating from a single fixation point and moving in a predictable linear path. These procedures (dictated by apparatus constraints), ensured observers knew when and from where targets would appear. Shevlin, Prestrude, and Shevlin (1997) examined DVA using computer-generated targets presented from fixed (left to right) and random (six possible) origins. As hypothesized, random targets were more difficult to resolve than fixed targets. Fixed target data supported the conventional DVA findings - faster targets and targets displayed more briefly were harder to resolve. Random target data contradicted the DVA literature suggesting increased target velocity actually improved DVA (Shevlin et al., 1997). In the current study all targets moved in similar fashion, eliminating type of movement as a confound from the 1997 study. Twenty-eight West Point cadets observed computer DVA targets under each of two viewing conditions. Prior to viewing each target, observers in the "known origin" condition saw text cues revealing the origin of the next target; whereas, observers in the "unknown origin" condition received text notification that a target would appear. As hypothesized, known origin target data supported conventional DVA relationships - faster targets and targets exposed more briefly were more difficult to resolve. As predicted, unknown origin data partially contradicted conventional DVA relationships. At the briefest duration (170 ms), faster targets were easier to resolve than slower targets. Observers in the known origin condition displayed a DVA advantage from the text cues. The patterns of individual differences in the data suggest not all observers benefited from the DVA advantage offered by the text cues. Analysis of target data indicated a slight DVA decrement for left-oriented Landolt C targets. Implications of the computerized DVA testing platform are discussed for future DVA research. / Ph. D.

Static Visual Acuity (SVA) has been called into question for some time as a measure of overall visual system function and as a predictor of performance on real-life tasks requiring vision (i.e., operating an automobile). Specifically, it has been pointed out that the targets employed in most SVA testing (high contrast, stationary letters) are an insufficient analog to actual targets encountered in everyday activities, which are often in motion and/or of less-than-perfect contrast. In addition, the size-threshold methodology typically used to measure SVA is incongruent with current theories of a multi-channel visual system. Dynamic Visual Acuity (DVA) and Contrast Sensitivity have been suggested as alternatives to SVA, but while each mitigates specific weaknesses of the SVA measure, neither addresses the shortcomings completely. Traditional DVA measures employ moving targets, but these targets are usually of perfect contrast and a size-threshold methodology is used to specify acuity levels. Contrast Sensitivity employs a contrast-threshold methodology and allows measurement of specific visual channels, but stationary targets are utilized. The present study combined the DVA and Contrast Sensitivity measures in an effort to retain the unique qualities of each while addressing their shortcomings, resulting in a more detailed picture of the human visual system and functioning than has yet been possible. By measuring contrast sensitivity to targets at a set of spatial frequencies spanning the human "window of visibility" and under conditions of motion representative of that encountered in everyday activities, it was hoped that a more powerful predictor of actual visual performance would be created. In addition, normative data was established for two separate age populations, in the hopes of learning more about specific changes that occur to the visual system during the aging process. Indeed, several effects and interactions among the three main variables (spatial frequency, velocity, age) were uncovered, which appears to indicate that the new test may provide more information about the visual system than DVA or contrast sensitivity by themselves. The ramifications of this effort to human factors and visual performance research are discussed along with recommendations for the continuation and application of this line of research.

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