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D.Phil.

M.Phil. / The anterior surface of the eye, especially the corneal curvature, is of importance in optometric and ophthalmic examinations. Pathological, surgical and contact lens induced changes to the cornea can have a significant influence on vision. It is therefore necessary to study the structure, curvature, and factors that influence the cornea. Each study contributes to a greater understanding about the nature of the anterior surface of the eye. Previous studies showed that physical exercise has an effect on the eye. These studies however looked at changes in intraocular pressure, visual acuity and other visual functions due to exercise. No study was found in the literature that investigated the effect of exercise on keratometric variation or on corneal curvature. A study done by Cronje-Dunn (1995) suggested the possibility of exercise influencing keratometric variation and the mean keratometric measurement. Due to little research in this area and the suggestions that exercise might influence keratometric variation, it was decided to investigate the influence of physical exercise on keratometric variation. In this study, 14 subjects took part in an experiment. The experiment consisted of three sets of keratometer readings obtained for each subject. The first set of readings was obtained before exercise. Directly after the first set of keratometer readings, the subject had to reach 85% of his predicted maximum heart rate on a stationary bicycle. Immediately after the cycling the second set of keratometric readings was obtained. After the second set of measurements the subject rested for an hour. The third set of keratometric readings was obtained after the hour of rest. The different sets of keratometric measurements were converted to h vectors. Transforming keratometric readings to h vectors and plotting the readings on threedimensional graphs representing symmetric dioptric power space make it possible to view the distribution or spread of the keratometric measurements and to define any variation in the measurements. The results from this dissertation indicate that keratometric variation and corneal curvature was influenced by physical exercise (cycling). Exercise increased variation in curvature around the vertical meridian and/or increased torsional variation in the horizontal and vertical meridians for most subjects. The increase in variation in curvature after exercise was greatest between the 80° and 120° meridian of the eye. This increase in keratometric variation after the cycling decreased after the rest period in most subjects. Little change in variation was noted in the curvital power around the horizontal meridian. Some subjects indicated a change in mean. The mean was greater around the vertical meridian either after the exercise and/or after the rest period.

D.Phil. / Under certain conditions the human visual system accommodates and postures at a position classically known as the dark focus. The dark focus is usually presented as a spherical phenomenon. The characteristics of the dark focus that can be conveyed by its spherical presentation are limiting: little representation can be given of the characteristics of the variation that occurs when measurements are taken of the dark focus (for example under dark conditions); no indication can be given of any antistigmatic (non-spherical) change or variation; differences in variation between light and dark conditions cannot be shown or detected using classical methods of analysis; meridional characteristics of the dark focus cannot be represented, and so on. In this thesis I have preferred to coin and use the term dark refraction shift (defined here as: 8F = F dark- Flight) for what has classically been known as the dark focus. I have done so because I believe that the term is a better description of what happens to the human visual system under dark conditions. Multivariate methods of analysis allow for a much more detailed, and complete, presentation ofthe dark refraction shift and its variation. The limitations of methods used previously and mentioned above are overcome when multivariate methods are used to analyze and present dark refraction shift data. This thesis presents the dark refraction shift and its various characteristics, making use of multivariate methods that are used for this purpose for the first time. A Hoya AR550 autorefractor, set to measure refractive state to the nearest 0.01 D, was used to take 50 measurements at a time of the refractive state of twenty subjects under varying conditions ofluminance. The autorefractor was re-focused after each measurement. In the light condition, the subject was positioned in front of the autorefractor, the room lights were left switched on and the fixation target inside the instrument was visible to the subject. 50 measurements were then taken under these conditions. A second set of measurements was then taken under the dark condition. In the dark condition measurements the subject was left in complete darkness for five minutes to allow the accommodative system to settle at the dark focus. No fixation target was visible to the subject who remained in complete darkness for the duration of the dark condition measurements. 50 autorefractor measurements were taken under these conditions. Two measurement sessions were conducted where the order of the light and dark conditions were reversed. In the case of each subject the order of light versus dark condition measurements was determined randomly for the initial session and reversed in the second session. Subjects had to fulfill certain selection criteria; the refractive state had to have a cylinder equivalent dioptric strength of less than or equal to 6 D, the visual acuity had to be 6/6 or better in the right eye, subjects with strabismus were eliminated and subjects with any observable ocular pathology were not accepted. Ten of the subjects were aged between 21 and 35 years of age. They constituted the prepresbyopic group. The other ten subjects were aged between 40 and 65 years of age and constituted the presbyopic group. Each subject had a total of 200 measurements taken, 100 measurements taken in the light condition and 1 00 taken in the dark condition.

The thesis presented in this paper is an attempt to quantify generally preferred amounts of virtual image sharpening in augmented reality applications. This preferred amount of sharpening is sought after in an effort to alleviate eye fatigue, and other negative symptoms, caused by accommodation switching between virtual images and real objects in augmented reality (AR) systems. This is an important area of research within the AR world due to the presence of many AR applications that supplement the real world with virtual information, often in the form of virtual text for users to read. An experiment, involving human subjects choosing between higher and lower sharpening amounts, was run to expose preferred amounts of sharpening or patterns of chosen amounts in relation to a number of variables within the experiment; those variables are: virtual text accommodative distance, real text accommodative distance, and the object of focus (real or virtual). The results of this experimentation may benefit future AR research and implementations, specifically in how they handle users switching focus.

Visual accommodation plays a critical role in one's visual perception and activities of daily living. The age-related accommodation loss poses a greater risk to older adults' safety and independence. Although extensive effort has been made to study the effects of aging on accommodation, the relationship between aging and the dynamic aspects of accommodation is still unknown. Furthermore, since light is the carrier of external stimuli for accommodation, it is of value to assess the influences of light on the age-related accommodation loss. Therefore, a study was conducted to investigate the age-related dynamic accommodative characteristics under various conditions of the intensity and chromaticity of light. To ascertain the effects of aging, ten individuals from each of three age groups (i.e., younger group: 20 to 29 years old, middle-aged group: 40 to 49 years old, and older group: 60 to 69 years old) were recruited, and their dynamic accommodation responses were examined. Laboratory experiments were designed to measure accommodation in a simulated condition where a person must alternate from viewing outside to reading the dashboard while driving. It was hypothesized that the advancing of age will lead to the deterioration of one's dynamic accommodative performance, and light of different intensities and chromaticities will interact with the effects of aging on accommodation. The results of the study supported the above hypotheses. It was found that the advancing of age, the decrease of light intensity, and the change of light chromaticity all led to the alteration of one's dynamic accommodative performance. The present study concluded with a biomechanical and neural model elaborating the mechanism of an accommodation process within the scope of the study. / Ph. D.

The educational practice known as inclusion, which is based on values of equal opportunity and diversity, enables students with disabilities to attend the same general education classes as typically developing peers. Inclusion is a legal requirement in the United States and South Korea, but factors facilitating inclusion likely differ across countries. The purpose of the study was to examine PreK-6 school teachers' beliefs about inclusive practices in the United States and South Korea and to present a more informed direction for the future of inclusive education in both countries. Seventy-four teachers from the US and 54 from South Korea participated via email for this study employing surveys. Teachers provided their beliefs about inclusion items on the My Thinking About Inclusion (MTAI) scale, a 28-question instrument, and also provided information about their own gender, years of experience, education level, and teaching practices. A statistically significant difference was found between the teachers of the two nations for the full survey scale. The teachers' training area (i.e., general education or special education) in the US was significantly associated with the belief toward inclusion, and special education teachers in both countries were more agreeable to inclusion than general education practitioners were as shown by the MTAI scale. A strong relationship between accommodation and preparedness for disabilities was found. Most of the barrier factors to practicing inclusive education were considered substantial obstacles, but more so for South Korea teachers than US teachers. University coursework was the least preferred method for improving inclusive practices according to teachers in both countries. Based on the outcomes of the two nations' teachers' beliefs about inclusion, the author suggests that supportive practices, including collaboration between educators, professional development, partnerships with parents and families, and peer supports, be implemented within the two countries for the upkeep of inclusive practices.

<p>The dark focus is a resting state of accommodation, which occurs when there are not enough stimuli for the eye to focus on. This means that the eye becomes more myopic and some people notice a blur for example at night time, more known as night myopia. In this study the dark focus in Swedish myopes is measured and any difference between early and late onset myopes is investigated.</p><p><strong>Method: </strong>The dominant eye of 56 myopes was first measured with static retinoscopy, using a distant target, and then with near retinoscopy, with the retinoscope beam as the target. The full working distance of 2.00 D was subtracted in both methods and the values were compared. The difference, if any, was the dark focus.</p><p><strong>Results: </strong>The mean value of dark focus was 0.53 D ± 0.26 for the entire group. The mean value for early onset myopes was 0.56 D ± 0.29 and for late onset myopes the mean value was 0.47 D ± 0.21. This showed no significant difference (p-value = 0.18). No significant correlation between amount of refractive error and dark focus was found.</p><p><strong>Conclusion: </strong>The Swedish myopes in this study have a smaller mean value of dark focus than mean values found in other studies using the same technique and the previous findings that early and late onset myopes differ in mean values of dark focus is not applied to this study.</p>

The dark focus is a resting state of accommodation, which occurs when there are not enough stimuli for the eye to focus on. This means that the eye becomes more myopic and some people notice a blur for example at night time, more known as night myopia. In this study the dark focus in Swedish myopes is measured and any difference between early and late onset myopes is investigated. Method: The dominant eye of 56 myopes was first measured with static retinoscopy, using a distant target, and then with near retinoscopy, with the retinoscope beam as the target. The full working distance of 2.00 D was subtracted in both methods and the values were compared. The difference, if any, was the dark focus. Results: The mean value of dark focus was 0.53 D ± 0.26 for the entire group. The mean value for early onset myopes was 0.56 D ± 0.29 and for late onset myopes the mean value was 0.47 D ± 0.21. This showed no significant difference (p-value = 0.18). No significant correlation between amount of refractive error and dark focus was found. Conclusion: The Swedish myopes in this study have a smaller mean value of dark focus than mean values found in other studies using the same technique and the previous findings that early and late onset myopes differ in mean values of dark focus is not applied to this study.

No description available.