A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / Background: Esotropic strabismus is a condition in which the eyes are not properly aligned with each other. In children, uncorrected esotropia may result in permanent loss of vision due to amblyopia, a condition where the nonpreferred, crossing eye is suppressed. Early identification and treatment of esotropia in children is critical, as doing so may prevent permanent loss of vision.

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.

The atypical chemokine receptor-2 (ACKR2) is a chemokine decoy receptor that recognises pro-inflammatory CC chemokines. Many studies showed up-regulated inflammation and delayed resolution of inflammatory responses in ACKR2-/- mice. Furthermore, in the absence of ACKR2, lymphatic endothelial cells (LEC) fail to regulate the expression of pro-inflammatory CC chemokines leading to the excessive peri-lymphatic accumulation of leukocytes. As a result, the migration of antigen presenting cells (APC) through lymphatic vessels may be impaired due to lymphatic congestion. In addition, ACKR2 was shown to regulate lymphatic vessel density in the embryonic skin by regulating the proximity of pro-lymphangiogenic macrophages to LEC. Therefore, to address the role of ACKR2 and its significance in 1) APC migration and 2) inflammation-associated lymphangiogenesis, three models of ocular inflammation were used in this work, experimental autoimmune uveoretinitis (EAU), corneal graft rejection and herpes simplex keratitis (HSK). With regard to APC migration, in both EAU and HSK models, this process was fine-tuned to the level of disease in that migration was significantly compromised in ACKR2-/- mice during severe inflammation, but not under mild inflammatory conditions. Furthermore, while the severity of EAU was associated with the migration of APC, this was not so in HSK. In order to study lymphangiogenesis, the transparent avascular cornea provides a good substrate and corneal lymphangiogenesis was studied using both corneal graft model and HSK model. I found that lymphatic vessel density was increased in ACKR2-/- mice compared to wild type mice in corneal graft induced lymphangiogenesis (macrophage mediated), but not altered during early stages of HSK associated lymphangiogenesis (non-macrophage mediated). These findings confirmed that ACKR2 indirectly regulates the process of lymphangiogenesis in a macrophage dependent manner. Although the severity of HSK correlated with the level of lymphangiogenesis, this does not seem to correlate with viral load but rather associated with inflammatory infiltrations in the cornea.

Master of Science / School of Family Studies and Human Services / Bronwyn S. Fees / Jennifer R. Francois / The mother-infant relationship affects the child’s exploratory and separation behavior, how the child perceives strangers, and significantly impacts the conceptual framework of typical social relationships in the infant’s brain. The purpose of this study was to examine infants’ regulatory strategies, specifically, the relationship between the mother-infant dyad, and the infant’s response to a stressful situation. Eight, 5-month-old infants and their mothers participated in the Face-to-Face Still-Face experiment and a play session to assess maternal sensitivity. Data from the mother-infant dyads were collected during each phase of the Face-to-Face Still-Face paradigm (i.e., play, still-face, and reunion). Maternal sensitivity was assessed using an adapted version of Ainsworth’s four scales of maternal sensitivity. The infant’s strategies for re-engagement with the mother were assessed using eye-tracking methodology to identify specific eye gaze behaviors used during each phase of the still-face experiment. The infants who had more sensitive mothers showed an increase in fixation duration during the reunion phase of the procedure, which could be indicative of a trusting relationship in which the child knows the mother is there to help them regain control of their emotions. Implications of these findings are discussed for the use of eye-tracking methodology as a more flexible and potentially more accurate measure of studying infants’ patterns of ocular focus.

Diagnosis of Major Depressive Disorder (MDD) is currently symptom-based and no externally validated tests are available for routine use to confirm clinical diagnoses. Eye movement abnormalities in schizophrenia (SCZ) and bipolar disorder (BPAD) have been consistently reported and their potential as a biological trait marker highlighted. Only a limited amount of research has been conducted in MDD. Eye movement performance of MDD patients (n = 99; F:M = 55:44; Mdn age = 48) was investigated using picture free-viewing, smooth pursuit and fixation stability tasks and recorded using a non-invasive EyeLink1000 infra-red eye tracker. Performance was compared with identical measures from SCZ, BPAD, Primary Care depression (DEP) and control participants. Analysis was conducted using analyses of variance and machine learning using Probabilistic Neural Networks (PNN). We discovered a unique MDD specific eye movement phenotype, which differentiated patients with MDD from other diagnostic groups with remarkable accuracy. MDDs generated a markedly poor smooth pursuit performance, characterised by small signal-to-noise ratio, small tracking gain and large positional error. Patients also exhibited a slow average saccade velocity during free-viewing and pursuit, and poor fixation maintenance on a centralised target. A PNN classifier delineated MDD from controls with exceptional statistical sensitivity (100%) and specificity (99%), independent of state or demographics. MDD was delineated from SCZ and BPAD in all models with above 89% sensitivity and 95% specificity. MDD and DEP patients were delineated with remarkable statistical sensitivity (90%) and specificity (98%). This emerging evidence suggests possible subtypes consistent with clinical features. Testretest reliability was high for a majority of performance measures; however some measures were less robust. Brief neuropsychology assessment advocated the role of frontal lobes in oculomotor behaviour. This preliminary evidence argues for a specific MDD oculomotor dysfunction and represents potential for a diagnostically applicable biological trait marker.

Dark adaptation thresholds have been determined for a group of ocular hypertensives and a group of equivantly aged normal controls under two separate conditions of colored pre-adaptation and test. The method relies on the Purkinje shift to obtain two dark adaptation curves for each subject that cross when the initially favored long wavelength (yellow) curve is superceded by the shorter one (blue-green): under photopic conditions, the yellow and blue-green stimuli are equally efficient in stimulating the retina, as they are equated for brightness during pre-adaptation; as dark adaptation proceeds the blue-green and yellow thresholds display an early relation wherein yellow light has the lower thresholds; then the curves cross and blue-green light displays lower thresholds. Each curve is obtained separately with a pre-adaptation of 80 ft. lamberts for 5 minutes and a centrally fixated 11° test patch that matches the spectral composition of the pre-adaptation. A variety of variables are derived from threshold intensity measurements and they are analyzed for age effects, disease effects, and their interactions. Age and disease both depress blue-green and yellow cone sensitivity, delay cross-over time, and increase the total change in sensitivity over 13 minutes of dark adaptation. Interactions magnify differences. Color discrimination is found to be associated with dark adaptation thresholds, sometimes specifically as to the type of color defect and the colored dark adaptation curve showing losses. Intraocular pressure, macular sensitivity, and diastolic blood pressure are also significantly correlated with dark adaptation thresholds. Disease and age effects are elaborated in terms of changes in the ocular media, macular pigmentation changes, as well as deterioration of rod and cone processes. In addition, aging is seen to be complicated by peculiarities in the selection of the normal population. The associations demonstrated for clinical and color vision variables with dark adaptation thresholds suggest (1) that open angle glaucoma may be caused by deficient nutrition to the optic nerve head or to the retina itself, (2) that central rod and cone vision undergo changes very early in the course of the disease. A preliminary study using the two-filter method with well-established glaucoma confirms that similar, more pronounced losses in dark adaptation take place later in the disease's development. / Arts, Faculty of / Psychology, Department of / Graduate

The structural and functional organization of the pinniped eye, as represented by the harbour seal, Phoca vitulina, is much more complex than previously realized. The retina of the harbour seal is similar to that of the harp seal, in that it shows little zonation of the inner nuclear layer, possesses large horizontal cells, and has similar nuclear densities within the different retinal layers throughout the retina. The outer nuclear layer is the thickest of all the retinal layers. Photoreceptor cells of types B and C were observed with a ratio of roughly 1:23 respectively. This ratio and photoreceptor density along with a well-developed and extensive tapetum, indicates a highly light-sensitive retina. The existence of retinal folding in marine mammals is also questioned and discussed. Refractive observations obtained through retinoscopy show that the harbour seal eye is very myopic and astigmatic in air, and hypermetropic with no discernable astigmatism in water. The axis of least corneal curvature is horizontal; current theories predict that the stenopeic pupil would thus correct for astigmatism in air. The functional significance of the astigmatism, which is in the order of 7 to 13 diopters, has not been adequately determined to date, however. These observations are in agreement with those recently reported for the harp seal. Behavioural studies have also confirmed the high sensitivity of the harbour seal eye to light, as suggested by the histological observations. Two captive harbour seals were trained to select a two-bar pattern over a one-bar pattern in both air and water, discriminating for the presence of a gap. Their abilities to carry out this task were measured as the gap in the two-bar pattern was gradually reduced in size. The light intensity of the white parts of the stimulus cards was 284-369 candela/m² . Under these conditions, the harbor seal can detect a gap as small as 1 mm at a distance of 1.7 m in both air and water. These studies fail to provide values of the visual acuity of the harbour seal in the strict sense, however, owing to the physics of the pattern utilized. Rather, they indicate a measure of the absolute sensitivity of the eye to light. / Science, Faculty of / Zoology, Department of / Graduate

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.

M.Ing. (Electrical And Electronic Engineering) / Iris recognition systems have attracted much attention for their uniqueness, stability and reliability. This recognition system is composed of four main modules, namely, iris acquisition, iris segmentation, feature extraction and encoding and - nally iris matching. However, performance of this system is a ected by poor image quality. In this research, a novel iris image quality assessment method based on character component is presented. This method is composed of two steps, individual assessment of character quality parameters and fusion of estimated quality parameters using Principal Component Analysis (PCA). The de ned quality parameters considered in this research are entropy, sharpness, occlusion, dilation, area ratio, contrast and blur. The designed technique was tested on three databases: Chinese Academy of Science Institute of Automation (CASIA), University of Beira Interior (UBIRIS) and Internal Collection (IC). Individual assessment of quality parameters has shown that dilation, sharpness and blur have more in uence on the quality score than the other parameters. The images were classi ed into two categories (good and bad) by human visual inspection. The e ect of the individual parameters on each database is illustrated, with CASIA exhibiting higher quality scores than the UBIRIS and IC databases. Support Vector Machine (SVM) and Linear Discriminant Analysis (LDA) were used to evaluate the performance of the proposed quality assessment algorithm. A k-fold cross validation technique was employed to the classi ers to obtain unbiased results. Two performance measures were used to rate the proposed algorithm, namely, Correct Rate (CR) and Area Under the Curve (AUC). Both performance measures showed that SVM classi er outperforms LDA in correctly classifying the quality of the images in all three databases. The experimental results demonstrated that the proposed algorithm is capable of detecting poor quality images as it yields an e ciency of over 84% and 90% in CR and AUC respectively. The use of character component to assess quality has been found to be su cient, though there is a need to develop a better technique for standardization of quality. The results found using a SVM classi er a rms the proposed algorithm is well-suited for quality assessment.

The purpose of this research was to develop a psycho-educational counselling programme for the handling of people suffering from a severe ophthalmologically challenge. It appears that people who are severely ophthalmologically challenged do not only experience it physically but also experience negative feelings such as a crumbling self-image, a lack of self-confidence, various fears as well as depression. Their state of mind induces a change with regard to their interpersonal relationships because they avoid social interaction, as well as feelings of loss and they experience a change regarding acceptance by others. However, it has transpired that people who are severely ophthalmologically challenged make use of various mechanisms such as support by others, the gathering of information and humour in order to handle their ophthalmological challenges. Society attaches so much importance to external appearance which does not make it easier for a person suffering from a physical "dissimilarity" and it influences the person's metal health. As a consequence the researcher began asking the following questions: 1. What does the world in which a severely ophthalmologically challenged person live, look like? 2. How can a psycho-educational counselling programme lead such a person to mental health and self-acceptance? A qualitative, explorative, descriptive and contextual research design was followed. The research took place in four phases: In phase 1 the experiences of people with severe ophthalmological challenges were explored and described, by means of phenomenological, unstructured, in-depth interviews with the patient and significant others such as parents, spouses and children. In phase 2 the psycho-educational programme for the person with severe ophthalmological challenges was developed based on the results of phase 1. In phase 3 this psycho-educational counselling programme was implemented. During phase 4 the evaluation of the psycho-educational programme took place by means of a single case study. The motivation behind the development of such a programme was to create a framework in which people with severe ophthalmological challenges could develop constructive interpersonal communication skills. They could also be afforded the opportunity to reflect through discourse. By attaching significance to their discourse they can accept their changing circumstances and act self-assertively. The programme has been facilitated so that psycho-educationists and other professionals may use it to facilitate the counselling programme to improve mental health for people who are severely ophthalmologically challenged. / Prof. C.P.H. Myburgh Prof. M.Poggenpoel