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The role of the FEF/FPA and SEF in oculomotor prediction was investigated using psychophysics, functional MRI (fMRI) and TMS. The separate contribution of advance knowledge of target direction and target timing to predictive saccades, and neural activity in frontal oculomotor structures was first investigated. The greatest proportion of predictive saccades were elicited when subjects had advance knowledge of both target direction and target timing; advance knowledge of target direction increased the proportion of predictive saccades, while advance knowledge of target timing decreased saccade latencies without increasing predictive saccades. Activity was greater in the FEF for all saccade tasks with a predictable component than reflexive saccades. Activity in the FEF was higher in tasks for which saccade latencies were lower. These data suggest that target direction and target timing independently reduce saccade latencies, and that this information converges in the FEF to allow the generation of predictive saccades. In the SEF, activity was greater only in the condition when both target direction and target timing were predictable. This finding may reflect a role of the SEF in oculomotor sequencing rather than in prediction per se. / In order to assess whether the FEF play a general role in oculomotor prediction, and not just in saccades, the role of the FPA in predictive pursuit was evaluated by applying TMS to the FPA and SEF during sinusoidal pursuit. TMS of the FPA modulated eye velocity both at peak target velocity and at the target turnaround. The induced changes in eye velocity occurred with a short latency, that is, before visual signals could travel from the retina to brainstem. This would suggest that TMS of the FPA likely increased the gain of the transformation of predictive signals, rather than visual signals, to motor commands. Stimulation of the SEF increased eye velocity only when applied at the target turnaround. Previous studies have demonstrated that stimulation of SEF increases eye velocity during pursuit initiation. Our finding that this facilitation also occurs at the target turnaround may berelated to similarities between pursuit initiation and the turnaround, including the necessity to rapidly increase eye velocity from zero.

Retinal image properties such as contrast and spatial frequency play important roles in the development of normal vision. For example, visual environments comprised solely of low contrast and/or low spatial frequencies induce myopia. The visual image is processed by the retina and it then locally controls eye growth. In terms of the retinal neurotransmitters that link visual stimuli to eye growth, there is strong evidence to suggest involvement of the retinal dopamine (DA) system. For example, effectively increasing retinal DA levels by using DA agonists can suppress the development of form-deprivation myopia (FDM). However, whether visual feedback controls eye growth by modulating retinal DA release, and/or some other factors, is still being elucidated. This thesis is chiefly concerned with the relationship between the dopaminergic system and retinal image properties in eye growth control. More specifically, whether the amount of retinal DA release reduces as the complexity of the image degrades was determined. For example, we investigated whether the level of retinal DA release decreased as image contrast decreased. In addition, the effects of spatial frequency, spatial energy distribution slope, and spatial phase on retinal DA release and eye growth were examined. When chicks were 8-days-old, a cone-lens imaging system was applied monocularly (+30 D, 3.3 cm cone). A short-term treatment period (6 hr) and a longer-term treatment period (4.5 days) were used. The short-term treatment tests for the acute reduction in DA release by the visual stimulus, as is seen with diffusers and lenses, whereas the 4.5 day point tests for reduction in DA release after more prolonged exposure to the visual stimulus. In the contrast study, 1.35 cyc/deg square wave grating targets of 95%, 67%, 45%, 12% or 4.2% contrast were used. Blank (0% contrast) targets were included for comparison. In the spatial frequency study, both sine and square wave grating targets with either 0.017 cyc/deg and 0.13 cyc/deg fundamental spatial frequencies and 95% contrast were used. In the spectral slope study, 30% root-mean-squared (RMS) contrast fractal noise targets with spectral fall-off of 1/f0.5, 1/f and 1/f2 were used. In the spatial alignment study, a structured Maltese cross (MX) target, a structured circular patterned (C) target and the scrambled versions of these two targets (SMX and SC) were used. Each treatment group comprised 6 chicks for ocular biometry (refraction and ocular dimension measurement) and 4 for analysis of retinal DA release. Vitreal dihydroxyphenylacetic acid (DOPAC) was analysed through ion-paired reversed phase high performance liquid chromatography with electrochemical detection (HPLC-ED), as a measure of retinal DA release. For the comparison between retinal DA release and eye growth, large reductions in retinal DA release possibly due to the decreased light level inside the cone-lens imaging system were observed across all treated eyes while only those exposed to low contrast, low spatial frequency sine wave grating, 1/f2, C and SC targets had myopic shifts in refraction. Amongst these treatment groups, no acute effect was observed and longer-term effects were only found in the low contrast and 1/f2 groups. These findings suggest that retinal DA release does not causally link visual stimuli properties to eye growth, and these target induced changes in refractive development are not dependent on the level of retinal DA release. Retinal dopaminergic cells might be affected indirectly via other retinal cells that immediately respond to changes in the image contrast of the retinal image.

Thesis (MAppSc in Physiotherapy)--University of South Australia, 1996

Accessible and affordable eye care is only a dream for much of the population of developing countries. Strategies for improving the visual welfare of these people need to be appropriate to the local situation. In 1992 a proposal was devised to address the lack of eye care in Papua New Guinea. This thesis examines the outcome of this proposal and reports on the ophthalmic data collected by these trained eye nurses.Method: In 1994, 11 National nurses were trained in a 3 month intensive course to become ‘eye nurses’. A basic set of equipment was provided to each eye nurse. Appropriate follow-up and annual conferences supported this initial training. A second group of 14 eye nurses were trained in 1997. Monthly eye clinic reports from the eye nurses provide significant data on eye conditions and visual welfare in PNGResults: After 6 years 80% of the eye nurses were still actively working in eye care. An analysis was made of the eye conditions of the 30,000 patients examined by the eye nurses over this 6 year period. The data is generally consistent with previous ophthalmic data from Papua New Guinea. The eye nurses were able to provide appropriate eye care for 80% of the presenting patients without Optometric or Ophthalmic assistance.Conclusions: Training nurses to become ‘eye nurses’ functioning as basic optometrists is an effective strategy in improving eye care in developing countries. The eye nurses were able to deliver sustainable, accessible, affordable and appropriate eye care, independently treating and managing the most common eye conditions in Papua New Guinea.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains viii, 42 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 39-40).

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains x, 93 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 86-90).

Thesis (M. Med. Sc.)--University of Hong Kong, 2007.

Thesis (M.S.)--State University of New York at Binghamton, Dept. of Psychology, 2007. / Includes bibliographical references.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 7 uppsatser.