No description available.

No description available.

No description available.

The use of amniotic membrane (AM) as a dressing for ocular surface injuries has attracted the interest of the military ophthalmological community. First applied in the 1930s, the tissue is widely used today, although clinical indications for treatment are incompletely defined. While AM is most commonly stored frozen and thawed before use, dried AM is preferred for logistical reasons. Optimal preservation of the tissue is necessary to preserve its quality. The effect of drying on the physical and biological properties of the tissue are unknown. A systematic review of the evidence of AM treatment of acute chemical injuries was conducted. A framework was proposed for optimising the dried tissue through thermal, moisture sorption and surface analytical techniques. The physical properties of AM preparations were compared by mechanical testing and mathematical modelling, and an attempt was made to cross-link the AM collagen. Inflammatory aspects of the tissue were assessed by immunological techniques, zymography and macrophage assays. There is a lack of high quality evidence to support the clinical application of AM for acute burns. Complex interactions were demonstrated between the dried tissue, its excipients and moisture, suggesting novel ways of optimising the product. The mechanical properties of the dried membrane indicated that the process adversely affected the tissue, and artificial cross-linking could not be achieved. While the presence of antimicrobial peptides was not clearly established, the elution of collagenolytic enzymes was shown in therapeutic preparations of AM. The production of tumour necrosis factor by macrophages, which adhere to the spongy layer of AM, was suppressed. This project makes original contributions relevant to the use of dried AM as a biomaterial in ophthalmic surgery. Further refinements of this work, animal model experimentation and clinical trials may support its future acceptance as a clinical application.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 93-94).

Based on the author's thesis entitled: An etymologic glossary of French medical terms referable to the eye.

The oldest and most prevalent optical system in the world is the human eye. Variations in the anatomical structure of the eye can cause errors in its optical performance, which in turn lead to errors in the overall performance of the visual system. Fortunately, these refractive errors can be measured and then corrected externally with spectacles, contact lenses, or refractive surgery. This dissertation describes the design, fabrication, and testing of a new autorefractor that can be used to objectively measure human refractive error. The new autorefractor is based on Shack-Hartmann wavefront sensing techniques and uses a novel, Fourier transform-based algorithm to estimate refractive error. The Fourier-based data analysis models the wavefront aberration as a combination of defocus and astigmatism only, expresses the simplified wavefront in terms of measurable quantities in Fourier-space, and relates the coefficients describing the wavefront to the patient's refraction. The Shack-Hartmann-based autorefractor (SHAR) is designed to be inexpensive and compact to facilitate its transition to a commercial device. It represents a significant improvement in automated clinical refraction because it can make accurate measurements of a wide range of refractive errors without relying on moving parts or the intensity of light reflected off the retina. To evaluate its performance, the SHAR was compared to the gold-standard among current commercially available autorefractors in a study of human refractive errors. The results from this limited study population suggested that the SHAR has the potential to perform at least as well as the commercial standard autorefractor.

The studies comprising this thesis were conducted to further understand how structural changes to the corneal extracellular matrix can affect the cornea’s unique properties, with the ultimate goal of improving novel treatments and their outcomes. Following refractive surgery, changes in matrix structure can cause loss of structural integrity and transparency, which may adversely affect the surgical outcome. The first objective was to define what governs corneal shape and ultrastructural organisation by analysing the abnormal post-hatch corneal collagen arrangement in an avian model (beg). Structural information was also obtained post-in vivo microwave keratoplasty to assess the treatment as a suitable alternative to more invasive correction procedures. In addition, modifying the resident cell type as a means of improving post-treatment wound healing following LASIK was also investigated using corneal stromal stem cells. Finally, the efficiency of transepithelial riboflavin/UVA collagen cross-linking in terms of riboflavin uptake and post-treatment corneal stiffness, was evaluated. X-ray scattering studies revealed that corneal flattening in beg chickens is related to biomechanical changes brought about by an alteration in collagen arrangement at the corneal periphery. This highlights the importance of the limbal fibril annulus in corneal shape preservation. X-ray studies also revealed that microwave keratoplasty may impact on peripheral vision by introducing spatial disruption of stromal collagen, resulting in localised corneal opacity in the treatment area. Loss of fibrillar structure and order could also have further implications for corneal biomechanics and shape. The application of human corneal stromal stem cells under LASIK-like flaps was revealed to be a promising approach for increasing flap adherence strength whilst maintaining corneal clarity. Introducing these cells in the early stages of flap-healing appears to improve the repair process, conceivably through an embryonic-like mechanism. Lastly, stress-strain and riboflavin uptake results for transepithelial riboflavin delivery during corneal cross-linking were encouraging, however refinements to the testing procedure are required to fully assess the treatment efficacy. Collectively these findings accentuate the importance of the precise stromal collagen fibril arrangement and composition for maintaining corneal transparency, shape and general functionality. All these factors must be taken into consideration when implementing novel correction procedures or modifying existing treatments for corneal defects.

The purpose of the studies described herein was to better understand the impact of involuntary eye movements on oculomotor control and perception in infantile nystagmus. Therapeutic interventions that result in slowed nystagmus oscillations often fail to elicit significant quantifiable improvements in visual function, despite patients reporting subjective benefits. It is difficult to justify surgical or pharmacological intervention when the only outcome measures are subjective. Objective quantification of nystagmus eye movements per se usually involves time-consuming manual marking of recordings to both calibrate and analyse data. As a result, analyses are rarely (if ever) performed in the clinical setting. Software was therefore developed to automate calibration and assessment. Psychophysical experiments were undertaken to quantify the spatiotemporal constraints of vision in infantile nystagmus. Visual acuity was measured in the absence of retinal image motion to reveal the maximum improvement to spatial vision that might be expected if nystagmus were halted altogether. The results indicate that poor spatial vision underlies infantile nystagmus, even in cases without comorbid pathology. Gaze acquisition time was compared to stimulus recognition time. The results indicate that infantile nystagmus does not increase visual processing time; rather, redeploying gaze takes longer. An incidental finding revealed a temporal relationship between voluntary saccades and involuntary nystagmus quick phases. Both typically occur together, presumably to maximise efficiency and minimise saccadic suppression. Clinical tests of gaze acquisition time must now be developed, to be used in conjunction with the software developed here, as objective outcome measures of therapeutic interventions.

Purpose: This thesis aimed to characterise and analyse the 3D micro- and nanoarchitecture of connective tissue within the lamina cribrosa (LC). Methods: The microarchitecture of load-bearing connective tissue components, elastin and fibrillar collagen, of the young, elderly and glaucomatous optic nerve head (ONH) was analysed following two-photon excited fluorescence, second harmonic generation and small angle light scattering. Microfocus and conventional small angle X-ray scattering were used to analyse ONH nanoarchitecture and the potential of X-ray microtomography (XMT) as a 3D imaging technique was evaluated. Results: Fibrillar collagen and elastic fibres stretched radially across the optic nerve (ON) canal in the LC, encircled the central retinal vessels and were absent in the prelamina. In the postlaminar ON septae, collagen was perpendicular to that in the LC. Differences in young and elderly ONH tissue included; wavy collagen bundles exclusively within the young ONH and distinct elastic fibres found in the elderly ONH. Analysis of ONH reconstructions of 3D SHG datasets revealed that elderly LCs contained higher fibrillar collagen content when compared to the young LCs. Interestingly, the connective tissue beams of the inferior-temporal LC quadrant were significantly more aligned in glaucoma when compared to age-matched controls. Distinct X-ray reflections, potentially elastin in the peripapillary sclera and representative of CNS myelin in the postlaminar ON were identified. XMT enabled quantification of the regional variation in LC thickness, connective tissue content, pore area and pore count, showing potential for 3D quantification without the need for tissue sectioning. Conclusion: Differences in the young and elderly ONH microarchitecture and nanoarchitecture include fibrillar collagen content, alignment and packing and the presence of elastic fibres. These data will be important for the development of finite element models that can predict ONHs at risk of developing glaucomatous optic neuropathy.