No description available.

No description available.

No / The EyeSys videokeratoscope (VK) measurements of the principal corneal meridians of 98 subjects already analysed by Douthwaite et al. [Ophthal. Physiol. Opt. (1999)19:467¿474] were re-analysed in order to revise the assessment of asphericity, to derive information on corneal tilt and to assess the degree to which the corneal section approximates to that of a conic section. The range of normality for the revised p-value (asphericity) was from 0.57 to 0.97 for the near horizontal and from 0.56 to 1.08 in the near vertical principal meridians. The approximate corneal tilt angles ranged from ¿3.95 to +8.13 degrees in the horizontal and from ¿8.99 to +9.33 degrees in the vertical meridian. A tilted conicoidal surface will display a linear relationship (r = 1) when a scatterplot is drawn of the perpendicular distance squared vs radius squared, after first averaging the two semimeridian results for each VK ring. Analysing the results from the human cornea in the same way allows an assessment of the degree to which the corneal section approximates to that of the conic section.

Yes / Microbial keratitis can arise from penetrating injuries to the cornea. Corneal trauma promotes bacterial attachment and biofilm growth, which decrease the effectiveness of antimicrobials against microbial keratitis. Improved therapeutic efficacy can be achieved by reducing microbial burden prior to antimicrobial therapy. This paper assesses a highly-branched poly(N-isopropyl acrylamide) with vancomycin end groups (HB-PNIPAM-van), for reducing bacterial attachment and biofilm formation. The polymer lacked antimicrobial activity against Staphylococcus aureus, but significantly inhibited biofilm formation (p = 0.0008) on plastic. Furthermore, pre-incubation of S. aureus cells with HB-PNIPAM-van reduced cell attachment by 50% and application of HB-PNIPAM-van to infected ex vivo rabbit corneas caused a 1-log reduction in bacterial recovery, compared to controls (p = 0.002). In conclusion, HB-PNIPAM-van may be a useful adjunct to antimicrobial therapy in the treatment of corneal infections. / Medical Research Council and the Department of Biotechnology, India under grant number, MR/N50188/2.

In a 1982 paper, Gould and Vrba argue that a conflation of the two components of adaptation of a feature, historical development of the feature and present utility, has caused evolutionists to overlook a missing term in the science of form, which they call 'exaptation'. In the present project, I show that evolutionary biology still contains a confusion in the use of 'adaptation' due to an inappropriate perception of the interaction between the two components of adaptation. Because of the confusion, evolutionists have missed another term in the science of form. Evolutionary theory, specifically the treatment of adaptation, would profit from the introduction of a term referring to features that have a selective history which causes them to appear overly well adapted to their present function. I suggest we refer to these features as hyperadaptations, since they appear to be hyperbolized adaptations. By introducing hyperadaptation into the conceptual framework of adaptation, we can sharpen our understanding of related concepts (adaptation to function, exaptation, maladaptation, etc.) and remove or reduce some confusion regarding the interplay between analysis of historical pathways and ascriptions of (current) function in the diagnosis of adaptation. Furthermore, the improved framework should allow evolutionists to more adequately explain biological phenomena. / Master of Arts

Local anesthesia is critical for performing corneal procedures in horses. Studying non- ophthalmic local anesthetics for corneal use is necessary because the efficacy and availability of ophthalmic preparations may be limited. This study aimed to evaluate the effects and potential adverse consequences of ropivacaine hydrochloride 0.5% and lidocaine hydrochloride 2% when applied topically to the corneas of eight healthy equids compared to an eyewash control. Data collection occurred over one week. Corneal touch threshold (CTT) was assessed via Cochet-Bonnet esthesiometry before and at pre-determined times after medication application. Ocular toxicity was assessed immediately following each trial and prior to the second trial using the semiquantitative preclinical ocular toxicity system (SPOTS). Ropivacaine and lidocaine significantly reduced CTT from baseline values. However, mean CTT and time to maximum anesthesia were not significantly different between drugs. No local side effects were seen. Ropivacaine and lidocaine could be used topically to reduce corneal sensitivity.

The conventional view for corneal epithelial maintenance suggests that a stem cell population found in the limbus (at the rim of the cornea) produces daughter cells, called transient amplifying cells, which migrate centripetally. This limbal stem cell (LSC) hypothesis was recently questioned and the alternative model suggests that stem cells are present throughout the corneal epithelium. The main aims of this thesis were to investigate whether age and Pax6 genotype affect LSC function. Previous work with X-inactivation mosaics revealed radial stripes of β-galactosidase-expressing cells in the corneal epithelium (from about 5 weeks of age), which decreased with age and were reduced in Pax6+/- mice (a model for aniridia, a human eye disease). The reduction in Pax6+/- mice could be due to either reduced LSCs function or a more coarse-grained mosaicism caused by reduced cell mixing during development. Comparison of patch sizes in Pax6+/- and wild-type X-inactivation mosaics showed that patches were smaller in Pax6+/- cornea epithelia before the initiation of stripes (3 weeks of age). This implies that stripe-number reduction is not caused by reduced cell mixing, so an effect on LSC function remained a possibility. Thus, the numbers of label-retaining cells (putative stem cells) in Pax6+/- were compared to controls at 15 and 30 weeks old but they were not reduced at 30 weeks or in Pax6+/- mice, as had been predicted. The failure to demonstrate the predicted result suggests either that the hypothesis was incorrect or the experimental approach was inappropriate. Furthermore, it was discovered that mice expressing β-galactosidase under the keratin 5 promoter produced rare stripes in the corneal epithelium, which are likely to represent clonal lineages derived from individual stem cells. Older mice demonstrated a significantly lower frequency of stripes, a result compatible with the predicted reduction of active LSC with age. Pax6+/- corneas were highly abnormal and stripes were not formed properly, so direct comparison was not possible. Finally, pilot experiments with conditional expression of a reporter gene revealed the successful formation of a stripe, and hence provide a plausible alternative approach to compare stripe numbers reflecting active LSCs but the method has yet to be optimised. Overall, the results suggest that LSCs are reduced with age and support the limbal location of stem cells maintaining the corneal epithelium.

No description available.

Optical Coherence Tomography (OCT) is a noninvasive imaging modality that has significantly contributed to the quantitative assessment of ocular diseases. Another tool available to ophthalmic clinicians is in-vivo confocal microscopy, which allows anatomical structures to be observed live at the cellular level. Incorporating both of these modalities for imaging the cornea allows us to take structural measurements to characterize disease-related changes in corneal anatomy. Notable diseases that directly impact or correlate with corneal structures include glaucoma and diabetic neuropathy. Given glaucoma's impact as the second leading cause of blindness in the world, great efforts have been made in researching and understanding the disease. Correlations have been found between the central corneal thickness (CCT) and the risk of developing visual field loss in patients diagnosed with glaucoma. It should come as no surprise that measuring CCT among glaucoma suspects has also now become a clinical standard of practice. Diabetes is a group of metabolic diseases where the body experiences high blood sugar levels over prolonged periods of time. It is a prominent disease that affects millions of Americans each day. While not necessarily an ocular disease in its own right, it has been shown that diabetes can still affect the corneal structures. Diabetics have decreased corneal sensitivity and a significant link has been established between neuropathic severity in diabetic patients and corneal nerve fiber density. Given the availability of these imaging tools and the significant impact these prominent diseases have on society a growing focus has developed on relating corneal structure measurements and ophthalmic diseases. However, manually acquiring structural measures of the cornea can be a labor intensive and daunting task. Hence, experts have sought to develop automatic alternatives. The goals of our work includes the ability to automatically segment the corneal structures from anterior segment-optical coherence tomography (AS-OCT) and in-vivo confocal microscopy (IVCM) to provide useful structural information from the cornea. The major contributions of this work include 1) utilizing the information of AS-OCT imagery to segment the cornea layers simultaneously in 3D, 2) increasing the region-of-interest of IVCM imagery using a feature-based registration approach to develop a panorama from the images, 3) incorporating machine-learning techniques to segment the corneal nerves in the IVCM imagery, and 4) extracting structural measurements from the segmentation results to determine correlations between the structural measurements known to differ from the corneal structures in various subject groups.

Medical imaging tools technologically supported by the recent advances in the areas of computer vision can provide systems that aid medical professionals to carry out their expert diagnostics and investigations more effectively and efficiently. Two medical application domains that can benefit by such tools are ophthalmology and Total Hip Replacement (THR). Although a literature review conducted within the research context of this thesis revealed a number of existing solutions these are either very much limited by their application scope, robustness or scope of the extensiveness of the functionality made available. Therefore this thesis focuses on initially investigating a number of requirements defined by leading experts in the respective specialisms and providing practical solutions, well supported by the theoretical advances of computer vision and pattern recognition. This thesis provides three novel algorithms/systems for use within image analysis in the areas of Ophthalmology and THR. The first approach uses Contourlet Transform to analyse and quantify corneal neovascularization. Experimental results are provided to prove that the proposed approach provides improved robustness in the presence of noise, non-uniform illumination and reflections, common problems that exist in captured corneal images. The second approach uses a colour based segmentation approach to segment, measure and analyse corneal ulcers using the HVS colour space. Literature review conducted within the research context of this thesis revealed that there is no such system available for analysis and measurement of corneal ulcers. Finally the thesis provides a robust approach towards detecting and analysing possible dislocations and misalignments in THR X-ray images. The algorithm uses localised histogram equalisation to enhance the quality of X-ray images first prior to using Hough Transforms and filtered back projections to locate and recognise key points of the THR x-ray images. These key points are then used to measure the possible presence of dislocations and misalignments. The thesis further highlights possible extensions and improvements to the proposed algorithms and systems.