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In addition to their sensory role, corneal nerves serve as a protective and trophic function in the cornea. Any alterations to this structure, such as those occurring during refractive surgery, may have significant implications for the maintenance of a healthy cornea. This study aimed to investigate 1) the morphological and functional changes in the cornea at two different locations (central and temporal), 2) symptomatology and 3) the possible relationship between specific neuroproteins detected in tears, and changes in structure and functional factors of the corneal nerves after various refractive surgery techniques including LASIK Mechanical Microkeratome (MM), LASIK FemtoSecond (FS), Photorefractive Keratectomy. Comparisons were made with age and gender matched controls. All subjects were followed for up to 3 months. Corneal nerve morphology and its function were severely altered after the surgery and these changes were evident in both central and temporal regions of the cornea. In all the surgical groups, corneal mechanical sensitivity recovered to pre-operative levels after three months whereas corneal nerve morphology did not return to its baseline values. This may suggest a degree of redundancy in the corneal sub epithelial nerve plexus. There was no difference between LASIK with MM and LASIK with FS in terms of the amount of nerve regeneration and its function. Most of the subjects exhibited increased symptoms of discomfort at three months after the surgery and there was an association between the signs and symptoms of ocular discomfort. In addition, differences were demonstrated in the clinical signs of ocular discomfort among various surgical groups, with patients undergoing PRK exhibiting fewer clinical signs of discomfort. This difference might be attributed in part to the higher expression of NGF levels measured after PRK in this study. All together, the evidence obtained during the course of this study suggests that there is a connection between alterations in the corneal nerve structure, persisting corneal staining, increased neurotrophic effect of NGF, and increased ocular discomfort three months after surgery. The processes underlying the increased symptoms of discomfort following refractive surgery might be influenced by changes in tear film such as modulation of NGF, changes in corneal epithelial integrity and altered nerve fibre density.

An emulsion is a dispersion of one liquid in another and is a thermodynamically unstable system and possesses a natural tendency to break. Stability to flocculation of acoustically formed emulsions and emulsion stability with simultaneous flocculation and creaming has been studied. The stability of acoustically prepared emulsions of C(,36)H(,74) in water was determined by measuring the particle growth rate. The stability was found to decrease with increasing ionic strength, indicating that these emulsions are electrostatically stabilized. Emulsion stability with simultaneous flocculation and creaming was studied by deriving a general dynamic equation (GDE) for emulsion particles. The GDE includes Brownian flocculation, sedimentation-flocculation and creaming. The GDE was solved numerically to predict changes in particle concentration and size distribution as a function of time and position. Cyclic changes in particle size distributions (PSD) are observed when flocculation and creaming occur simultaneously. Initially, the PSD shifts to the right towards larger particle sizes and then reverses and shifts to the left towards smaller particle sizes. An experimental technique has been developed to study the emulsion stability with simultaneous flocculation and creaming. Experiments were carried out by using different ionic strengths, two different dispersants in water (C(,36)H(,74) and C(,28)H(,58)) and different particle size distributions. Experimentally measured changes in particle size distributions are compared with theoretically predicted results. The reverse shift in PSD had been observed both in theory and experiment. There are no adjustable parameters in the theory and the agreement between the theory and experiment is good. A general map presenting regimes of dominant particle loss mechanisms has been developed from which one can determine the dominant particle loss mechanism for a given particle size and density difference between the particles and the continuous medium. The relative importance of flocculation and creaming has been delineated for a monodispersed system. The effect of particle size, surface potential, concentration, density difference, temperature and ionic strength on the relative importance of flocculation and creaming have been delineated.

The use of bio-mimetic receptor systems have been considered in a quest for affinities and specificities that are on a par with natural receptors for rapid in-situ analysis based on coupled-sensor techniques. The work describes the experimental optimisation and characterisation of hydrogel-based molecularly imprinted polymers (MIPs) for a range of proteins and pathogens, including plant viruses. A variety of acrylamide-based functional monomers, along with several integrated metal complexes for signal transduction have been exploited in the fabrication of both bulk and surface imprinting of MIPs. Spectrophotochemical, electrochemical and quartz crystal microbalance (QCM) analytical techniques were utilised for quantifying imprinting effects by assessing specific and/or non-specific binding. Bulk imprinting exhibited high selectivities (rebinding efficiencies ≈ 80%) and imprinting factors of ≈ 14 (MIP/NIP ratio) across varied templates. MIP-coupled QCM sensors illustrated binding and elution of target proteins through distinct frequency and impedance transitions at 3 mg mL-1. QCM surface imprinting via electrochemically-induced polymerisation (ECIP) was less successful. Whereas electrochemical ECIP methods using glassy carbon electrodes (GCEs) illustrated good compatibility, higher sensitivities, and a limit of detection (LOD) of 16 μg mL-1 and a limit of quantification (LOQ) of 56 μg mL-1 for BHb. Pattern recognition techniques using multivariate analysis were also implemented to reduce complex data sets. Principle component analysis (PCA) and linear discriminant analysis (LDA) techniques illustrated unique binding pattern profiles depending on the sample matrix analysed, significance (ρ) ≤ 0.0005. The latter ECIP methods were also transposed onto disposable screen-printed carbon electrodes (SPCEs) based on the introduction of redox tracers (both externally and within the MIP matrix). SPCEs offer an attractive opportunity for the development of miniaturised low cost electrochemical sensors. However, several complications arose and little sensitivity was observed in terms of MIP binding. Once fully developed, the benefits of sensitivity, specificity and stability of MIPs coupled with discriminatory sensor techniques, as described here, could be crucial to the future impact of portable diagnostics for personal healthcare and use by health professionals. This technology also presents major potential benefits to environmental and food monitoring as it could provide an inexpensive, fast, and efficient diagnostic method for highly sensitive analytical procedures.