Clinical relevance: Mobility and fall risk may be important considerations in choosing between intraocular lenses. Background: Fall risk in older adults increases when wearing multifocal spectacles, but little is known about mobility among individuals with different types of intraocular lenses. This study compared visual function, fall risk and balance control following bilateral implantation of monofocal or multifocal intraocular lenses. Methods: This was a non-randomised, cross-sectional study involving adults with bilateral intraocular lenses. Participants completed questionnaires concerning physical functioning, fall history and balance-related confidence. Binocular visual acuity, contrast sensitivity (Pelli-Robson chart and computerized testing), depth perception and glare sensitivity were assessed. Physical performance measures included the Sensory Organization Test, preferred gait speed, Dynamic Gait Index and wayfinding in a virtual environment. Results: Fifteen participants (mean ± standard deviation, 67.1 ± 6.8 years) had monofocal intraocular lenses and 14 participants (68.1 ± 6.1 years) had multifocal intraocular lenses. Contrast sensitivity in the monofocal group was significantly better than that in the multifocal group (p = 0.02) at intermediate and high spatial frequencies. Contrast sensitivity of the monofocal group also was less affected by glare than the contrast sensitivity of the multifocal group, at an intermediate spatial frequency (p = 0.02). However, the multifocal group had significantly better Dynamic Gait Index scores (p = 0.04), even after controlling for perceived physical function. Conclusions: The participants with monofocal intraocular lenses generally had better contrast sensitivity than did those with multifocal intraocular lenses. However, the scores on a mobility test that is associated with fall risk were worse for those with monofocal lenses.

No description available.

The pursuit of optimizing soft contact lens performance has been extensive, given that approximately over 140 million contact lens wearers globally seek the convenience and visual acuity they offer. However, a persistent challenge is the prevalence of ocular dryness and discomfort experienced by almost half of these wearers, particularly towards the end of the day. The occurrence of these symptoms is primarily attributed to diminished compatibility between the contact lens and the ocular surface leading to contact lens discontinuation. A promising method to improve overall contact lens properties is to incorporate novel monomers with unique functionalities during the initial manufacturing stage. Monomers bearing ionic functional groups have been extensively explored to improve bulk and surface properties of biomaterials. The incorporation of cationic and zwitterionic monomers in the fabrication of hydrogel materials has shown to have anti-fouling and anti-bacterial properties and improved surface wetting. In this work, a series of novel materials using cationic and zwitterionic monomers were prepared and their impact on bulk and surface properties of contact lens materials were assessed. Furthermore, the impact of a novel hydrophilic silicone-based monomer bearing zwitterionic phosphocholine was investigated for water-based extraction, physiochemical and structural stability in candidate contact lens materials. In Chapter 2, a library of eleven positively charged (cationic) and electrically neutral with both positive and negative charges (zwitterionic) functional methacrylate ester monomers was produced through the reaction of 2-(dimethylamino) ethyl methacrylate (DMAEMA) with different alkyl halides. The Menshutkin reaction was carried out with a high level of success, resulting in moderate to high yields of the desired monomers. The monomers were purified and characterized using analytical techniques, including 1H-NMR (proton nuclear magnetic resonance), 13C-NMR (carbon-13 nuclear magnetic resonance), LCMS (liquid chromatography-mass spectrometry), and XRD (X-ray diffraction). Six monomers were chosen based on controlled end group hydrophilicity and chain length to investigate the relationship between chemical structure and overall performance in hydrogel and silicone hydrogel systems. In Chapters 3 and 4, model hydrogel and silicone hydrogel systems via UV free-radical polymerization at increasing input concentrations (10 and 20 wt%) were manufactured using the monomers and HEMA (hydrogel) or HEMA + SIGMA (silicone hydrogel). The novel materials demonstrated an increase in bulk equilibrium water content, reduced contact angle and nonspecific lysozyme and albumin adsorption, while maintaining optical transparency at higher than 90%. In vitro studies demonstrated the ionically charged hydrogel materials did not show any toxicity to human corneal epithelial cells. In Chapter 5, a super hydrophilic silicone-based SIGMAPC monomer was synthesized using the siloxane functional monomer (SIGMA) as the main building block. The introduction of the novel hydrophilic SIGMAPC monomer led to significant improvements in the silicone materials. The hydrogels showed increased water content and reduced water contact angles, indicating their superior hydrophilicity. Moreover, the rate of dehydration was decreased, and the nonspecific deposition of lysozyme and albumin was minimized. Importantly, the optical transparency of the hydrogel silicone remained above 90%. Based on these findings, it can be concluded that the siloxane-based monomer bearing a zwitterionic phosphocholine has great potential for applications in contact lenses, given its desirable properties and biocompatibility. Furthermore, in Chapter 6, 31P-NMR and weight extraction analysis showed model contact lens materials made with SIGMAPC were effectively extracted in aqueous media at elevated temperature. Candidate materials showed good dimensional and optical stability pre- and post-thermal sterilization and over 6-month storage period. / Thesis / Doctor of Philosophy (PhD)

No description available.

Code V, an optical design program, was used to design a lens for a three-dimensional mapping application. The purpose of the lens system is to project an array of spots of light onto the object of interest. The size of the projected spots can be used to determine the distance from the lens to the object. The design criterion for this system was a 2% accuracy of position with a two lens system. The use of anamorphic and aspheric surfaces was also investigated as a means to improve the design performance.

No / Aspheric intraocular lenses (IOLs) are designed to correct spherical aberration in pseudophakic eyes. We predict the benefit from correcting spherical aberration based on simulations and aberrometry of pseudophakic eyes implanted with spherical IOLs. METHODS Ray tracing was performed through a model eye with an equi-biconvex spherical IOL and with a spherical aberration-correcting aspheric IOL. The IOLs were increasingly tilted and/or displaced, and the resulting transverse aberrations of 169 rays were transformed into Zernike coefficients for different pupil sizes. The benefit from correcting spherical aberration at individual mesopic pupils was investigated by canceling in the sets of Zernike coefficients for 41 eyes implanted with a spherical IOL. RESULTS Both the model eye and the real eye data predict that age-related miosis reduces spherical aberration in the eye implanted with a spherical IOL to approximately 1/3 of the spherical aberration at a 6-mm pupil. A reduction of similar magnitude occurs when spherical aberration-induced non-paraxial defocus is corrected by a spectacle lens. For natural mesopic pupils, canceling the Zernike coefficient improved the objective image quality at a rate similar to changing defocus by 0.05 diopters. Average centration and tilt levels diminish the lead of aspheric IOLs over spherical IOLs, depending on the direction of decentration. CONCLUSIONS The benefit from correcting spherical aberration in a pseudophakic eye is limited for some or all of the following reasons: wearing glasses, age-related miosis, tilt and decentration of IOL, small contribution of spherical aberration to all aberrations, and intersubject variability

Yes / Around 3-6% of children in the United Kingdom have substantial difficulties learning to read, a condition often referred to as dyslexia. They are at high risk of educational underachievement. In a 1996 editorial in The BMJ, Margaret Snowling argued that dyslexia is a verbal (not a visual) disorder.1 An accumulation of evidence supports this position and shows that reading difficulties are best dealt with by interventions that target underlying weaknesses in phonological language skills and letter knowledge.2 The 2009 Rose report, which provides guidance for professionals in schools on identifying and teaching young people with dyslexia and reading difficulties, stresses the importance of early, phonological interventions.3 Despite this evidence, dyslexia is often associated with subjective experiences of visual distortions that lead to discomfort during reading (sometimes termed visual stress). It has been argued that these symptoms can be alleviated by using coloured overlays and lenses.4 Symptoms of visual stress are not unique to dyslexia, and proponents do not claim that the use of colour directly addresses the underlying cause of the reading difficulty. However, they argue that the reduction in visual distortion brought about by a change in colour can improve reading accuracy and fluency.4

Yes / We thank Professors Evans and Allen for their interest in our article.1 2 The charity websites we reviewed refer to colour as though it offers a scientific, evidence based treatment; none referred to feedback from the membership. For example, one charity website makes the claim that “Research in the UK and in Australia shows that people who need coloured filters, who are said to have visual stress, need to have exactly the right colour.” This is incorrect. The research overwhelmingly shows little advantage, or at best conflicting results.3 4 5

M.Phil.(Optometry) / The concept of contact lenses was conceived over 500 years ago and has now evolved into a fundamental component of optometric practice. Soft contact lenses have become a convenient, aesthetically pleasing and comfortable alternative to spectacles that are becoming increasingly popular. The use of rigid contact lenses is imperative in the management of conditions such as keratoconus due to spectacles being insufficient in providing adequate vision. Placing a contact lens onto the cornea is an invasive procedure. The contact lens is a foreign body to the eye hence it is expected that the eye would react to that foreign body. Literature has revealed that the general reactions of the eye to contact lens wear are initial tearing, alteration of the tear layer and oedema due to reduced oxygen transmission but these are just a few of the known consequences amongst the multitude of the unknown consequences. What exactly goes on under a contact lens remains an enigma which contact lens researchers have strived to uncover over the past century. The consequence of contact lens wear is a vast area of research and can best be investigated by focusing on one aspect at a time. The aim of this study was to use dioptric power matrices and multivariate statistics to explore the effects of both gas permeable and gas non-permeable rigid contact lenses on corneal curvature. This study involves auto-keratometric measurements of the corneal curvature before and after lens wear to establish if there are any curvature changes induced by the contact lens. Keratometric data was collected with an automated keratometer (Nidek ARK-700) and was analysed correctly and completely using multivariate statistics. This thesis presents the findings of a study done in an effort to establish the short-term effects of rigid contact lens wear on keratometric behaviour by using complete methods of multivariate statistical analysis. Twenty four subjects were equally divided into three groups. One group wore polymethyl methacrylate (PMMA) rigid lenses, another group wore rigid gas permeable (RGP) contact lenses and the third group served as the control. The control group was included in the study to establish a reference for normal diurnal changes in keratometric behaviour. Fifty autoii keratometric measurements were taken before and immediately after three hours of rigid contact lens wear for the experimental groups and 50 auto-keratometric measurements were taken before and immediately after three hours of no lens wear for the control group. Data collected was analysed using multivariate statistical methods that in the past have been used infrequently in this area of research.

by Poon Wai-cheong. / Bibliography: leaf 47 / Thesis (M.B.A.)--Chinese University of Hong Kong, 1983