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Accommodation is the change in the dioptric power of the eye altering the focus from distance to near. Presbyopia is the loss of accommodative function that occurs with age. There are many techniques used to measure accommodation, however, there is little consensus as to how clinical data should be collected and analysed. The overarching theme of this thesis is the in vivo examination of accommodation and how lifestyle can affect the onset of presbyopia. An open-field autorefractor with badal adaption was used to examine accommodative dynamic profiles under varying demands of vergence. From this data a new metric for assessing the time for accommodative change was derived. Furthermore this thesis describes a bespoke automated accommodative facility instrument that was developed to provide further assessment of accommodative speeds. Defocus curves are used for assessing accommodation and depth-of-focus; the work presented explores the use of non-linear regression models to define the most appropriate method of assessing defocus curves in phakic subjects, and pseudophakic subjects implanted with an extended depth-of-focus intraocular lens. Using an absolute cut-off criteria of +0.30logMAR improved the repeatability and reliability of the depth-of-focus metrics over a cut-off criteria relative to the best corrected visual acuity. A swept-source anterior segment optical coherence tomographer (AS-OCT) was used to image the morphology of the ciliary muscle during accommodation. The accuracy of ciliary muscle measurements was improved when using reference points on the sclera to align the AS-OCT scan. The use of a ciliary muscle area metric demonstrated poor repeatability and reliability when compared to the traditional assessment of muscle morphology via thickness measurements. Physiological ageing in the crystalline lens occurs in line with ageing in other structures in the body. The methods for assessing accommodative function examined in previous chapters, were used to examine whether lifestyle factors which affect the rate of systemic ageing, such as smoking, also affect accommodative function. Although being a current smoker and having greater central adiposity was associated with a slower time for accommodative change, further research is required before these findings can be applied to the target population.

Lietuvoje pirmą kartą nagrinėjama daugiažidinių intraokulinių lęšių (DIOL) implantacija. Atliktas tyrimas leidžia detaliau vertinti regėjimo funkcijas po DIOL implantacijos. Keturi skirtingi DIOL lyginami pagal tą pačią meto¬diką ir pateikiami ilgos pooperacinės stebėsenos duomenys. Pirmą kartą aprašomos paciento pasitenkinimo po DIOL implantacijos ir Didžiojo penketo asmenybės dimensijų sąsajos. Darbo tikslas - įvertinti regėjimo kokybę ir pacientų pasitenkinimo rezultatais sąsajas su asmenybės bruožais po skirtingų modelių daugiažidinių intraokulinių lęšių implantacijos. Uždaviniai: 1) įvertinti regėjimo aštrumą implantavus skirtingus DIOL modelius; 2) įvertinti kontrastinį jautrumą implantavus skirtingus DIOL mo¬de¬lius; 3) įvertinti paciento poreikį papildomai korekcijai akiniais po DIOL implantacijos; 4) įvertinti pašalinių optinių fenomenų pasireiškimą su DIOL; 5) įvertinti pacientų pasitenkinimo regėjimo rezultatais dažnumą ir sąsajas su asmenybės bruožais po DIOL implantacijos. / In this study, postoperative follow-up data that cover a rather long period after the multifocal intraocular lens (MIOL) implantation are presented. It is the first time that the same methodology was used to compare four different types of MIOL. The influence of personality traits on the visual function has been defined. The aim of the study - to assess the influence of different MIOL on the quality of vision and the links between the satisfaction of patients with the results and their personality traits after the implanting of different MIOL models. The objectives of the study: 1) to compare the visual acuity between different MIOLs models; 2) to compare the contrast sensitivity between different MIOLs models; 3) to establish the need of patients for additional correction with glasses after the implanting of MIOLs; 4) to assess the occurrence of photic phenomena after the implanting of MIOLs; 5) to assess the level of visual function and the influence of personality traits on patients’ satisfaction with the visual function following the MIOL implantation.

Dans un contexte de vieillissement de la population, et donc d’augmentation du nombre de presbytes, l’amélioration des optiques destinées à la correction de ce défaut visuel est un enjeu crucial. Nous avons cherché à optimiser le design des optiques bifocales, qui ne présentent que deux puissances différentes: une pour la vision de loin et une pour la vision de près. Pour cela, nous avons simulé des images telles qu’elles seraient vues à travers nos designs, et les avons fait noter par des sujets. La première étude s’est penchée sur le ratio d’aire optimisant la vision au loin comme au près. Les meilleurs résultats ont été obtenus pour un ratio de 40% de vision de près au centre, même si des valeurs de 20 à 50% étaient satisfaisantes. Cependant, ces optiques à deux zones concentriques ont un défaut : elles sont très sensibles au changement de diamètre pupillaire, qui est très fréquent. Un changement de taille de pupille entrainant une modification du ratio d’aires, la solution consiste à utiliser plusieurs zones concentriques alternant entre correction de loin et de près. La seconde étude s’est focalisée sur l’optimisation du nombre de zones concentriques dans ces optiques bifocales par la même méthode. Lorsque le nombre de zones est augmenté suffisamment, des interférences permettent d’augmenter également la qualité de vision intermédiaire, nos profils étant disposés comme des réseaux de Fresnel. Les profils à 5 zones permettent une bonne vision de loin et de près en redonnant une légère vision intermédiaire, et les profils à 8 zones donnent une qualité de vision similaire au loin, en intermédiaire et au près. Ces profils ont ensuite été évalués dans des conditions plus réalistes, en présence d’aberrations, de décentrement, de différents diamètres pupillaires par deux populations d’âge différent. L’âge des sujets n’influence pas leur évaluation des optiques. Les aberrations ont plus d’impact sur la qualité visuelle que le décentrement. Le diamètre pupillaire a une influence plus forte sur les profils possédant moins de zones. Enfin, nous avons comparé nos profils optimisés avec des lentilles de contact disponibles sur le marché. Du point de vue de la qualité visuelle comme de la profondeur de champ, nos profils étaient meilleurs que les lentilles du marché. Il serait donc intéressant d’en créer des prototypes pour effectuer des tests au porté. Les designs développés dans cette thèse pourraient servir à effectuer une personnalisation de la correction optique des presbytes. Différents designs pourraient être proposés pour chaque oeil, permettant de combiner deux profils par sujets. De nombreuses variations inter-individuelles, également observées dans les études précédentes, restent toujours imprévisibles. Elles pourraient être dues à des différences de sensibilité au contraste ou de tolérance au flou. Il serait donc intéressant de développer un test optométrique, consistant à faire évaluer des images floues par le sujet, de façon à prédire s’il s’agit d’un bon candidat au port de lentilles bifocales. / Giving the aging of the population, and therefore the augmentation of presbyopes, the improvement of optics used to compensate for this visual impairment are at stake. We optimized bifocal optics designs, which only have two powers: one dedicated to distance vision and one dedicated to near vision. For this, we simulated images as they would appear through our designed optics, and asked subjects to grade the quality of these simulated images. First study dealt with the ratio of area optimizing visual quality at distance and at near. The best results were obtained for a ratio of 40% of central near vision, even if values from 20 to 50% gave quite comparable satisfying results. However, these 2 zone optics have a drawback they are very sensitive to the change of pupil diameter, which happens very often. A change in pupil size leads to a change of ratio of areas, the solution consists in using several concentric zones alternating between distance and near correction. The second study was about the optimization of the number of concentric zones in these bifocal optics using the same method. When the number of zones is increased enough, interferences allow to improve intermediate visual quality, as our profiles are built as Fresnel networks. Five zone profiles give a good distance and near vision with a little intermediate vision, and 8 zone profiles give an acceptable quality of vision from far to near. These profiles were evaluated in more realistic conditions, in presence of aberrations, decentration and different pupil diameters by two populations with different age. The age of subjects did not influence their evaluation of the optics. Aberrations had more impact on visual quality than decentration. Pupil diameter had a stronger influence on the optics with less number of zones. Eventually, we compared our optimized profiles with actual contact lenses available on the market. When looking at visual quality and depth-of-focus, our profiles were better than the ones available on the market. Therefore, it would be interesting to make prototypes to try them on real subjects. The designs developed in this work could be used to personalize presbyopes optical compensation. Different designs could be tried on each eye, allowing to combine two profiles per subject. A lot of inter-individual variations, also observed in previous studies, remain unpredictable. They could be linked to differences in contrast sensitivity or tolerance to blur. It would be interesting to create a visual test consisting in evaluating blurred images, in order to predict of a subject is a good candidate to fit with bifocal optics.

En este trabajo se describe un simulador visual de óptica adaptativa (SVOA) empleado con dos objetivos: primero, el testeo y diseño de perfiles de fase progresivos para extender la profundidad de foco y segundo el estudio del efecto de la aberración cromática longitudinal y su acoplamiento con la aberración esférica en el ojo humano.Diversos perfiles de fase progresivos fueron analizados en el SVOA, resultando un excelente acuerdo con las simulaciones teóricas. Algunos de estos perfiles fueron implementados físicamente en lentes de contacto y evaluados visualmente. La buena concordancia que se encontró entre esta evaluación y la obtenida simulando el perfil con el SVOA validan todo el procedimiento y el sistema.También se llevaron a cabo medidas de la capacidad visual combinando la corrección de las aberraciones cromática y esférica. Los resultados indican que la mejor calidad de visión se produce al eliminar al mismo tiempo ambas aberraciones. / An adaptive optics visual simulator (AOVS) is described in this work. It was used to test and design progressive phase profiles to extend depth of focus, and to study the combined effect of both, the longitudinal chromatic aberration and the spherical aberration in the human eye.A set of progressive phase profiles were tested using the AOVS, obtaining an excellent agreement with the theoretical simulations. Some of these phase profiles were implemented on contact lenses and visually tested. Again the results agreed with the evaluation carried out through the AOVS, validating the instrument.Visual performance was also tested correcting either chromatic aberration or spherical aberration or both, resulting the best performance when both aberrations are simultaneously corrected.

Quantitative, descriptive, cross-sectional study was conducted to determine the level of knowledge and extent of Computer Vision Syndrome (CVS) among computer users in the Securities and Exchange Commission (SEC), Abuja, Nigeria. Structured questionnaires were administered to 100 computer users aged between 18 and 40 years. The study findings revealed that 40 respondents (40%) were aware of CVS and 27 (27%) of them had knowledge of the disorder. 74 (74%) of the respondents experienced at least one symptom of CVS. Headache and eyestrain were the most common symptom of CVS among the population. The study also revealed that the internet (accounting for 50%) was the major source of information about CVS awareness. The study concluded that 27% knowledge level is too low and much emphasis is needed to educate the people at risk of CVS / Health Studies / M.A. (Public Health)

Quantitative, descriptive, cross-sectional study was conducted to determine the level of knowledge and extent of Computer Vision Syndrome (CVS) among computer users in the Securities and Exchange Commission (SEC), Abuja, Nigeria. Structured questionnaires were administered to 100 computer users aged between 18 and 40 years. The study findings revealed that 40 respondents (40%) were aware of CVS and 27 (27%) of them had knowledge of the disorder. 74 (74%) of the respondents experienced at least one symptom of CVS. Headache and eyestrain were the most common symptom of CVS among the population. The study also revealed that the internet (accounting for 50%) was the major source of information about CVS awareness. The study concluded that 27% knowledge level is too low and much emphasis is needed to educate the people at risk of CVS / Health Studies / M.A. (Public Health)

Actuellement, la presbytie peut être corrigée chirurgicalement à l’aide d’implants intraoculaires réfractifs ou diffractifs multifocaux (chirurgie endoculaire invasive et irréversible) ou en intracornéen avec une correction multifocale réfractive (correction laser irréversible, ou insertion d’un implant dans le stroma). L’objectif de ce travail est de développer un nouvel implant permettant de corriger la presbytie, qui allie l’innocuité et la réversibilité d’une correction intracornéenne, à l’efficacité du diffractif. Le design des profils optiques bifocaux a été permis grâce au développement d’outils de simulation optique. Les efficacités de diffraction sont calculées à partir de la propagation du champ électrique par spectre angulaire. La qualité optique est déterminée d’après les simulations de Fonction de Transfert de Modulation obtenues sous Zemax. Des simulations de rendu d’images permettent de visualiser les effets de différents profils envisagés. Les paramètres critiques du design optique sont déterminés. Le choix du matériau dépend des contraintes de biocompatibilité de l’implant et des techniques de fabrication. La solution retenue est un hydrogel à forte teneur en eau, couplé à une nouvelle architecture de l’implant. L’hydrogel est obtenu par polymérisation radicalaire de macromonomères difonctionnels de poly(éthylène glycol) de masses molaires de l’ordre de 8000 g.mol‐1 qui conduisent à des propriétés mécaniques et une perméabilité aux nutriments compatibles avec l’application. La réalisation, la stérilisation et la caractérisation optique de prototypes ont abouti à la preuve du concept d’un implant bifocal diffractif intracornéen / Presbyopia can be corrected with surgery by means of refractive or diffractive multifocal intraocular lenses (which imply an irreversible and invasive endocular surgery) or by intracorneal multifocal refractive correction (irreversible laser correction, or insertion of an intrastromal implant). This work aims at developing a new implant to correct presbyopia, which takes advantage of both the harmlessness and the reversibility of an intracorneal correction, and the efficiency of diffractive optics. The design of the bifocal optical profiles was based on the development of optical simulation tools. The diffractive efficiencies are calculated from the distribution of the electric field with the method of angular spectrum. The optical quality is determined according to the simulations of Modulation Transfer Function obtained with Zemax. Images simulations show the effects of the different profiles studied. The critical parameters of the optical design are also determined. The choice of the material depends on several constraints such as biocompatibility and techniques of manufacturing. The adopted solution relies on the used of an hydrogel with high water content and the design of a new implant architecture. The hydrogel is obtained by radical polymerization of difunctional macromonomers of poly(ethylene glycol) with molar masses around 8000 g.mol‐1, allowing mechanical properties and permeability to nutriments compatible with the application. The realization, the sterilization and the characterization of prototypes showed the proof of the concept of a diffractive bifocal intracorneal implant