Failing eyesight causes a dramatic change in life. The aim of this project is to help people with large central visual field loss to better utilize their remaining vision. Central visual field loss means that the person has to rely on peripheral vision since the direct vision is lost, often due to a dysfunctional macula. In these cases, a full restoration of vision would require replacement or repair of the damaged retinal tissue, which is not yet possible. Instead, the present study seeks to improve peripheral vision by enhancing the image quality on the remaining functional part of the retina by optical corrections. The off-axis optics of the human eye often suffers from large optical errors, which together with the lower sampling density of the retina explain the limited visual function in the periphery. The dominating aberrations are field curvature and oblique astigmatism, which induce an effective eccentric refractive error. However, the irregular character of the aberrations and the limited neural function in the periphery will make it difficult to find the optimal refractive correction; the conventional subjective refraction, for example, is not suitable for subjects with large central visual field loss. Within the work of this thesis a Hartmann-Shack wavefront sensor has been constructed for oblique aberration measurements. Wavefront sensing is an objective method to assess detailed information about the optical errors in the human eye. Theory and methods have been developed to allow accurate off-axis measurements of the large aberrations, enable eccentric fixation, and handle the elliptical pupil. The study has mainly concentrated on sphero-cylindrical correction of peripheral vision. Peripheral resolution and detection acuity thresholds have been evaluated for seven subjects with central visual field loss and ten control subjects with normal vision. Five of the subjects with field loss showed improved resolution acuity with eccentric refractive correction compared to their habitual central correction, whereas little change was found for the control subjects. These results demonstrate that correction of peripheral optical errors can be beneficial to people with large central visual field loss in situations where a normal healthy eye does not experience any improvements. In conclusion, it is worthwhile to investigate the peripheral refractive errors in low-vision rehabilitation of central visual field loss and prescribe spectacle correction when those errors are large. / QC 20100809

La aberración de onda ocular está estrechamente vinculada con la calidad visual y presenta valores característicos en cada ojo. Su medida y corrección tienen un gran interés tanto en el ámbito de ciencia básica como en la práctica clínica. En el presente trabajo se desarrolla un sistema experimental de medida del frente de onda ocular con gran rango dinámico basado en un sensor Shack-Hartmann. Con él se miden las aberraciones oculares monocromáticas en dos grupos de sujetos: uno de jóvenes con ojos sanos y otro de sujetos que han sido intervenidos de transplante de córnea (queratoplastia penetrante). Los resultados muestran que el valor RMS medio de las aberraciones de alto orden es 10 veces superior en estos últimos. Además se encontró una alta correlación entre las aberraciones corneales (obtenidas de la topografía corneal) y las aberraciones oculares del grupo con patología corneal.Se estudia, de forma simulada y real, la corrección de las aberraciones por medio de lentes de contacto hidrofílicas, diseñadas a partir del patrón de aberraciones de cada sujeto. El estudio se realiza para tres tipos de ojos: normales, con queratoconos y con transplante de córnea. Los resultados muestran que las principales limitaciones de este tipo de corrección se originan debido a la posición y orientación media de la lente de contacto en el ojo. Si tenemos en cuenta desplazamientos realistas de la lente de contacto encontramos que los sujetos normales presentan una pérdida de calidad óptica respecto de la corrección estándar (corrección esfero-cilíndrica). Sin embargo, existen casos patológicos en los que a pesar de las típicas rotaciones y traslaciones de las lentes de contacto, se podría disminuir el RMS de las aberraciones y aumentar la calidad visual, como se comprueba experimentalmente en los queratoconos. / The ocular wave aberration is strongly related with the visual quality having specific values for each eye. Its measurement and correction is challenging for fundamental research as well as for clinical practice. In this work we develop an experimental apparatus to measure the ocular wavefront based on a Shack-Hartmann sensor with a high dynamic range. We use it for measuring monochromatic ocular aberration in two subject groups: a) normal young subjects (normal group hereafter) and b) penetrating queratoplasty eyes (pathologic group hereafter). The results show that mean RMS values of the high order aberrations in the pathologic group was ten times higher than that of the normal group. Further, there is a strong correlation between the corneal aberrations (obtained by corneal topography) and ocular aberrations in the pathological group. We study the aberration correction using soft contact lenses, custom designed from each subject aberrations, by mean of both experiments and theoretical predictions. The study is carried out for three types of eyes: normal, keratoconus and penetrating queratoplasty. Results show that the main factors limiting this correction method are owing to both the mean position and rotation of the contact lenses on eye. We found that the normal subjects show a loss of optical quality relative to standard correction (sphere and cylinder), caused by expected displacements of the lenses contacts. In spite of the rotations and translations expected of contact lenses, there are, however, pathologic cases in which it is possible to reduce the RMS and increase visual quality, such as it was experimentally demonstrated in the keratoconus eyes.

Thesis (Ph. D.)--University of Nevada, Reno, 1999. / Includes bibliographical references. Online version available on the World Wide Web.

This thesis consists of two parts: a report on the use of a binocular Shack-Hartmann (SH) sensor to study the dynamic correlation of ocular aberrations; and the application of an adaptive optics (AO) system to investigate the effect of the manipulation of aberrations on the accommodation control. The binocular SH sensor consists of one laser source and one camera to reduce system cost and complexity. Six participants took part in this study. Coherence function analysis showed that coherence values were dependent on the subject, aberration and frequency component. Inter-ocular correlations of the aberration dynamics were fairly weak for all participants. Binocular and monocular viewing conditions produced similar wavefront error dynamics. The AO system has a dual wavefront sensing channel. The extra sensing channel permits direct measurement of the eye's aberrations independent of the deformable mirror. Dynamic correction of aberrations during steady-state fixation did not affect the accommodation microfluctuations, possibly due to the prior correction of the static aberration level and/or the limited correction bandwidth. The inversion of certain aberrations during dynamic accommodation affected the gain and latency of accommodation response (AR), suggesting that the eye used the aberrations to guide its initial path of accommodative step response. Corrections of aberrations at various temporal locations of AR cycle produced subject- and aberration-dependent results. The gain and phase lag of the AR to a sinusoidally moving target were unaffected by aberration correction. The predictable nature of the target had been suggested as the reason for its failure to produce any significant effect on the AR gain and phase lag.

Fortschritte in der molekulargenetischen Charakterisierung von Tumorerkrankungen haben in den letzten Jahren die klinische Praxis zunehmend beeinflusst. Das Ziel dieser Arbeit war die Untersuchung von astrozytären Tumoren der WHO-Grade II bis IV und ihre Subtypisierung anhand der gefundenen chromosomalen Aberrationen. Ferner sollte der Einfluss der gefundenen Aberrationen auf klinische Parameter wie das Gesamtüberleben oder die rezidivfreie Zeit untersucht werden. Dazu wurden paraffinfixierte Proben von insgesamt 184 primären astrozytären Tumoren (28 low-grade Astrozytome, 6 low-grade Oligoastrozytome, 50 anaplastische Astrozytome, 4 anaplastische Oligoastrozytome, 96 Glioblastoma multiforme) mit der Comparativen Genomischen Hybridisierung (CGH) untersucht. Häufige Aberrationen in allen Malignitätsgruppen stellten chromosomale Zugewinne auf Chromosom 7 sowie Verluste von Chromosom 10 und 9p dar. High-grade Astrozytome zeigten ferner häufig Zugewinne von Chromosom 19 und 20 sowie Verluste von 13q, 14q und 15q. WHO-Grad-II-Astrozytome wiesen häufig Zugewinne auf Chromosom 8 sowie Verluste von Chromosom 4q und 6q auf. Eine kürzeres Gesamtüberleben zeigten high-grade Gliome mit Verlusten von Chromosom 10q und Zugewinnen auf 7p. In Glioblastomen verursachten zusätzlich Zugewinne auf 7q sowie Verluste von 14q, in anaplastischen Astrozytomen zusätzlich Verluste von 10p ein verringertes Gesamtüberleben. WHO-Grad-II-Astrozytome zeigten bei Verlusten von 3p ein schlechteres Gesamtüberleben. Chromosomale Aberrationen, die zu einem verlängerten Gesamtüberleben führten, waren Verluste von 1p und Zugewinne von 10p in WHO-Grad-III-Tumoren. Die rezidivfreie Zeit wurde in high-grade Gliomen durch Zugewinne auf 7p und Verluste von 10p verringert. Eine Verkürzung der rezidivfreien Zeit in Glioblastomen zeigten außerdem Tumoren mit Verlusten von 7q, 10q und 14q. In anaplastischen Astrozytomen führten Verluste von 1p und 19q sowie Zugewinne auf 8q und 10p, in WHO-Grad-II-Astrozytomen Verluste von Chromosom 6 zu einer verlängerten Zeit bis zum Rezidiv. Die Anfertigung onkogenetischer Baummodelle stellte verschiedene genetische Wege der Tumorgenese dar. Ein Cluster war gekennzeichnet durch einen Verlust von 6q, ein weiterer wurde initialisiert durch den Verlust von 13q, der dritte durch den Verlust von 9p. Der vierte Cluster wurde charakterisiert durch Zugewinne auf Chromosom 7 und Verluste von Chromosom 10, während der fünfte Cluster Zugewinne auf 8q sowie Verluste von 4q aufwies.

Šiame darbe analizuojami didesnio lūžio rodiklio lęšių įtaka, akinių lęšių nešiotojams. Išnagrinėta mokslinės literatūros lęšių ir jų esamų aberacijų klausimais. Išanalizuota didesnio lūžio rodiklio plonintų lęšių, sferinių ir asferinių optinės charakteristikos. Išsiaiškinta kokių refrakcijos ydų turintys klientai netoleruoja labiausiai didesnio lūžio rodiklio plonintų lęšių. Pateikti tyrimo grafikai ir jų analizė bei išvados. Tyrime dalyvavo 90 respondentų. Tiriamieji suskirstyti pagal amžių, išsilavinimą, refrakcijos ydas bei nešiojamus akinių lęšius (plonintus ar neplonintus, sferinius ar asferinius). Analizuojant šio darbo temą, pastebėta, kad ši problema susijusi su akinių lęšių nepageidaujamais efektais, analizuojama mažai. Gauti tyrimo rezultatai rodo, kad didesnio lūžio rodiklio ploninti lęšiai, ypač asferiniai sukelia nepageidaujamus efektus. Tuos vaizdo iškraipymus labiau pajaučia tie klientai, kurie turi toliaregystės (hipermetropijos) refrakcijos ydas. Esant vidutinio laipsnio (nuo ±3.0 D iki ±6.0 D) ir didesnio laipsnio miopijai (nuo ±6.0 D ir daugiau), klientai nori lengvesnių ir plonesnių akinių lęšių. Todėl užsisako didesnio lūžio rodiklio asferinius akinių lęšius, kurie esant didesnėms dioptrijoms nedidina akių ir yra žymiai plonesni bei lengvesni. Tačiau tokie akinių lęšiai ne visada pateisina laukiamus lūkesčius. Asferinius lęšius užsisakė 30 respondentų: 22 žmonės buvo su trumparegystės (miopijos) refrakcijos yda, iš kurių nepageidaujamus vaizdo efektus... [toliau žr. visą tekstą] / In this work, effect of lenses with higher refractive index for glasses wearers is analysed. Scientific literature in field of lenses and current aberration in them is examined. Optical characteristics of thin lenses with higher refractive index both spherical and aspherical are investigated. It has been find out what kind of refractive defects have clients who do not tolerate thin lenses with higher refractive index. Graphs of the research, their analysis and conclusions are presented. The research involved 90 respondents. Participants of the research were divided according to age, education, refractive defects and eyeglass lenses worn (thin or non-thin, spherical or aspherical). While analysing the topic of the work, it was noticed that this problem, related with adverse effect of glasses, is analysed a little. The results of research shows that thin lenses with higher refractive index and especially aspherical ones cause adverse effects. Image distortions are felt by these clients who have refraction defects of long-sightedness (hypermetropia). At moderate (from ± 3.0 to ± 6.0 D D) and higher degree of myopia (from ± 6.0 D, and more), clients want lighter, thinner eyeglass lenses. Therefore, they order aspherical eyeglass lenses with higher refractive index, which consisting higher dioptres do not increase eye and are much thinner and lighter. Unfortunately these kind of eyeglass lenses do not always justify expectations. Aspherical lenses was ordered by 30 respondents:... [to full text]

The 2010 National Education Technology Plan steadily replaces paper textbooks with study materials on computers. One risk of increased computer usage is increased Computer Vision Syndrome (CVS) symptoms. I researched multiple studies to analyze the effects of computer use on dry eye and eye strain and how these symptoms can progress to musculoskeletal pain, headaches, decreased quality of life, loss of confidence and even anxiety and depression. Currently, there is not much data on tablet use so I propose two future experiments to determine if tablets can also cause CVS ocular symptoms.

Myopia is a major cause of vision loss throughout the world. High myopia is associated with severe eye diseases like maculopathy, retinal detachment and glaucoma. The prevalence of myopia is increasing, and varies by country and by ethnic group. In some Asian populations the prevalence is 70%-80%.  This thesis includes five experiments. In experiment I we investigated the effects of added positive and negative spherical aberration on accommodative response accuracy. We found that the accommodative response can be altered by modulating the spherical aberration of the eye with soft contact lenses. There was an improvement in the accommodative response slopes and a decrease in the lag of accommodation with the negative spherical aberration lenses compared to positive spherical aberration lenses.  In experiment II we investigated whether the negative spherical aberration in contact lenses could be tolerated visually in terms of wearability and comfort. We found that all the subjects were satisfied with the contact lens comfort, distance and near vision and the stability of the vision with the lenses. The accommodative response was stable through out the treatment period. In experiment III we investigated the efficacy of a novel dual treatment for the improvement of accommodative accuracy and dynamics in myopes. The spherical aberration of the eye was effectively altered to negative in the treatment group as predicted. In the control group as expected there was no significant change in the spherical aberration of the eye with and without contact lenses. The treatment lenses decreased the lag of accommodation and increased the accommodative response slope at 3 months. In the experiment IV we investigated the effect of the treatment lenses used in the previous experiment on high and low contrast visual acuities after a one year treatment period. The results showed a significant improvement in both high and low contrast visual acuities after the one year period in the treatment group compared to the control group, even though it was not clinically significant. In experiment V we investigated the intrasession repeatability of peripheral aberrations using COAS-HD VR aberrometer and also reported the distribution of higher order aberrations in a group of young emmetropes. There was no significant difference in the variance of total higher-order RMS between on- and off-axis measurements. There was a significant change in the horizontal coma, spherical aberration and higher-order RMS with off-axis angle along the horizontal visual field. We demonstrated that fast, repeatable and valid peripheral aberration measurements can be obtained with this instrument. This thesis contributes new results in this field of myopia, aberration and accommodation.

The notion that forces from the eyelids can alter the shape of the cornea has been proposed for many years. In recent times, there has been a marked improvement in our ability to measure and define the corneal shape, allowing subtle changes in the cornea to be measured. These improvements have led to the findings that pressure from the eyelids can cause alterations in corneal shape following everyday visual tasks such as reading. There are also theories to suggest that pressure from the eyelids may be involved in the aetiology of corneal astigmatism. In this program of research, a series of experiments were undertaken to investigate the influence of the eyelids on the shape of the cornea. In the first experiment, an investigation into the diurnal variation of corneal shape was carried out by measuring corneal topography at three different times (approximately 9 am, 1 pm and 5 pm) during the day over three days of the week (Monday, Tuesday and Friday). Highly significant diurnal changes were found to occur in the corneal topography of 15 of the 17 subjects. This change typically consisted of horizontal bands of distortion in the superior, and to a lesser extent, inferior cornea, increasing throughout the day (and returning to baseline the next morning). These changes appeared to be related to forces from the eyelids on the anterior cornea. Some changes were also found in corneal astigmatism. Corneal astigmatism power vector J0 (astigmatism 90/180°) was found to increase slightly over the course of the week. Whilst the changes in astigmatism were small in magnitude, this result leaves open the possibility that pressure from the eyelid may cause changes in corneal astigmatism. If pressure from the eyelids is involved in the aetiology of corneal astigmatism, then one may expect associations to exist between certain characteristics of the eyelids and corneal shape. An experiment was then undertaken to explore these possible associations. We defined the average morphology of the palpebral fissure in different angles of vertical gaze for 100 young normal subjects. This was achieved through analysis of digital images that were captured in primary gaze, 20° downgaze and 40° downgaze. Parameters defining the size, position, angle and contour of the eyelids were determined. Highly significant changes were found to occur in the palpebral fissure with downward gaze. The palpebral aperture narrows in downward gaze, and the angle of the eyelids changes from being slightly upward slanted in primary gaze, to being slightly downward slanted in downward gaze. The eyelid margin contour also flattens significantly in downward gaze. The average topography of the central and peripheral cornea was also defined for this same population. A technique was used that allowed the capture and subsequent combination of topography data from both the central and the peripheral cornea. The use of this technique provided a large corneal topography map, with data extending close to the limbus for each subject. Marked flattening was found to occur in the peripheral cornea and a conic section was found to be a poor descriptor of corneal contour in the periphery (i.e. greater than 6 mm diameter). Corneal astigmatism was also found on average to reduce in the periphery. However a number of distinct patterns of peripheral corneal astigmatism were noted in the population. Corneal astigmatism in the peripheral cornea was either found to remain stable (59% of subjects), increase (10% of subjects) or reduce (31% of subjects) in magnitude in comparison to the amount of central corneal astigmatism. We also investigated associations between the parameters defining the palpebral fissure and parameters describing corneal shape in this population of subjects. A number of highly significant associations were found between the morphology of the palpebral fissure in primary gaze and the shape of the cornea. A general tendency was found for subjects with wider horizontal palpebral fissure widths to exhibit larger corneas and also flatter central corneal powers. There were also highly significant associations found between the angle of the eyelids and the axis of corneal astigmatism, but not the magnitude of corneal astigmatism. The associations found between corneal astigmatism and palpebral fissure morphology is further evidence supporting the hypothesis that pressure from the eyelids is involved in the aetiology of corneal astigmatism. The results of these investigations have shown that corneal changes as a result of eyelid forces occur in the majority of young subjects tested over the course of a normal working day. The average morphology of the palpebral fissure and topography of the central and peripheral cornea has also been defined in detail for a large population of young subjects. Significant associations were found between corneal astigmatism and the morphology of the palpebral fissure. Whilst these results support a model of corneal astigmatism development based on eyelid morphology, they do not prove causation. Further research including measurement of eyelid pressure and corneal rigidity may aid in understanding the exact aetiology of the magnitude and axis of corneal astigmatism.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.