<p>Optical coherence tomography (OCT) is a noninvasive three-dimensional interferometric imaging technique capable of achieving micrometer scale resolution. It is now a standard of care in ophthalmology, where it is used to improve the accuracy of early diagnosis, to better understand the source of pathophysiology, and to monitor disease progression and response to therapy. In particular, retinal imaging has been the most prevalent clinical application of OCT, but researchers and companies alike are developing OCT systems for cardiology, dermatology, dentistry, and many other medical and industrial applications. </p><p>Adaptive optics (AO) is a technique used to reduce monochromatic aberrations in optical instruments. It is used in astronomical telescopes, laser communications, high-power lasers, retinal imaging, optical fabrication and microscopy to improve system performance. Scanning laser ophthalmoscopy (SLO) is a noninvasive confocal imaging technique that produces high contrast two-dimensional retinal images. AO is combined with SLO (AOSLO) to compensate for the wavefront distortions caused by the optics of the eye, providing the ability to visualize the living retina with cellular resolution. AOSLO has shown great promise to advance the understanding of the etiology of retinal diseases on a cellular level.</p><p>Broadly, we endeavor to enhance the vision outcome of ophthalmic patients through improved diagnostics and personalized therapy. Toward this end, the objective of the work presented herein was the development of advanced techniques for increasing the imaging speed, reducing the form factor, and broadening the versatility of OCT and AOSLO. Despite our focus on applications in ophthalmology, the techniques developed could be applied to other medical and industrial applications. In this dissertation, a technique to quadruple the imaging speed of OCT was developed. This technique was demonstrated by imaging the retinas of healthy human subjects. A handheld, dual depth OCT system was developed. This system enabled sequential imaging of the anterior segment and retina of human eyes. Finally, handheld SLO/OCT systems were developed, culminating in the design of a handheld AOSLO system. This system has the potential to provide cellular level imaging of the human retina, resolving even the most densely packed foveal cones.</p> / Dissertation

The eye is our window to the world. Human vision has therefore been extensively studied over the years. However, in-depth studies are often either limited to our central visual field, or, when extended to the periphery, only correct optical errors related to a narrow spectrum of light. This thesis extends the current knowledge by considering the full visible spectrum over a wide visual field. A broad spectrum means that the wavelength dependence of light propagation inside the eye has to be considered; the optics of the eye will therefore not form a retinal image in the same location for all wavelengths, a phenomenon called chromatic aberration. We present here a new methodology to objectively measure the magnitude of transverse chromatic aberration (TCA) across the visual field of the human eye, and show that the ocular TCA increases linearly with off-axis angle (about 0.21 arcmin per degree for the spectral range from 543 nm to 842 nm). Moreover, we have implemented adaptive psychophysical methods to quantify the impact of TCA on central and peripheral vision. We have found that inducing additional TCA degrades peripheral grating detection acuity more than foveal resolution acuity (more than 0.05 logMAR per arcmin of induced TCA peripherally compared to 0.03 logMAR/arcmin foveally). As stimuli to evaluate peripheral vision, we recommend gratings that are obliquely-oriented relative to the visual field meridian. The results of this thesis have clinical relevance for improving peripheral vision and are equally important for retinal imaging techniques. To limit the negative impacts of TCA on vision, inducing additional TCA should be avoided when the peripheral refractive errors are to be corrected, such as for people suffering from macular degeneration and central visual field loss. In retinal imaging applications, TCA leads to lateral offsets when imaging is performed in more than one wavelength. Consequently, the measurement of TCA together with careful pupil alignment and subsequent compensation can improve the functionality of these instruments. / Ögat är vårt fönster mot världen, och syn har mätts och studerats i stor utsträckning över åren. Trots detta är forskningen om mänsklig syn oftast begränsad till det centrala synfältet, och i studier av det perifera synfältet korrigeras optiska fel endast över ett smalt våglängdsområde. Denna avhandling vidgar forskningen om vår syn till att inkludera hela det synliga spektrumet över ett stort synfält. Ett brett spektrum innebär att vi måste ta hänsyn till våglängdsberoendet i ljusets brytning i ögat; ögats optik kan därför inte avbilda ett objekt till samma bildläge på näthinnan för alla våglängder, ett fenomen som kallas kromatisk aberration. Vi presenterar här en ny metod för att mäta mängden transversell kromatisk aberration (TCA) över ögats synfält och visar att ögats TCA ökar linjärt med vinkeln ut i synfältet (ungefär 0,21 bågminuter per grad från 543 nm till 842 nm). Dessutom har vi implementerat adaptiva psykofysiska mätmetoder för att kvantifiera effekten av TCA på central och perifer syn. Våra resultat visar att extra inducerad TCA påverkar den perifera förmågan att upptäcka sinusformade randmönster mer än den centrala förmågan att upplösa motsvarande ränder (mer än 0,05 logMAR per bågminut inducerad TCA i periferin jämfört med 0,03 logMAR/bågminut centralt). Vid utvärdering av perifer syn rekommenderar vi att använda sinusformade randmönster med en sned riktning jämfört med synfältsmeridianen. Resultaten som presenteras i avhandlingen har klinisk betydelse för att förbättra den perifera synen och är även viktiga för tekniker som avbildar ögats näthinna. För att begränsa den negativa effekt TCA har på synen ska man undvika att inducera extra TCA, t.e.x. när ögats perifera refraktiva fel korrigeras med glasögon för människor med makula degeneration och centralt synfältsbortfall. Vid avbildning av näthinnan ger ögats TCA förskjutningar mellan bilder i olika våglängder. Därför kan mätningar av TCA, tillsammans med välkontrollerad linjering av pupillens position och efterföljande kompensation, förbättra funktionen hos dessa instrument. / <p>QC 20160511</p>