Studies in Physiological Optics and Microwave Hyperthermia
This thesis deals with the optics of the eye, the sky and microwave induced hyperthermia treatment of cancer. Light scattering in normal eyes is reviewed and its influence on vision is discussed in some detail. It is noted that artists usually take intraocularly scattered light into account when depicting scenes, and a photographic method to achieve similar effects is demonstrated. A new method for in vivo light scattering measurements in living rabbit eyes is presented and preliminary results are reported. Using both theoretical models and clinical measurements the importance of increased light scattering for retinal image quality is studied in cataractous eyes. In the analysis an assumed neural contrast sensitivity function is used, derived from results from previous investigations. The analysis shows that visual acuity is quite insensitive even to substantial diffusive scattering provided that glare sources are not present in the field of view. Different glare test methods are studied. A versatile and simple apparatus for clinical glare testing is constructed. It utilizes a flickering glare source and is optimized for maximum accuracy. A diffractive, bifocal intraocular lens is studied through computer simulation, optical bench measurements, and visual acuity testing. This lens combines a traditional intraocular lens with a blazed Fresnel lens structure on one of its surfaces, supposedly allowing the patient good distant as well as near vision. It is found that a pupil displacement of the order of 1 mm considerably reduces the lens' resolution. A possible side-effect of new headlights for cars, which utilize ultraviolet radiation, is intraocular stray-light increase, a study of which is reported. The widely held notion that the Vikings utilized polarization of skylight on overcast days for navigational purposes is demonstrated to have no scientific basis. A microwave applicator for intracavitary hyperthermia treatment of cancer is designed and tested. The applicator is a section of a dielectric-loaded circular ridge waveguide closed at both ends forming a transmission cavity. An aperture in the cavity wall produces a directed heating of a tumour growing in the wall of a body cavity such as the vagina.