Glaucoma is a blinding disease characterized by damage to the optic nerve and often caused by an increase in the intra-ocular pressure. Glaucoma affects from 2% to 8% of the South African population, depending on race and age. Primary Open-angle Glaucoma (POAG) is found mostly in patients above the age of 40 years. POAG is more prevalent in black people, with the number of black persons contracting the disease double that of persons of European origin. In South Africa, the prevalence of blindness is estimated to be 0,6%, thus 240 000 out of a total of 40 million. Glaucoma is responsible for an estimated 20% of the total number of blind people, thus approximately 48 000. The treatment of glaucoma in Africa, and particularly in rural areas, presents many unresolved problems. Conventional conservative treatment with eye drops is difficult, due to the following reasons: -- Logistical problems of providing patients with a supply of medication. -- Appropriate use of drops requires education, together with a high degree of personal compliance. -- Cost of medical treatment. Patients require life-long treatment. Eye drops cost approximately R100,00 per person per month. Thus, over a ten-year period, the cost would be R12 000,00 per person and R576 million for the estimated 48 000 sufferers. Conventional surgery is not very effective, due to the following reasons: -- Scarring takes place at the surgical site. -- Can be performed only in main centres with microsurgical facilities and competent staff. -- Requires travelling expenses, not only for surgery, but also for periodical follow-up examinations. -- Surgical complications are not uncommon. Conventional laser surgery is not effective, for the following reasons: -- Can be performed only in main centres with laser surgery facilities and competent staff. -- Requires travelling expenses, not only for surgery, but also for periodical follow-up examinations. -- Complications of surgery are not uncommon. This dissertation describes an investigation concerning treatment of glaucoma, with specific reference to the use of optical energy sources. The spectral transmission of the human sclera is investigated. Alternative methods of sourcing optical energy to the ciliary processes are presented and compared. Results obtained can be summarized as follows: -- The spectral transmission of the sclera was measured. -- Trans-scleral transmission was measured to be very low (less than 5%). The result was confirmed by means of histological investigation, where high scleral absorption was found. -- Since no well-defined transmission window could be found, the application source need not be monochromatic. -- Results published in literature were found to be inconsistent. / Dissertation (MEng (Bio-engineering))--University of Pretoria, 2006. / Electrical, Electronic and Computer Engineering / unrestricted

CdSe thin films were deposited by thermal evaporation and e-beam evaporation techniques on to well cleaned glass substrates. Low dose of boron have been implanted on a group of samples. EDAX and X-ray patterns revealed that almost stoichiometric polycrystalline films have been deposited in (002) preferred orientation. An analysis of optical measurements revealed a sharp increase in absorption coefficient below 700 nm and existence of a direct allowed transition. The calculated band gap was around 1.7 eV. The room temperature conductivity values of the samples were found to be between 9.4 and 7.5x10-4 (&amp / #937 / -cm)-1 and 1.6x10-6 and 5.7x10-7 (&amp / #937 / -cm)-1for the thermally evaporated and e-beam evaporated samples respectively. After B implantation conductivity of these films increased 5 and 8 times respectively. Hall mobility measurements could be performed only on the thermally evaporated and B-implanted e-beam evaporated samples and found to be between 8.8 and 86.8 (cm2/V.s). The dominant conduction mechanism were determined to be thermionic emission above 250 K for all samples. Tunneling and v variable range hopping mechanisms have been observed between 150-240 K and 80- 140 K respectively. Photoconductivity &amp / #8211 / illumination intensity plots indicated two recombination centers dominating at the low and high regions of studied temperature range of 80-400 K. Photoresponse measurements have corrected optical band gap measurements by giving peak value at 1.72 eV.

This thesis deals with the possibilities of energy transmission by optical fiber for the purpose of powering of electronic systems. It comprises issues of electrical energy conversion to optical energy, coupling the power into the optical fiber, coupling between fiber and opto-electric transducer, conversion of optical energy to electrical energy, and transformation on required voltage levels. The principles of such Power-Over-Fiber are discussed in the first part of the work. Various technologies for the implementation of key system parts and their effectivity are discussed. In the next part, several Power-Over-Fiber commercial devices are compared. Subsequently, systems for Power-Over-Fiber experimental implementations are proposed. They are based on the utilization of semiconductor laser, multimode fiber, photovoltaic cell and related electronic circuits. The final part of the thesis deals with the construction of experimental systems and measurement of parameters of transmitted power and efficiency.