An investigation into the application of light sources in the treatment of glaucoma

Abstract

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.