| Popis: |
The pathogenesis of optic nerve (ON) atrophy and visual field defects in glaucoma is a subject of controversy. Mechanical and vascular factors have been claimed to cause damage to the optic nerve head. The mechanical theory, including impaired axonal flow, can account for nerve fiber defects through raised intraocular pressure (IOP).1,2,3,4 Support for the vascular theory stems from histological and fluorescein angiographic studies in advanced glaucoma,5,6 but there is little evidence for impaired microcirculation in the ON in the early stage of the disease, in part due to the lack of an objective, precise and noninvasive technique for measuring ON circulation in humans. The development of such a technique is highly desirable to help substantiate or dismiss the vasogenic theory. If neuronal degenerations are associated with vascular changes, the detection of subtle changes in ON blood flow may allow early diagnosis of nerve damage. This may be important since it appears that 20-30% loss of fibers can occur without being detected by current methods of examination.7 |
