Reflectance and ultrastructure of the retinal nerve fiber layer in normal and glaucomatous retinas

Glaucomatous damage to the RNFL usually precedes detectable visual field loss; clinical assessment of RNFL optical properties has been valuable in diagnosis of glaucoma and other neuropathic diseases. In this dissertation, we aimed to improve the understanding of the changes of RNFL reflectance and its underlying ultrastructure under the development of glaucoma.;We used simultaneous immunohistochemical labeling and both en face and in-depth confocal imaging to study axonal cytoskeletal alteration of F-actin, MTs and NFs across the retina in the context of glaucoma. We have found that alteration of each cytoskeletal components is different from each other, and different degree of RNFL change could happen in the same retina. These findings help to understand selective damage mechanisms of human glaucoma.;We proposed a new method to classify RGCs based on the content of each cytoskeletal component in axons, and investigated the cytoskeletal distribution across the retina. We have discovered axonal subtypes that contain different proportions of cytoskeletal components. This classification method provides enhanced understanding of selective damage mechanisms in glaucoma and other ocular neuropathic diseases.;RNFL reflectance arises from light scattering by axonal ultrastructures. Structural change of axons should result in change of RNFL reflectance. We used an imaging microreflectometer (IMR) and in vitro retinas to study the reflectance of RNFL at different wavelengths, and related their changes to different degrees of glaucomatous damage. The results provide significant information for non-invasive assessment of ultrastructure or tissue diagnosis.;Currently, measurement of RNFL reflectance is limited to assess RNFL structure. This dissertation also explored a new idea to provide assessment of axonal dynamic activity by measuring the temporal change of RNFL speckle. The results provide a new concept to non-invasively detect functional change in axons, which may precede loss of axonal structure in glaucoma.