Abstract Glaucoma is a progressive neuropathy of the optic nerve. It causes degeneration of ganglion cell axons resulting in defects in the retinal nerve fibre layer (RNFL) and characteristic changes in the optic nerve head (ONH). The Heidelberg Retina Tomograph (HRT) is a confocal scanning laser imaging device, which measures the topography of the ONH and the adjacent RNFL. To quantify the measurements of the ONH topography, various stereometric parameters are calculated. The change in the stereometric parameters of the HRT was studied in 34 eyes with glaucomatous progression in RNFL photographs and 34 eyes without progression. The change in only one stereometric parameter, the cup shape measure, showed a statistically significant correlation with the progression of the RNFL defect. An optimised change in the best three-parameter combination had 77% sensitivity and 79% specificity for progression. The change in the stereometric parameters was compared in 51 eyes with glaucomatous progression in stereoscopic ONH photographs and 425 eyes without progression. The parameters having the best correlation with progression include cup:disc area ratio, vertical cup:disc ratio, cup volume and rim area. The parameter with the largest area under the receiver operating characteristics curve (0.726) was the vertical cup:disc ratio. A change of 0.007 in the vertical cup:disc ratio had a sensitivity of 80% and a specificity of 65% for progression. The factors having the most significant effect on the sensitivity and specificity of the stereometric parameters for progression were the reference height difference and the mean topography standard deviation, indicating image quality. The change in image quality and age also showed a consistent, but variably significant influence on all parameters tested. Exercise was associated with an increase in variance in 17 of the 18 stereometric parameters. In conclusion, the change in the stereometric parameters provides useful information on ONH topography, especially when image quality is excellent. However, the evaluation of glaucomatous progression should not rely solely on the stereometric parameters of the HRT.

This thesis describes a series of investigations into the use of optic nerve head (ONH) imaging in primary open-angle glaucoma (POAG), and its relation to visual function. Accurate diagnosis is a key issue in POAG, particularly the difficult task of separating those with early disease from those healthy individuals who display signs of POAG. The purpose of this work is to improve diagnostic methods in glaucoma through use of ONH imaging and its relationship with visual field (VF) loss. First, the performance of a group of expert clinicians evaluating ONH photographs for glaucomatous damage was investigated. The results showed that even when their assessments are combined discrimination between eyes with and without POAG (based on VF loss) is far from perfect, highlighting the need for improvements in diagnosis. The possibility of combining structural and functional data to aid diagnosis was then considered. This requires VF loss and ONH damage to be strongly topographically related. The strength of this relationship was evaluated in 185 patients with POAG. 10,000 computer-generated maps between the ONH and VF were tested and the topographic relationship measured with each of these was compared to that using a published structure-based map. The weak topographic relationships found suggest that the application of these maps to individual patients is limited with current measures. The next chapter describes how a multispectral imaging (MSI, also called hyperspectral imaging) system was set-up for spatial evaluation of ONH oxygenation using a Beer-Lambert law model. Test-retest repeatability was tested and found to be acceptable for the purposes of the following studies. The MSI system was then used for an investigation of the relationship between ONH oxygenation and VF loss. 33 eyes of 18 patients underwent VF testing, MSI and HRT3 imaging. Superior-inferior asymmetries in VF sensitivity were compared to superior-inferior asymmetries in ONH oxygenation measured by MSI and in neuroretinal rim (NRR) area measured by HRT3. This way we take advantage of the typical progression of POAG and each eye acts as its own reference, negating the effect of a wide normal range and overlap between health and disease. This study found, for the first time, a strong association between ONH oxygenation and VF sensitivity. A re-analysis of the 33 ONH oxygenation maps was then performed to assess oxygenation only in the area of the NRR as defined by the HRT. Superior-inferior asymmetries in NRR oxygenation were then compared to superior-inferior asymmetries in VF loss, and the associations found were similarly strong. This study shows that MSI is capable of detecting areas of NRR deemed healthy tissue by structural imaging techniques, which are in fact poorly oxygenated and associated with VF defects. These findings show that NRR oxygenation measured by MSI is strongly related to VF loss. This important information complements existing technologies and may aid in the future diagnosis and management of patients with POAG.