Dichoptic multifocal visual evoked potentials in glaucoma detection, and their structural and functional correlates

Glaucoma is the leading cause of preventable blindness in the western world. Effective treatment of glaucoma relies on early detection of a disease that is without symptoms in the initial stages. Identification of damage often relies on visual field testing which can be unreliable. The Multifocal VEP (mfVEP) was developed to provide an objective measure of visual field function in glaucoma. The newly designed dichoptic (binocular) mfVEP creates a testing environ which is most conducive to calculating inter-eye symmetry, as both eyes are tested at the same time, under the same conditions. However, the sensitivity of this testing technology, the role of inter-ocular suppression in asymmetry analysis and the ideal stimulus for detecting glaucoma using dichoptic mfVEP are largely unknown. Experiments focusing on dichoptic mfVEP and interocular suppression demonstrated sensitivity to eccentricity, contrast and speed of presentation. Building on these relationships, dichoptic mfVEP with targeted stimuli was shown to be more effective than monocular in detecting unilateral early glaucoma. Furthermore this project sought to provide further insight into the structure/function relationship that underlies the pathogenesis of glaucoma by studying correlations of glaucomatous field defects as detected by Humphrey visual field testing and mfVEP with structural changes characterised by high resolution retinal imaging techniques. The results showing that newer imaging technologies exhibited closer correlation to glaucomatous change but that the relationship is still variable highlighted the one of the many challenges in monitoring glaucoma. Correlation analysis comparing HVF and mfVEP showed similarities in structure-function patterns.