Structure and Function in Early Glaucoma
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Glaucoma is a general term that includes an array of ocular conditions that cause a specific neuropathy of the optic nerve (Greenfield, Bagga, et al. 2003) of which abnormalities associated with this disorder are localized at the level of the retinal ganglion cell layer (Epstein 1997; Quigley & Broman 2006). This structure-function relationship is not clear as it relies on several factors such as variability from the structural and functional tests, differences in measurement scales between the two modalities (Greaney et al. 2002; Katz 1999; Drance 1985; Hood et al. 2007) and physiological variation amongst individuals (Pan & Swanson 2006). The global aim of this thesis was to relate visual function of the retinal ganglion cells to structure of the optic nerve head and retinal nerve fiber layer with respect to the following perimetry techniques: i) standard automated perimetry (SAP), ii) frequency doubling technology (FDT), iii) flicker defined form (FDF), and iv) the motion detection test (MDT), and the following imaging instruments: i) confocal scanning laser ophthalmoscopy (HRT), ii) optical coherence tomography (OCT), and iii) scanning laser polarimetry (GDx VCC). The specific purpose of this study was to i) compare the test-retest characteristics of the perimetry techniques, ii) determine which may be more sensitive for early detection, iii) evaluate the structure-function relationship between measures of retinal nerve fiber layer and visual function, and iv) perform a preliminary study to determine which techniques may be most suitable to monitor progression, in patients with early stage glaucoma. MDT showed little change in the 1-year follow-up study thus being unsuitable for monitoring change. FDT and FDF gave a similar performance and are likely optimal for the detection of early functional damage. Poor diagnostic agreement was seen between the HRT and each perimetry technique. Because no one perimetry test showed both high sensitivity and high specificity, it is recommended that a combination of FDF with either SAP, FDT or MDT be used as the functional component in the diagnosis and follow-up of patients with glaucoma. The strongest global structure-function correlations for OCT were seen with SAP, FDT and MDT; for GDx, the strongest association was seen with FDF. These results suggest that FDF and GDx used in combination are best to detect early glaucomatous changes.
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Carmen Balian (2017). Structure and Function in Early Glaucoma. UWSpace. http://hdl.handle.net/10012/11256