Visual manifestations of migraine are largely considered transient, without permanent sequelae. Recent findings raise the possibility of persistent ocular and neural manifestations. This thesis investigates visual function in migraine during the period between episodes by applying various psychophysical tests to two migraine groups (migraine with aura ( n = 20) and migraine without aura (n = 20)) and comparing the results to those of a nonheadache control group (n = 20). Tests were designed to address the level of visual system involvement, and to investigate the extent to which selective visual processes, specifically, motion and other forms of temporal modulation are adversely affected in migraine. / The first experiment assessed global processing of complex form and motion in Glass patterns. Compared to nonheadache participants, the migraine groups demonstrated significantly elevated motion detection than motion discrimination thresholds. In contrast, average form detection thresholds were almost identical between subject groups. The second experiment measured perimetrically, in each eye, global motion sensitivity in fifteen localized visual field regions and compared these results in the same subjects to those obtained from conventional luminance-based perimetry. Perimetry testing revealed that two-thirds of migraineurs had localized deficits in motion coherence. Almost all motion field defects occurred in regions of normal sensitivity to the luminance targets. Over 80% of migrainous visual field defects were nonhomonymous, indicating that dysfunction occurs largely prior to the optic chiasm. Homonymous defects were also detected, raising the possibility of postchiasmal dysfunction, although several of these defects may represent independent monocular losses. The stability of a sample of field defects was retested after a 4--6 week delay. Sixty-percent of the motion defects persisted. These regions could support normal resolution acuity, but in most cases, not the discrimination of small increments in speed in globally coherent motion. / Also included is a study of the spatial and temporal frequency characteristics of visual discomfort to grating patterns. Visual discomfort was experienced by a greater proportion of migraineurs than nonheadache controls, and at significantly lower levels of stimulus contrast in migraineurs than in controls. Gratings modulated at high temporal frequencies were particularly effective in eliciting discomfort in migraineurs. / Comparison of individual results across the various tests suggests that functional deficits in migraine (i) are demonstrated on tasks that involve global motion and other forms of temporal modulation, (ii) occur primarily prior to the optic chiasm, but may, in some cases, also involve higher-levels of the visual pathway. Theoretical and clinical implications on migraine pathology and the visual system are discussed.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.82931 |
| Date | January 2002 |
| Creators | McColl, Shelley L. |
| Contributors | Chaudhuri, Avi (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Psychology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001985024, proquestno: AAINQ88527, Theses scanned by UMI/ProQuest. |
Page generated in 0.0029 seconds