Introduction:
Functional MRI signal changes in primary visual cortex of patients with primary open angle glaucoma
Purpose:
. To investigate the impact of glaucomatous neuropathy of primary open angle glaucoma (POAG) using functional MRI on neuronal activity in primary visual cortex corresponding to the central normal visual field.
Methods:
. Six POAG patients with asymmetric visual field damage and spared central vision were enrolled in this study. Contrasting to the glaucomatous eye, the follow eye was either unaffected or less affected as revealed by automated perimetry. All patients received detailed ophthalmologic examination including: visual acuity, intraocular pressure, refraction, gonioscopy, and fundus examination. Scanning laser polarimetry with variable corneal compensation (GDx VCC), confocal scanning laser ophthalmoscopy (HRT II), posterior segment optical coherence tomography (OCT) and Humphrey SITA-standard 30-2 and 10-2 visual field analysis were also performed on each patient. Block-design fMRI was then carried out. The stimulus was a hemifield checkerboard contrast-reversing at 8 Hz. It was viewed by the examined eye monocularly during fMRI scanning, with the fellow eye occluded.
Results:
. For every patient, the blood oxygen level dependent (BOLD) fMRI signal change in primary visual cortex corresponding to central visual input from the more severely affected eye was less than that of the fellow eye (Fig. 1). Such difference in fMRI response did not correlate with inter-ocular differences in measurements of GDxVCC, OCT, and HRT II, but showed a negative correlation with interocular pattern standard deviation (PSD) difference of Humphrey visual field analysis.
Conclusions:
. Glaucomatous neuropathy from POAG may lead to decreased cortical activity in primary visual cortex corresponding to the central normal visual field.1
Keywords: visual cortex • neuro-ophthalmology: cortical function/rehabilitation • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)