Brain Function in Glaucoma

Glaucoma is a chronic ophthalmic pathology, which can lead to irreversible
blindness and it is nowadays recognised as a neurodegenerative disease as well.
Recent work of our laboratory and of others suggests indeed that glaucoma may
affect not only the eyes and the optic nerves, but also the remainder of the
visual pathways and visual system in glaucoma patients. Therefore, it appears
that glaucoma should not only be considered as *just an eye disease* but also a
brain disease. The present study aims to further test the hypothesis of
glaucoma also being a brain disease. We will do so by focusing on three
aspects: integrity of cortical motion processing (study 1), the functional
integrity of the brain *at rest* (study 2) and the plasticity of the visual
cortex during *filling-in* (study 3). Using (functional) magnetic resonance
imaging (fMRI), this can be done non-invasively in human observers. Because the
studies can be conducted in the same patients, and because they share many
methodological aspects, they are presented here in a single protocol.

We expect our study to reveal specific glaucomatous deficits in the visual
system by probing motion processing and filling-in related activity using
psychophysics and functional MRI, as well as by assessing neural activity using
resting-state fMRI (rs-fMRI). We expect this knowledge to advance our
understanding of the aetiology of glaucoma, providing pointers for developing
new diagnostic tools and more effective rehabilitation methods.

To examine the presence of structural and functional brain changes in glaucoma
patients. Specifically, we are interested in the presence of glaucomatous
functional brain changes that are beyond those that can be explained on the
basis of propagated retinal and optic nerve structural damage. Ultimately, such
changes may serve as early - independent - markers of glaucoma.

The study will be an exploratory and observational study; a cross-sectional
case-control design with participants with glaucoma (primary open angle (mild,
severe), and normal tension (mild, severe)), ocular hypertension (OHT) and
controls. Groups will be matched for age and gender. The study consists of two
parts: 1) psychophysical experiments (serving study 1), and 2) (f)MRI
experiments (serving study 1, 2 and 3). Additionally, for the healthy
participants, an ophthalmologic exam will take place prior the start of these
two parts. For the glaucoma patients, this information already exists.

There are no direct risks associated with the proposed study. The planned
ophthalmological examination is akin to the standard examination one receives
on a visit to an ophthalmologist, which involves no risks. The MRI scanner that
will be used has a magnetic field strength of 3 Tesla, which is a very common
field strength used extensively in both clinical practice and research. No side
effects have been reported so far from the use of such scanners.