Dry eyes and blurred vision is a common complaint of many sufferers of GDD. There are many locations that eye problems can occur: from internal eye issues, optic nerves, orbital muscles, and optic nerve tracks in the brain through to the brain locations of vision in the occipital lobes. Gd can affect all locations in the vision pathway, and there may be variability in the structures involved between patients.
My current opinion is that the most prominent cause for this set of findings is local involvement at the level of the eye-balls themselves. Sodium chloride (NaCl) is the major constituent of tears. As it occurs with Ca in many locations throughout the body, that Gd substitutes in for Ca in many metabolic pathways, it is likely that Gd substitutes in for Na, and GdCl is not an effective lubricant and protection for the eye surface. So the presence of GdCl in tears almost certainly accounts for the dry eyes, and may also inhibit tear production with its presence. The dryness affects normal eye-ball motion with some lag in each eye such that they move out of sync, and this has the net result of blurred vision.
The presence of Gd in all the other above mentioned components of the vision pathway is likely also contributory, for instance in neural synapses, as occurs elsewhere with nerves. Pins and needles and fasciculations are examples of neural involvement in other locations.