Hello, PD can cause eye movement impairment and subsequently bring on to problems such as double vision, unable to converge the eye upon reading and also trouble while following reading lines. PD might also cause decrease in blinking /excessive blinking which can impair the tear film distribution and hence blurring of vision. As you know,and neuro-degenerative disease will affect the brain neuron which is also thought to be connected to the optic nerve and retina as they belong to central nervous system in a whole,so it may cause a reduction of contrast sensitivity as well as visual acuity reduction. Hope I have answered your query. Let me know if I can assist you further.